ADOPTS WITH AMENDMENTS:

International Energy Conservation Code 2018 (IECC 2018)

Heads up: There are no amended sections in this chapter.
The provisions in this chapter are applicable to commercial buildings and their building sites.

Commercial buildings shall comply with one of the following:

  1. The requirements of Sections C402, C403, C404, C405, C406, C408, C409, C410 and C411.
  2. The requirements of Section C407.
  3. When adopted by the local jurisdiction, the requirements of Appendix CF, Outcome-Based Energy Budget, Sections C408, C409, C410, C411 and any specific section in Table C407.2 as determined by the local jurisdiction. The Proposed Total UA of the proposed building shall be no more than 20 percent higher than the Allowed Total UA as defined in Section C402.1.5.
Work on existing buildings shall comply with Chapter 5 in addition to the applicable provisions of Chapter 4.

Building thermal envelope assemblies for buildings that are intended to comply with the code on a prescriptive basis, in accordance with the compliance path described in Item 1 of Section C401.2, shall comply with the following:

  1. The opaque portions of the building thermal envelope shall comply with the specific insulation requirements of Section C402.2 and the thermal requirements of either the R-value-based method of Section C402.1.3, the U-, C- and F-factor-based method of Section C402.1.4, or the component performance alternative of Section C402.1.5.
  2. Fenestration in the building envelope assemblies shall comply with Section C402.4, or the component performance alternative of Section C402.1.5.
  3. Air leakage of building envelope assemblies shall comply with Section C402.5.
Low-energy buildings shall comply with Section C402.1.1.1. Semi-heated buildings and spaces shall comply with Section C402.1.1.2. Greenhouses shall comply with Section C402.1.1.3.

The following buildings, or portions thereof, separated from the remainder of the building by building thermal envelope assemblies complying with this code shall be exempt from all thermal envelope provisions of this code:

  1. Those that are heated and/or cooled with a peak design rate of energy usage less than 3.4 Btu/h × ft2 (10.7 W/m2) or 1.0 watt/ft2 (10.7 W/m2) of floor area for space conditioning purposes.
  2. Those that do not contain conditioned space.
  3. Unstaffed equipment shelters or cabinets used solely for personal wireless service facilities.

The building envelope of semi-heated buildings, or portions thereof, shall comply with the same requirements as that for conditioned spaces in Section C402, except as modified by this section. The total installed output capacity of mechanical space conditioning systems serving a semi-heated building or space shall comply with Section C202. Building envelope assemblies separating conditioned space from semi-heated space shall comply with the exterior envelope insulation requirements. Semi-heated spaces heated by mechanical systems that do not include electric resistance heating equipment are not required to comply with the opaque wall insulation provisions of Section C402.2.3 for walls that separate semi-heated spaces from the exterior or low-energy spaces. Semi-heated spaces shall be calculated separately from other conditioned spaces for compliance purposes.

Opaque walls in semi-heated spaces shall be calculated as fully code compliant opaque walls for both the target and proposed for the Target UA calculations for the component performance alternative in Section C402.1.5, and for the Standard Reference Design for Total Building Performance compliance per Section C407. The capacity of heat trace temperature maintenance systems complying with Section C404.7.2 that are provided for freeze protection of piping and equipment only, shall not be included in the total installed output capacity of mechanical space conditioning systems.

Exception: Building or space may comply as semi-heated when served by one or more of the following system alternatives:

  1. Electric infrared heating equipment for localized heating applications.
  2. Heat pumps with cooling capacity permanently disabled, as preapproved by the jurisdiction.

Greenhouse structures or areas that comply with all of the following shall be exempt from the building envelope requirements of this code:

  1. Exterior opaque envelope assemblies complying with Sections C402.2 and C402.4.4.

    Exception: Low-energy greenhouses that comply with Section C402.1.1.1.

  2. Interior partition building thermal envelope assemblies that separate the greenhouse from conditioned space complying with Sections C402.2, C402.4.3 and C402.4.4.
  3. Nonopaque envelope assemblies complying with the thermal envelope requirements in Table C402.1.1.3. The U-factor for the nonopaque roof shall be for the roof assembly or a roof that includes the assembly and an internal curtain system.

    Exception: Unheated greenhouses.

  4. No mechanical cooling is provided.
  5. For heated greenhouses, heating is provided by a radiant heating system, a condensing natural gas-fired or condensing propane-fired heating system, or a heat pump with cooling capacity permanently disabled as preapproved by the jurisdiction.

TABLE C402.1.1.3

NONOPAQUE THERMAL ENVELOPE MAXIMUM REQUIREMENTS

COMPONENT U-FACTOR
BTU/h × ft2 × °F
CLIMATE ZONE 5
AND MARINE 4
Nonopaque roof 0.5
Nonopaque SEW wall 0.7
Nonopaque N wall 0.6

SEW = Orientations other than N.

Buildings that comply with all of the following shall be exempt from the building thermal envelope provisions of this code:

  1. Are separate buildings with floor area no more than 500 square feet (50 m2).
  2. Are intended to house electronic equipment with installed equipment power totaling at least 7 watts per square foot (75 W/m2) and not intended for human occupancy.
  3. Are served by mechanical cooling and heating systems sized in accordance with Sections C403.1.2 and C403.3.1.
  4. Have a heating system capacity not greater than 17,000 Btu/hr (5 kW) and a heating thermostat set point that is restricted to not more than 50°F (10°C).
  5. Have an average wall and roof U-factor less than 0.200.

    Exception: Where the cooling and heating system is a heat pump, the heating system capacity is allowed to exceed 17,000 Btu/h provided the heat pump cooling efficiency is at least 15 percent better than the requirements in Table C403.3.2(2).

Elevator hoistways that comply with all of the following shall be exempt from the building thermal envelope and envelope air barrier provisions of this code:

  1. Are separate from any other conditioned spaces in the building (do not serve or open into any conditioned, semi-heated or indirectly conditioned space).
  2. Have heating and/or cooling equipment sized only to serve the expected elevator loads with thermostat set points restricted to heating to no higher than 40°F (4.5°C) and cooling to no lower than 95°F (35°C).
  3. Have an area-weighted average wall, roof, and floor (where applicable) U-factor of less than or equal to 0.20. Calculations must include any floor-slab-edges that penetrate the hoistway and thus are considered part of the above-grade walls.

Building thermal envelope opaque assemblies shall comply with the requirements of Section C402.2 based on the climate zone specified in Chapter 3. For opaque portions of the building thermal envelope intended to comply on an insulation component R-value basis, the R-values for insulation shall not be less than that specified in Table C402.1.3. Commercial buildings or portions of commercial buildings enclosing Group R occupancies shall use the R-values from the "Group R" column of Table C402.1.3. Commercial buildings or portions of commercial buildings enclosing occupancies other than Group R shall use the R-values from the "All other" column of Table C402.1.3.

TABLE C402.1.3

OPAQUE THERMAL ENVELOPE INSULATION COMPONENT MINIMUM REQUIREMENTS, R-VALUE METHODa, i

CLIMATE ZONE 5 AND MARINE 4
All Other Group R
Roofs
Insulation entirely
above deck
R-38ci R-38ci
Metal buildingsb R-25 + R-11 LS R-25 + R-11 LS
Attic and other R-49 R-49
Walls, Above Grade
Massh R-9.5c ci R-13.3ci
Mass transfer deck slab edge R-5 R-5
Metal building R-19ci or
R-13 + R-13ci
R-19ci or
R-13 + R-13ci
Steel framed R-13 + R-10ci R-19 + R-8.5ci
Wood framed and
other
R-21 int or
R-15 + R-5ci std
R-13 + R-7.5ci std or
R-20 + R-3.8ci std or
R-25 std
Walls, Below Grade
Below-grade walld, h Same as above grade Same as above grade
Floors
Massf R-30ci R-30ci
Joist/framing R-30e R-30e
Slab-on-Grade Floors
Unheated slabs R-10 for 24" below R-10 for 24" below
Heated slabsd R-10 perimeter &
under entire slab
R-10 perimeter &
under entire slab
Opaque Doorsg
Nonswinging R-4.75 R-4.75

For SI: 1 inch = 25.4 mm, 1 pound per square foot = 4.88 kg/m2; 1 pound per cubic foot = 16 kg/m3.

ci = Continuous insulation. NR = No requirement. LS = Liner system, Liner system, int = Intermediate framing, std = Standard framing

  1. Assembly descriptions can be found in Chapter 2 and Appendix CA.
  2. Where using R-value compliance method, a thermal spacer block with minimum thickness of 1/2 inch and minimum R-value of R-3.5 shall be provided, otherwise use the U-factor compliance method in Table C402.1.4.
  3. Exception: Integral insulated concrete block walls complying with ASTM C90 with all cores filled and meeting both of the following:

    1. At least 50 percent of cores must be filled with vermiculite or equivalent fill insulation; and
    2. The building thermal envelope encloses one or more of the following uses: Warehouse (storage and retail), gymnasium, auditorium, church chapel, arena, kennel, manufacturing plant, indoor swimming pool, pump station, water and waste water treatment facility, storage facility, storage area, motor vehicle service facility. Where additional uses not listed (such as office, retail, etc.) are contained within the building, the exterior walls that enclose these areas may not utilize this exception and must comply with the appropriate mass wall R-value from Table C402.1.3/U-factor from Table C402.1.4.
  4. Where heated slabs are below grade, they shall comply with the insulation requirements for heated slabs.
  5. Steel floor joist systems shall be insulated to R-38 + R-10ci.
  6. "Mass floors" shall include floors weighing not less than:

    1. 35 pounds per square foot of floor surface area; or
    2. 25 pounds per square foot of floor surface area where the material weight is not more than 120 pounds per cubic foot.
  7. Not applicable to garage doors. See Table C402.1.4.
  8. Peripheral edges of intermediate concrete floors are included in the above-grade mass wall category and therefore must be insulated as above-grade mass walls unless they meet the definition of Mass Transfer Deck Slab Edge. The area of the peripheral edges of concrete floors shall be defined as the thickness of the slab multiplied by the perimeter length of the edge condition. See Table A103.3.7.2 for typical default U-factors for above grade slab edges and Note c for typical conditions of above-grade slab edges.
  9. For roof, wall or floor assemblies where the proposed assembly would not be continuous insulation, an alternate nominal R-value compliance option for assemblies with isolated metal penetrations of otherwise continuous insulation is:

    Assemblies with
    continuous
    insulation
    (see definition)
    Alternate option for
    assemblies with metal
    penetrations, greater
    than 0.04% but less
    than 0.08%
    Alternate option for
    assemblies with metal
    penetrations, greater
    than or equal to 0.08%
    but less than 0.12%
    R-9.5ciR-11.9ciR-13ci
    R-11.4ciR-14.3ciR-15.7ci
    R-13.3ciR-16.6ciR-18.3ci
    R-15.2ciR-19.0ciR-21ci
    R-30ciR-38ciR-42ci
    R-38ciR-48ciR-53ci
    R-13 + R-7.5ciR-13 + R-9.4ciR-13 + R-10.3ci
    R-13 + R-10ciR-13 + R-12.5ciR-13 + R-13.8ci
    R-13 + R-12.5ciR-13 + R-15.6ciR-13 + R-17.2ci
    R-13 + R-13ciR-13 + R-16.3ciR-13 + R-17.9ci
    R-19 + R-8.5ciR-19 + R-10.6ciR-19 + R-11.7ci
    R-19 + R-14ciR-19 + R-17.5ciR-19 + R-19.2ci
    R-19 + R-16ciR-19 + R-20ciR-19 + R-22ci
    R-20 + R-3.8ciR-20 + R-4.8ciR-20 .+ R-5.3ci
    R-21 + R-5ciR-21 + R-6.3ciR-21 + R-6.9ci

    This alternate nominal R-value compliance option is allowed for projects complying with all of the following:

    1. The ratio of the cross-sectional area, as measured in the plane of the surface, of metal penetrations of otherwise continuous insulation to the opaque surface area of the assembly is greater than 0.0004 (0.04%), but less than 0.0012 (0.12%).
    2. The metal penetrations of otherwise continuous insulation are isolated or discontinuous (e.g., brick ties or other discontinuous metal attachments, offset brackets supporting shelf angles that allow insulation to go between the shelf angle and the primary portions of the wall structure). No continuous metal elements (e.g., metal studs, z-girts, z-channels, shelf angles) penetrate the otherwise continuous portion of the insulation.
    3. Building permit drawings shall contain details showing the locations and dimensions of all the metal penetrations (e.g., brick ties or other discontinuous metal attachments, offset brackets, etc.) of otherwise continuous insulation. In addition, calculations shall be provided showing the ratio of the cross-sectional area of metal penetrations of otherwise continuous insulation to the overall opaque wall area.

    For other cases where the proposed assembly is not continuous insulation, see Section C402.1.4 for determination of U-factors for assemblies that include metal other than screws and nails.

Building thermal envelope opaque assemblies shall meet the requirements of Section C402.2 based on the climate zone specified in Chapter 3. Building thermal envelope opaque assemblies intended to comply on an assembly U-, C-, or F-factor basis shall have a U-, C-, or F-factor not greater than that specified in Table C402.1.4. Commercial buildings or portions of commercial buildings enclosing Group R occupancies shall use the U-, C-, or F-factor from the "Group R" column of Table C402.1.4. Commercial buildings or portions of commercial buildings enclosing occupancies other than Group R shall use the U-, C-, or F-factor from the "All Other" column of Table C402.1.4. The U-factors for typical construction assemblies are included in Appendix CA. These values shall be used for all calculations. Where proposed construction assemblies are not represented in Appendix CA, values shall be calculated in accordance with the ASHRAE Handbook of Fundamentals using the framing factors listed in Appendix A where applicable and shall include the thermal bridging effects of framing materials.

TABLE C402.1.4

OPAQUE THERMAL ENVELOPE ASSEMBLY MAXIMUM REQUIREMENTS, U-FACTOR METHODa, f

CLIMATE ZONE 5 AND MARINE 4
All Other Group R
Roofs
Insulation entirely above deck U-0.027 U-0.027
Metal buildings U-0.031 U-0.031
Attic and other U-0.021 U-0.021
Joist or single rafter U-0.027 U-0.027
Walls, Above Grade
Massg U-0.104d U-0.078
Mass transfer deck slab edge U-0.20 U-0.20
Metal building U-0.052 U-0.052
Steel framed U-0.055 U-0.055
Wood framed and other U-0.054 U-0.051
Walls, Below Grade
Below-grade wallb,g Same as above grade Same as above grade
Floors
Masse U-0.031 U-0.031
Joist/framing U-0.029 U-0.029
Slab-on-Grade Floors
Unheated slabs F-0.54 F-0.54
Heated slabsc F-0.55 F-0.55
Opaque Doors
Swinging door U-0.37 U-0.37
Nonswinging door U-0.34 U-0.34
Garage door <14% glazing U-0.31 U-0.31

For SI: 1 pound per square foot = 4.88 kg/m2; 1 pound per cubic foot = 16 kg/m3.

  1. Use of opaque assembly U-factors, C-factors, and F-factors from Appendix CA is required unless otherwise allowed by Section C402.1.4.
  2. Where heated slabs are below grade, they shall comply with the F-factor requirements for heated slabs.
  3. Heated slab F-factors shall be determined specifically for heated slabs. Unheated slab factors shall not be used.
  4. Exception: Integral insulated concrete block walls complying with ASTM C90 with all cores filled and meeting both of the following:

    1. At least 50 percent of cores must be filled with vermiculite or equivalent fill insulation; and
    2. The building thermal envelope encloses one or more of the following uses: Warehouse (storage and retail), gymnasium, auditorium, church chapel, arena, kennel, manufacturing plant, indoor swimming pool, pump station, water and waste water treatment facility, storage facility, storage area, motor vehicle service facility. Where additional uses not listed (such as office, retail, etc.) are contained within the building, the exterior walls that enclose these areas may not utilize this exception and must comply with the appropriate mass wall R-value from Table C402.1.3/U-factor from Table C402.1.4.
  5. "Mass floors" shall include floors weighing not less than:

    1. 35 pounds per square foot of floor surface area; or
    2. 25 pounds per square foot of floor surface area where the material weight is not more than 120 pounds per cubic foot.
  6. Opaque assembly U-factors based on designs tested in accordance with ASTM C1363 shall be permitted. The R-value of continuous insulation shall be permitted to be added or subtracted from the original test design.
  7. Peripheral edges of intermediate concrete floors are included in the above-grade mass wall category and therefore must be insulated as above-grade mass walls unless they meet the definition of Mass Transfer Deck Slab Edge. The area of the peripheral edges of concrete floors shall be defined as the thickness of the slab multiplied by the perimeter length of the edge condition. See Table A103.3.7.2 for typical default U-factors for above-grade slab edges and Note c for typical conditions of above-grade slab edges.

U-factors of walls with cold-formed steel studs shall be permitted to be determined in accordance with Equation 4-1:


(Equation 4-1)

where:

Rs = The cumulative R-value of the wall components along the path of heat transfer, excluding the cavity insulation and steel studs.

ER = The effective R-value of the cavity insulation with steel studs.

TABLE C402.1.4.1

EFFECTIVE R-VALUES FOR STEEL STUD WALL ASSEMBLIES

NOMINAL
STUD
DEPTH
(inches)
SPACING
OF
FRAMING
(inches)
CAVITY
R-VALUE
(insulation)
CORRECTION
FACTOR (Fc)
EFFECTIVE
R-VALUE (ER)
(Cavity
R-Value × Fc)
31/2 16 13 0.46 5.98
15 0.43 6.45
31/2 24 13 0.55 7.15
15 0.52 7.80
6 16 19 0.37 7.03
21 0.35 7.35
6 24 19 0.45 8.55
21 0.43 9.03
8 16 25 0.31 7.75
24 25 0.38 9.50

For SI: 1 inch = 25.4 mm.

Building envelope values and fenestration areas determined in accordance with Equation 4-2 shall be permitted in lieu of compliance with the U-factors and F-factors in Table C402.1.4 and C402.4 and the maximum allowable fenestration areas in Section C402.4.1.

For buildings with more than one space conditioning category, component performance compliance shall be demonstrated separately for each space conditioning category. Interior partition ceilings, walls, fenestration and floors that separate space conditioning areas shall be applied to the component performance calculations for the space conditioning category with the highest level of space conditioning.


(Equation 4-2)

where:

Proposed Total UA = UA-glaz-prop + UA-sky-prop + UA-opaque-prop + FL-slab-prop.

Allowable Total UA = UA-glaz-allow + UA-glaz-excess + UA-sky-allow + UA-sky-excess + UA-opaque-allow + FL-slab-allow.

UA-glaz-prop = Sum of (proposed U-value × proposed area) for each distinct vertical fenestration type, up to code maximum area.

UA-sky-prop = Sum of (proposed U-value × proposed area) for each distinct skylight type, up to the code maximum area.

UA-opaque-prop = Sum of (proposed U-value × proposed area) for each distinct opaque thermal envelope type.

FL-slab-prop = Sum of (proposed F-value × proposed length) for each distinct slab-on-grade perimeter assembly.

UA-glaz-allow = Sum of (code maximum vertical fenestration U-value from Table C402.4, or Section C402.4.1.1.2 if applicable, × proposed area) for each distinct vertical fenestration type, not to exceed the code maximum area 1.

UA-glaz-excess = U-value for the proposed wall type from Table C402.42 × vertical fenestration area in excess of the code maximum area.

UA-sky-allow = Sum of (code maximum skylight U-value from Table C402.4 × proposed area) for each distinct skylight type proposed, not to exceed the code maximum area.

UA-sky-excess = U-value for the proposed roof type from Table C402.43 × skylight area in excess of the code maximum area.

UA-opaque-allow = Code maximum opaque envelope U-value from Table C402.1.4 for each opaque door, wall, roof, and floor assembly × proposed area.

FL-slab-allow = Code maximum F-value for each slab-on-grade perimeter assembly × proposed length.

Notes:

  1. Where multiple vertical fenestration types are proposed and the code maximum area is exceeded, the U-value shall be the average Table C402.1.4 U-value weighted by the proposed vertical fenestration area of each type.
  2. Where multiple wall types are proposed, the U-value shall be the average Table C402.1.4 U-value weighted by the proposed above-grade wall area of each type.
  3. Where multiple roof types are proposed, the U-value shall be the average Table C402.1.4 U-value weighted by the proposed roof area of each type.

The U-factors for typical construction assemblies are included in Chapter 3 and Appendix CA. These values shall be used for all calculations. Where proposed construction assemblies are not represented in Chapter 3 or Appendix CA, values shall be calculated in accordance with the ASHRAE Handbook of Fundamentals, using the framing factors listed in Appendix CA.

For envelope assemblies containing metal framing, the U-factor shall be determined by one of the following methods:

  1. Results of laboratory measurements according to acceptable methods of test.
  2. ASHRAE Handbook of Fundamentals where the metal framing is bonded on one or both sides to a metal skin or covering.
  3. The zone method as provided in ASHRAE Handbook of Fundamentals.
  4. Effective framing/cavity R-values as provided in Appendix CA. When return air ceiling plenums are employed, the roof/ceiling assembly shall:

    1. 4.1. For thermal transmittance purposes, not include the ceiling proper nor the plenum space as part of the assembly; and
    2. 4.2. For gross area purposes, be based upon the interior face of the upper plenum surface.
  5. Tables in ASHRAE 90.1 Normative Appendix A.
  6. Calculation method for steel-framed walls in accordance with Section C402.1.4.1 and Table C402.1.4.1.

Fenestration SHGC values for individual components and/or fenestration are permitted to exceed the SHGC values in Table C402.4 and/or the maximum allowable fenestration areas in Section C402.4.1 where the proposed total SHGC × A is less than the allowable total SHGC × A as determined by Equation 4-3.

(Equation 4-3)

Where:

Proposed Total SHGC × A =  SHGC × A-glaz-prop + SHGC × A sky-prop
Allowable Total SHGC × A =  SHGC × A-glaz-allow + SHGC × A-sky-allow
SHGC × A-glaz-prop Sum of (proposed SHGC × proposed area) for each distinct vertical fenestration type
SHGC × A-sky-prop Sum of (proposed SHGC × proposed area) for each distinct skylight type
SHGC × A-glaz-allow Sum of (code maximum vertical fenestration SHGC from Table C402.4, or Section C402.4.1.3 if applicable, × proposed area) for each distinct vertical fenestration type, not to exceed the code maximum area
SHGC × A-sky-allow Sum of (code maximum skylight SHGC from Table C402.4 × proposed area) for each distinct skylight type, not to exceed the code maximum area

If the proposed vertical fenestration area does not exceed the Vertical Fenestration Area allowed, the target area for each vertical fenestration type shall equal the proposed area. If the proposed vertical fenestration area exceeds the Vertical Fenestration Area allowed, the target area of each vertical fenestration element shall be reduced in the base envelope design by the same percentage and the net area of each above-grade wall type increased proportionately by the same percentage so that the total vertical fenestration area is exactly equal to the Vertical Fenestration Area allowed.

If the proposed skylight area does not exceed the Allowable Skylight Area from Section C402.4.1, the target area shall equal the proposed area. If the proposed skylight area exceeds the Allowable Skylight Area from Section C402.4.1, the area of each skylight element shall be reduced in the base envelope design by the same percentage and the net area of each roof type increased proportionately by the same percentage so that the total skylight area is exactly equal to the allowed percentage per Section C402.3.1 of the gross roof area.

Insulation in building thermal envelope opaque assemblies shall comply with Sections C402.2.1 through C402.2.6 and Table C402.1.3.

Where this section refers to installing insulation levels as specified in Section C402.1.3, assemblies complying with Section C402.1.5 are allowed to install alternate levels of insulation so long as the U-factor of the insulated assembly is less than or equal to the U-factor required by the respective path.

The minimum thermal resistance (R-value) of the insulating material installed either between the roof framing or continuously on the roof assembly shall be as specified in Table C402.1.3, based on construction materials used in the roof assembly. Continuous insulation board shall be installed in not less than two layers and the edge joints between each layer of insulation shall be staggered. Insulation installed on a suspended ceiling with removable ceiling tiles shall not be considered part of the minimum thermal resistance of the roof insulation.

