ADOPTS WITH AMENDMENTS:

International Energy Conservation Code 2018 (IECC 2018)

Heads up: There are no amended sections in this chapter.
This appendix establishes criteria for demonstrating compliance using the HVAC total system performance ratio (HVAC TSPR) for systems serving office, retail, library, and education occupancies and buildings, which are subject to the requirements of Section C403.3.5 without exception. Those HVAC systems shall comply with Section C403 and this appendix as required by Section C403.1.1.

Compliance based on HVAC total system performance ratio requires that the provisions of Section C403.3 are met and the HVAC total system performance ratio of the proposed design is more than or equal to the HVAC total system performance ratio of the standard reference design. The HVAC TSPR is calculated according to the following formula:

HVAC TSPR = annual heating and cooling load/annual carbon emissions from energy consumption of the building HVAC systems

where:

Annual carbon emissions from energy consumption of the building HVAC systems = sum of the annual carbon emissions in pounds for heating, cooling, fans, energy recovery, pumps, and heat rejection calculated by multiplying site energy consumption by the carbon emission factors from Table CD407.1

Annual heating and cooling load = sum of the annual heating and cooling loads met by the building HVAC system in thousands of Btus.

TABLE CD407.1

CARBON EMISSIONS FACTORS

Type CO2e (lb/unit) Unit
Electricity 0.70 kWh
Natural gas 11.70 Therm
Oil 19.2 Gallon
Propane 10.5 Gallon
Othera 195.00 mmBtu
On-site renewable energy 0.00
  1. District energy systems may use alternative emissions factors supported by calculations approved by the code official.
The simulation program shall calculate the HVAC TSPR based only on the input for the proposed design and the requirements of this appendix. The calculation procedure shall not allow the user to directly modify the building component characteristics of the standard reference design.
Performance analysis tools meeting the applicable subsections of Appendix CD and tested according to ASHRAE Standard 140 shall be permitted to be approved. Tools are permitted to be approved based on meeting a specified threshold for a jurisdiction. The code official shall be permitted to approve tools for a specified application or limited scope.
The simulation program shall perform the simulation using hourly values of climatic data, such as temperature and humidity, using TMY3 data for the site as specified here: https://buildingenergyscore.energy.gov/resources
Documentation conforming to the provisions of this section shall be provided to the code official.

Building permit submittals shall include:

  1. A report produced by the simulation software that includes the following:

    1. 1.1. Address of the building.
    2. 1.2. Name of individual completing the compliance report.
    3. 1.3. Name and version of the compliance software tool.
    4. 1.4. The dimensions, floor heights and number of floors for each block.
    5. 1.5. By block, the U-factor, C-factor, or F-factor for each simulated opaque envelope component and the U-factor and SHGC for each fenestration component.
    6. 1.6. By block or by surface for each block, the fenestration area.
    7. 1.7. By block, a list of the HVAC equipment simulated in the proposed design including the equipment type, fuel type, equipment efficiencies and system controls.
    8. 1.8. The HVAC total system performance ratio for both the standard reference design and the proposed design.
  2. A mapping of the actual building HVAC component characteristics and those simulated in the proposed design showing how individual pieces of HVAC equipment identified above have been combined into average inputs as required by Section CD601.11 including:

    1. 2.1. Fans.
    2. 2.2. Hydronic pumps.
    3. 2.3. Air handlers.
    4. 2.4. Packaged cooling equipment.
    5. 2.5. Furnaces.
    6. 2.6. Heat pumps.
    7. 2.7. Boilers.
    8. 2.8. Chillers.
    9. 2.9. Cooling towers.
    10. 2.10. Electric resistance coils.
    11. 2.11. Condensing units.
    12. 2.12. Motors for fans and pumps.
    13. 2.13. Energy recovery devices.