Exceptions:

  1. Continuously insulated roof assemblies where the thickness of insulation varies 1 inch (25 mm) or less and where the area-weighted U-factor is equivalent to the same assembly with the R-value specified in Table C402.1.3.
  2. Where tapered insulation is used with insulation entirely above deck, those roof assemblies shall show compliance on a U-factor basis per Section C402.1.4. The effective U-factor shall be determined through the use of Tables CA102.2.6(1), CA102.2.6(2) and CA102.2.6(3).
  3. Two layers of insulation are not required where insulation tapers to the roof deck, such as at roof drains. At roof drains, the immediate 24" × 24" (610 mm by 610 mm) plan area around each roof drain has a minimum insulation requirement of R-13, but otherwise is permitted to be excluded from roof insulation area-weighted calculations.

Skylight curbs shall be insulated to the level of roofs with insulation entirely above deck or R-5, whichever is less.

Exception: Unit skylight curbs included as a component of skylight listed and labeled in accordance with NFRC 100 shall not be required to be insulated.

Structural curbs installed to support rooftop HVAC equipment are allowed to interrupt the above-roof insulation. The area under the HVAC equipment inside of the equipment curb shall be insulated to a minimum of R-13 in all locations where there are not roof openings for ductwork. The annular space between the roof opening and the ductwork shall be sealed to maintain the building air barrier. The plan-view area of the HVAC equipment curb shall be excluded from the prescriptive roof insulation requirements or the area-weighted component performance calculations.

The minimum thermal resistance (R-value) of materials installed in the wall cavity between the framing members and continuously on the walls shall be as specified in Table C402.1.3, based on framing type and construction materials used in the wall assembly. The R-value of integral insulation installed in concrete masonry units (CMU) shall not be used in determining compliance with Table C402.1.3 except as otherwise noted in the table. In determining compliance with Table C402.1.4, the use of the U-factor of concrete masonry units with integral insulation shall be permitted.

"Mass walls" where used as a component in the thermal envelope of a building shall comply with one of the following:

  1. Weigh not less than 35 pounds per square foot (psf) (170 kg/m2) of wall surface area.
  2. Weigh not less than 25 psf (120 kg/m2) of wall surface area where the material weight is not more than 120 pounds per cubic foot (pcf) (1900 kg/m3).
  3. Have a heat capacity exceeding 7 Btu/ft2 × °F (144 kJ/m2 × K).
  4. Have a heat capacity exceeding 5 Btu/ft2 × °F (103 kJ/m2 × K) where the material weight is not more than 120 pcf (1900 kg/m3).
The R-value of the insulating material installed in, or continuously on, the below-grade walls shall be in accordance with Table C402.1.3. The U-factor or R-value required shall extend to the level of the lowest floor of the conditioned space enclosed by the below-grade wall.

The thermal properties (component R-values or assembly U- or F-factors) of floor assemblies over outdoor air or unconditioned space shall be as specified in Table C402.1.3 or C402.1.4 based on the construction materials used in the floor assembly. Floor framing cavity insulation or structural slab insulation shall be installed to maintain permanent contact with the underside of the subfloor decking or structural slabs.

"Mass floors" where used as a component of the thermal envelope of a building shall provide one of the following weights:

  1. 35 pounds per square foot (171 kg/m2) of floor surface area.
  2. 25 pounds per square foot (122 kg/m2) of floor surface area where the material weight is not more than 120 pounds per cubic foot (1923 kg/m3).

Exceptions:

  1. The floor framing cavity insulation or structural slab insulation shall be permitted to be in contact with the top side of sheathing or continuous insulation installed on the bottom side of floor assemblies where combined with insulation that meets or exceeds the minimum R-value in Table C402.1.3 for "Metal framed" or "Wood framed and other" values for "Walls, Above Grade" and extends from the bottom of the top of all perimeter floor framing or floor assembly members.
  2. Insulation applied to the underside of concrete floor slabs shall be permitted an air space of not more than 1 inch (25 mm) where it turns up and is in contact with the underside of the floor under walls associated with the building thermal envelope.

Where the slab-on-grade is in contact with the ground, the minimum thermal resistance (R-value) of the insulation around the perimeter of unheated or heated slab-on-grade floors designed in accordance with the R-value method of Section C402.1.3 shall be as specified in Table C402.1.3. The insulation shall be placed on the outside of the foundation or on the inside of the foundation wall. The insulation shall extend downward from the top of the slab for a minimum distance as shown in the table or to the top of the footing, whichever is less, or downward to at least the bottom of the slab and then horizontally to the interior or exterior for the total distance shown in the table. Insulation extending away from the building shall be protected by pavement or by a minimum of 10 inches (254 mm) of soil. Insulation complying with Table C402.1.3 shall be provided under the entire area of heated slabs-on-grade.

Exception: Where the slab-on-grade floor is greater than 24 inches (61 mm) below the finished exterior grade, perimeter insulation is not required.

Where the thermal properties of airspaces are used to comply with this code in accordance with Section C401.2, such airspaces shall be enclosed in an unventilated cavity constructed to minimize airflow into and out of the enclosed airspace. Airflow shall be deemed minimized where the enclosed airspace is located on the interior side of the continuous air barrier and is bounded on all sides by building components.

Exception: The thermal resistance of airspaces located on the exterior side of the continuous air barrier and adjacent to and behind the exterior wall covering material shall be determined in accordance with ASTM C1363 modified with an airflow entering the bottom and exiting the top of the airspace at a minimum air movement rate of not less than 70 mm/sec.

Radiant heating system panels and their associated components that are installed in interior or exterior assemblies shall be insulated to an R-value of not less than R-3.5 on all surfaces not facing the space being heated. Radiant heating system panels that are installed in the building thermal envelope shall be separated from the exterior of the building or unconditioned or exempt spaces by not less than the R-value of the insulation installed in the opaque assembly in which they are installed or the assembly shall comply with Section C402.1.4.

Exception: Heated slabs-on-grade insulated in accordance with Section C402.2.6.

Fenestration shall comply with Sections C402.4 through C402.4.4 and Table C402.4. Daylight responsive controls shall comply with this section and Section C405.2.4.1.

TABLE C402.4

BUILDING ENVELOPE FENESTRATION MAXIMUM U-FACTOR AND SHGC REQUIREMENTS

CLIMATE ZONE 5 AND MARINE 4
U-factor for Class AW windows rated in accordance
with AAMA/CSA101/I.S.2/A440, vertical curtain
Fixedb U-factor U-0.38
Operablec U-factor U-0.40
Entrance doorsd
U-factor U-0.60
U-factor for all other vertical fenestration
U-factor U-0.30
SHGC for all vertical fenestration
ORIENTATIONe, f SEW N
PF < 0.2 0.38 0.51
0.2 ≤ PF < 0.5 0.46 0.56
PF ≥ 0.5 0.61 0.61
Skylights
U-factor U-0.50
SHGC 0.35
  1. U-factor and SHGC shall be rated in accordance with NFRC 100.
  2. "Fixed" includes curtain wall, storefront, picture windows, and other fixed windows.
  3. "Operable" includes openable fenestration products other than "entrance doors."
  4. "Entrance door" includes glazed swinging entrance doors. Other doors which are not entrance doors, including sliding glass doors, are considered "operable."
  5. "N" indicates vertical fenestration oriented within 30 degrees of true north. "SEW" indicates orientations other than "N."
  6. Fenestration that is entirely within the conditioned space or is between conditioned and other enclosed space is exempt from solar heat gain coefficient requirements and not included in the SHGC calculation.

The total building vertical fenestration area (not including opaque doors and opaque spandrel panels) shall not exceed 30 percent of the total building gross above-grade wall area. The skylight area shall not exceed 5 percent of the total building gross roof area (skylight-to-roof ratio).

For buildings with more than one space conditioning category, compliance with the maximum allowed window-to-wall ratio and skylight-to-roof ratio shall be demonstrated separately for each space conditioning category. Interior partition ceiling, wall, fenestration and floor areas that separate space conditioning areas shall not be applied to the window-to-wall ratio and skylight-to-roof ratio calculations.

For buildings that comply with Section C402.4.1.1.1 or C402.4.1.1.2, the total building vertical fenestration area is permitted to exceed 30 percent but shall not exceed 40 percent of the gross above grade wall area for the purpose of prescriptive compliance with Section C402.1.4.

When determining compliance using the component performance alternative in accordance with Section C402.1.5, the total building vertical fenestration area allowed in Equation 4-2 is 40 percent of the above grade wall area for buildings that comply with the vertical fenestration alternates described in this section.

All of the following requirements shall be met:

  1. Not less than 50 percent of the total conditioned floor area in the building is within a daylight zone that includes daylight responsive controls complying with Section C405.2.4.1.
  2. Visible transmittance (VT) of all vertical fenestration in the building is greater than or equal to 1.1 times the required solar heat gain coefficient (SHGC) in accordance with Section C402.4, or 0.50, whichever is greater. It shall be permitted to demonstrate compliance based on the area weighted average VT being greater than or equal to the area weighted average of the minimum VT requirements.

Exception: Fenestration that is outside the scope of NFRC 200 is not required to comply with Item 2.

All of the following requirements shall be met:

  1. All vertical fenestration in the building shall comply with the following U-factors:

    1. 1.1. U-factor for Class AW windows rated in accordance with AAMA/CSA101/I.S.2/A440, vertical curtain walls and site-built fenestration products (fixed) = 0.34.
    2. 1.2. U-factor for Class AW windows rated in accordance with AAMA/CSA101/I.S.2/A440, vertical curtain walls and site-built fenestration products (operable) = 0.36.
    3. 1.3. Entrance doors = 0.60.
    4. 1.4. U-factor for all other vertical fenestration = 0.28.
  2. The SHGC of the vertical fenestration shall be less than or equal to 0.35, adjusted for projection factor in compliance with Section C402.4.3.

An area-weighted average shall be permitted to satisfy the U-factor requirement for each fenestration product category listed in Item 1 of this section. Individual fenestration products from different fenestration product categories shall not be combined in calculating the area-weighted average U-factor.

For buildings with single-story enclosed spaces greater than 2,500 square feet (232 m2) in floor area that are directly under a roof and have a ceiling height greater than 15 feet (4572 mm) for no less than 75 percent of the ceiling area; these single-story spaces shall be provided with skylights and daylight responsive controls in accordance with Section C405.2.4. Space types required to comply with this provision include office, lobby, atrium, concourse, corridor, gymnasium/exercise center, convention center, automotive service, manufacturing, nonrefrigerated warehouse, retail store, distribution/sorting area, transportation, and workshop. Skylights in these spaces are required to provide a total toplit zone area not less than 50 percent of the floor area and shall provide one of the following:

  1. A minimum ratio of skylight area to toplit zone area of not less than 3 percent where all skylights have a VT of at least 0.40 as determined in accordance with Section C303.1.3.
  2. A minimum skylight effective aperture of at least 1 percent determined in accordance with Equation 4-5.


    (Equation 4-5)

    where:

    Skylight area = Total fenestration area of skylights.

    Skylight VT = Area weighted average visible transmittance of skylights.

    WF = Area weighted average well factor, where well factor is 0.9 if light well depth is less than 2 feet (610 mm), or 0.7 if light well depth is 2 feet (610 mm) or greater, or 1.0 for tubular daylighting devices with VT-annual ratings measured according to NFRC 203.

    Light well depth = Measure vertically from the underside of the lowest point of the skylight glazing to the ceiling plane under the skylight.

Exceptions:

  1. Skylights above daylight zones of enclosed spaces are not required in:

    1. 1.1. Reserved.
    2. 1.2. Spaces where the designed general lighting power densities are less than 0.5 W/ft2 (5.4 W/m2) and at least 10 percent lower than the lighting power allowance in Section C405.4.2.
    3. 1.3. Areas where it is documented that existing structures or natural objects block direct beam sunlight on at least half of the roof over the enclosed area for more than 1,500 daytime hours per year between 8 a.m. and 4 p.m.
    4. 1.4. Spaces where the daylight zone under rooftop monitors is greater than 50 percent of the enclosed space floor area.
    5. 1.5. Spaces where the total floor area minus the sidelit zone area is less than 2,500 square feet (232 m2), and where the lighting in the daylight zone is controlled in accordance with Section C405.2.3.1.
  2. The skylight effective aperture, calculated in accordance with Equation 4-5, is permitted to be 0.66 percent in lieu of one percent if the VT-annual of the skylight or TDD, as measured by NFRC 203, is greater than 38 percent.
Daylight responsive controls complying with Section C405.2.4.1 shall be provided to control all electric lights within toplit zones.

Skylights in office, storage, automotive service, manufacturing, nonrefrigerated warehouse, retail store, and distribution/sorting area spaces shall have a glazing material or diffuser with a haze factor greater than 90 percent when tested in accordance with ASTM D1003.

Exception: Skylights designed and installed to exclude direct sunlight entering the occupied space by the use of fixed or automated baffles, or the geometry of skylight and light well.

Daylight zones referenced in Sections C402.4.1.1 through C402.4.2.2 shall comply with Section C405.2.4.2 and C405.2.4.3, as applicable. Daylight zones shall include toplit zones and sidelit zones.

The maximum U-factor and solar heat gain coefficient (SHGC) for fenestration shall be as specified in Table C402.4.

The window projection factor shall be determined in accordance with Equation 4-6.


(Equation 4-6)

where:

PF= Projection factor (decimal).

A = Distance measured horizontally from the furthest continuous extremity of any overhang, eave, or permanently attached shading device to the vertical surface of the glazing.

B = Distance measured vertically from the bottom of the glazing to the underside of the overhang, eave, or permanently attached shading device.

Where different windows or glass doors have different PF values, they shall each be evaluated separately.

Where dynamic glazing is intended to satisfy the SHGC and VT requirements of Table C402.4, the ratio of the higher to lower labeled SHGC shall be greater than or equal to 2.4, and the dynamic glazing shall be automatically controlled to modulate the amount of solar gain into the space in multiple steps. Dynamic glazing shall be considered separately from other fenestration, and area-weighted averaging with other fenestration that is not dynamic glazing shall not be permitted.

Exception: Dynamic glazing is not required to comply with this section where both the lower and higher labeled SHGC already comply with the requirements of Table C402.4.

An area-weighted average shall be permitted to satisfy the U-factor requirements for each fenestration product category listed in Table C402.4. Individual fenestration products from different fenestration product categories listed in Table C402.4 shall not be combined in calculating area-weighted average U-factor.
Opaque swinging doors shall comply with Table C402.1.4. Opaque nonswinging doors shall comply with Table C402.1.3. Opaque doors shall be considered part of the gross area of above-grade walls that are part of the building thermal envelope. Other doors shall comply with the provisions of Section C402.4.3 for vertical fenestration and the entire door area, including the frame, shall be considered part of the fenestration area of the building thermal envelope.
The thermal envelope of buildings shall comply with Sections C402.5.1 through C402.5.8.
A continuous air barrier shall be provided throughout the building thermal envelope. The air barriers shall be permitted to be located on the inside or outside of the building envelope, located within the assemblies composing the envelope, or any combination thereof. The air barrier shall comply with Sections C402.5.1.1 and C402.5.1.2.

The continuous air barrier shall be constructed to comply with the following:

  1. The air barrier shall be continuous for all assemblies that are the thermal envelope of the building and across the joints and assemblies.
  2. Air barrier joints and seams shall be sealed, including sealing transitions in places and changes in materials. The joints and seals shall be securely installed in or on the joint for its entire length so as not to dislodge, loosen or otherwise impair its ability to resist positive and negative pressure from wind, stack effect and mechanical ventilation.
  3. Penetrations of the air barrier shall be caulked, gasketed or otherwise sealed in a manner compatible with the construction materials and location. Sealing shall allow for expansion, contraction and mechanical vibration. Joints and seams associated with penetrations shall be sealed in the same manner or taped. Sealing materials shall be securely installed around the penetrations so as not to dislodge, loosen or otherwise impair the penetrations' ability to resist positive and negative pressure from wind, stack effect, and mechanical ventilation. Sealing of concealed fire sprinklers, where required, shall be in a manner that is recommended by the manufacturer. Caulking or other adhesive sealants shall not be used to fill voids between fire sprinkler cover plates and walls or ceilings.
  4. Recessed lighting fixtures shall comply with Section C402.5.8. Where similar objects are installed which penetrate the air barrier, provisions shall be made to maintain the integrity of the air barrier.
  5. Construction documents shall contain a diagram showing the building's pressure boundary in plan(s) and section(s) and a calculation of the area of the pressure boundary to be considered in the test.

The completed building shall be tested and the air leakage rate of the building envelope shall not exceed 0.25 cfm/ft2 at a pressure differential of 0.3 inches water gauge (2.0 L/s × m2 at 75 Pa) at the upper 95 percent confidence interval in accordance with ASTM E779 or an equivalent method approved by the code official. A report that includes the tested surface area, floor area, air by volume, stories above grade, and leakage rates shall be submitted to the building owner and the code official. If the tested rate exceeds that defined here by up to 0.15 cfm/ft2, a visual inspection of the air barrier shall be conducted and any leaks noted shall be sealed to the extent practicable. An additional report identifying the corrective actions taken to seal air leaks shall be submitted to the building owner and the code official and any further requirement to meet the leakage air rate will be waived. If the tested rate exceeds 0.40 cfm/ft2, corrective actions must be made and the test completed again. A test above 0.40 cfm/ft2 will not be accepted.

  1. Test shall be accomplished using either (1) both pressurization and depressurization or (2) pressurization alone, but not depressurization alone. The test results shall be plotted against the correct P for pressurization in accordance with Section 9.4 of ASTM E779.
  2. The test pressure range shall be from 25 Pa to 80 Pa per Section 8.10 of ASTM E779, but the upper limit shall not be less than 50 Pa, and the difference between the upper and lower limit shall not be less than 25 Pa.
  3. If the pressure exponent n is less than 0.45 or greater than 0.85 per Section 9.6.4 of ASTM E779, the test shall be rerun with additional readings over a longer time interval.
Where a building is three or fewer stories above grade plane and contains both commercial and residential uses, the air barrier of the R-2 and R-3 occupancy areas of the building is permitted to be separately tested according to Section R402.4.1.2. Alternatively, it is permissible to test the air barrier of the entire building according to Section C402.5.1.2, provided that the tested air leakage rate does not exceed the rate specified in Section C402.5.1.2.

Where combustion air is supplied through openings in an exterior wall to a room or space containing a space conditioning fuel-burning appliance, one of the following shall apply:

  1. The room or space containing the appliance shall be located outside of the building thermal envelope.
  2. The room or space containing the appliance shall be enclosed and isolated from conditioned spaces inside the building thermal envelope. Such rooms shall comply with all of the following:

    1. 2.1. The walls, floor and ceiling that separate the enclosed room or space from the conditioned spaces shall be insulated to be at least equivalent to the insulation requirement of below-grade walls as specified in Table C402.1.3 or C402.1.4.
    2. 2.2. The walls, floors and ceiling that separate the enclosed room or space from conditioned spaces shall be sealed in accordance with Section C402.5.1.1.
    3. 2.3. The doors into the enclosed room or space shall be fully gasketed.
    4. 2.4. Water lines and ducts in the enclosed room or space shall be insulated in accordance with Section C403.
    5. 2.5. Where the air duct supplying combustion air to the enclosed room or space passes through conditioned space, the duct shall be insulated to an R-value of not less than R-8.

Exception: Fireplaces and stoves complying with Sections 901 through 905 of the International Mechanical Code, and Section 2111.13 of the International Building Code.

Doors and access openings from conditioned space to shafts, chutes, stairways and elevator lobbies shall be gasketed, weatherstripped or sealed.

Exceptions:

  1. Door openings required to comply with Section 716 of the International Building Code.
  2. Doors and door openings required to comply with UL 1784 by the International Building Code.
Stairway enclosures, elevator shaft vents and other outdoor air intake and exhaust openings integral to the building envelope shall be provided with dampers in accordance with Section C403.7.9.
Cargo door openings and loading dock door openings shall be equipped with weatherseals that restrict infiltration and provide direct contact along the top and sides of vehicles that are parked in the doorway.

All building entrances shall be protected with an enclosed vestibule, with all doors opening into and out of the vestibule equipped with self-closing devices. Vestibules shall be designed so that in passing through the vestibule it is not necessary for the interior and exterior doors to open at the same time. The installation of one or more revolving doors in the building entrance shall not eliminate the requirement that a vestibule be provided on any doors adjacent to revolving doors. For the purposes of this section, "building entrances" shall include exit-only doors in buildings where separate doors for entering and exiting are provided.

Interior and exterior doors shall have a minimum distance between them of not less than 7 feet (2134 mm). The exterior envelope of conditioned vestibules shall comply with the requirements for a conditioned space. Either the interior or exterior envelope of unconditioned vestibules shall comply with the requirements for a conditioned space. The building lobby is not considered a vestibule.

Exception: Vestibules are not required for the following:

  1. Doors not intended to be used as building entrances.
  2. Unfinished ground-level space greater than 3,000 square feet (298 m2) if a note is included on the permit documents at each exterior entrance to the space stating "Vestibule required at time of tenant build-out if entrance serves a space greater than 3,000 square feet in area."
  3. Doors opening directly from a sleeping unit or dwelling unit.
  4. Doors between an enclosed space smaller than 3,000 square feet (298 m2) in area and the exterior of the building or the building entrance lobby, where those doors do not comprise one of the primary building entrance paths to the remainder of the building. The space must be enclosed and separated without transfer air paths from the primary building entrance paths. If there are doors between the space and the primary entrance path then the doors shall be equipped with self-closing devices so the space acts as a vestibule for the primary building entrance.
  5. Revolving doors.
  6. Doors used primarily to facilitate vehicular movement or material handling and adjacent personnel doors.
  7. In buildings less than three stories above grade or in spaces that do not directly connect with the building elevator lobby, doors that have an air curtain with a velocity of not less than 6.56 feet per second (2 m/s) at the floor that have been tested in accordance with ANSI/AMCA 220 and installed in accordance with the manufacturer's instructions. Manual or automatic controls shall be provided that will operate the air curtain with the opening and closing of the door. Air curtains and their controls shall comply with Section C408.2.3
  8. Building entrances in buildings that are less than four stories above grade and less than 10,000 square feet (929 m2) in area.
  9. Elevator doors in parking garages provided that the elevators have an enclosed lobby at each level of the garage.
  10. Entrances to semi-heated spaces.

Recessed luminaires installed in the building thermal envelope shall be all of the following:

  1. IC Rated.
  2. Labeled as having an air leakage rate of not more than 2.0 cfm (0.944 L/s) when tested in accordance with ASTM E283 at a 1.57 psf (75 Pa) pressure differential.
  3. Sealed with a gasket or caulk between the housing and interior wall or ceiling covering.

Mechanical systems and equipment serving heating, cooling, ventilating, and other needs shall comply with this section.

Exceptions:

  1. Energy-using equipment used by a manufacturing, industrial or commercial process other than for conditioning spaces or maintaining comfort and amenities for the occupants and not otherwise regulated by Section C403.3.2, Tables C403.3.2(1) through (12) inclusive, Sections C403.7.7, C403.9.2.1, C403.10.3, C403.11.2, C403.11.3, C404.2, Table C404.2, C405.8 and C410. Data center and computer room HVAC equipment is not covered by this exception.
  2. Data center systems are exempt from Sections C403.4 and C403.5.

For systems serving office, retail, library and education occupancies and buildings, which are subject to the requirements of Section C403.3.5 without exceptions, the HVAC total system performance ratio (HVAC TSPR) of the proposed design HVAC system shall be more than or equal to the HVAC TSPR of the standard reference design as calculated according to Appendix CD, Calculation of HVAC Total System Performance Ratio.