      For each piece of equipment identified above include the following as applicable:

    14. 2.14. Equipment name or tag consistent with that found on the design documents.
    15. 2.15. Efficiency level.
    16. 2.16. Capacity.
    17. 2.17. Input power for fans and pumps.
  3. Floor plan of the building identifying how portions of the buildings are assigned to the simulated blocks and areas of the building that are not covered under the requirements of Section C403.1.1.
Except as specified by this appendix, the standard reference design and proposed design shall be configured and analyzed using identical methods and techniques.
The proposed design shall be configured and analyzed as specified in this section.

For the purpose of calculating the HVAC TSPR the following simple utility rate determined by the Washington State Department of Commerce shall be used:

  • $0.112/kWh of electricity
  • $1.158/therm of fossil fuel

The geometry of buildings shall be configured using one or more blocks. Each block shall define attributes including block dimensions, number of floors, floor-to-floor height and floor-to-ceiling height. Simulation software may allow the use of simplified shapes (such as rectangle, L shape, H Shape, U shape or T shape) to represent blocks. Where actual building shape does not match these pre-defined shapes, simplifications are permitted providing the following requirements are met:

  1. The conditioned floor area and volume of each block shall match the proposed design within 10 percent.
  2. The area of each exterior envelope component from Table C402.1.4 is accounted for within 10 percent of the actual design.
  3. The area of vertical fenestration and skylights is accounted for within 10 percent of the actual design.
  4. The orientation of each component in Items 2 and 3 above is accounted for within 45 degrees of the actual design.

The creation of additional blocks may be necessary to meet these requirements.

Exception: Portions of the building that are unconditioned or served by systems not covered by the requirements of Section C403.1.1 shall be omitted.

One or more blocks may be required per building based on the following restrictions:

  1. Each block can have only one occupancy type (office, library, education, or retail). Therefore, at least one single block shall be created for each unique use type.
  2. Each block can be served by only one type of HVAC system. Therefore, a single block shall be created for each unique HVAC system and use type combination. Multiple HVAC units of the same type may be represented in one block. Table CD601.11.2 provides directions for combining multiple HVAC units or components of the same type into a single block.
  3. Each block can have a single definition of floor-to-floor or floor-to-ceiling heights. Where floor heights differ by more than 2 feet (51 mm), unique blocks should be created for the floors with varying heights.
  4. Each block can include either above-grade or belowgrade floors. For buildings with both above-grade and below-grade floors, separate blocks should be created for each. For buildings with floors partially above grade and partially below grade, if the total wall area of the floor(s) in consideration is greater than or equal to 50 percent above grade, then it should be simulated as a completely above-grade block, otherwise it should be simulated as a below-grade block.
  5. Each wall on a façade of a block shall have similar vertical fenestration. The product of the proposed design U-factor times the area of windows (UA) on each façade of a given floor cannot differ by more than 15 percent of the average UA for that façade in each block. If either of these conditions are not met, additional blocks shall be created consisting of floors with similar fenestration.
  6. For a building model with multiple blocks, the blocks should be configured together to have the same adjacencies as the actual building design.
Each floor in a block shall be modeled as a single thermal zone or as five thermal zones consisting of four perimeter zones and a core zone. Belowgrade floors shall be modeled as a single thermal block. If any façade in the block is less than 45 feet (13.7 m) in length, there shall only be a single thermal zone per floor. Otherwise each floor shall be modeled with five thermal zones. A perimeter zone shall be created extending from each façade to a depth of 15 feet (4572 mm). Where facades intersect, the zone boundary shall be formed by a 45-degree angle with the two facades. The remaining area or each floor shall be modeled as a core zone with no exterior walls.
The occupancy type for each block shall be consistent with the building area type as determined in accordance with Section C405.4.2.1. Portions of the building that are building area types other than office, school (education), library, or retail shall not be included in the simulation.
The occupant density, heat gain, and schedule shall be for office, retail, library, or school as specified by ASHRAE Standard 90.1 Normative Appendix C.
Roofs will be modeled with insulation above a steel roof deck. The roof U-factor and area shall be modeled as in the proposed design. If different roof thermal properties are present in a single block, an area weighted U-factor shall be used. Roof solar absorptance shall be modeled at 0.70 and emittance at 0.90.
Walls will be modeled as steel frame construction. The U-factor and area of abovegrade walls shall be modeled as in the proposed design. If different wall constructions exist on the façade of a block, an area-weighted U-factor shall be used.
The C-factor and area of below-grade walls shall be modeled as in the proposed design. If different slab-on-grade floor constructions exist in a block, an area-weighted C-factor shall be used.
Exterior floors shall be modeled as steel frame. The U-factor and area of floors shall be modeled as in the proposed design. If different wall constructions exist in the block, an area-weighted U-factor shall be used.
The F-factor and area of slab-on-grade floors shall be modeled as in the proposed design. If different below-grade wall constructions exist in a block, an area-weighted F-factor shall be used.
The window area and area weighted U-factor and SHGC shall be modeled for each façade based the proposed design. Each exterior surface in a block must comply with Section CD601.2.1, Item 5. Windows will be combined into a single window centered on each façade based on the area and sill height input by the user.
The skylight area and area weighted U-factor and SHGC shall be modeled for each floor based the proposed design. Skylights will be combined into a single skylight centered on the roof of each zone based on the area and sill height input by the user.
Interior lighting power density shall be equal to the allowance in Table C405.4.2(1) for office, retail, library, or school. The lighting schedule shall be for office, retail, library, or school as specified by ASHRAE Standard 90.1 Normative Appendix C. The impact of lighting controls is assumed to be captured by the lighting schedule and no explicit controls shall be modeled. Exterior lighting shall not be modeled.
The miscellaneous equipment schedule and power shall be for office, retail, library, or school as specified by ASHRAE Standard 90.1 Normative Appendix C. The impact of miscellaneous equipment controls is assumed to be captured by the equipment schedule and no explicit controls shall be modeled.
Elevators shall not be modeled.
HVAC systems shall meet the requirements of Section C403, Mechanical Systems.