Exceptions:

  1. Buildings with conditioned floor area less than 5,000 square feet (465 m2).
  2. HVAC systems using district heating water, chilled water or steam.
  3. HVAC systems not included in Table CD601.11.1.
  4. HVAC systems with chilled water supplied by absorption chillers, heat recovery chillers, water-to-water heat pumps, air-to-water heat pumps, or a combination of air and water-cooled chillers on the same chilled water loop.
  5. HVAC system served by heating water plants that include air-to-water or water-to-water heat pumps.
  6. Underfloor air distribution HVAC systems.
  7. Space conditioning systems that do not include mechanical cooling.
  8. Alterations to existing buildings that do not substantially replace the entire HVAC system.
  9. HVAC systems meeting all the requirements of the standard reference design HVAC system in Table CD602.11, Standard Reference Design HVAC Systems.
Design loads associated with heating, ventilating and air conditioning of the building shall be determined in accordance with the procedures described in ANSI/ASHRAE/ACCA Standard 183 or by an approved equivalent computational procedure, using the design parameters specified in Chapter 3. Heating and cooling loads shall be adjusted to account for load reductions that are achieved where energy recovery systems are utilized in the HVAC system in accordance with the ASHRAE HVAC Systems and Equipment Handbook by an approved equivalent computational procedure.

Data center systems shall comply with Sections 6 and 8 of ASHRAE Standard 90.4, with the following changes:

  1. Replace design MLC in ASHRAE Standard 90.4 Table 6.2.1.1 "Maximum Design Mechanical Load Component (Design MLC)" with the following per applicable climate zone:

    Zone 4C Design MLC = 0.22

    Zone 5B Design MLC = 0.24

  2. Replace annualized MLC values of Table 6.2.1.2 "Maximum Annualized Mechanical Load Component (Annualized MLC)" in ASHRAE Standard 90.4 with the following per applicable climate zone:

    Zone 4C Annual MLC = 0.18

    Zone 5B Annual MLC = 0.17

Mechanical systems shall be designed to comply with Sections C403.2.1 and C403.2.2. Where elements of a building's mechanical systems are addressed in Sections C403.3 through C403.13, such elements shall comply with the applicable provisions of those sections.

HVAC systems serving zones that are intended to operate or be occupied nonsimultaneously shall be divided into isolation areas. Zones may be grouped into a single isolation area provided it does not exceed 25,000 square feet (2323 m2) of conditioned floor area nor include more than one floor. Each isolation area shall be equipped with isolation devices and controls configured to automatically shut off the supply of conditioned air and outdoor air to and exhaust air from the isolation area. Each isolation area shall be controlled independently by a device meeting the requirements of Section C403.4.2.2. Central systems and plants shall be provided with controls and devices that will allow system and equipment operation for any length of time while serving only the smallest isolation area served by the system or plant.

Exceptions:

  1. Exhaust air and outdoor air connections to isolation areas where the fan system to which they connect is not greater than 5,000 cfm (2360 L/s).
  2. Exhaust airflow from a single isolation area of less than 10 percent of the design airflow of the exhaust system to which it connects.
  3. Isolation areas intended to operate continuously or intended to be inoperative only when all other isolation areas in a zone are inoperative.

Ventilation, either natural or mechanical, shall be provided in accordance with Chapter 4 of the International Mechanical Code. Where mechanical ventilation is provided, the system shall be configured to provide no greater than 150 percent of the minimum outdoor air required by Chapter 4 of the International Mechanical Code or other applicable code or standard, whichever is greater.

Exceptions:

  1. The mechanical system may supply outdoor air at rates higher than the limit above when it is used for particulate or VOC dilution, economizer, night flushing, dehumidification, pressurization, exhaust make-up, or other process air delivery. Outdoor air shall be reduced to the minimum ventilation rates when not required for the preceding uses.
  2. Air systems supplying Group R-1, R-2 or I-2 occupancies.
  3. Alterations that replace less than half of the total heating and cooling capacity of the system.
  4. Systems with energy recovery complying with the requirements of Section C403.7.6.1 that utilize sensible only active chilled beams for space cooling without any additional zonal fan power. Active chilled beams shall be permitted to utilize the increased outdoor airflow to increase space sensible capacity and to maintain space latent cooling loads without additional controls to reduce the outdoor airflow to each zone.

Exhaust shall be provided in accordance with Chapters 4 and 5 of the International Mechanical Code. Where exhaust is provided, the system shall be configured to provide no greater than 150 percent of the minimum exhaust air required by Chapters 4 and 5 of the International Mechanical Code or other applicable code or standard, whichever is greater.

Exceptions:

  1. The mechanical system may exhaust air at rates higher than the limit above when it is used for particulate or VOC dilution, economizer, night flushing, dehumidification, pressure equalization, relief, or other process exhaust air requirements. Outdoor air and exhaust air shall be reduced to the minimum exhaust rates when not required for the preceding uses.
  2. Domestic range hood exhaust in Group R occupancies.
  3. Exhaust for Group I occupancies.

For fan and pump motors 7.5 hp and greater including motors in or serving custom and packaged air handlers serving variable air volume fan systems, constant volume fans, heating and cooling hydronic pumping systems, pool and service water pumping systems, domestic water pressure-booster systems, cooling tower fan, and other pump or fan motors where variable flows are required, there shall be:

  1. Variable speed drives; or
  2. Other controls and devices that will result in fan and pump motor demand of no more than 30 percent of design wattage at 50 percent of design air volume for fans when static pressure set point equals 1/3 the total design static pressure, and 50 percent of design water flow for pumps, based on manufacturer's certified test data. Variable inlet vanes, throttling valves (dampers), scroll dampers or bypass circuits shall not be allowed.

Exception: Variable speed devices are not required for motors that serve:

  1. Fans or pumps in packaged equipment where variable speed drives are not available as a factory option from the equipment manufacturer.
  2. Fans or pumps that are required to operate only for emergency fire-life-safety events (e.g., stairwell pressurization fans, elevator pressurization fans, fire pumps, etc.).
Heating and cooling equipment installed in mechanical systems shall be sized in accordance with Section C403.3.1 and shall be not less efficient in the use of energy than as specified in Section C403.3.2.

The output capacity of heating and cooling equipment shall be not greater than that of the smallest available equipment size that exceeds the loads calculated in accordance with Section C403.1.2. A single piece of equipment providing both heating and cooling shall satisfy this provision for one function with the capacity for the other function as small as possible, within available equipment options.

Exceptions:

  1. Required standby equipment and systems provided with controls and devices that allow such systems or equipment to operate automatically only when the primary equipment is not operating.
  2. Multiple units of the same equipment type with combined capacities exceeding the design load and provided with controls that are configured to sequence the operation of each unit based on load.

Equipment shall meet the minimum efficiency requirements of Tables C403.3.2(1) through C403.3.2(12) when tested and rated in accordance with the applicable test procedure. Plate-type liquid-to-liquid heat exchangers shall meet the minimum requirements of Table C403.3.2(10). The efficiency shall be verified through certification and listed under an approved certification program or, if no certification program exists, the equipment efficiency ratings shall be supported by data furnished by the manufacturer. Where multiple rating conditions or performance requirements are provided, the equipment shall satisfy all stated requirements. Where components, such as indoor or outdoor coils, from different manufacturers are used, calculations and supporting data shall be furnished by the designer that demonstrates that the combined efficiency of the specified components meets the requirements herein.

Gas-fired and oil-fired forced air furnaces with input ratings of 225,000 Btu/h (65 kW) or greater and all unit heaters shall also have an intermittent ignition or interrupted device (IID), and have either mechanical draft (including power venting) or a flue damper. A vent damper is an acceptable alternative to a flue damper for furnaces where combustion air is drawn from the conditioned space. All furnaces with input ratings of 225,000 Btu/h (65 kW) or greater, including electric furnaces, that are not located within the conditioned space shall have jacket losses not exceeding 0.75 percent of the input rating.

TABLE C403.3.2(1)A

MINIMUM EFFICIENCY REQUIREMENTS: ELECTRICALLY OPERATED UNITARY AIR CONDITIONERS AND CONDENSING UNITS

EQUIPMENT
TYPE
SIZE
CATEGORY
HEATING
SECTION TYPE
SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCY
TEST
PROCEDUREa
Air conditioners,
air cooled
< 65,000 Btu/h b All Split System 13.0 SEER AHRI 210/240
Single Package 14.0 SEER
Through-the-wall
(air cooled)
≤ 30,000 Btu/h b All Split system 12.0 SEER
Single Package 12.0 SEER
Small duct high
velocity, air cooled
≤ 65,000 Btu/h b All Split system 11.0 SEER
Air conditioners,
air cooled
≥ 65,000 Btu/h and
< 135,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
11.2 EER
12.9 IEER
AHRI 340/360
All other Split System and
Single Package
11.0 EER
12.7 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
11.0 EER
12.4 IEER
All other Split System and
Single Package
10.8 EER
12.2 IEER
≥ 240,000 Btu/h and
< 760,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
10.0 EER
11.6 IEER
All other Split System and
Single Package
9.8 EER
11.4 IEER
≥ 760,000 Btu/h Electric Resistance
(or None)
Split System and
Single Package
9.7 EER
11.2 IEER
All other Split System and
Single Package
9.5 EER
11.0 IEER
Air conditioners,
water cooled
< 65,000 Btu/hb All Split System and
Single Package
12.1 EER
12.3 IEER
AHRI 210/240
≥ 65,000 Btu/h and
< 135,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
12.1 EER
13.9 IEER
AHRI 340/360
All other Split System and
Single Package
11.9 EER
13.7 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
12.5 EER
13.9 IEER
All other Split System and
Single Package
12.3 EER
13.7 IEER
≥ 240,000 Btu/h and
< 760,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
12.4 EER
13.6 IEER
All other Split System and
Single Package
12.2 EER
13.4 IEER
≥ 760,000 Btu/h Electric Resistance
(or None)
Split System and
Single Package
12.2 EER
13.5 IEER
All other Split System and
Single Package
12.0 EER
13.3 IEER
Air conditioners,
evaporatively cooled
< 65,000 Btu/hb All Split System and
Single Package
12.1 EER
12.3 IEER
AHRI 210/240
≥ 65,000 Btu/h and
< 135,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
12.1 EER
12.3 IEER
AHRI 340/360
All other Split System and
Single Package
11.9 EER
12.1 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
12.0 EER
12.2 IEER
All other Split System and
Single Package
11.8 EER
12.0 IEER
≥ 240,000 Btu/h and
< 760,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
11.9 EER
12.1 IEER
All other Split System and
Single Package
11.7 EER
11.9 IEER
≥ 760,000 Btu/h Electric Resistance
(or None)
Split System and
Single Package
11.7 EER
11.9 IEER
All other Split System and
Single Package
11.5 EER
11.7 IEER
Condensing units,
air cooled
≥ 135,000 Btu/h     10.5 EER
11.8 IEER
AHRI 365
Condensing units,
water cooled
≥ 135,000 Btu/h     13.5 EER
14.0 IEER
Condensing units,
evaporatively cooled
≥ 135,000 Btu/h     13.5 EER
14.0 IEER

For SI: 1 British thermal unit per hour = 0.2931 W.

  1. Chapter 6 of the referenced standard contains a complete specification of the referenced test procedure, including the reference year version of the test procedure.
  2. Single-phase, air-cooled air conditioners less than 65,000 Btu/h are regulated by NAECA. SEER values are those set by NAECA.

TABLE C403.3.2(1)B

MINIMUM EFFICIENCY REQUIREMENTS: ELECTRICALLY OPERATED VARIABLE REFRIGERANT FLOW AIR CONDITIONERS

EQUIPMENT TYPE SIZE CATEGORY HEATING
SECTION TYPE
SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCY
TEST
PROCEDURE
VRF
Air Conditioners,
Air Cooled
< 65,000 Btu/h All VRF Multi-split System 13.0 SEER AHRI 1230
≥ 65,000 Btu/h and
< 135,000 Btu/h
Electric Resistance
(or None)
VRF Multi-split System 11.2 EER
15.5 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
Electric Resistance
(or None)
VRF Multi-split System 11.0 EER
14.9 IEER
≥ 240,000 Btu/h Electric Resistance
(or None)
VRF Multi-split System 10.0 EER
13.9 IEER

For SI: 1 British thermal unit per hour = 0.2931 W.

TABLE C403.3.2(1)C

MINIMUM EFFICIENCY REQUIREMENTS: ELECTRICALLY OPERATED VARIABLE REFRIGERANT FLOW AIR-TO-AIR AND APPLIED HEAT PUMPS

EQUIPMENT
TYPE
SIZE
CATEGORY
HEATING
SECTION TYPE
SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCY
TEST
PROCEDURE
VRF
Air Cooled,
(cooling mode)
< 65,000 Btu/h All VRF Multi-split System 13.0 SEER AHRI 1230
≥ 65,000 Btu/h and
< 135,000 Btu/h
Electric Resistance
(or None)
VRF Multi-split System 11.0 EER
14.6 IEER
≥ 65,000 Btu/h and
< 135,000 Btu/h
Electric Resistance
(or None)
VRF Multi-split System
with Heat Recovery
10.8 EER
14.4 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
Electric Resistance
(or None)
VRF Multi-split System 10.6 EER
13.9 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
Electric Resistance
(or None)
VRF Multi-split System
with Heat Recovery
10.4 EER
13.7 IEER
≥ 240,000 Btu/h Electric Resistance
(or None)
VRF Multi-split System 9.5 EER
12.7 IEER
≥ 240,000 Btu/h Electric Resistance
(or None)
VRF Multi-split System
with Heat Recovery
9.3 EER
12.5 IEER
VRF
Water source
(cooling mode)
< 65,000 Btu/h All VRF Multi-split systems
86°F entering water
12.0 EER
16.0 IEER
AHRI 1230
< 65,000 Btu/h All VRF Multi-split systems
with Heat Recovery
86°F entering water
11.8 EER
15.8 IEER
≥ 65,000 Btu/h and
< 135,000 Btu/h
All VRF Multi-split System
86°F entering water
12.0 EER
16.0 IEER
≥ 65,000 Btu/h and
< 135,000 Btu/h
All VRF Multi-split System
with Heat Recovery
86°F entering water
11.8 EER
15.8 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
All VRF Multi-split System
86°F entering water
10.0 EER
14.0 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
All VRF Multi-split System
with Heat Recovery
86°F entering water
9.8 EER
13.8 IEER
≥ 240,000 Btu/h All VRF Multi-split System
86°F entering water
12.0 IEER
≥ 240,000 Btu/h All VRF Multi-split System
with Heat Recovery
86°F entering water
11.8 IEER
VRF
Groundwater source
(cooling mode)
< 135,000 Btu/h All VRF Multi-split System
59°F entering water
16.2 EER AHRI 1230
< 135,000 Btu/h All VRF Multi-split System
with Heat Recovery
59°F entering water
16.0 EER
≥ 135,000 Btu/h All VRF Multi-split System
59°F entering water
13.8 EER
≥ 135,000 Btu/h All VRF Multi-split System
with Heat Recovery
59°F entering water
13.6 EER
VRF
Ground source
(cooling mode)
< 135,000 Btu/h All VRF Multi-split System
77°F entering water
13.4 EER AHRI 1230
< 135,000 Btu/h All VRF Multi-split System with
Heat Recovery
77°F entering water
13.2 EER
≥ 135,000 Btu/h All VRF Multi-split System
77°F entering water
11.0 EER
≥ 135,000 Btu/h All VRF Multi-split System with
Heat Recovery
77°F entering water
10.8 EER
VRF
Air Cooled
(heating mode)
< 65,000 Btu/h
(cooling capacity)
VRF Multi-split System 7.7 HSPF AHRI 1230
≥ 65,000 Btu/h and
< 135,000 Btu/h
(cooling capacity)
VRF Multi-split system
47°F db/43°F wb outdoor air
17°F db/15°F wb outdoor air
3.3 COP
2.25 COP
≥ 135,000 Btu/h
(cooling capacity)
VRF Multi-split System
47°F db/43°F wb outdoor air
17°F db/15°F wb outdoor air
3.2 COP
2.05 COP
VRF
Water source
(heating mode)
< 135,000 Btu/h
(cooling capacity)
VRF Multi-split System
68°F entering water
4.3 COP AHRI 1230
≥ 135,000 Btu/h
and < 240,000 Btu/h
(cooling capacity)
VRF Multi-split System
68°F entering water
4.0 COP
≥ 240,000 Btu/h
(cooling capacity)
VRF Multi-split System
68°F entering water
3.9 COP
VRF
Groundwater source
(heating mode)
< 135,000 Btu/h
(cooling capacity)
VRF Multi-split System
50°F entering water
3.6 COP AHRI 1230
≥ 135,000 Btu/h
(cooling capacity)
VRF Multi-split System
50°F entering water
3.3 COP
VRF
Ground source
(heating mode)
< 135,000 Btu/h
(cooling capacity)
VRF Multi-split System
32°F entering water
3.1 COP AHRI 1230
≥ 135,000 Btu/h
(cooling capacity)
VRF Multi-split System
32°F entering water
2.8 COP

For SI: 1 British thermal unit per hour = 0.2931 W, °C = [(°F) - 32]/1.8.

TABLE C403.3.2(2)

MINIMUM EFFICIENCY REQUIREMENTS: ELECTRICALLY OPERATED UNITARY AND APPLIED HEAT PUMPS

EQUIPMENT
TYPE
SIZE
CATEGORY
HEATING
SECTION TYPE
SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCY
TEST
PROCEDUREa
Air cooled (cooling mode) < 65,000 Btu/hb All Split System 14.0 SEER AHRI 210/240
Single Packaged 14.0 SEER
Through-the-wall,
air cooled (cooling mode)
≤ 30,000 Btu/hb All Split System 12.0 SEER
Single Packaged 12.0 SEER
Small duct high velocity,
air cooled
< 65,000 Btu/ hb All Split System 11.0 SEER
Air cooled
(cooling mode)
≥ 65,000 Btu/h and
< 135,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
11.0 EER
12.2 IEER
AHRI 340/360
All other Split System and
Single Package
10.8 EER
12.0 IEER
≥ 135,000 Btu/h and
< 240,000 Btu/h
Electric Resistance
(or None)
Split System and
Single Package
10.6 EER
11.6 IEER
All other Split System and
Single Package
10.4 EER
11.4 IEER
≥ 240,000 Btu/h Electric Resistance
(or None)
Split System and
Single Package
9.5 EER
10.6 IEER
All other Split System and
Single Package
9.3 EER
10.4 IEER
Water to air, water loop
(cooling mode)
< 17,000 Btu/h All 86°F entering water 12.2 EER ISO 13256-1
≥ 17,000 Btu/h and
< 65,000 Btu/h
All 86°F entering water 13.0 EER
≥ 65,000 Btu/h and
< 135,000 Btu/h
All 86°F entering water 13.0 EER
Water to air, ground water
(cooling mode)
< 135,000 Btu/h All 59°F entering water 18.0 EER
Brine to air, ground loop
(cooling mode)
< 135,000 Btu/h All 77°F entering water 14.1 EER
Water- to water, water loop
(cooling mode)
< 135,000 Btu/h All 86°F entering water 10.6 EER ISO 13256-2
Water to water, ground water
(cooling mode)
< 135,000 Btu/h All 59°F entering water 16.3 EER
Brine to water, ground loop
(cooling mode)
< 135,000 Btu/h All 77°F entering fluid 12.1 EER
Air cooled (heating mode) < 65,000 Btu/hb Split System 8.2 HSPF AHRI 210/240
Single Package 8.0 HSPF
Through-the-wall, (air cooled,
heating mode)
≥ 30,000 Btu/hb
(cooling capacity)
Split System 7.4 HSPF
Single Package 7.4 HSPF
Small-duct high velocity
(air cooled, heating mode)
< 65,000 Btu/hb Split System 6.8 HSPF
Air cooled (heating mode) ≥ 65,000 Btu/h and
< 135,000 Btu/h
(cooling capacity)
47°F db/43°F wb
Outdoor Air
3.3 COP AHRI 340/360
17°F db/15°F wb
Outdoor Air
2.25 COP
≥ 135,000 Btu/h
(cooling capacity)
47°F db/43°F wb
Outdoor Air
3.2 COP
17°F db/15°F wb
Outdoor Air
2.05 COP
Water to air, water loop
(heating mode)
< 135,000 Btu/h
(cooling capacity)
68°F entering water 4.3 COP ISO 13256-1
Water to air, ground water
(heating mode)
< 135,000 Btu/h
(cooling capacity)
50°F entering water 3.7 COP
Brine to air, ground loop
(heating mode)
< 135,000 Btu/h
(cooling capacity)
32°F entering fluid 3.2 COP
Water- to water, water loop
(heating mode)
< 135,000 Btu/h
(cooling capacity)
68°F entering water 3.7 COP ISO 13256-2
50°F entering water 3.1 COP
Brine to water, ground loop
(heating mode)
< 135,000 Btu/h
(cooling capacity)
32°F entering fluid 2.5 COP

For SI: 1 British thermal unit per hour = 0.2931 W, °C = [(°F) - 32]/1.8.

  1. Chapter 6 of the referenced standard contains a complete specification of the referenced test procedure, including the reference year version of the test procedure.
  2. Single-phase, air-cooled air conditioners less than 65,000 Btu/h are regulated by NAECA. SEER values are those set by NAECA.

TABLE C403.3.2(3)

MINIMUM EFFICIENCY REQUIREMENTS: ELECTRICALLY OPERATED PACKAGED TERMINAL AIR CONDITIONERS, PACKAGED TERMINAL HEAT PUMPS, SINGLE-PACKAGE VERTICAL AIR CONDITIONERS, SINGLE-PACKAGE VERTICAL HEAT PUMPS, ROOM AIR CONDITIONERS AND ROOM AIR-CONDITIONER HEAT PUMPS

EQUIPMENT
TYPE
SIZE CATEGORY (INPUT) SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCY
TEST
PROCEDUREa
PTAC (cooling mode)
new construction
All Capacities 95°F db outdoor air 14.0 - (0.300 × Cap/1000) EER AHRI 310/380
PTAC (cooling mode)
replacementsb
All Capacities 95°F db outdoor air 10.9 - (0.213 × Cap/1000) EER
PTHP (cooling mode)
new construction
All Capacities 95°F db outdoor air 14.0 - (0.300 × Cap/1000) EER
PTHP (cooling mode)
replacementsb
All Capacities 95°F db outdoor air 10.8 - (0.213 × Cap/1000) EER
PTHP (heating mode)
new construction
All Capacities 3.7 - (0.052 × Cap/1000) COP
PTHP (heating mode)
replacementsb
All Capacities 2.9 - (0.026 × Cap/1000) COP
SPVAC
(cooling mode)
< 65,000 Btu/h 95°F db/ 75°F wb outdoor air 11.0 EER AHRI 390
≥ 65,000 Btu/h and
< 135,000 Btu/h
95°F db/ 75°F wb outdoor air 10.0 EER
≥ 135,000 Btu/h and
< 240,000 Btu/h
95°F db/ 75°F wb outdoor air 10.0 EER
SPVHP
(cooling mode)
< 65,000 Btu/h 95°F db/ 75°F wb outdoor air 11.0 EER
≥ 65,000 Btu/h and
< 135,000 Btu/h
95°F db/ 75°F wb outdoor air 10.0 EER
≥ 135,000 Btu/h and
< 240,000 Btu/h
95°F db/ 75°F wb outdoor air 10.0 EER
SPVHP
(heating mode)
< 65,000 Btu/h 47°F db/ 43°F wb outdoor air 3.3 COP AHRI 390
≥ 65,000 Btu/h and
< 135,000 Btu/h
47°F db/ 43°F wb outdoor air 3.0 COP
≥ 135,000 Btu/h and
< 240,000 Btu/h
47°F db/ 43°F wb outdoor air 3.0 COP
Room air conditioners,
with louvered sides
< 6,000 Btu/h 11.0 CEER ANSI/AHAM RAC-1
≥ 6,000 Btu/h and
< 8,000 Btu/h
11.0 CEER
≥ 8,000 Btu/h and
< 14,000 Btu/h
10.9 CEER
≥ 14,000 Btu/h and
< 20,000 Btu/h
10.7 CEER
≥ 20,000 Btu/h and
< 25,000 Btu/h
9.4 CEER
≥ 25,000 Btu/h 9.0 CEER
Room air conditioners,
without louvered sides
< 6,000 Btu/h 10.0 CEER
≥ 6,000 Btu/h and
< 8,000 Btu/h
10.0 CEER
≥ 8,000 Btu/h
< 11,000 Btu/h
9.6 CEER
≥ 11,000 Btu/h and
< 14,000 Btu/h
9.5 CEER
≥ 14,000 Btu/h and
< 20,000 Btu/h
1/m 9.3 CEER
≥ 20,000 Btu/h 9.4 CEER
Room air-conditioner
heat pumps with
louvered sides
< 20,000 Btu/h 9.8 CEER
≥ 20,000 Btu/h 9.3 CEER
Room air-conditioner
heat pumps without
louvered sides
< 14,000 Btu/h 9.3 CEER
≥ 14,000 Btu/h 8.7 CEER
Room air conditioner
casement only
All capacities 9.5 CEER ANSI/AHAM RAC-1
Room air conditioner
casement-slider
All capacities 10.4 CEER

For SI: 1 British thermal unit per hour = 0.2931 W, °C = [(°F) - 32]/1.8.