At a minimum, the HVAC systems shown in Table CD601.11.1 shall be supported by the simulation program.

TABLE CD601.11.1

PROPOSED BUILDING HVAC SYSTEMS SUPPORTED BY HVAC TSPR SIMULATION SOFTWARE

SYSTEM
NO.
SYSTEM NAME SYSTEM
ABBREVIATION
1 Packaged Terminal Air Conditioner PTAC
2 Packaged Terminal Air Heat Pump PTHP
3 Packaged Single Zone Gas Furnace PSZGF
4 Packaged Single Zone Heat Pump (air to
air only)
PSZHP
5 Variable Refrigerant Flow (air-cooled only) VRF
6 Four Pipe Fan Coil FPFC
7 Water Source Heat Pump WSHP
8 Ground Source Heat Pump GSHP
9 Packaged Variable Air Volume (DX cooling) PVAV
10 Variable Air Volume (hydronic cooling) VAV
11 Variable Air Volume with Fan-Powered
Terminal Units
VAVFPTU
12 Dedicated Outdoor Air System (in
conjunction with systems 1-8)
DOAS

The HVAC systems shall be modeled as in the proposed design with clarifications and simplifications as described in Table CD601.11.2. System parameters not described in the following sections shall be simulated to meet the minimum requirements of Section C403. All zones within a block shall be served by the same HVAC system type as described in Section CD601.2.1, Item 2. Where multiple system components serve a block, average values weighed by the appropriate metric as described in this section shall be used. Heat loss from ducts and pipes shall not be modeled.

Exception: Where the building permit applies to only a portion of an HVAC system and remaining components will be designed under a future building permit, the future components shall be modeled to meet, but not exceed, the requirements of Section C403.