"Cap" = The rated cooling capacity of the product in Btu/h. If the unit's capacity is less than 7000 Btu/h, use 7000 Btu/h in the calculation. If the unit's capacity is greater than 15,000 Btu/h, use 15,000 Btu/h in the calculations.

  1. Chapter 6 of the referenced standard contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.
  2. Replacement unit shall be factory labeled as follows: "MANUFACTURED FOR NONSTANDARD SIZE APPLICATIONS ONLY: NOT TO BE INSTALLED IN NEW STANDARD PROJECTS" or "MANUFACTURED FOR REPLACEMENT APPLICATIONS ONLY: NOT TO BE INSTALLED IN NEW CONSTRUCTION PROJECTS." Replacement efficiencies apply only to units with existing sleeves less than 16 inches (406 mm) in height and less than 42 inches (1067 mm) in width.

TABLE C403.3.2(4)

WARM AIR FURNACES AND COMBINATION WARM AIR FURNACES/AIR-CONDITIONING UNITS, WARM AIR DUCT FURNACES AND UNIT HEATERS, MINIMUM EFFICIENCY REQUIREMENTS

EQUIPMENT TYPE SIZE CATEGORY
(INPUT)
SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCYd, e
TEST PROCEDUREa
Warm air furnaces,
gas fired
< 225,000 Btu/h 80% AFUE or 80%Etc DOE 10 CFR Part 430 or
ANSI Z21.47
≥ 225,000 Btu/h Maximum capacityc 80%Etf ANSI Z21.47
Warm air furnaces,
oil fired
< 225,000 Btu/h 83% AFUE or 80%Etc DOE 10 CFR Part 430
or UL 727
≥ 225,000 Btu/h Maximum capacityb 81%Etg UL 727
Warm air duct furnaces,
gas fired
All capacities Maximum capacityb 80%Ec ANSI Z83.8
Warm air unit heaters,
gas fired
All capacities Maximum capacityb 80%Ec ANSI Z83.8
Warm air unit heaters,
oil fired
All capacities Maximum capacityb 80%Ec UL 731

For SI: 1 British thermal unit per hour = 0.2931 W.

  1. Chapter 6 of the referenced standard contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.
  2. Minimum and maximum ratings as provided for and allowed by the unit's controls.
  3. Combination units not covered by the National Appliance Energy Conservation Act of 1987 (NAECA) (3-phase power or cooling capacity greater than or equal to 65,000 Btu/h [19 kW]) shall comply with either rating.
  4. Et = Thermal efficiency. See test procedure for detailed discussion.
  5. Ec = Combustion efficiency (100% less flue losses). See test procedure for detailed discussion.
  6. Ec = Combustion efficiency. Units must also include an IID, have jackets not exceeding 0.75 percent of the input rating, and have either power venting or a flue damper. A vent damper is an acceptable alternative to a flue damper for those furnaces where combustion air is drawn from the conditioned space.
  7. Et = Thermal efficiency. Units must also include an IID, have jacket losses not exceeding 0.75 percent of the input rating, and have either power venting or a flue damper. A vent damper is an acceptable alternative to a flue damper for those furnaces where combustion air is drawn from the conditioned space.

TABLE C403.3.2(5)

MINIMUM EFFICIENCY REQUIREMENTS: GAS- AND OIL-FIRED BOILERS

EQUIPMENT TYPEa SUBCATEGORY OR
RATING CONDITION
SIZE CATEGORY (INPUT) MINIMUM EFFICIENCY TEST PROCEDURE
Boilers, hot water Gas-fired < 300,000 Btu/hd, e 82% AFUE 10 CFR Part 430
≥ 300,000 Btu/h and
≤ 2,500,000 Btu/hb
80% Et 10 CFR Part 431
> 2,500,00 Btu/ha 82% Ec
Oil-firedc < 300,000 Btu/he 84% AFUE 10 CFR Part 430
≥ 300,000 Btu/h and
≤ 2,500,000 Btu/hb
82% Et 10 CFR Part 431
> 2,500,000 Btu/ha 84% Ec
Boilers, steam Gas-fired < 300,000 Btu/hd 80% AFUE 10 CFR Part 430
Gas-fired- all, except natural draft ≥ 300,000 Btu/h and
≤ 2,500,000 Btu/hb
79% Et 10 CFR Part 431
> 2,500,000 Btu/ha 79% Et
Gas-fired-natural draft ≥ 300,000 Btu/h and
≤ 2,500,000 Btu/hb
79% Et
> 2,500,000 Btu/ha 79% Et
Oil-firedc < 300,000 Btu/h 82% AFUE 10 CFR Part 430
≥ 300,000 Btu/h and
≤ 2,500,000 Btu/hb
81% Et 10 CFR Part 431
> 2,500,000 Btu/ha 81% Et

For SI: 1 British thermal unit per hour = 0.2931 W.

Ec = Combustion efficiency (100 percent less flue losses). Et = Thermal efficiency. See referenced standard document for detailed information.

  1. These requirements apply to boilers with rated input of 8,000,000 Btu/h or less that are not packaged boilers and to all packaged boilers. Minimum efficiency requirements for boilers cover all capacities of packaged boilers.
  2. Maximum capacity — minimum and maximum ratings as provided for and allowed by the unit's controls.
  3. Includes oil-fired (residual).
  4. Boilers shall not be equipped with a constant burning ignition pilot.
  5. A boiler not equipped with a tankless domestic water heating coil shall be equipped with an automatic means for adjusting the temperature of the water such that an incremental change in inferred heat load produces a corresponding incremental change in the temperature of the water supplied.

TABLE C403.3.2(6)

RESERVED

TABLE C403.3.2(7)

MINIMUM EFFICIENCY REQUIREMENTS: WATER CHILLING PACKAGESa, b

EQUIPMENT TYPE SIZE CATEGORY UNITS PATH A PATH B TEST
PROCEDUREc
FULL LOAD IPLV FULL LOAD IPLV
Air-cooled chillers < 150 tons EER ≥ 10.100 ≥ 13.700 ≥ 9.700 ≥ 15.800 AHRI 550/590
≥ 150 tons EER ≥ 10.100 ≥ 14.000 ≥ 9.700 ≥ 16.100
Air cooled without
condenser, electrical
operated
All capacities EER Air-cooled chillers without condensers shall be
rated with matching condensers and comply with
the air-cooled chiller efficiency requirements
Water cooled, electrically
operated, positive
displacement
< 75 tons kW/ton ≤ 0.750 ≤ 0.600 ≤ 0.780 ≤ 0.500
≥ 75 tons and
< 150 tons
kW/ton ≤ 0.720 ≤ 0.560 ≤ 0.750 ≤ 0.490
≥ 150 tons and
< 300 tons
kW/ton ≤ 0.660 ≤ 0.540 ≤ 0.680 ≤ 0.440
≥ 300 tons and
< 600 tons
kW/ton ≤ 0.610 ≤ 0.520 ≤ 0.625 ≤ 0.410
≥ 600 tons kW/ton ≤ 0.560 ≤ 0.500 ≤ 0.585 ≤ 0.380
Water cooled, electrically
operated, centrifugal
< 150 tons kW/ton ≤ 0.610 ≤ 0.550 ≤ 0.695 ≤ 0.440
≥ 150 tons and
< 300 tons
kW/ton ≤ 0.610 ≤ 0.550 ≤ 0.695 ≤ 0.400
≥ 300 tons and
< 400 tons
kW/ton ≤ 0.560 ≤ 0.520 ≤ 0.595 ≤ 0.390
≥ 400 tons kW/ton ≤ 0.560 ≤ 0.500 ≤ 0.585 ≤ 0.380
Air cooled, absorption
single effect
All capacities COP ≥ 0.600 NR NA NA AHRI 560
Water cooled, absorption
single effect
All capacities COP ≥ 0.700 NR NA NA
Absorption double effect,
indirect fired
All capacities COP ≥ 1.000 ≥ 1.050 NA NA
Absorption double effect,
direct fired
All capacities COP ≥ 1.000 ≥ 1.000 NA NA

For SI: 1 ton = 3517 W, 1 British thermal unit per hour = 0.2931 W, °C = [(°F) - 32]/1.8.

NA = Not applicable, not to be used for compliance; NR = No requirement.

  1. The centrifugal chiller equipment requirements, after adjustment in accordance with Section C403.3.2.2 or Section C403.3.2.3, do not apply to chillers used in low-temperature applications where the design leaving fluid temperature is less than 36°F. The requirements do not apply to positive displacement chillers with leaving fluid temperatures less than or equal to 32°F. The requirements do not apply to absorption chillers with design leaving fluid temperatures less than 40°F.
  2. Compliance with this standard can be obtained by meeting the minimum requirements of Path A or B. However, both the full load and IPLV shall be met to fulfill the requirements of Path A or B.
  3. Chapter 12 of the referenced standard contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.

TABLE C403.3.2(8)

MINIMUM EFFICIENCY REQUIREMENTS: HEAT REJECTION EQUIPMENT

EQUIPMENT
TYPEa
TOTAL SYSTEM HEAT
REJECTION CAPACITY AT
RATED CONDITIONS
SUBCATEGORY OR
RATING CONDITIONi
PERFORMANCE
REQUIREDb, c, d, g, h
TEST PROCEDUREe f
Propeller or axial fan open
circuit cooling towers
All 95°F Entering Water
85°F Leaving Water
75°F Entering wb
≥ 40.2 gpm/hp CTI ATC-105 and
CTI STD-201 RS
Centrifugal fan open
circuit cooling towers
All 95°F Entering Water
85°F Leaving Water
75°F Entering wb
≥ 20.0 gpm/hp CTI ATC-105 and
CTI STD-201 RS
Propeller or axial
fan closed circuit
cooling towers
All 102°F Entering Water
90°F Leaving Water
75°F Entering wb
≥ 16.1 gpm/hp CTI ATC-105S and
CTI STD-201 RS
Centrifugal closed
circuit cooling towers
All 102°F Entering Water
90°F Leaving Water
75°F Entering wb
≥ 7.0 gpm/hp CTI ATC-105S and
CTI STD-201 RS
Propeller or axial fan
evaporative condensers
All R-507A Test Fluid
165°F Entering Gas Temperature
105°F Condensing Temperature
75°F Entering wb
≥ 157,000 Btu/h • hp CTI ATC-106
Propeller or axial fan
evaporative condensers
All Ammonia Test Fluid
140°F Entering Gas Temperature
96.3°F Condensing Temperature
75°F Entering wb
≥ 134,000 Btu/h • hp CTI ATC-106
Centrifugal fan
evaporative condensers
All R-507A Test Fluid
165°F Entering Gas Temperature
105°F Condensing Temperature
75°F Entering wb
≥ 135,000 Btu/h • hp CTI ATC-106
Centrifugal fan
evaporative condensers
All Ammonia Test Fluid
140°F Entering Gas Temperature
96.3°F Condensing Temperature
75°F Entering wb
≥ 110,000 Btu/h • hp CTI ATC-106
Air-cooled condensers All 125°F Condensing Temperature
R-22 Test Fluid
190°F Entering Gas Temperature
15°F Subcooling
95°F Entering db
≥ 176,000 Btu/h • hp AHRI 460

For SI: °C = [(°F)-32]/1.8, L/s × kW = (gpm/hp)/(11.83), COP = (Btu/h × hp)/(2550.7).

db = dry bulb temperature, °F, wb = wet bulb temperature, °F.

  1. The efficiencies and test procedures for both open and closed circuit cooling towers are not applicable to hybrid cooling towers that contain a combination of wet and dry heat exchange sections.
  2. For purposes of this table, open circuit cooling tower performance is defined as the water flow rating of the tower at the thermal rating condition divided by the fan nameplate rated motor power.
  3. For purposes of this table, closed circuit cooling tower performance is defined as the water flow rating of the tower at the thermal rating condition divided by the sum of the fan nameplate rated motor power and the spray pump nameplate rated motor power.
  4. For purposes of this table, air-cooled condenser performance is defined as the heat rejected from the refrigerant divided by the fan nameplate rated motor power.
  5. Chapter 6 of the referenced standard contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.
  6. Where a certification program exists for a covered product, and it includes provisions for verification and challenge of equipment efficiency ratings, then the product shall be listed in the certification program, or, if a certification program exists for a covered product, and it includes provisions for verification and challenge of equipment efficiency ratings, but the product is not listed in the existing certification program, the ratings shall be verified by an independent laboratory test report.
  7. Cooling towers shall comply with the minimum efficiency listed in the table for that specific type of tower with the capacity effect of any project-specific accessories and/or options included in the capacity of the cooling tower.
  8. For purposes of this table, evaporative condenser performance is defined as the heat rejected at the specified rating condition in the table, divided by the sum of the fan motor nameplate power and the integral spray pump nameplate power.
  9. Requirements for evaporative condensers are listed with ammonia (R-717) and R-507A as test fluids in this table. Evaporative condensers intended for use with halocarbon refrigerants other than R-507A must meet the minimum efficiency requirements listed above with R-507A as the test fluid.

TABLE C403.3.2(9)

MINIMUM EFFICIENCY REQUIREMENTS: AIR CONDITIONERS AND CONDENSING UNITS SERVING COMPUTER ROOMS AND DATA CENTERS

EQUIPMENT
TYPE
NET SENSIBLE
COOLING
CAPACITY
STANDARD MODEL MINIMUM NET SENSIBLE COPc TEST
PROCEDURE
Return Air Dry-Bulb Temperature/
Dew-Point Temperature
Class 1 Class 2 Class 3
75°F/52°F 85°F/52°F 95°F/52°F
Air cooled < 65,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.09 2.30
2.10
2.45 AHRI 1360
≥ 65,000 Btu/h and
< 240,000 Btu/h
Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
1.99 2.20
2.05
2.35
≥ 240,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
1.79 2.00
1.85
2.15
Water cooled < 65,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.25 2.50
2.30
2.70 AHRI 1360
≥ 65,000 Btu/h and
< 240,000 Btu/h
Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.15 2.40
2.20
2.60
≥ 240,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.05 2.25
2.10
2.45
Water cooled
with fluid
economizer
< 65,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.20 2.45
2.25
2.60 AHRI 1360
≥ 65,000 Btu/h and
< 240,000 Btu/h
Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.10 2.35
2.15
2.55
≥ 240,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.00 2.20
2.05
2.40
Glycol cooled < 65,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.00 2.30
2.10
2.40 AHRI 1360
≥ 65,000 Btu/h and
< 240,000 Btu/h
Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
1.85 2.05
1.85
2.15
≥ 240,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
1.75 1.95
1.80
2.10
Glycol cooled
with fluid
economizer
< 65,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
2.00 2.25
2.10
2.35 AHRI 1360
≥ 65,000 Btu/h and
< 240,000 Btu/h
Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
1.75 1.95
1.80
2.10
≥ 240,000 Btu/h Downflow unit
Upflow unit—ducted
Upflow unit—unducted
Horizontal-flow unit
1.70 1.90
1.80
2.10

For SI: 1 British thermal unit per hour = 0.2931W, °C = [(°F)-32]/1.8, L/s × kW = (gpm/hp)/(11.83), COP = (Btu/h × hp)/(2550.7).

TABLE C403.3.2(10)

MINIMUM EFFICIENCY REQUIREMENTS: HEAT TRANSFER EQUIPMENT

EQUIPMENT TYPE SUBCATEGORY MINIMUM EFFICIENCY TEST PROCEDUREa
Liquid-to-liquid heat exchangers Plate type NR AHRI 400

NR = No Requirement.

  1. Chapter 6 of the referenced standard contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.

TABLE C403.3.2(11)

MINIMUM EFFICIENCY REQUIREMENTS: ELECTRICALLY OPERATED DX-DOAS UNITS, SINGLE-PACKAGE AND REMOTE CONDENSER, WITHOUT ENERGY RECOVERY

EQUIPMENT
TYPE
SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCY
TEST
PROCEDURE
Air cooled
(dehumidification mode)
  4.0 ISMRE AHRI 920
Air source heat pumps
(dehumidification mode)
  4.0 ISMRE AHRI 920
Water cooled
(dehumidification mode)
Cooling tower condenser water 4.9 ISMRE AHRI 920
Chilled water 6.0 ISMRE
Air source heat pump
(heating mode)
  2.7 ISCOP AHRI 920
Water source heat pump
(dehumidification mode)
Ground source, closed loop 4.8 ISMRE AHRI 920
Ground-water source 5.0 ISMRE
Water source 4.0 ISMRE
Water source heat pump
(heating mode)
Ground source, closed loop 2.0 ISCOP AHRI 920
Ground-water source 3.2 ISCOP
Water source 3.5 ISCOP

TABLE C403.3.2(12)

MINIMUM EFFICIENCY REQUIREMENTS: ELECTRICALLY OPERATED DX-DOAS UNITS, SINGLE-PACKAGE AND REMOTE CONDENSER, WITH ENERGY RECOVERY

EQUIPMENT
TYPE
SUBCATEGORY OR
RATING CONDITION
MINIMUM
EFFICIENCY
TEST
PROCEDURE
Air cooled
(dehumidification mode)
  5.2 ISMRE AHRI 920
Air source heat pumps
(dehumidification mode)
  5.2 ISMRE AHRI 920
Water cooled
(dehumidification mode)
Cooling tower condenser water 5.3 ISMRE AHRI 920
Chilled water 6.6 ISMRE
Air source heat pump
(heating mode)
  3.3 ISCOP AHRI 920
Water source heat pump
(dehumidification mode)
Ground source, closed loop 5.2 ISMRE AHRI 920
Ground-water source 5.8 ISMRE
Water source 4.8 ISMRE
Water source heat pump
(heating mode)
Ground source, closed loop 3.8 ISCOP AHRI 920
Ground-water source 4.0 ISCOP
Water source 4.8 ISCOP

Chilled water plants and buildings with more than 500 tons total capacity shall not have more than 100 tons provided by air-cooled chillers.

Exceptions:

  1. Where the designer demonstrates that the water quality at the building site fails to meet manufacturer's specifications for the use of water-cooled equipment.
  2. Air-cooled chillers with minimum efficiencies at least 10 percent higher than those listed in Table C403.3.2(7).
  3. Replacement of existing air-cooled chiller equipment.
  4. Air-to-water heat pump units that are configured to provide both heating and cooling and that are rated in accordance with AHRI 550/590. Where the air-to-water heat pumps are designed for a maximum supply leaving water temperature of less than 140°F, the efficiency rating will be calculated and reported at the maximum unit leaving water temperature for this test condition.

Equipment not designed for operation at AHRI Standard 550/590 test conditions of 44°F (7°C) leaving chilled-water temperature and 2.4 gpm/ton evaporator fluid flow and 85°F (29°C) entering condenser water temperature with 3 gpm/ton (0.054 L/s × kW) condenser water flow shall have maximum full-load kW/ton (FL) and part-load ratings adjusted using Equations 4-7 and 4-8.


(Equation 4-7)

(Equation 4-8)

where:

Kadj = A × B

FL = Full-load kW/ton values as specified in Table C403.3.2(7)

FLadj = Maximum full-load kW/ton rating, adjusted for nonstandard conditions

IPLV = Values as specified in Table C403.3.2(7)

PLVadj = Maximum NPLV rating, adjusted for nonstandard conditions.

A = 0.00000014592 × (LIFT)4 - 0.0000346496 × (LIFT)3 + 0.00314196 × (LIFT)2 - 0.147199 × LIFT + 3.9302

B = 0.0015 × LvgEvap (°F) + 0.934

LIFT = LvgCond - LvgEvap

LvgCond = Full-load condenser leaving fluid temperature (°F)

LvgEvap = Full-load evaporator leaving temperature (°F)

The FLadj and PLVadj values are only applicable for centrifugal chillers meeting all of the following full-load design ranges:

  1. Minimum evaporator leaving temperature: 36°F.
  2. Maximum condenser leaving temperature: 115°F.
  3. LIFT is not less than 20°F and not greater than 80°F.
Equipment with a leaving fluid temperature higher than 32°F (0°C) and water-cooled positive displacement chilling packages with a condenser leaving fluid temperature below 115°F (46°C) shall meet the requirements of Table C403.3.2(7) when tested or certified with water at standard rating conditions, in accordance with the referenced test procedure.

Packaged electric equipment providing both heating and cooling with a total cooling capacity greater than 6,000 Btu/h shall be a heat pump.

Exception: Unstaffed equipment shelters or cabinets used solely for personal wireless service facilities.

If an air economizer is required on a cooling system for which humidification equipment is to be provided to maintain minimum indoor humidity levels, then the humidifier shall be of the adiabatic type (direct evaporative media or fog atomization type).

Exceptions:

  1. Health care facilities licensed by the state where Chapter 246-320 or 246-330 WAC requires steam injection humidifiers in duct work downstream of final filters.
  2. Systems with water economizer.
  3. 100% outside air systems with no provisions for air recirculation to the central supply fan.
  4. Nonadiabatic humidifiers cumulatively serving no more than 10% of a building's air economizer capacity as measured in cfm. This refers to the system cfm serving rooms with stand-alone or duct-mounted humidifiers.

Cooling systems shall not use hot gas bypass or other evaporator pressure control systems unless the system is designed with multiple steps of unloading or continuous capacity modulation. The capacity of the hot gas bypass shall be limited as indicated in Table C403.3.3, as limited by Section C403.5.1.

TABLE C403.3.3

MAXIMUM HOT GAS BYPASS CAPACITY

RATED CAPACITY MAXIMUM HOT GAS
BYPASS CAPACITY
(% of total capacity)
≤ 240,000 Btu/h 50
> 240,000 Btu/h 25

For SI: 1 British thermal unit per hour = 0.2931 W.

Boiler systems with design input of greater than 1,000,000 Btu/h (293 kW) shall comply with the turndown ratio specified in Table C403.3.4.

The system turndown requirement shall be met through the use of multiple single input boilers, one or more modulating boilers or a combination of single input and modulating boilers.

TABLE C403.3.4

BOILER TURNDOWN

BOILER SYSTEM
DESIGN INPUT (BTU/H)
MINIMUM
TURNDOWN RATIO
≥ 1,000,000 and
less than or equal to 5,000,000
3 to 1
> 5,000,000 and
less than or equal to 10,000,000
4 to 1
> 10,000,000 5 to 1

For buildings with occupancies as shown in Table C403.3.5, outdoor air shall be provided to each occupied space by a dedicated outdoor air system (DOAS) which delivers 100 percent outdoor air without requiring operation of the heating and cooling system fans for ventilation air delivery.

Exceptions:

  1. Occupied spaces that are not ventilated by a mechanical ventilation system and are only ventilated by a natural ventilation system in accordance with Section 402 of the International Mechanical Code.
  2. High efficiency variable air volume (VAV) systems complying with Section C403.6.10 for occupancy classifications other than Groups A-1, A-2 and A-3 as specified in Table C403.3.5, and high efficiency VAV systems complying with Section C403.12 for occupancy classifications Groups A-1, A-2 and A-3 as specified in Table C403.3.5. This exception shall not be used as a substitution for a DOAS per Section C406.6.