TABLE CD601.11.2

PROPOSED BUILDING SYSTEM PARAMETERS

CATEGORY PARAMETER FIXED OR
USER DEFINED
REQUIRED APPLICABLE SYSTEMS
HVAC System Type System Type User Defined Selected from Table CD601.11.1 All
System Sizing Design Day Information Fixed 99.6% heating design and 1% dry-bulb and 1% wet-bulb
cooling design
All
Zone Coil Capacity Fixed Sizing factors used are 1.25 for heating equipment and 1.15
for cooling equipment
All
Supply Airflow Fixed Based on a supply-air-to-room-air temperature set-point
difference of 20°F
1-11
Fixed Equal to required outdoor air ventilation 12
Outdoor Ventilation Air Outdoor Ventilation Air Flow Rate Fixed As specified in ASHRAE Standard 90.1 Normative
Appendix C, adjusted for proposed DCV control
All
System Operation Space temperature Set points Fixed As specified in ASHRAE Standard 90.1 Normative
Appendix C
1-11
Fan Operation — Occupied User Defined Runs continuously during occupied hours or cycled to meet load 1-11
Fan Operation — Occupied Fixed Fan runs continuously during occupied hours 12
Fan Operation — Night Cycle Fixed Fan cycles on to meet setback temperatures 1-11
Packaged
Equipment
Efficiency
DX Cooling
Efficiency
User Defined Cooling COP without fan energy calculated in accordance
with ASHRAE Standard 90.1 Section 11.5.2c.b
1, 2, 3, 4, 5, 7, 8,
9, 11, 12
Heat Pump
Efficiency
User Defined Heating COP without fan energy calculated in accordance with ASHRAE Standard 90.1 Section 11.5.2c.c 2, 4, 5, 7, 8
Furnace Efficiency User Defined Furnace thermal efficiencyc 3, 11
Heat Pump
SupplementalHeat
Control Fixed Supplemental electric heat locked out above 40°F. Runs in conjunction with compressor between 40°F and 0°F. 2, 4
System Fan Power Design Fan Power (W/cfm) User Defined Input electric power for all fans required to operate at fan system design conditions divided by the supply airflow rate All
Single Zone System Fan Power During Dead band (W/cfm) User Defined W/cfm during dead band for VAV or multispeed single zone fans 3, 4, 5, 6, 7, 8
Variable Air
Volume Systems
Part Load Fan Controls User Defined VFD included. User specifies presence of static pressure reset. 9, 10, 11
Supply Air
Temperature Controls
User Defined If not SAT reset constant at 55°F, SAT reset results in 60°F SAT during low load conditions 9, 10, 11
Minimum Terminal Unit airflow percentage User Defined Average minimum terminal unit airflow percentage for block weighted by cfm 9, 10, 11
Terminal Unit Heating Source User Defined Electric or hydronic 9, 10, 11
Fan Powered Terminal Unit (FPTU) Type User Defined Series or parallel FPTU 11
Parallel FPTU Fan Fixed Sized for 50% peak primary air at 0.35 W/cfm 11
Series FPTU Fan Fixed Sized for 50% peak primary air at 0.35 W/cfm 11
Economizer Economizer Presence User Defined Yes or No 3, 4, 9, 10, 11
Economizer High Limit Fixed 75°F fixed dry-bulb 3, 4, 9, 10, 11
Energy Recovery Sensible Effectiveness User Defined Heat exchanger sensible effectiveness at design heating and cooling conditions 3, 4, 9, 10, 11, 12