TABLE C403.3.5

OCCUPANCY CLASSIFICATIONS REQUIRING DOAS

OCCUPANCY
CLASSIFICATIONa
INCLUSIONS EXEMPTED
A-1 All occupancies not specifically exempted Television and radio studios
A-2 Casinos (gaming area) All other A-2 occupancies
A-3 Lecture halls, community halls, exhibition
halls, gymnasiums, courtrooms,
libraries, places of religious worship
All other A-3 occupancies
A-4, A-5 All occupancies excluded
B All occupancies not specifically exempted
Food processing establishments including commercial kitchens,
restaurants, cafeterias; laboratories for testing and research; data
processing facilities and telephone exchanges; air traffic control towers;
animal hospitals, kennels, pounds; ambulatory care facilities.
F, H, I, R, S, U All occupancies excluded
E, M All occupancies included
  1. Occupancy classification from the International Building Code, Chapter 3.

The DOAS shall include energy recovery ventilation. The energy recovery system shall have a 60 percent minimum sensible recovery effectiveness or have 50 percent enthalpy recovery effectiveness in accordance with Section C403.7.6. For DOAS having a total fan system motor nameplate hp less than 5 hp, total combined fan power shall not exceed 1 W/cfm of outdoor air. For DOAS having a total fan system motor hp greater than or equal to 5 hp, refer to fan power limitations of Section C403.8.1. This fan power restriction applies to each dedicated outdoor air unit in the permitted project, but does not include the fan power associated with the zonal heating/cooling equipment. The airflow rate thresholds for energy recovery requirements in Tables C403.7.6(1) and C403.7.6(2) do not apply.

Exceptions:

  1. Occupied spaces with all of the following characteristics: Complying with Section C403.7.6, served by equipment less than 5000 cfm, with an average occupant load greater than 25 people per 1000 square feet (93 m2) of floor area (as established in Table 403.3.1.1 of the International Mechanical Code) that include demand control ventilation configured to reduce outdoor air by at least 50 percent below design minimum ventilation rates when the actual occupancy of the space served by the system is less than the design occupancy.
  2. Systems installed for the sole purpose of providing makeup air for systems exhausting toxic, flammable, paint, or corrosive fumes or dust, dryer exhaust, or commercial kitchen hoods used for collecting and removing grease vapors and smoke.

Heating and cooling equipment fans, heating and cooling circulation pumps, and terminal unit fans shall cycle off and terminal unit primary cooling air shall be shut off when there is no call for heating or cooling in the zone.

Exception: Fans used for heating and cooling using less than 0.12 watts per cfm may operate when space temperatures are within the set point dead band (Section C403.4.1.2) to provide destratification and air mixing in the space.

The DOAS supply air shall be delivered directly to the occupied space or downstream of the terminal heating and/or cooling coils.

Exceptions:

  1. Active chilled beam systems.
  2. Sensible only cooling terminal units with pressure independent variable airflow regulating devices limiting the DOAS supply air to the greater of latent load or minimum ventilation requirements.
  3. Terminal heating and/or cooling units that comply with the low fan power allowance requirements in the exception of Section C403.3.5.2.
Where the code official determines that full compliance with all of the requirements of Section C403.3.5.1 and C403.3.5.2 would be impractical, it is permissible to provide an approved alternate means of compliance that achieves a comparable level of energy efficiency. For the purposes of this section, impractical means that an HVAC system complying with Section C403.3.5 cannot effectively be utilized due to an unusual use or configuration of the building.
For all Group R-2 dwelling and sleeping units, a balanced ventilation system with heat recovery system with minimum 60 percent sensible recovery effectiveness shall provide outdoor air directly to all habitable space. The ventilation system shall allow for the design flow rates to be tested and verified at each habitable space as part of the commissioning process in accordance with Section C408.2.2.
HVAC systems shall be provided with controls in accordance with Sections C403.4.1 through C403.4.11 and shall be capable of and configured to implement all required control functions in this code.

The supply of heating and cooling energy to each zone shall be controlled by individual thermostatic controls capable of responding to temperature within the zone. Controls in the same zone or in neighboring zones connected by openings larger than 10 percent of the floor area of either zone shall not allow for simultaneous heating and cooling. At a minimum, each floor of a building shall be considered as a separate zone. Controls on systems required to have economizers and serving single zones shall have multiple cooling stage capability and activate the economizer when appropriate as the first stage of cooling. See Section C403.5 for further economizer requirements. Where humidification or dehumidification or both is provided, at least one humidity control device shall be provided for each humidity control system.

Exceptions:

  1. Independent perimeter systems that are designed to offset only building envelope heat losses or gains or both serving one or more perimeter zones also served by an interior system provided:

    1. 1.1. The perimeter system includes at least one thermostatic control zone for each building exposure having exterior walls facing only one orientation (within +/-45 degrees) (0.8 rad) for more than 50 contiguous feet (15 240 mm);
    2. 1.2. The perimeter system heating and cooling supply is controlled by a thermostat located within the zones served by the system; and
    3. 1.3. Controls are configured to prevent the perimeter system from operating in a different heating or cooling mode from the other equipment within the zones or from neighboring zones connected by openings larger than 10 percent of the floor area of either zone.
  2. Any interior zone open to a perimeter zone shall have set points and dead bands coordinated so that cooling in the interior zone shall not operate while the perimeter zone is in heating until the interior zone temperature is 5°F (2.8°C) higher than the perimeter zone temperature, unless the interior and perimeter zones are separated by a partition whose permanent openings are smaller than 10 percent of the perimeter zone floor area.
  3. Dedicated outdoor air units that provide ventilation air, makeup air or replacement air for exhaust systems are permitted to be controlled based on supply air temperature. The supply air temperature shall be controlled to a maximum of 65°F (18.3°C) in heating and a minimum of 72°F (22°C) in cooling unless the supply air temperature is being reset based on the status of cooling or heating in the zones served or it being reset based on outdoor air temperature.

Unitary air-cooled heat pumps shall include microprocessor controls that minimize supplemental heat usage during start-up, set-up, and defrost conditions. These controls shall anticipate need for heat and use compression heating as the first stage of heat. Controls shall indicate when supplemental heating is being used through visual means (e.g., LED indicators). Heat pumps equipped with supplementary heaters shall be installed with controls that prevent supplemental heater operation above 40°F (4.4°C).

Exception: Packaged terminal heat pumps (PTHPs) of less than 2 tons (24,000 Btu/hr) cooling capacity provided with controls that prevent supplementary heater operation above 40°F (4.4°C).

Where used to control both heating and cooling, zone thermostatic controls shall be configured to provide a temperature range or dead band of at least 5°F (2.8°C) within which the supply of heating and cooling energy to the zone is shut off or reduced to a minimum.

Exceptions:

  1. Thermostats requiring manual changeover between heating and cooling modes.
  2. Occupancies or applications requiring precision in indoor temperature control as approved by the code official.
Where a zone has a separate heating and a separate cooling thermostatic control located within the zone, a limit switch, mechanical stop or direct digital control system with software programming shall be configured to prevent the heating set point from exceeding the cooling set point and to maintain a dead band in accordance with Section C403.4.1.2.

The heating system for heated vestibules and air curtains with integral heating shall be provided with controls configured to shut off the source of heating when the outdoor air temperature is greater than 45°F (7°C). Vestibule heating and cooling systems shall be controlled by a thermostat located in the vestibule configured to limit heating to a temperature not greater than 60°F (16°C) and cooling to a temperature not less than 85°F (29°C).

Exceptions:

  1. Control of heating or cooling provided by transfer air that would otherwise be exhausted.
  2. Vestibule heating only systems are permitted to be controlled without an outdoor air temperature lockout when controlled by a thermostat located in the vestibule configured to limit heating to a temperature not greater than 45°F (7°C) where required for freeze protection of piping and sprinkler heads located in the vestibule.
Hot water boilers that supply heat to the building through one- or two-pipe heating systems shall have an outdoor setback control that lowers the boiler water temperature based on the outdoor temperature.

Doors that open to the outdoors from a conditioned space must have controls configured to do the following once doors have been open for 5 minutes:

  1. Disable the mechanical heating to the zone or reset the space heating temperature set point to 55°F (13°C) or less within 5 minutes of the door open enable signal.
  2. Disable the mechanical cooling to the zone or reset the space cooling temperature set point to 85°F (29°C) or more within 5 minutes of the door open enable signal.

Exceptions:

  1. Building entrances with vestibules.
  2. Alterations to existing buildings.
  3. Loading docks.

For all occupancies other than Group R, each zone shall be provided with thermostatic setback controls that are controlled by either an automatic time clock or programmable control system.

Exceptions:

  1. Zones that will be operated continuously.
  2. Zones with a full HVAC load demand not exceeding 6,800 Btu/h (2 kW) and having a manual shutoff switch located with ready access.
Thermostatic setback controls shall be configured to set back or temporarily operate the system to maintain zone temperatures down to 55°F (13°C) or up to 85°F (29°C).
Automatic time clock or programmable controls shall be capable of starting and stopping the system for seven different daily schedules per week and retaining their programming and time setting during a loss of power for at least 10 hours. Additionally, the controls shall have a manual override that allows temporary operation of the system for up to 2 hours; a manually operated timer configured to operate the system for up to 2 hours; or an occupancy sensor.
Automatic start and stop controls shall be provided for each HVAC system. The automatic start controls shall be configured to automatically adjust the daily start time of the HVAC system in order to bring each space to the desired occupied temperature immediately prior to scheduled occupancy. The automatic stop controls shall be configured to reduce the HVAC system's heating temperature set point and increase the cooling temperature set point by at least 2°F (1.1°C) before scheduled unoccupied periods based upon the thermal lag and acceptable drift in space temperature that is within comfort limits. At a minimum, the controls shall be a function of the space temperature, occupied and unoccupied temperatures, and the amount of time prior to scheduled occupancy.

For all occupancies other than Group R, exhaust systems serving spaces within the conditioned envelope shall be controlled by either an automatic time clock, thermostatic controls or programmable control system to operate on the same schedule as the HVAC systems providing their makeup air.

Exceptions:

  1. Exhaust systems requiring continuous operation.
  2. Exhaust systems that are controlled by occupancy sensor control configured with automatic on and automatic shutoff within 15 minutes after occupants have left the space.

For all occupancies other than Group R, transfer fan or mixing fan systems serving spaces within the conditioned envelope shall be controlled by either an automatic time clock, thermostatic controls or programmable control system to operate on the same schedule as the associated HVAC systems.

Exception: Transfer fan and destratification fan systems that are controlled by occupancy sensor control configured with manual on and automatic shutoff within 15 minutes after occupants have left the space.

The heating of fluids that have been previously mechanically cooled and the cooling of fluids that have been previously mechanically heated shall be limited in accordance with Sections C403.4.3.1 through C403.4.3.3. Hydronic heating systems comprised of multiple-packaged boilers and designed to deliver conditioned water or steam into a common distribution system shall include automatic controls configured to sequence operation of the boilers. Hydronic heating systems comprised of a single boiler and greater than 500,000 Btu/h (146 550 W) input design capacity shall include either a multi-staged or modulating burner.
Hydronic systems that use a common return system for both hot water and chilled water are prohibited.
Systems that use a common distribution system to supply both heated and chilled water shall be designed to allow a dead band between changeover from one mode to the other of at least 15°F (8.3°C) outside air temperatures; be designed to and provided with controls that will allow operation in one mode for at least 4 hours before changing over to the other mode; and be provided with controls that allow heating and cooling supply temperatures at the changeover point to be no more than 30°F (16.7°C) apart.
Hydronic heat pump systems shall comply with Sections C403.4.3.3.1 through C403.4.3.3.3.

Hydronic heat pumps connected to a common heat pump water loop with central devices for heat rejection and heat addition shall have controls that are configured to provide a heat pump water supply temperature dead band of at least 20°F (11.1°C) between initiation of heat rejection and heat addition by the central devices.

Exception: Where a system loop temperature optimization controller is installed and can determine the most efficient operating temperature based on real-time conditions of demand and capacity, dead bands of less than 20°F (11°C) shall be permitted.

The following shall apply to hydronic water loop heat pump systems:

  1. Where a closed-circuit cooling tower is used directly in the heat pump loop, either an automatic valve shall be installed to bypass the flow of water around the closed-circuit cooling tower, except for the minimum flow necessary for freeze protection. Flow controls for freeze protection shall not allow water through the closed-circuit cooling tower when outdoor temperatures are above the freezing point of the glycol/water solution, i.e., 32°F (0°C) for 100-percent water applications, and 18°F (7.8°C) for 20 percent by mass propylene glycol solution.
  2. Where an open-circuit cooling tower is used directly in the heat pump loop, an automatic valve shall be installed to bypass all heat pump water flow around the open-circuit cooling tower.
  3. Where an open-circuit cooling tower is used in conjunction with a separate heat exchanger to isolate the open-circuit cooling tower from the heat pump loop, heat loss shall be controlled by shutting down the circulation pump on the cooling tower loop.

Exception: Where it can be demonstrated that a heat pump system will be required to reject heat throughout the year.

Each hydronic heat pump on the hydronic system having a total pump system power exceeding 10 horsepower (hp) (7.5 kW) shall have a two-way (but not three-way) valve. For the purposes of this section, pump system power is the sum of the nominal power demand (i.e., nameplate horsepower at nominal motor efficiency) of motors of all pumps that are required to operate at design conditions to supply fluid from the heating or cooling source to all heat transfer devices (e.g., coils, heat exchanger) and return it to the source. This converts the system into a variable flow system and, as such, the primary circulation pumps shall comply with the variable flow requirements in Section C403.4.6.

Hydronic systems greater than or equal to 300,000 Btu/h (88 kW) in design output capacity supplying heated or chilled water to comfort conditioning systems shall include controls that are configured to:

  1. Automatically reset the supply-water temperatures in response to varying building heating and cooling demand using coil valve position, zone-return water temperature or outdoor air temperature. The temperature shall be reset by not less than 25 percent of the design supply-to-return water temperature difference.

    Exception: Hydronic systems serving hydronic heat pumps.

  2. Automatically vary fluid flow for hydronic systems with a combined pump motor capacity of 2 hp or larger with three or more control valves or other devices by reducing the system design flow rate by not less than 50 percent or the maximum reduction allowed by the equipment manufacturer for proper operation of equipment by valves that modulate or step open and close, or pumps that modulate or turn on and off as a function of load.
  3. Automatically vary pump flow on heating water systems, chilled-water systems and heat rejection loops serving water-cooled unitary air conditioners as follows:

    1. 3.1. Where pumps operate continuously or operate based on a time schedule, pumps with nominal output motor power of 2 hp or more shall have a variable speed drive.
    2. 3.2. Where pumps have automatic direct digital control configured to operate pumps only when zone heating or cooling is required, a variable speed drive shall be provided for pumps with motors having the same or greater nominal output power indicated in Table C403.4.4 based on the climate zone and system served.
  4. Where a variable speed drive is required by Item 3 of this Section, pump motor power input shall be not more than 30 percent of design wattage at 50 percent of the design water flow. Pump flow shall be controlled to maintain one control valve nearly wide open or to satisfy the minimum differential pressure.

Exceptions:

  1. Supply-water temperature reset is not required for chilled-water systems supplied by off-site district chilled water or chilled water from ice storage systems.
  2. Variable pump flow is not required on dedicated coil circulation pumps where needed for freeze protection.
  3. Variable pump flow is not required on dedicated equipment circulation pumps where configured in primary/secondary design to provide the minimum flow requirements of the equipment manufacturer for proper operation of equipment.
  4. Variable speed drives are not required on heating water pumps where more than 50 percent of annual heat is generated by an electric boiler.

TABLE C403.4.4

VARIABLE SPEED DRIVE (VSD) REQUIREMENTS FOR DEMAND-CONTROLLED PUMPS

CLIMATE ZONES 4c, 5b VSD REQUIRED FOR
MOTORS WITH RATED
OUTPUT OF AT LEAST
Heating Water Pumps ≥ 7.5 hp
Chilled water and Heat Rejection
Loop Pumps
≥ 7.5 hp

Chilled water plants including more than one chiller shall be capable of and configured to reduce flow automatically through the chiller plant when a chiller is shut down and automatically shut off flow to chillers that are shut down. Chillers piped in series for the purpose of increased temperature differential shall be considered as one chiller.

Boiler systems including more than one boiler shall be capable of and configured to reduce flow automatically through the boiler system when a boiler is shut down.

Individual pumps required by this code to have variable speed control shall be controlled in one of the following manners:

  1. For systems having a combined pump motor horsepower less than or equal to 20 hp (15 kW) and without direct digital control of individual coils, pump speed shall be a function of either:

    1. 1.1. Required differential pressure; or
    2. 1.2. Reset directly based on zone hydronic demand, or other zone load indicators; or
    3. 1.3. Reset directly based on pump power and pump differential pressure; or
    4. 1.4. Reset directly by an integral controller based on the relationship between variable speed controller frequency and power.
  2. For systems having a combined pump motor horsepower that exceeds 20 hp (15 kW) or smaller systems with direct digital control, pump speed shall be a function of either:

    1. 2.1. The static pressure set point as reset based on the valve requiring the most pressure; or
    2. 2.2. Directly controlled based on zone hydronic demand; or
    3. 2.3. Reset directly by an integral controller based on the relationship between variable speed controller frequency and power.

Combustion heating equipment with a capacity over 225,000 Btu/h shall have modulating or staged combustion control.

Exceptions:

  1. Boilers.
  2. Radiant heaters.
Combustion decorative vented appliances, combustion fireplaces and fire pits shall be equipped with local controls to limit operation to a maximum duration of one hour without override hold capability or shall be controlled by occupancy sensor control configured with manual on and automatic shutoff within 15 minutes after occupants have left the space.

The primary space conditioning system within each dwelling unit shall be provided with at least one programmable thermostat for the regulation of space temperature. The thermostat shall allow for, at a minimum, a 5-2 programmable schedule (weekdays/weekends) and be capable of providing at least two programmable setback periods per day.

Each additional system provided within the dwelling unit shall be provided with at least one adjustable thermostat for the regulation of temperature.

Exceptions:

  1. Systems controlled by an occupant sensor that is configured to shut the system off when no occupant is sensed for a period of up to 30 minutes.
  2. Systems controlled solely by a manually operated timer configured to operate the system for no more than two hours.
  3. Ductless heat pumps.

Each thermostat shall be capable of being set by adjustment or selection of sensors and configured as follows:

  1. When used to control heating only: 55°F to 75°F.
  2. When used to control cooling only: 70°F to 85°F.
  3. All other: 55°F to 85°F with an adjustable dead band configured to at least 5°F in accordance with Section C403.4.1.2.

The primary space conditioning system within each sleeping unit shall be provided with at least one programmable thermostat for the regulation of space temperature. The thermostat shall allow for, at a minimum, a 5-2 programmable schedule (weekdays/weekends) and be capable of providing at least two programmable setback periods per day.

Each additional system provided within the sleeping unit shall be provided with at least one adjustable thermostat for the regulation of temperature.

Exceptions:

  1. Systems controlled by an occupant sensor that is configured to shut the system off when no occupant is sensed for a period of up to 30 minutes.
  2. Systems controlled solely by a manually operated timer configured to operate the system for no more than two hours.
  3. Zones with a full HVAC load demand not exceeding 3,400 Btu/h (1 kW) and having a manual shutoff switch located with ready access.
  4. Ductless heat pumps.

Each thermostat shall be capable of being set by adjustment or selection of sensors and configured as follows:

  1. When used to control heating only: 55°F to 75°F;
  2. When used to control cooling only: 70°F to 85°F;
  3. All other: 55°F to 85°F with an adjustable dead band configured to at least 5°F in accordance with Section C403.4.1.2.
Direct digital control (DDC) shall be required as specified in Sections C403.4.11.1 through C403.4.11.3.

DDC shall be provided in the applications and qualifications listed in Table C403.4.11.1.

TABLE C403.4.11.1

DDC APPLICATIONS AND QUALIFICATIONS

BUILDING STATUS APPLICATION QUALIFICATIONS
New Building Air-handling system and all zones served
by the system
All air-handling systems in buildings with building cooling capacity
greater than 780,000 Btu/h
Air-handling system and all zones served
by the system
Individual systems supplying more than three zones and with fan system
bhp of 10 hp and larger
Chilled-water plant and all coils and terminal
units served by the system
Individual plants supplying more than three zones and with design cooling
capacity of 300,000 Btu/h and larger
Hot-water plant and all coils and terminal
units served by the system
Individual plants supplying more than three zones and with design heating
capacity of 300,000 Btu/h and larger
Alteration or addition Zone terminal units such as VAV box Where existing zones served by the same air-handling, chilled-water, or
hot-water system have DDC
Air-handling system or fan coil Where existing air-handling system(s) and fan coil(s) served by the
same chilled- or hot-water plant have DDC
New air-handling system and all new
zones served by the system
Individual systems with fan system bhp 10 hp and larger and supplying
more than three zones and more than 75% of zones are new
New or upgraded chilled-water plant Where all chillers are new and plant design cooling capacity is 300,000
Btu/h and larger
New or upgraded hot-water plant Where all boilers are new and plant design heating capacity is 300,000
Btu/h and larger

For SI: 1 British thermal unit per hour = 0.2931 W.

Where DDC is required by Section C403.4.11.1, the DDC system shall be capable of all of the following, as required to provide the system and zone control logic required in Sections C403.2, C403.4.3, C403.5, and C403.6.8:

  1. Monitoring zone and system demand for fan pressure, pump pressure, heating and cooling.
  2. Transferring zone and system demand information from zones to air distribution system controllers and from air distribution systems to heating and cooling plant controllers.
Where DDC is required by Section C403.4.11.1 for new buildings, the DDC system shall be capable of trending and graphically displaying input and output points.

Air economizers shall be provided on all new cooling systems including those serving computer server rooms, electronic equipment, radio equipment, and telephone switchgear. Economizers shall comply with Sections C403.5.1 through C403.5.5.

Exception: Economizers are not required for the systems listed below:

  1. Cooling systems not installed outdoors nor in a mechanical room adjacent to outdoors and installed in conjunction with DOAS complying with Section C403.3.5 and serving only spaces with year-round cooling loads from lights and equipment of less than 5 watts per square foot.
  2. Unitary or packaged systems serving one zone with dehumidification that affect other systems so as to increase the overall building energy consumption. New humidification equipment shall comply with Section C403.3.2.5.
  3. Unitary or packaged systems serving one zone where the cooling efficiency meets or exceeds the efficiency requirements in Table C403.5.
  4. Equipment serving chilled beams and chilled ceiling space cooling systems only which are provided with a water economizer meeting the requirements of Section C403.5.4.
  5. For Group R occupancies, cooling units installed outdoors or in a mechanical room adjacent to outdoors with a total cooling capacity less than 20,000 Btu/h and other cooling units with a total cooling capacity less than 54,000 Btu/h provided that these are high-efficiency cooling equipment with IEER, CEER, SEER, and EER values more than 15 percent higher than minimum efficiencies listed in Tables C403.3.2(1) through (3), in the appropriate size category, using the same test procedures. Equipment shall be listed in the appropriate certification program to qualify for this exception. For split systems, compliance is based on the cooling capacity of individual fan coil units.
  6. Equipment used to cool Controlled Plant Growth Environments provided these are high-efficiency cooling equipment with SEER, EER and IEER values a minimum of 20 percent greater than the values listed in Tables C403.3.2(1), (3) and (7).
  7. Equipment serving a space with year-round cooling loads from lights and equipment of 5 watts per square foot or greater complying with the following criteria:

    1. 7.1. Equipment serving the space utilizes chilled water as the cooling source; and
    2. 7.2. The chilled water plant includes a condenser heat recovery system that meets the requirements of Section C403.9.2.1 or the building and water-cooled system meets the following requirements:

      1. 7.2.1. A minimum of 90 percent (capacity-weighted) of the building space heat is provided by hydronic heating water.
      2. 7.2.2. Chilled-water plant includes a heat recovery chiller or water-to-water heat pump capable of rejecting heat from the chilledwater system to the hydronic heating equipment capacity.
    3. 7.3. Heat recovery chillers shall have a minimum COP of 7.0 when providing heating and cooling water simultaneously.
  8. Water-cooled equipment served by systems meeting the requirements of Section C403.9.2.4, Condenser heat recovery.
  9. Dedicated outdoor air systems that include energy recovery as required by Section C403.7.6 but that do not include mechanical cooling.
  10. Dedicated outdoor air systems not required by Section C403.7.6 to include energy recovery that modulate the supply airflow to provide only the minimum outdoor air required by Section C403.2.2.1 for ventilation, exhaust air make-up, or other process air delivery.
  11. Equipment used to cool any dedicated server room, electronic equipment room or telecom switch room provided the system complies with Option a, b or c in the table below. The total cooling capacity of all fan systems without economizers shall not exceed 240,000 Btu/h per building or 10 percent of its air economizer capacity, whichever is greater. This exception shall not be used for Total Building Performance.