Latent Effectiveness User Defined Heat exchanger latent effectiveness at design heating and cooling conditions 3, 4, 9, 10, 11, 12
Economizer Bypass User Defined If ERV is bypassed during economizer conditions 3, 4, 9, 10, 11, 12
Energy Recovery Temp Control User Defined If bypass, target supply air temperature 3, 4, 9, 10, 11, 12
Fan Power Reduction during Bypass (W/cfm) User Defined If ERV system include bypass, static pressure set point and variable speed fan, fan power can be reduced during economizer conditions 3, 4, 9, 10, 11,
12
DemandControlled DCV Application User Defined Percent of block floor area under DCV control 3, 4, 9, 10, 11,
12
DOAS DOAS Fan Power
W/cfm
User Defined Fan input power in W/cfm of supply airflowa 12
DOAS Supplemental
Heating and Cooling
User Defined Heating source, cooling source 12
DOAS Supply Air
Temperature Control
User Defined SAT set point if DOAS includes supplemental heating or
cooling and active temperature controls
12
Heating Plant Boiler Efficiencyd User Defined Boiler thermal efficiency 1, 6, 7, 9, 10, 11,
12
Heating Water Pump
Power (W/gpm)
User Defined Pump input W/gpm heating water flow 1, 6, 7, 9, 10, 11,
12
Heating Water Loop
Temperature
Fixed 180°F supply, 130°F return 1, 6, 9, 10,11
Chilled Water
Plant
Chiller Compressor
Type
User Defined Screw/Scroll, Centrifugal or Reciprocating 6, 10, 11, 12
Chiller Condenser
Type
User Defined Air cooled or water cooled 6, 10, 11, 12
Chiller Full Load
Efficiency
d
User Defined Chiller COP 6, 10, 11, 12
Chilled Water loop
Configuration
User Defined
Variable flow primary only, constant flow primary —
variable flow secondary
6, 10, 11, 12
Chilled Water Pump
Power (W/gpm)
User Defined Pump input W/gpm chilled water flow 6, 10, 11, 12
Chilled Water
Temperature Reset
Included
User Defined Yes/No 6, 10, 11, 12
Chilled Water
Plant
Chilled Water
Temperature Reset
Schedule (if included)
Fixed
Outdoor air reset: CHW supply temperature of 44°F at 80°F
outdoor air dry-bulb and above, CHW supply temperature of
54°F at 60°F outdoor air dry-bulb temperature and below,
ramped linearly between
6, 10, 11, 12
Condenser Water
Pump Power (W/gpm)
User Defined Pump input W/gpm condenser water flow 6, 7, 8, 9, 10, 11,
12
Condenser Water
Pump Control
User Defined Constant speed or variable speed 6, 7, 10, 11, 12
Cooling Tower
Efficiency
User Defined Gpm/hp tower fan 6, 10, 11, 12
Cooling Tower Cooling Tower Fan
Control
User Defined Constant or variable speed 6, 10, 11, 12
Cooling Tower
Approach and Range
User Defined Design cooling tower approach and range temperature 6, 10, 11, 12
Heat Pump Loop
Flow Control
Loop Flow and Heat
Pump Control Valve
Fixed Two position Valve with VFD on Pump.
Loop flow at 3 gpm/ton
7, 8
Heat Pump Loop
Temperature
Control
Fixed Set to maintain temperature between 50°F and 70°F 7
GLHP Well Field Fixed Bore depth = 250'
Bore length 200'/ton for greater of cooling or heating load
Bore spacing = 15'
Bore diameter = 5"
3/4" Polyethylene pipe
Ground and grout conductivity = 4.8 Btu × in/h × ft2 × °F
8