      EQUIPMENT TYPE HIGHER EQUIPMENT
    EFFICIENCY
    PART-LOAD CONTROL ECONOMIZER
    Option a Tables C403.3.2(1) and C403.3.2(2)a +15%b Required over 85,000 Btu/hc None Required
    Option b Tables C403.3.2(1) and C403.3.2(2)a +5%d Required over 85,000 Btu/hc Water-side Economizere
    Option c ASHRAE Standard 127f +0%g Required over 85,000 Btu/hc Water-side Economizere

    Notes for Exception 11:

    1. For a system where all of the cooling equipment is subject to the AHRI standards listed in Tables C403.3.2(1) and C403.3.2(2), the system shall comply with all of the following (note that if the system contains any cooling equipment that exceeds the capacity limits in Table C403.3.2(1) or C403.3.2(2), or if the system contains any cooling equipment that is not included in Table C403.3.2(1) or C403.3.2(2), then the system is not allowed to use this option).
    2. The cooling equipment shall have an EER value and an IPLV value that is a minimum of 15 percent greater than the value listed in Tables C403.3.2(1) and C403.3.2(2).
    3. For units with a total cooling capacity over 85,000 Btu/h, the system shall utilize part-load capacity control schemes that are able to modulate to a part-load capacity of 50 percent of the load or less that results in the compressor operating at the same or higher EER at part loads than at full load (e.g., minimum of two-stages of compressor unloading such as cylinder unloading, two-stage scrolls, dual tandem scrolls, but hot gas bypass is not credited as a compressor unloading system).
    4. The cooling equipment shall have an EER value and an IPLV value that is a minimum of 5 percent greater than the value listed in Tables C403.3.2(1) and C403.3.2(2).
    5. The system shall include a water economizer in lieu of air economizer. Water economizers shall meet the requirements of Sections C403.5.1 and C403.5.2 and be capable of providing the total concurrent cooling load served by the connected terminal equipment lacking airside economizer, at outside air temperatures of 50°F dry-bulb/45°F wet-bulb and below. For this calculation, all factors including solar and internal load shall be the same as those used for peak load calculations, except for the outside temperatures. The equipment shall be served by a dedicated condenser water system unless a non-dedicated condenser water system exists that can provide appropriate water temperatures during hours when water-side economizer cooling is available.
    6. For a system where all cooling equipment is subject to ASHRAE Standard 127.
    7. The cooling equipment subject to ASHRAE Standard 127 shall have an EER value and an IPLV value that is equal or greater than the value listed in Tables C403.3.2(1) and C403.3.2(2) when determined in accordance with the rating conditions in ASHRAE Standard 127 (i.e., not the rating conditions in AHRI Standard 210/240 or 340/360). This information shall be provided by an independent third party.

TABLE C403.5

EQUIPMENT EFFICIENCY PERFORMANCE EXCEPTION FOR ECONOMIZERS

CLIMATE ZONE EFFICIENCY IMPROVEMENTa
4C 64%
5B 59%
  1. If a unit is rated with an IPLV, IEER or SEER then to eliminate the required air or water economizer, the minimum cooling efficiency of the HVAC unit must be increased by the percentage shown. If the HVAC unit is only rated with a full load metric like EER or COP cooling, then these must be increased by the percentage shown.

Economizer systems shall be integrated with the mechanical cooling system and be configured to provide partial cooling even where additional mechanical cooling is required to provide the remainder of the cooling load. Controls shall not be capable of creating a false load in the mechanical cooling system by limiting or disabling the economizer or any other means, such as hot gas bypass, except at the lowest stage of mechanical cooling.

Units that include an air economizer shall comply with the following:

  1. Unit controls shall have the mechanical cooling capacity control interlocked with the air economizer controls such that the outdoor air damper is at the 100 percent open position when mechanical cooling is on and the outdoor air damper does not begin to close to prevent coil freezing due to minimum compressor run time until the leaving air temperature is less than 45°F (7°C).
  2. Direct expansion (DX) units with cooling capacity 65,000 Btu/h (19 kW) or greater of rated capacity shall comply with the following:

    1. 2.1. DX units that control the capacity of the mechanical cooling directly based on occupied space temperature shall have not fewer than two stages of mechanical cooling capacity.
    2. 2.2. Other DX units, including those that control space temperature by modulating the airflow to the space, shall be in accordance with Table C403.5.1.

TABLE C403.5.1

DX COOLING STAGE REQUIREMENTS FOR MODULATING AIRFLOW UNITS

RATING CAPACITY MINIMUM NUMBER
OF MECHANICAL
COOLING STAGES
MINIMUM
COMPRESSOR
DISPLACEMENTa
≥ 65,000 Btu/h and
< 240,000 Btu/h
3 stages ≤ 35% of full load
≥ 240,000 Btu/h 4 stages ≤ 25% of full load

For SI: 1 Btu/h = 0.2931 W

  1. For mechanical cooling stage control that does not use variable compressor displacement, the percent displacement shall be equivalent to the mechanical cooling capacity reduction evaluated at the full load rating conditions for the compressor.

HVAC system design and economizer controls shall be such that economizer operation does not increase building heating energy use during normal operation.

Exception: Economizers on VAV systems that cause zone level heating to increase due to a reduction in supply air temperature.

Air economizers shall comply with Sections C403.5.3.1 through C403.5.3.5.
Air economizer systems shall be configured to modulate outdoor air and return air dampers to provide up to 100 percent of the design supply air quantity as outdoor air for cooling.

Economizer controls and dampers shall be configured to sequence the dampers with mechanical cooling equipment and shall not be controlled by only mixed air temperature. Air economizers on systems with cooling capacity greater than 65,000 Btu/h shall be configured to provide partial cooling even when additional mechanical cooling is required to meet the remainder of the cooling load.

Exception: The use of mixed air temperature limit control shall be permitted for systems that are both controlled from space temperature (such as single zone systems) and having cooling capacity less than 65,000 Btu/h.

Air economizers shall be configured to automatically reduce outdoor air intake to the design minimum outdoor air quantity when outdoor air intake will no longer reduce cooling energy usage. High-limit shutoff control types shall be chosen from Table C403.5.3.3. High-limit shutoff control settings for these control types shall be those specified in Table C403.5.3.3.

TABLE C403.5.3.3

HIGH-LIMIT SHUTOFF CONTROL SETTING FOR AIR ECONOMIZERSb

DEVICE TYPE REQUIRED HIGH LIMIT
(Economizer Off When):
REQUIRED HIGH LIMIT FOR CYCLING FANSc
(Economizer Off When):
EQUATION DESCRIPTION EQUATION DESCRIPTION
Fixed dry bulb TOA > 75°F Outdoor air temperature
exceeds 75°F
TOA > 70°F Outdoor air temperature
exceeds 70°F
Differential dry bulb TOA > TRA Outdoor air temperature
exceeds return air temperature
TOA > (TRA - 5) Outdoor air temperature exceeds
return air temperature - 5°F
Fixed enthalpy with fixed
dry-bulb temperatures
hOA > 28 Btu/lba
or
TOA > 75°F
Outdoor air enthalpy exceeds
28 Btu/lb of dry aira or outdoor
temperature exceeds 75°F
hOA > 26 Btu/lba
or
TOA > 70°F
Outdoor air enthalpy exceeds 26
Btu/lb of dry aird or outdoor
temperature exceeds 70°F
Differential enthalpy with
fixed dry-bulb temperatures
hOA > hRA
or
TOA > 75°F
Outdoor air enthalpy exceeds
return air enthalpy or outdoor
temperature exceeds 75°F
hOA > (hRA — 2)
or
TOA > 70°F
Outdoor air enthalpy exceeds
return air enthalpy or outdoor
temperature exceeds 70°F

For SI: °C = (°F - 32) × 5/9, 1 Btu/lb = 2.33 kJ/kg, 1 foot = 304.8 mm.

  1. At altitudes substantially different than sea level, the Fixed Enthalpy limit shall be set to the enthalpy value at 75°F and 50-percent relative humidity. As an example, at approximately 6,000 feet elevation the fixed enthalpy limit is approximately 30.7 Btu/lb.
  2. Devices with selectable set point shall be capable of being set to within 2°F and 2 Btu/lb of the set point listed.
  3. Where fans cycle on only to provide heating and cooling, limits are adjusted lower to compensate for fan energy use in economizer mode.
  4. For cycling fans, at altitudes substantially different than sea level, the fixed enthalpy limit shall be set to the enthalpy value at 70°F and 50% relative humidity.
Systems shall be capable of relieving excess outdoor air during air economizer operation to prevent over-pressurizing the building. The relief air outlet shall be located to avoid recirculation into the building.
Return, exhaust/relief and outdoor air dampers used in economizers shall comply with Section C403.7.8.
Water-side economizers shall comply with Sections C403.5.4.1 and C403.5.4.2.

Water economizer systems shall be configured to cool supply air by indirect evaporation and providing up to 100 percent of the expected system cooling load at outdoor air temperatures of not greater than 50°F dry-bulb (10°C dry-bulb)/45°F wet-bulb (7.2°C wet-bulb).

Exception: Systems where dehumidification requirements cannot be met using outdoor air temperatures of 50°F dry-bulb (10°C dry-bulb)/45°F wet-bulb (7.2°C wet-bulb) and where 100 percent of the expected system cooling load at 45°F dry-bulb (7.2°C dry-bulb)/40°F wet-bulb (4.5°C wet-bulb) is met with evaporative water economizers.

Precooling coils and water-to-water heat exchangers used as part of a water economizer system shall either have a water-side pressure drop of less than 15 feet (4572 mm) of water or a secondary loop shall be created so that the coil or heat exchanger pressure drop is not seen by the circulating pumps when the system is in the normal cooling (noneconomizer) mode.

Air-cooled unitary direct-expansion units with a cooling capacity of 54,000 Btu/h or greater listed in Tables C403.3.2(1) through C403.3.2(3) that are equipped with an economizer in accordance with Section C403.5 shall include a fault detection and diagnostics (FDD) system complying with the following:

  1. The following temperature sensors shall be permanently installed to monitor system operation:

    1. 1.1. Outside air.
    2. 1.2. Supply air.
    3. 1.3. Return air.
  2. Temperature sensors shall have an accuracy of ±2°F (1.1°C) over the range of 40°F to 80°F (4°C to 26.7°C).
  3. Refrigerant pressure sensors, where used, shall have an accuracy of ±3 percent of full scale.
  4. The unit controller shall be configured to provide system status by indicating the following:

    1. 4.1. Free cooling available.
    2. 4.2. Economizer enabled.
    3. 4.3. Compressor enabled.
    4. 4.4. Heating enabled.
    5. 4.5. Mixed air low limit cycle active.
    6. 4.6. The current value of each sensor.
  5. The unit controller shall be capable of manually initiating each operating mode so that the operation of compressors, economizers, fans and the heating system can be independently tested and verified.
  6. The unit shall be configured to report faults to a fault management application available for access by day-to-day operating or service personnel or annunciated locally on zone thermostats.
  7. The FDD system shall be configured to detect the following faults:

    1. 7.1. Air temperature sensor failure/fault.
    2. 7.2. Not economizing when the unit should be economizing.
    3. 7.3. Economizing when the unit should not be economizing.
    4. 7.4. Damper not modulating.
    5. 7.5. Excess outdoor air.
Sections C403.6.1 through C403.6.10 shall apply to mechanical systems serving multiple zones.

Supply air systems serving multiple zones shall be VAV systems that have zone controls configured to reduce the volume of air that is reheated, recooled or mixed in each zone to one of the following:

  1. Twenty percent of the zone design peak supply for systems with DDC and 30 percent of the maximum supply air for other systems.
  2. Systems with DDC where Items 2.1 through 2.3 apply.

    1. 2.1. The airflow rate in the dead band between heating and cooling does not exceed 20 percent of the zone design peak supply rate or higher allowed rates under Items 3, 4 or 5 of this section.
    2. 2.2. The first stage of heating modulates the zone supply air temperature set point up to a maximum set point while the airflow is maintained at the dead band flow rate.
    3. 2.3. The second stage of heating modulates the airflow rate from the dead band flow rate up to the heating maximum flow rate that is less than 50 percent of the zone design peak supply rate.
  3. The outdoor airflow rate required to meet the minimum ventilation requirements of Chapter 4 of the International Mechanical Code.
  4. Any higher rate that can be demonstrated to reduce overall system annual energy use by offsetting reheat/recool energy losses through a reduction in outdoor air intake for the system as approved by the code official.
  5. The airflow rate required to comply with applicable codes or accreditation standards such as pressure relationships or minimum air change rates.

Exception: The following individual zones or entire air distribution systems are exempted from the requirement for VAV control:

  1. Zones or supply air systems where not less than 75 percent of the energy for reheating or for providing warm air in mixing systems is provided from a site-recovered source, including condenser heat.
  2. Systems that prevent reheating, recooling, mixing or simultaneous supply of air that has been previously cooled, either mechanically or through the use of economizer systems, and air that has been previously mechanically heated.


  3. Ventilation systems complying with Section C403.3.5, DOAS, with ventilation rates complying with Section C403.2.2.
Single duct VAV systems shall use terminal devices capable of and configured to reduce the supply of primary supply air before reheating or recooling takes place.
Systems that have one warm air duct and one cool air duct shall use terminal devices which are capable of and configured to reduce the flow from one duct to a minimum before mixing of air from the other duct takes place.

Multiple zone HVAC systems shall include controls that automatically reset the supply-air temperature in response to representative building loads, or to outdoor air temperature. The controls shall be configured to reset the supply air temperature at least 25 percent of the difference between the design supply-air temperature and the design room air temperature.

Exceptions:

  1. Systems that prevent reheating, recooling or mixing of heated and cooled supply air.


  2. Seventy-five percent (75%) of the energy for reheating is from a site-recovered source.
  3. Zones with peak supply air quantities of 300 cfm (142 L/s) or less.

Multiple-zone VAV systems with direct digital control of individual zone boxes reporting to a central control panel shall have automatic controls configured to reduce outdoor air intake flow below design rates in response to changes in system ventilation efficiency (Ev) as defined by the International Mechanical Code.

Exceptions:

  1. VAV systems with zonal transfer fans that recirculate air from other zones without directly mixing it with outdoor air, dual-duct dual-fan VAV systems, and VAV systems with fan-powered terminal units.
  2. Systems where total design exhaust airflow is more than 70 percent of total design outdoor air intake flow requirements.

Parallel-flow fan-powered VAV air terminals shall have automatic controls configured to:

  1. Turn off the terminal fan except when space heating is required or where required for ventilation.
  2. Turn on the terminal fan as the first stage of heating before the heating coil is activated.
  3. During heating for warmup or setback temperature control, either:

    1. 3.1. Operate the terminal fan and heating coil without primary air.
    2. 3.2. Reverse the terminal damper logic and provide heating from the central air handler by primary air.

Hydronic and multiple-zone HVAC system controls and equipment shall comply with this section.

For buildings with a total equipment cooling capacity of 300 tons and above, the equipment shall comply with one of the following:

  1. No one unit shall have a cooling capacity of more than 2/3 of the total installed cooling equipment capacity.
  2. The equipment shall have a variable speed drive.
  3. The equipment shall have multiple compressors.


For systems with direct digital control of individual zones reporting to the central control panel, the static pressure set point shall be reset based on the zone requiring the most pressure. In such cases, the set point is reset lower until one zone damper is nearly wide open. The direct digital controls shall be capable of monitoring zone damper positions or shall have an alternative method of indicating the need for static pressure that is configured to provide all of the following:

  1. Automatically detecting any zone that excessively drives the reset logic.
  2. Generating an alarm to the system operational location.
  3. Allowing an operator to readily remove one or more zones from the reset algorithm.

Static pressure sensors used to control VAV fans shall be located such that the controller set point is no greater than 1.2 inches w.c. (299 Pa). Where this results in one or more sensors being located downstream of major duct splits, not less than one sensor shall be located on each major branch to ensure that static pressure can be maintained in each branch.

Exception: Systems complying with Section C403.6.8.

For HVAC systems subject to the requirements of Section C403.3.5 but utilizing Exception 2 of that section, a high efficiency multiple-zone VAV system may be provided without a separate parallel DOAS when the system is designed, installed, and configured to comply with all of the following criteria (this exception shall not be used as a substitution for a DOAS per Section C406.6:

  1. Each VAV system must serve a minimum of 3,000 square feet (278.7 m2) and have a minimum of five VAV zones.
  2. The VAV systems are provided with airside economizer per Section C403.5 without exceptions.
  3. A direct-digital control (DDC) system is provided to control the VAV air handling units and associated terminal units per Section C403.4.11 regardless of sizing thresholds of Table C403.4.11.1.
  4. Multiple-zone VAV systems with a minimum outdoor air requirement of 2,500 cfm (1180 L/s) or greater shall be equipped with a device capable of measuring outdoor airflow intake under all load conditions. The system shall be capable of increasing or reducing the outdoor airflow intake based on feedback from the VAV terminal units as required by Section C403.6.5, without exceptions, and Section C403.7.1, Demand controlled ventilation.
  5. Multiple-zone VAV systems with a minimum outdoor air requirement of 2,500 cfm (1180 L/s) or greater shall be equipped with a device capable of measuring supply airflow to the VAV terminal units under all load conditions.
  6. In addition to meeting the zone isolation requirements of Section C403.2.1, a single VAV air handling unit shall not serve more than 50,000 square feet (4645 m2) unless a single floor is greater than 50,000 square feet (4645 m2) in which case the air handler is permitted to serve the entire floor.
  7. The primary maximum cooling air for the VAV terminal units serving interior cooling load driven zones shall be sized for a supply air temperature that is a minimum of 5°F greater than the supply air temperature for the exterior zones in cooling.
  8. Air terminal units with a minimum primary airflow set point of 50 percent or greater of the maximum primary airflow set point shall be sized with an inlet velocity of no greater than 900 feet per minute.
  9. Allowable fan motor horsepower shall not exceed 90 percent of the allowable HVAC fan system bhp (Option 2) as defined by Section C403.8.1.1.
  10. All fan-powered VAV terminal units (series or parallel) shall be provided with electronically commutated motors. The DDC system shall be configured to vary the speed of the motor as a function of the heating and cooling load in the space. Minimum speed shall not be greater than 66 percent of design airflow required for the greater of heating or cooling operation. Minimum speed shall be used during periods of low heating and cooling operation and ventilation-only operation.

    Exception: For series fan-powered terminal units where the volume of primary air required to deliver the ventilation requirements at minimum speed exceeds the air that would be delivered at the speed defined above, the minimum speed set point shall be configured to exceed the value required to provide the required ventilation air.

  11. Fan-powered VAV terminal units shall only be permitted at perimeter zones with an envelope heating load requirement. All other VAV terminal units shall be single duct terminal units.

    Exception: Fan powered VAV terminal units are allowed at interior spaces with an occupant load greater than or equal to 25 people per 1000 square feet of floor area (as established in Table 403.3.1.1 of the International Mechanical Code) with demand control ventilation in accordance with Section C403.7.1.

  12. When in occupied heating or in occupied dead band between heating and cooling, all fan-powered VAV terminal units shall be configured to reset the primary air supply set point, based on the VAV air handling unit outdoor air vent fraction, to the minimum ventilation airflow required per International Mechanical Code.
  13. Spaces that are larger than 150 square feet (14 m2) and with an occupant load greater than or equal to 25 people per 1000 square feet (93 m2) of floor area (as established in Table 403.3.1.1 of the International Mechanical Code) shall be provided with all of the following features:

    1. 13.1. A dedicated VAV terminal unit capable of controlling the space temperature and minimum ventilation shall be provided.
    2. 13.2. Demand control ventilation (DCV) shall be provided that utilizes a carbon dioxide sensor to reset the ventilation set point of the VAV terminal unit from the design minimum to design maximum ventilation rate as required by Chapter 4 of the International Mechanical Code.
    3. 13.3. Occupancy sensors shall be provided that are configured to reduce the minimum ventilation rate to zero and setback room temperature set points by a minimum of 5°F, for both cooling and heating, when the space is unoccupied.
  14. Dedicated data centers, computer rooms, electronic equipment rooms, telecom rooms, or other similar spaces with cooling loads greater than 5 watts/ft2 shall be provided with separate cooling systems to allow the VAV air handlers to turn off during unoccupied hours in the office space and to allow the supply air temperature reset to occur.

    Exception: The VAV air handling unit and VAV terminal units may be used for secondary backup cooling when there is a failure of the primary HVAC system.

    Additionally, computer rooms, electronic equipment rooms, telecom rooms, or other similar spaces shall be provided with airside economizer in accordance with Section C403.5 without using the exceptions to Section C403.5.

    Exception: Heat recovery per Exception 9 of Section C403.5 may be in lieu of airside economizer for the separate, independent HVAC system.

  15. HVAC system central heating or cooling plant will include a minimum of one of the following options:

    1. 15.1. VAV terminal units with hydronic heating coils connected to systems with hot water generation equipment limited to the following types of equipment: gas-fired hydronic boilers with a thermal efficiency, Et, of not less than 92 percent, airto-water heat pumps or heat recovery chillers. Hydronic heating coils shall be sized for a maximum entering hot water temperature of 120°F (48.9°C) for peak anticipated heating load conditions.
    2. 15.2. Chilled water VAV air handing units connected to systems with chilled water generation equipment with IPLV values more than 25 percent higher than the minimum part load efficiencies listed in Table C403.3.2(7), in the appropriate size category, using the same test procedures. Equipment shall be listed in the appropriate certification program to qualify. The smallest chiller or compressor in the central plant shall not exceed 20 percent of the total central plant cooling capacity or the chilled water system shall include thermal storage sized for a minimum of 20 percent of the total central cooling plant capacity.
  16. The DDC system shall include a fault detection and diagnostics (FDD) system complying with the following:

    1. 16.1. The following temperature sensors shall be permanently installed to monitor system operation:

      1. 16.1.1. Outside air.
      2. 16.1.2. Supply air.
      3. 16.1.3. Return air.
    2. 16.2. Temperature sensors shall have an accuracy of ±2°F (1.1°C) over the range of 40°F to 80°F (4°C to 26.7°C).
    3. 16.3. The VAV air handling unit controller shall be configured to provide system status by indicating the following:

      1. 16.3.1. Free cooling available.
      2. 16.3.2. Economizer enabled.
      3. 16.3.3. Compressor enabled.
      4. 16.3.4. Heating enabled.
      5. 16.3.5. Mixed air low limit cycle active.
      6. 16.3.6. The current value of each sensor.
    4. 16.4. The VAV air handling unit controller shall be capable of manually initiating each operating mode so that the operation of compressors, economizers, fans and the heating system can be independently tested and verified.
    5. 16.5. The VAV air handling unit shall be configured to report faults to a fault management application able to be accessed by day-to-day operating or service personnel or annunciated locally on zone thermostats.
    6. 16.6. The VAV terminal unit shall be configured to report if the VAV inlet valve has failed by performing the following diagnostic check at a maximum interval of once a month:

      1. 16.6.1. Command VAV terminal unit primary air inlet valve closed and verify that primary airflow goes to zero.
      2. 16.6.2. Command VAV thermal unit primary air inlet valve to design airflow and verify that unit is controlling to within 10% of design airflow.
    7. 16.7. The VAV terminal unit shall be configured to report and trend when the zone is driving the following VAV air handling unit reset sequences. The building operator shall have the capability to exclude zones used in the reset sequences from the DDC control system graphical user interface:

      1. 16.7.1. Supply air temperature set point reset to lowest supply air temperature set point for cooling operation.
      2. 16.7.2. Supply air duct static pressure set point reset for the highest duct static pressure set point allowable.
    8. 16.8. The FDD system shall be configured to detect the following faults:

      1. 16.8.1. Air temperature sensor failure/fault.
      2. 16.8.2. Not economizing when the unit should be economizing.
      3. 16.8.3. Economizing when the unit should not be economizing.
      4. 16.8.4. Outdoor air or return air damper not modulating.
      5. 16.8.5. Excess outdoor air.
      6. 16.8.6. VAV terminal unit primary air valve failure.
In addition to other requirements of Section C403 applicable to the provisions of ventilation air or the exhaust of air, ventilation and exhaust systems shall be in accordance with Sections C403.7.1 through C403.7.8.

Demand control ventilation (DCV) shall be provided for spaces larger than 500 square feet (46 m2) and with an occupant load greater than or equal to 25 people per 1000 square feet (93 m2) of floor area (as established in Table 403.3.1.1 of the International Mechanical Code) and served by systems with one or more of the following:

  1. An air-side economizer.
  2. Automatic modulating control of the outdoor air damper.
  3. A design outdoor airflow greater than 3,000 cfm (1416 L/s).

Exception: Demand control ventilation is not required for systems and spaces as follows:

  1. Systems with energy recovery complying with Section C403.7.6.1 or Section C403.3.5.1. This exception is not available for space types located within the "inclusions" column of Groups A-1 and A-3 occupancy classifications of Table C403.3.5.
  2. Multiple-zone systems without direct digital control of individual zones communicating with a central control panel.
  3. System with a design outdoor airflow less than 750 cfm (354 L/s).
  4. Spaces where the supply airflow rate minus any makeup or outgoing transfer air requirement is less than 1,200 cfm (566 L/s).
  5. Ventilation provided for process loads only.
  6. Spaces with one of the following occupancy categories (as defined by the International Mechanical Code): Correctional cells, daycare sickrooms, science labs, barbers, beauty and nail salons, and bowling alley seating.

Classrooms, gyms, auditoriums, conference rooms, and other spaces with an occupant load greater than or equal to 25 people per 1000 square feet (93 m2) of floor area (as established in Table 403.3.1.1 of the International Mechanical Code) that are larger than 500 square feet (46 m2) of floor area shall have occupancy sensor control that will either close outside air dampers, close ventilation supply dampers or turn off ventilation equipment when the space is unoccupied except where equipped with another means to automatically reduce outside air intake below design rates when spaces are partially occupied.

Exceptions:

  1. Spaces with one of the following occupancy categories (as defined by the International Mechanical Code):

    1. 1.1. Correctional cells.
    2. 1.2. Daycare sickrooms.
    3. 1.3. Science labs.
    4. 1.4. Barbers.
    5. 1.5. Beauty and nail salons.
    6. 1.6. Bowling alley seating.
  2. When the space is unoccupied during occupied building hours, a ventilation rate equal to or less than the zone outdoor airflow as defined in Section 403.3.1.1.1 of the International Mechanical Code with a zone population of zero.
Units that provide ventilation air to multiple zones and operate in conjunction with zone heating and cooling systems shall not use heating or heat recovery to warm supply air to a temperature greater than 60°F (16°C) when representative building loads or outdoor air temperature indicate that the majority of zones require cooling.
In Group R-1 buildings containing more than 50 guestrooms, each guestroom shall be provided with controls complying with the provisions of Sections C403.7.4.1 and C403.7.4.2. Card key controls comply with these requirements.
Controls shall be provided on each HVAC system that are capable of and configured to automatically raise the cooling set point and lower the heating set point by not less than 4°F (2°C) from the occupant set point within 30 minutes after the occupants have left the guestroom. The controls shall be capable of and configured to automatically raise the cooling set point to not lower than 80°F (27°C) and lower the heating set point to not higher than 60°F (16°C) when the guestroom is unrented or has been continuously unoccupied for over 16 hours or a networked guestroom control system indicates that the guestroom is unrented and the guestroom is unoccupied for more than 30 minutes. A networked guestroom control system that is capable of returning the thermostat set points to default occupied set points 60 minutes prior to the time a guestroom is scheduled to be occupied is not precluded by this section. Cooling that is capable of limiting relative humidity with a set point not lower than 65 percent relative humidity during unoccupied periods is not precluded by this section

Controls shall be provided on each HVAC system that are capable of and configured to automatically turn off the ventilation and exhaust fans within 30 minutes of the occupants leaving the guestroom, or isolation devices shall be provided to each guestroom that are capable of automatically shutting off the supply of outdoor air to and exhaust air from the guestroom.

Exception: Guestroom ventilation systems are not precluded from having an automatic daily pre-occupancy purge cycle that provides daily outdoor air ventilation during unrented periods at the design ventilation rate for 60 minutes, or at a rate and duration equivalent to one air change.

Mechanical ventilation systems for enclosed loading docks and parking garages shall be designed to exhaust the airflow rates (maximum and minimum) determined in accordance with the International Mechanical Code.

Ventilation systems shall be equipped with a control device that operates the system automatically by means of carbon monoxide detectors applied in conjunction with nitrogen dioxide detectors. Controllers shall be configured to shut off fans or modulate fan speed to 50 percent or less of design capacity, or intermittently operate fans less than 20 percent of the occupied time or as required to maintain acceptable contaminant levels in accordance with the International Mechanical Code provisions.

Gas sensor controllers used to activate the exhaust ventilation system shall stage or modulate fan speed upon detection of specified gas levels. All equipment used in sensor-controlled systems shall be designed for the specific use and installed in accordance with the manufacturer's recommendations. The system shall be arranged to operate automatically by means of carbon monoxide detectors applied in conjunction with nitrogen dioxide detectors. Garage and loading docks shall be equipped with a controller and a full array of carbon monoxide (CO) sensors set to maintain levels of carbon monoxide below 35 parts per million (ppm). Additionally, a full array of nitrogen dioxide detectors shall be connected to the controller set to maintain the nitrogen dioxide level below the OSHA standard for 8-hour exposure.

Spacing and location of the sensors shall be installed in accordance with manufacturer recommendations.

Ventilation systems for enclosed loading docks shall be activated by one of the following:

  1. Gas sensors installed in accordance with the International Mechanical Code; or
  2. Occupant detection sensors used to activate the system that detects entry into the loading area along both the vehicle and pedestrian pathways.

Ventilation systems for enclosed parking garages shall be activated by gas sensors.

Exception: A parking garage ventilation system having a total design capacity under 8,000 cfm may use occupant sensors.

Any system with minimum outside air requirements at design conditions greater than 5,000 cfm or any system where the system's supply airflow rate exceeds the value listed in Tables C403.7.6(1) and C403.7.6(2), based on the climate zone and percentage of outdoor airflow rate at design conditions, shall include an energy recovery system. Table C403.7.6(1) shall be used for all ventilation systems that operate less than 8,000 hours per year, and Table C403.7.6(2) shall be used for all ventilation systems that operate 8,000 hours or more per year. The energy recovery system shall have the capability to provide a change in the enthalpy of the outdoor air supply of not less than 50 percent of the difference between the outdoor air and return air enthalpies, at design conditions. Where an air economizer is required, the energy recovery system shall include a bypass of the energy recovery media for both the outdoor air and exhaust air or return air dampers and controls which permit operation of the air economizer as required by Section C403.5. Where a single room or space is supplied by multiple units, the aggregate ventilation (cfm) of those units shall be used in applying this requirement. The return/exhaust air stream temperature for heat recovery device selection shall be 70°F (21°C) at 30-percent relative humidity, or as calculated by the registered design professional.

Exception: An energy recovery ventilation system shall not be required in any of the following conditions:

  1. Where energy recovery systems are restricted per Section 514 of the International Mechanical Code to sensible energy, recovery shall comply with one of the following:

    1. 1.1. Kitchen exhaust systems where they comply with Section C403.7.7.1.
    2. 1.2. Laboratory fume hood systems where they comply with Exception 2 of Section C403.7.6.
    3. 1.3. Other sensible energy recovery systems with the capability to provide a change in dry-bulb temperature of the outdoor air supply of not less than 50 percent of the difference between the outdoor air and the return air dry-bulb temperatures, at design conditions.
  2. Laboratory fume hood systems that include at least one of the following features and also comply with Section C403.7.7.2:

    1. 2.1. Variable-air-volume hood exhaust and room supply systems capable of reducing exhaust and makeup air volume to 50 percent or less of design values.
    2. 2.2. Direct makeup (auxiliary) air supply equal to at least 75 percent of the exhaust rate, heated no warmer than 2°F (1.1°C) above room set point, cooled to no cooler than 3°F (1.7°C) below room set point, no humidification added, and no simultaneous heating and cooling used for dehumidification control.
  3. Systems serving spaces that are heated to less than 60°F (15.5°C) and are not cooled.
  4. Where more than 60 percent of the outdoor air heating energy is provided from site-recovered energy.
  5. Systems exhausting toxic, flammable, paint or corrosive fumes or dust.
  6. Cooling energy recovery in Climate Zones 3C, 4C, 5B, 5C, 6B, 7 and 8.
  7. Systems requiring dehumidification that employ energy recovery in series with the cooling coil.
  8. Multi-zone systems where the supply airflow rate is less than the values specified in Tables C403.7.6(1) and C403.7.6(2) for the corresponding percent of outdoor air. Where a value of NR is listed, energy recovery shall not be required.
  9. Equipment which meets the requirements of Section C403.9.2.4.
  10. Systems serving Group R-1 and R-3 dwelling or sleeping units where the largest source of air exhausted at a single location at the building exterior is less than 25 percent of the design outdoor air flow rate.

TABLE C403.7.6(1)

ENERGY RECOVERY REQUIREMENT (VENTILATION SYSTEMS OPERATING LESS THAN 8,000 HOURS PER YEAR)

CLIMATE PERCENT (%) OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE
≥ 10%
and < 20%
≥ 20%
and < 30%
≥ 30%
and < 40%
≥ 40%
and < 50%
≥ 50%
and < 60%
≥ 60%
and < 70%
≥ 70%
and < 80%
≥ 80%
DESIGN SUPPLY FAN AIRFLOW RATE (cfm)
4C, 5B NR NR NR NR NR NR ≥ 5000 ≥ 5000

NR = Not Required.

TABLE C403.7.6(2)

ENERGY RECOVERY REQUIREMENT (VENTILATION SYSTEMS OPERATING NOT LESS THAN 8,000 HOURS PER YEAR)

CLIMATE PERCENT (%) OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE
≥ 10%
and < 20%
≥ 20%
and < 30%
≥ 30%
and < 40%
≥ 40%
and < 50%
≥ 50%
and < 60%
≥ 60%
and < 70%
≥ 70%
and < 80%
≥ 80%
DESIGN SUPPLY FAN AIRFLOW RATE (cfm)
4C NR ≥ 19,500 ≥ 9000 ≥ 5000 ≥ 4000 ≥ 3000 ≥ 1500 ≥ 120
5B ≥ 2500 ≥ 2000 ≥ 1000 ≥ 500 ≥ 140 ≥ 120 ≥ 100 ≥ 80

NR = Not Required.

Replacement air introduced directly into the exhaust hood cavity shall not be greater than 10 percent of the hood exhaust airflow rate.

Where a kitchen or kitchen/dining facility has a total kitchen hood exhaust airflow rate that is greater than 2,000 cfm, each hood shall be a factory-built commercial exhaust hood listed by a nationally recognized testing laboratory in compliance with UL 710 and each hood shall have a maximum exhaust rate as specified in Table C403.7.7.1.2. Where a single hood, or hood section, is installed over appliances with different duty ratings, the maximum allowable flow rate for the hood or hood section shall be based on the requirements for the highest appliance duty rating under the hood or hood section.

Exception: Type II dishwasher exhaust hoods that have an exhaust airflow of 1000 cfm or less.

TABLE C403.7.7.1.2

MAXIMUM NET EXHAUST FLOW RATE, CFM PER LINEAR FOOT OF HOOD LENGTH

TYPE OF HOOD LIGHT-DUTY
EQUIPMENT
MEDIUM-DUTY
EQUIPMENT
HEAVY-DUTY
EQUIPMENT
EXTRA-HEAVY-DUTY
EQUIPMENT
Wall-mounted canopy 140 210 280 385
Single island 280 350 420 490
Double island (per side) 175 210 280 385
Eyebrow 175 175 NA NA
Backshelf/Pass-over 210 210 280 NA

For SI: 1 Cubic foot per minute = 0.4719 L/s; 1 foot = 304.8 mm.

NA = Not Allowed.

Where a kitchen or kitchen/dining facility has a total kitchen hood exhaust airflow rate greater than 2000 cfm, it shall comply with one of the following:

  1. Not less than 50 percent of all replacement air shall be transfer air that would otherwise be exhausted.
  2. Demand ventilation systems on not less than 75 percent of the total exhaust hood airflow that are configured to provide not less than a 50-percent reduction in exhaust and replacement air system airflow rates, including controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent and combustion products during cooking and idle.
  3. Listed energy recovery devices with a sensible heat recovery effectiveness of not less than 40 percent on not less than 50 percent of the total exhaust hood airflow.

Exceptions:

  1. Where not less than 75 percent of all the replacement air is transfer air that would otherwise be exhausted.
  2. UL 710 listed exhaust hoods that have a design maximum exhaust flow rate no greater than 250 cfm per linear foot of hood that serve kitchen or kitchen/dining facilities with a total kitchen hood exhaust airflow rate less than 5000 cfm.
  3. Type II dishwasher exhaust hoods that have an exhaust airflow of 1000 cfm or less.

Buildings with laboratory exhaust systems having a total exhaust rate greater than 5,000 cfm (2,360 L/s) shall include heat recovery systems to preconditioned replacement air from laboratory exhaust. The heat recovery system shall be capable of increasing the outside air supply temperature at design heating conditions by 25°F (13.9°C). A provision shall be made to bypass or control the heat recovery system to permit air economizer operation as required by Section C403.5.

Exceptions:

  1. Variable air volume laboratory exhaust and room supply systems configured to reduce exhaust and makeup air volume to 50 percent or less of design values; or
  2. Direct makeup (auxiliary) air supply equal to at least 75 percent of the exhaust rate, heated no warmer than 2°F (1.1°C) below room set point, cooled to no cooler than 3°F (1.7°C) above room set point, no humidification added, and no simultaneous heating and cooling used for dehumidification control; or
  3. Combined energy reduction method: VAV exhaust and room supply system configured to reduce exhaust and makeup air volumes and a heat recovery system to precondition makeup air from laboratory exhaust that when combined will produce the same energy reduction as achieved by a heat recovery system with a 50-percent sensible recovery effectiveness as required above. For calculation purposes, the heat recovery component can be assumed to include the maximum design supply airflow rate at design conditions. The combined energy reduction (QER) shall meet the following:

    where:

    QMIN = Energy recovery at 60-percent sensible effectiveness (Btu/h).

    QER = Combined energy reduction (Btu/h).

    CFMS = The maximum design supply airflow rate to conditioned spaces served by the system in cubic feet per minute.

    TR = Space return air dry-bulb at winter design conditions.

    TO = Outdoor air dry-bulb at winter design conditions.

    A = Percentage that the exhaust and makeup air volumes can be reduced from design conditions.

    B = Percentage sensible heat recovery effectiveness.

Conditioned supply air delivered to any space with mechanical exhaust shall not exceed the greater of:

  1. The supply flow required to meet the space heating or cooling load;
  2. The ventilation rate required by the authority having jurisdiction, the facility Environmental Health and Safety department, or Section C403.2.2; or
  3. The mechanical exhaust flow minus the available transfer air from conditioned spaces or return air plenums that at their closest point are within 15 feet of each other on the same floor that are not in different smoke or fire compartments. Available transfer air is that portion of outdoor ventilation air that:

    1. 3.1. Is not required to satisfy other exhaust needs;
    2. 3.2. Is not required to maintain pressurization of other spaces; and
    3. 3.3. Is transferable according to applicable codes and standards and per the International Mechanical Code.

Exceptions:

  1. Laboratories classified as biosafety level 3 or higher.
  2. Vivarium spaces.
  3. Spaces that are required by applicable codes and standards to be maintained at positive pressure relative to adjacent spaces. For spaces taking this exception, any transferable air that is not directly transferred shall be made available to the associated air-handling unit and shall be used whenever economizer or other options do not save more energy.
  4. Spaces where the demand for transfer air may exceed the available transfer airflow rate and where the spaces have a required negative pressure relationship. For spaces taking this exception, any transferable air that is not directly transferred shall be made available to the associated air-handling unit and shall be used whenever economizer or other options do not save more energy.
Mechanical openings shall be provided with shutoff dampers in accordance with Sections C403.7.8.1 through C403.7.8.4.

Outdoor air supply, exhaust openings and relief outlets and stairway and elevator hoistway shaft vents shall be provided with Class I motorized dampers. See Sections C403.10.1 and C403.10.2 for ductwork insulation requirements upstream and downstream of the shutoff damper.

Exceptions:

  1. Gravity (nonmotorized) dampers shall be permitted in lieu of motorized dampers as follows:

    1. 1.1. Relief dampers serving systems less than 5,000 cfm total supply shall be permitted in buildings less than three stories in height.
    2. 1.2. Gravity (nonmotorized) dampers where the design outdoor air intake or exhaust capacity does not exceed 400 cfm (189 L/s).
    3. 1.3. Systems serving areas which require continuous operation for 24/7 occupancy schedules.
  2. Shutoff dampers are not required in:

    1. 2.1. Combustion air intakes.
    2. 2.2. Systems serving areas which require continuous operation in animal hospitals, kennels and pounds, laboratories, and Group H, I and R occupancies.
    3. 2.3. Subduct exhaust systems or other systems that are required to operate continuously by the International Mechanical Code.
    4. 2.4. Type I grease exhaust systems or other systems where dampers are prohibited by the International Mechanical Code to be in the airstream.
    5. 2.5. Unconditioned stairwells or unconditioned elevator hoistway shafts that are only connected to unconditioned spaces.
Return air openings used for airside economizer operation shall be equipped with Class I motorized dampers.

Class I dampers shall have a maximum leakage rate of 4 cfm/ft2 (20.3 L/s × m2) at 1.0 inch water gauge (w.g.) (249 Pa) when tested in accordance with AMCA 500D and shall be labeled by an approved agency for such purpose. Gravity (nonmotorized) dampers shall have an air leakage rate not greater than 20 cfm/ft2 where not less than 24 inches (610 mm) in either dimension and 40 cfm/ft2 where less than 24 inches in either dimension. The rate of air leakage shall be determined at 1.0 inch w.g. (249 Pa) when tested in accordance with AMCA 500D for such purpose. The dampers shall be labeled by an approved agency. Gravity dampers for ventilation air intakes shall be protected from direct exposure to wind.

Exceptions:

  1. Gravity (nonmotorized) dampers are not required to be tested to verify the air leakage rating when installed in exhaust systems where the exhaust capacity does not exceed 400 cfm (189 L/s) and the gravity damper is provided with a gasketed seal.
  2. Motorized dampers on return air openings in unitary packaged equipment that have the minimum leakage rate available from the manufacturer.
Outdoor air intake, relief and exhaust shutoff dampers shall be installed with automatic controls configured to close when the systems or spaces served are not in use or during unoccupied period warm-up and setback operation, unless the systems served require outdoor or exhaust air in accordance with the International Mechanical Code or the dampers are opened to provide intentional economizer cooling. Stairway and elevator hoistway shaft vent dampers shall be installed with automatic controls configured to open upon the activation of any fire alarm initiating device of the building's fire alarm system or the interruption of power to the damper.

Fans in HVAC systems shall comply with Sections C403.8.1 through C403.8.5.1.

The airflow requirements of Section C403.8.5.1 shall apply to all fan motors. Group R occupancy exhaust fans shall also comply with Section C403.8.4.

Each HVAC system having a total fan system motor nameplate horsepower exceeding 5 hp (3.7 kW) at fan system design conditions shall not exceed the allowable fan system motor nameplate hp (Option 1) or fan system bhp (Option 2) as shown in Table C403.8.1(1). This includes supply fans, exhaust fans, return/relief fans, and fan-powered VAV air terminal units associated with systems providing heating or cooling capability. Single zone variable-air-volume systems shall comply with the constant volume fan power limitation. Zone heating and/or cooling terminal units installed in conjunction with a dedicated outdoor air system (DOAS) shall be evaluated as separate HVAC systems for allowable fan motor horsepower.

Exceptions:

  1. Hospital, vivarium and laboratory systems that utilize flow control devices on exhaust or return to maintain space pressure relationships necessary for occupant health and safety or environmental control shall be permitted to use variable volume fan power limitation.
  2. Individual exhaust fans with motor nameplate horsepower of 1 hp or less are exempt from the allowable fan motor horsepower requirements.

TABLE C403.8.1(1)

FAN POWER LIMITATION

LIMIT CONSTANT VOLUME VARIABLE VOLUME
Option 1: Fan system motor nameplate hp Allowable nameplate motor hp hp ≤ CFMS × 0.0011 hp ≤ CFMS × 0.0015
Option 2: Fan system bhp Allowable fan system bhp bhp ≤ CFMS × 0.00094 + A bhp ≤ CFMS × 0.0013 + A

For SI: 1 bhp = 735.5 W, 1 hp = 745.5 W, 1 cfm = 0.471 L/s.

where:

CFMS = The maximum design supply airflow rate to conditioned spaces served by the system in cubic feet per minute.

Hp = The maximum combined motor nameplate horsepower.

Bhp = The maximum combined fan brake horsepower.

A = Sum of [PD × CFMD / 4131]

where:

PD = Each applicable pressure drop adjustment from Table C403.8.1(2) in. w.c.

CFMD = The design airflow through each applicable device from Table C403.8.1(2) in cubic feet per minute.

TABLE C403.8.1(2)

FAN POWER LIMITATION PRESSURE DROP ADJUSTMENT

DEVICE ADJUSTMENT
Credits
Return air or exhaust system required by code or accreditation
standards to be fully ducted, or systems required to maintain air
pressure differentials between adjacent rooms
0.5 inch w.c. (2.15 inches w.c. for laboratory and vivarium systems)
Return and/or exhaust airflow control devices 0.5 inch w.c.
Exhaust filters, scrubbers, or other exhaust treatment The pressure drop of device calculated at fan system design condition
Particulate filtration credit: MERV 9 - 12 0.5 inch w.c.
Particulate filtration credit: MERV 13 - 15 0.9 inch w.c.
Particulate filtration credit: MERV 16 and greater and
electronically enhanced filters
Pressure drop calculated at 2x clean filter pressure drop at fan system
design condition
Carbon and other gas-phase air cleaners Clean filter pressure drop at fan system design condition
Biosafety cabinet Pressure drop of device at fan system design condition
Energy recovery device, other than coil runaround loop For each airstream (2.2 × energy recovery effectiveness — 0.5 inch w.c.)
Coil runaround loop 0.6 inch w.c. for each airstream
Evaporative humidifier/cooler in series with another cooling coil Pressure drop of device at fan system design conditions
Sound attenuation section (fans serving spaces with design
background noise goals below NC35)
0.15 inch w.c.
Exhaust system serving fume hoods 0.35 inch w.c.
Laboratory and vivarium exhaust systems in high-rise buildings 0.25 inch w.c./100 feet of vertical duct exceeding 75 feet
Deductions
Systems without central cooling device -0.6 inch w.c.
Systems without central heating device -0.3 inch w.c.
Systems with central electric resistance heating -0.2 inch w.c.

For SI: 1 inch w.c. = 249 Pa, 1 inch = 25.4 mm.

w.c. = water column, NC = Noise criterion.

For each fan, the selected fan motor shall be no larger than the first available motor size greater than the brake horsepower (bhp). The fan bhp shall be indicated on the design documents to allow for compliance verification by the code official.

Exceptions:

  1. For fans less than 6 bhp (4413 W), where the first available motor larger than the brake horsepower has a nameplate rating within 50 percent of the bhp, selection of the next larger nameplate motor size is allowed.
  2. For fans 6 bhp (4413 W) and larger, where the first available motor larger than the bhp has a nameplate rating within 30 percent of the bhp, selection of the next larger nameplate motor size is allowed.
  3. For fans used only in approved life safety applications such as smoke evacuation.
  4. Fans with motor nameplate horsepower less than 1 hp (746 W) are exempt from this section.