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, °C = [(°F) - 32]/1.8, 1 cubic foot per minute = 0.47 L/s, 1 ton = 3517 W.

  1. Where multiple fan systems serve a single block, fan power is based on weighted average using on supply air cfm.
  2. Where multiple cooling systems serve a single block, COP is based on a weighted average using cooling capacity.
  3. Where multiple heating systems serve a single block, thermal efficiency or heating COP is based on a weighted average using heating capacity.
  4. Where multiple boilers or chillers serve a heating water or chilled water loop, efficiency is based on a weighted average for using heating or cooling capacity.
The standard reference design shall be configured and analyzed as specified in this section.
Same as proposed.
Same as proposed.
Same as proposed.
Same as proposed.
Same as proposed.
Not modeled. Same as proposed.
Not modeled. Same as proposed.
Not modeled. Same as proposed.

The standard reference design HVAC equipment consists of separate space conditioning systems and dedicated outside air systems as described in Table CD602.12 for the appropriate building occupancies.

TABLE CD602.12

STANDARD REFERENCE DESIGN HVAC SYSTEMS

PARAMETER BUILDING TYPE
Large Officea Small Office and Librariesa Retail School
System Type Water-source
Heat Pump
Packaged air-source
Heat Pump
Packaged air-source
Heat Pump
Packaged air-source
Heat Pump
Fan controlb Cycle on load Cycle on load Cycle on load Cycle on load
Space condition fan power (W/cfm) 0.528 0.528 0.522 0.528
Heating/Cooling sizing factorc 1.25/1.15 1.25/1.15 1.25/1.15 1.25/1.15
Supplemental heating availability NA < 40°F < 40°F < 40°F
Modeled cooling COP (Net of fan) d 4.46 3.83 4.25 3.83
Modeled heating COP (Net of fan) d 4.61 3.81 3.57 3.81
Cooling Source DX (heat pump) DX (heat pump) DX (heat pump) DX (heat pump)
Heat source Heat Pump Heat Pump Heat Pump Heat Pump
OSA Economizere No No Yes Yes
Occupied ventilation sourcef DOAS DOAS DOAS DOAS
DOAS Fan Power
(W/cfm of outside air)
0.819 0.819 0.730 0.742
DOAS temperature control g, h Bypass Wild Bypass Bypass
ERV efficiency (sensible only) 70% 70% 70% 70%
WSHP Loop Heat Rejection Cooling Toweri NA NA NA
WSHP Loop Heat Source Gas Boiler j NA NA NA
WSHP Loop Temperature Controlk 50°F to 70°F NA NA NA
WSHP Circulation Pump W/gpml 16 NA NA NA
WSHP Loop Pumping Controlm HP Valves & pump VSD NA NA NA

NA = Not Applicable.

  1. Offices <50,000 ft2 use "Small Office" parameters; otherwise use "Large Office" parameters.
  2. Space conditioning system shall cycle on to meet heating and cooling set point schedules as specified in ASHRAE Standard 90.1 Normative Appendix C. One space conditioning system is modeled in each zone. Conditioning system fan operation is not necessary for ventilation delivery.
  3. The equipment capacities (i.e., system coil capacities) for the standard reference design building design shall be based on design day sizing runs and shall be oversized by 15% for cooling and 25% for heating.
  4. COPs shown are direct heating or cooling performance and do not include fan energy use. See ASHRAE 90.1 Appendix G (G3.1.2.1) for separation of fan from COP in packaged equipment for units where the efficiency rating includes fan energy (e.g., SEER, EER, HSPF, COP).
  5. Economizer on space conditioning systems shall be simulated when outdoor air conditions allow free cooling. Economizer high limit shall be based on differential dry-bulb control. DOAS system continues to operate during economizer mode.
  6. Airflow equal to the outside air ventilation requirements is supplied and exhausted through a separate DOAS system including a supply fan, exhaust fan, and sensible only heat exchanger. No additional heating or cooling shall be provided by the DOAS. A single DOAS system will be provided for each block. The DOAS supply and return fans shall run whenever the HVAC system is scheduled to operate in accordance with ASHRAE Standard 90.1 Normative Appendix C.
  7. "Wild" DOAS control indicates no active control of the supply air temperature leaving the DOAS system. Temperature will fluctuate based only on entering and leaving conditions and the effectiveness of ERV.
  8. "Bypass" DOAS control includes modulating dampers to bypass ERV with the intent to maintain supply air temperature at a maximum of 60°F when outside air is below 75°F. Once outside air is above 75°F bypass dampers will be fully closed.
  9. Includes a single axial fan cooling tower with variable-speed fans at 40.2 gpm/hp, sized for an approach of 10°F and a range of 10°F.
  10. Includes a single natural draft boiler with 80% Et.
  11. Loop boiler and heat rejection shall be controlled to maintain loop temperature entering heat pumps between 50°F and 70°F.
  12. Pump motor input power shall be 16 W/gpm.
  13. Loop flow shall be variable with variable speed drive pump and unit fluid flow shutoff at each heat pump when its compressor cycles off.
UpCodes Premium
Leverage the most sophisticated code compliance platform.
TRY FREE FOR TWO WEEKS VISIT PRICING