Fans shall have a fan efficiency grade (FEG) of 67 or higher based on manufacturers' certified data, as defined by AMCA 205. The total efficiency of the fan at the design point of operation shall be within 15 percentage points of the maximum total efficiency of the fan.

Exception: The following fans are not required to have a fan efficiency grade:

  1. Individual fans with a motor nameplate horsepower of 5 hp (3.7 kW) or less that are not part of a group operated as the functional equivalent of a single fan.
  2. Multiple fans in series or parallel that have a combined motor nameplate horsepower of 5 hp (3.7 kW) or less and are operated as the functional equivalent of a single fan.
  3. Fans that are part of equipment covered under Section C403.3.2.
  4. Fans included in an equipment package certified by an approved agency for air or energy performance.
  5. Powered wall/roof ventilators.
  6. Fans outside the scope of AMCA 205.
  7. Fans that are intended to operate only during emergency conditions.

The Group R occupancies of the building shall be provided with ventilation that meets the requirements of the International Mechanical Code, as applicable, or with other approved means of ventilation. Mechanical ventilation system fans with 400 cfm or less in capacity shall meet the efficacy requirements of Table C403.8.4.

Exceptions:

  1. Group R heat recovery ventilator and energy recovery ventilator fans that are less than 400 cfm.
  2. Where whole house ventilation fans are integrated with forced-air systems that are tested and listed HVAC equipment, provided they are powered by an electronically commutated motor where required by Section C405.8
  3. Domestic clothes dryer booster fans, domestic range rood exhaust fans, and domestic range booster fans that operate intermittently.

TABLE C403.8.4

GROUP R EXHAUST FAN EFFICACY

FAN LOCATION AIRFLOW
RATE
MINIMUM
(cfm)
MINIMUM
EFFICACY
(cfm/watt)
AIRFLOW
RATE
MINIMUM
(cfm)
Exhaust fan: Bathroom,
utility room, whole
house
10 2.8 < 90
Exhaust fan: Bathroom,
utility room, whole
house
90 3.5 Any
In-line (single-port and
multi-port) fans
Any 3.8 Any
Controls shall be provided for fans in accordance with Section C403.8.5.1 and as required for specific systems provided in Section C403.

Each cooling system listed in Table C403.8.5.1 shall be designed to vary the indoor fan airflow as a function of load and shall comply with the following requirements:

  1. Direct expansion (DX) and chilled water cooling units that control the capacity of the mechanical cooling directly based on space temperature shall have not fewer than two stages of fan control. Low or minimum speed shall not be greater than 66 percent of full speed. At low or minimum speed, the fan system shall draw not more than 40 percent of the fan power at full fan speed. Low or minimum speed shall be used during periods of low cooling load and ventilation-only operation.
  2. Other units including DX cooling units and chilled water units that control the space temperature by modulating the airflow to the space shall have modulating fan control. Minimum speed shall be not greater than 50 percent of full speed. At minimum speed, the fan system shall draw no more than 30 percent of the power at full fan speed. Low or minimum speed shall be used during periods of low cooling load and ventilation-only operation.
  3. Units that include an airside economizer in accordance with Section C403.5 shall have not fewer than two speeds of fan control during economizer operation.

Exceptions:

  1. Modulating fan control is not required for chilled water and evaporative cooling units with fan motors of less than 1 hp (0.746 kW) where the units are not used to provide ventilation air and the indoor fan cycles with the load.
  2. Where the volume of outdoor air required to comply with the ventilation requirements of the International Mechanical Code at low speed exceeds the air that would be delivered at the minimum speed defined in Section C403.8.5, the minimum speed shall be selected to provide the required ventilation air.

TABLE C403.8.5.1

FAN CONTROL

COOLING
SYSTEM TYPE
FAN MOTOR
SIZE
MECHANICAL
COOLING CAPACITY
DX cooling Any ≥ 42,000 Btu/h
Chilled water and
evaporative cooling
1/4 hp Any

For SI: 1 British thermal unit per hour = 0.2931 W, 1 hp = 0.746 kW.

Heat rejection equipment, including air-cooled condensers, dry coolers, open-circuit cooling towers, closed-circuit cooling towers and evaporative condensers, shall comply with this section.

Exception: Heat rejection devices where energy use is included in the equipment efficiency ratings listed in Tables C403.3.2(1)A, C403.3.2(1)B, C403.3.2(1)C, C403.3.2(2), C403.3.2(3), C403.3.2(7) and C403.3.2(9).

Heat rejection equipment shall have a minimum efficiency performance not less than values specified in Table C403.3.2(8).

Each fan powered by an individual motor or array of motors with a connected power, including the motor service factor, totaling 5 hp (3.7 kW) or more shall have controls and devices configured to automatically modulate the fan speed to control the leaving fluid temperature or condensing temperature and pressure of the heat rejection device. Fan motor power input shall be not more than 30 percent of design wattage at 50 percent of the design airflow.

Exceptions:

  1. Fans serving multiple refrigerant or fluid cooling circuits.
  2. Condenser fans serving flooded condensers.


Multiple-cell heat rejection equipment with variable speed fan drives shall be controlled to operate the maximum number of fans allowed that comply with the manufacturer's requirements for all system components and so that all fans can operate at the same fan speed required for the instantaneous cooling duty, as opposed to staged (on/off) operation. The minimum fan speed shall be the minimum allowable speed of the fan drive system in accordance with the manufacturer's recommendations.
Centrifugal fan open-circuit cooling towers with a combined rated capacity of 1,100 gpm (4164 L/m) or greater at 95°F (35°C) condenser water return, 85°F (29°C) condenser water supply, and 75°F (24°C) outdoor air wet-bulb temperature shall meet the energy efficiency requirement for axial fan open-circuit cooling towers listed in Table C403.3.2(8).
Open-circuit cooling towers used on water-cooled chiller systems that are configured with multiple- or variable-speed condenser water pumps shall be designed so that all open circuit cooling tower cells can be run in parallel with the larger of the flow that is produced by the smallest pump at its minimum expected flow rate or at 50 percent of the design flow for the cell.

Condenser heat recovery shall be installed for heating or reheating of service hot water provided the facility operates 24 hours a day, the total installed heat capacity of water-cooled systems exceeds 1,500,000 Btu/hr of heat rejection, and the design service water heating load exceeds 250,000 Btu/hr.

The required heat recovery system shall have the capacity to provide the smaller of:

  1. Sixty percent of the peak heat rejection load at design conditions; or
  2. The preheating required to raise the peak service hot water draw to 85°F (29°C).

Exceptions:

  1. Facilities that employ condenser heat recovery for space heating or reheat purposes with a heat recovery design exceeding 30 percent of the peak water-cooled condenser load at design conditions.
  2. Facilities that provide 60 percent of their service water heating from site recovered energy.

On-site steam heating systems shall have condensate water heat recovery. On-site includes a system that is located within or adjacent to one or more buildings within the boundary of a contiguous area or campus under one ownership and which serves one or more of those buildings.

Buildings using steam generated off-site with steam heating systems which do not have condensate water recovery shall have condensate water recovery.

Facilities having food service, meat or deli departments and having 500,000 Btu/h or greater of remote refrigeration condensers shall have condenser waste heat recovery from freezers and coolers and shall use the waste heat for service water heating, space heating or for dehumidification reheat. Facilities having a gross conditioned floor area of 40,000 square feet (3716 m2) or greater and 1,000,000 Btu/h or greater of remote refrigeration shall have condenser waste heat recovery from freezers and coolers and shall use the waste heat for service water heating, and either for space heating or for dehumidification reheat for maintaining low space humidity.

A water-source condenser heat recovery system meeting the requirements of Sections C403.9.2.4.1 through C403.9.2.4.4 shall be installed to serve space and ventilation heating systems in new buildings and additions meeting the following criteria:

  1. The facility operates greater than 70 hours per week.
  2. The sum of all heat rejection equipment capacity serving the new building or addition exceeds 1,500,000 Btu/h.
  3. The sum of zone minimum airflows in all zones with zone reheat coils divided by the conditioned floor area served by those systems is at least 0.45 cfm per square foot.

Exception: Systems complying with Section C403.3.5, Dedicated outdoor air systems (DOAS).

Ninety percent (90%) of the total building space and ventilation heating system design load shall be served by systems that include heat recovery chiller or water-to-water heat pump equipment capable of rejecting heat from the cooling loop to the space and ventilation heating loop as the first stage of heating.

Heat shall be recovered by the heat recovery system from 90 percent of the total building exhaust airflow. The maximum leaving air temperature of exhaust air after heat recovery shall be 55°F dry-bulb when operating at full capacity in heat recovery mode.

Exceptions:

  1. Where energy recovery systems are restricted by Section 514 of the International Mechanical Code to sensible energy, those systems shall not be included in the calculation of total building exhaust airflow.
  2. Exhaust air systems handling contaminated airstreams that are regulated by applicable codes or accreditation standards and pose a health risk to maintenance personnel to maintain heat recovery devices, those systems shall not be included in the calculation of total building exhaust airflow.
Spaces with year-round cooling loads from lights and equipment of 5 watts and greater per square foot shall be served by water-cooled equipment. Cooling loops serving the water-cooled equipment shall be served by water source heat recovery systems meeting the requirements of Section C403.9.2.4.1. If such spaces are provided with an air or water economizer, the economizer controls shall be configured with an override signal from the building automation system to disable economizer operation during heat recovery mode.

The minimum total combined capacity of heat recovery chillers or water-to-water heat pumps shall match the total combined capacity of installed equipment sized to meet the requirements of Sections C403.9.2.4.2 and C403.9.2.4.3.

Ducts, plenums, piping and other elements that are part of an HVAC system shall be constructed and insulated in accordance with Sections C403.10.1 through C403.10.3.1

Ducts, shafts and plenums conveying outdoor air from the exterior of the building to the mechanical system shall meet all air leakage and building envelope insulation requirements of Section C402, plus building envelope vapor control requirements from the International Building Code, extending continuously from the building exterior to an automatic shutoff damper or heating or cooling equipment. For the purposes of building envelope insulation requirements, duct surfaces shall be insulated with the minimum insulation values in Table C403.10.1.1. Duct surfaces included as part of the building envelope shall not be used in the calculation of maximum glazing area as described in Section C402.4.1.

Exceptions:

  1. Outdoor air ducts serving individual supply air units with less than 2,800 cfm of total supply air capacity, provided these are insulated to the minimum insulation values in Table C403.10.1.1.
  2. Unheated equipment rooms with combustion air louvers, provided they are isolated from conditioned space at sides, top and bottom of the room with R-11 nominal insulation.

TABLE C403.10.1.1

OUTDOOR AIR DUCTWORK INSULATION

DUCT SYSTEM DUCT LOCATION AND USE CLIMATE AIRFLOW MINIMUM
INSTALLED DUCT
INSULATION
R-VALUE a,b
NOTES
Outdoor air Inside conditioned space and upstream
of automatic shutoff damper
4C and 5B ≥ 2800 cfm R-16 See Section C403.10.1.1
for additional requirements
Outdoor air Inside conditioned space and
downstream of automatic shutoff damper to
HVAC unit or room
4C ≥ 2800 cfm R-8
Outdoor air Inside conditioned space and
downstream of automatic shutoff damper to
HVAC unit or room
5B ≥ 2800 cfm R-12
Outdoor air Inside conditioned space 4C and 5B < 2800 cfm R-7 See Exception 1 to Section C403.10.1.1 for additional details
  1. Insulation R-values, measured in h × ft2 × °F/Btu, are for the insulation as installed and do not include film resistance. The required minimum thicknesses do not consider water vapor transmission and possible surface condensation. Insulation resistance measured on a horizontal plane in accordance with ASTM C518 at a mean temperature of 75°F at the installed thickness.
  2. See International Mechanical Code Sections 603.12 and 604 for further details on duct insulation requirements.

All other supply and return air ducts and plenums shall be insulated with a minimum of R-6 insulation where located in unconditioned spaces, and where located outside the building with a minimum of R-8 insulation in Climate Zone 4 and R-12 insulation in Climate Zone 5. Where located within a building envelope assembly, the duct or plenum shall be separated from the building exterior or unconditioned or exempt spaces by minimum insulation value as required for exterior walls by Section C402.1.3.

Exceptions:

  1. Where located within equipment.
  2. Supply and return ductwork located in unconditioned spaces where the design temperature difference between the interior and exterior of the duct or plenum does not exceed 15°F (8°C) and insulated in accordance with Table C403.10.1.2.

Where located within conditioned space, supply ducts which convey supply air at temperatures less than 55°F (12.8°C) or greater than 105°F (41°C) shall be insulated with a minimum insulation R-value in accordance with Table C403.10.1.2.

Exception: Ductwork exposed to view within a zone that serves that zone is not required to be insulated.

Where located within conditioned space, return or exhaust air ducts that convey return or exhaust air downstream of an energy recovery media shall be insulated with a minimum R-value in accordance with Table C403.10.1.2.

All ducts, air handlers, and filter boxes shall be sealed. Joints and seams shall comply with Section 603.9 of the International Mechanical Code.

TABLE C403.10.1.2

SUPPLY, RETURN, EXHAUST, AND RELIEF AIR DUCTWORK INSULATION

DUCT SYSTEM DUCT LOCATION AND USE CLIMATE ZONE MINIMUM
INSTALLED DUCT
INSULATION
R-VALUE a,b
NOTES
Supply Air or
Return Air
Outside the building (outdoors and exposed to
weather)c
4C R-8 See Section C403.10.1.2 for details
Supply Air or
Return Air
Outside the building (outdoors and exposed to
weather)c
5B R-12 See Section C403.10.1.2 for details
Supply Air or
Return Air
Unconditioned space (enclosed but not in the
building conditioned envelope)
4C and 5B R-6 See Section C403.10.1.2 for details
Supply Air or
Return Air
Unconditioned space where the duct conveys air
that is within 15°F of the air temperature of the
surrounding unconditioned space
4C and 5B R-3.3 See IMC Section 603.12 for
additional requirements for condensation
control at ductwork
Supply Air or
Return Air
Where located in a building envelope assembly 4C and 5B R-16 Duct or plenum is separated from
building envelope assembly with the
minimum insulation value
Supply Air Within conditioned space where the supply duct
conveys air that is less than 55°F or greater than
105°F
4C and 5B R-3.3 See Section C403.10.1.2 for details
Supply Air Within conditioned space that the duct directly
serves where the supply duct conveys air that is
less than 55°F or greater than 105°F
4C and 5B None See Section C403.10.1.2 for details
Supply Air Within conditioned space where the supply duct
conveys air that is 55°F or
greater and 105°F or less
4C and 5B None
Return or Exhaust Air Within conditioned space, downstream of an
energy recovery media, upstream of an automatic
shutoff damper
4C R-8
Return or Exhaust Air Within conditioned space, downstream of an
energy recovery media, upstream of an automatic
shutoff damper
5B R-12
Relief or Exhaust Air Conditioned space and downstream of an
automatic shutoff damper
4C and 5B R-16
  1. Insulation R-values, measured in h × ft2 × °F/Btu, are for the insulation as installed and do not include film resistance. The required minimum thicknesses do not consider water vapor transmission and possible surface condensation. Insulation resistance measured on a horizontal plane in accordance with ASTM C518 at a mean temperature of 75°F at the installed thickness.
  2. See International Mechanical Code Sections 603.12 and 604 for further details on duct insulation requirements.
  3. Includes attics above insulated ceilings, parking garages and crawl spaces.
Ductwork shall be constructed and erected in accordance with the International Mechanical Code.

Longitudinal and transverse joints, seams and connections of supply and return ducts operating at a static pressure less than or equal to 2 inches water gauge (w.g.) (500 Pa) shall be securely fastened and sealed with welds, gaskets, mastics (adhesives), mastic-plus embedded-fabric systems or tapes installed in accordance with the manufacturer's installation instructions. Pressure classifications specific to the duct system shall be clearly indicated on the construction documents in accordance with the International Mechanical Code.

Exception: Continuously welded and locking-type longitudinal joints and seams on ducts operating at static pressures less than 2 inches water gauge (w.g.) (500 Pa) pressure classification.

Ducts and plenums designed to operate at a static pressure greater than 2 inches water gauge (w.g.) (500 Pa) but less than 3 inches w.g. (750 Pa) shall be insulated and sealed in accordance with Section C403.10.1. Pressure classifications specific to the duct system shall be clearly indicated on the construction documents in accordance with the International Mechanical Code.

Ducts designed to operate at static pressures equal to or greater than 3 inches water gauge (w.g.) (750 Pa) shall be insulated and sealed in accordance with Section C403.10.1. In addition, ducts and plenums shall be leak-tested in accordance with the SMACNA HVAC Air Duct Leakage Test Manual and shown to have a rate of air leakage (CL) less than or equal to 4.0 as determined in accordance with Equation 4-9.


(Equation 4-9)

where:

F = The measured leakage rate in cfm per 100 square feet of duct surface.

P = The static pressure of the test.

Documentation shall be furnished by the designer demonstrating that representative sections totaling at least 25 percent of the duct area have been tested and that all tested sections meet the requirements of this section.

All piping serving as part of a heating or cooling system shall be thermally insulated in accordance with Table C403.10.3.

Exceptions:

  1. Factory-installed piping within HVAC equipment tested and rated in accordance with a test procedure referenced by this code.
  2. Factory-installed piping within room fan-coils and unit ventilators tested and rated according to AHRI 440 (except that the sampling and variation provisions of Section 6.5 shall not apply) and 840, respectively.
  3. Piping that conveys fluids that have a design operating temperature range between 60°F (15°C) and 105°F (41°C).
  4. Piping that conveys fluids that have not been heated or cooled through the use of fossil fuels or electric power.
  5. Strainers, control valves, and balancing valves associated with piping 1 inch (25 mm) or less in diameter.
  6. Direct buried piping that conveys fluids at or below 60°F (15°C).

TABLE C403.10.3

MINIMUM PIPE INSULATION THICKNESS (thickness in inches)a, c

FLUID OPERATING
TEMPERATURE RANGE
AND USAGE (°F)
INSULATION CONDUCTIVITY NOMINAL PIPE OR TUBE SIZE (inches)
Conductivity
Btu • in./(h • ft2 • °F)b
Mean Rating
Temperature, °F
< 1 1 to < 11/2 11/2 to < 4 4 to < 8 ≥ 8
> 350 0.32 — 0.34 250 4.5 5.0 5.0 5.0 5.0
251 — 350 0.29 — 0.32 200 3.0 4.0 4.5 4.5 4.5
201 — 250 0.27 — 0.30 150 2.5 2.5 2.5 3.0 3.0
141 — 200 0.25 — 0.29 125 1.5 1.5 2.0 2.0 2.0
105 — 140 0.21 — 0.28 100 1.0 1.0 1.5 1.5 1.5
40 — 60 0.21 — 0.27 75 0.5 0.5 1.0 1.0 1.0
< 40 0.20 — 0.26 75 0.5 1.0 1.0 1.0 1.5
  1. For piping smaller than 11/2 inch (38 mm) and located in partitions within conditioned spaces, reduction of these thicknesses by 1 inch (25 mm) shall be permitted (before thickness adjustment required in footnote b) but not to a thickness less than 1 inch (25 mm).
  2. For insulation outside the stated conductivity range, the minimum thickness (T) shall be determined as follows:

    where:

    T = minimum insulation thickness.

    r = actual outside radius of pipe.

    t = insulation thickness listed in the table for applicable fluid temperature and pipe size.

    K = conductivity of alternate material at mean rating temperature indicated for the applicable fluid temperature (Btu × in/h × ft2 × °F).

    k = the upper value of the conductivity range listed in the table for the applicable fluid temperature.

  3. For direct-buried heating and hot water system piping, reduction of these thicknesses by 11/2 inches (38 mm) shall be permitted (before thickness adjustment required in footnote b but not to thicknesses less than 1 inch (25 mm).
Piping insulation exposed to weather shall be protected from damage, including that due to sunlight, moisture, equipment maintenance and wind, and shall provide shielding from solar radiation that can cause degradation of the material. Adhesive tape shall not be permitted.
Mechanical systems providing heat outside of the thermal envelope of a building shall comply with Section C403.11.1 through C403.11.3.

Systems installed to provide heat outside a building shall be radiant systems.

Such heating systems shall be controlled by an occupancy sensing device or a timer switch, so that the system is automatically deenergized when no occupants are present.

Snow- and ice-melting systems, supplied through energy service to the building, shall include automatic controls configured to shut off the system when the pavement temperature is above 50°F (10°C) and no precipitation is falling and an automatic control that is configured to shut off when the outdoor temperature is above 40°F (4°C) so that the potential for snow or ice accumulation is negligible.
Freeze protection systems, such as heat tracing of outdoor piping and heat exchangers, including self-regulating heat tracing, shall include automatic controls configured to shut off the systems when outdoor air temperatures are above 40°F (4°C) or when the conditions of the protected fluid will prevent freezing.

For HVAC systems subject to the requirements of Section C403.3.5 but utilizing Exception 2 of that section, a high-efficiency single-zone VAV system may be provided without a separate parallel DOAS when the system is designed, installed, and configured to comply with all of the following criteria (this exception shall not be used as a substitution for a DOAS per Section C406.6 or as a modification to the requirements for the Standard Reference Design in accordance with Section C407):

  1. The single-zone VAV system is provided with airside economizer in accordance with Section 403.3 without exceptions.
  2. A direct-digital control (DDC) system is provided to control the system as a single zone in accordance with Section C403.4.11 regardless of sizing thresholds of Table C403.4.11.1.
  3. Single-zone VAV systems with a minimum outdoor air requirement of 1,000 cfm (472 L/s) or greater shall be equipped with a device capable of measuring outdoor airflow intake under all load conditions. The system shall be capable of increasing or reducing the outdoor airflow intake based on Section C403.7.1, Demand controlled ventilation.
  4. Allowable fan motor horsepower shall not exceed 90 percent of the allowable HVAC fan system bhp (Option 2) as defined by Section C403.8.1.1.
  5. Each single-zone VAV system shall be designed to vary the supply fan airflow as a function of heating and cooling load and minimum fan speed shall not be more than the greater of:

    1. 5.1. 30 percent of peak design airflow; or
    2. 5.2. The required ventilation flow assuming no occupants.
  6. Spaces that are larger than 150 square feet (14 m2) and with an occupant load greater than or equal to 25 people per 1000 square feet (93 m2) of floor area (as established in Table 403.3.1.1 of the International Mechanical Code) shall be provided with all of the following features:

    1. 6.1. Demand control ventilation (DCV) shall be provided that utilizes a carbon dioxide sensor to reset the ventilation set point of the single-zone VAV system from the design minimum to design maximum ventilation rate as required by Chapter 4 of the International Mechanical Code.
    2. 6.2. Occupancy sensors shall be provided that are configured to reduce the minimum ventilation rate to zero and setback room temperature set points by a minimum of 5°F, for both cooling and heating, when the space is unoccupied.
  7. Single-zone VAV systems shall comply with one of the following options:

    1. 7.1. Single-zone VAV air handling units with a hydronic heating coil connected to systems with hot water generation equipment limited to the following types of equipment: gas-fired hydronic boilers with a thermal efficiency, Et, of not less than 92 percent, air-to-water heat pumps or heat recovery chillers. Hydronic heating coils shall be sized for a maximum entering hot water temperature of 120°F (49°C) for peak anticipated heating load conditions.
    2. 7.2. Single-zone VAV air handing units with a chilled water coil connected to systems with chilled water generation equipment with IPLV values more than 25 percent higher than the minimum part load efficiencies listed in Table C403.3.2(7), in the appropriate size category, using the same test procedures. Equipment shall be listed in the appropriate certification program to qualify. The smallest chiller or compressor in the central plant shall not exceed 20 percent of the total central plant cooling capacity or the chilled water system shall include thermal storage sized for a minimum of 20 percent of the total central cooling plant capacity.
    3. 7.3. Single-zone VAV air handling units with DX cooling, heat pump heating or gas-fired furnace shall comply with the following requirements as