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 2 of Section C401.2, shall comply with the following:
- 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.
- Roof solar reflectance and thermal emittance shall comply with Section C402.3.
- Fenestration in building envelope assemblies shall comply with Section C402.4.
- Air leakage of building envelope assemblies shall comply with Section C402.5.
Alternatively, where buildings have a vertical fenestration area or skylight area exceeding that allowed in Section C402.4, the building and building thermal envelope shall comply with Section C401.2, Item 1 or Section C401.2, Item 3.
Walk-in coolers, walk-in freezers, refrigerated warehouse coolers and refrigerated warehouse freezers shall comply with Section C403.2.15 or C403.2.16.
The following low-energy buildings, or portions thereof separated from the remainder of the building by building thermal envelope assemblies complying with this section, shall be exempt from the building thermal envelope provisions of Section C402.
- Those with a peak design rate of energy usage less than 3.4 Btu/h • ft2 (10.7 W/m2) or 1.0 watt per square foot (10.7 W/m2) of floor area for space conditioning purposes.
- Those that do not contain conditioned space.
- Greenhouses.
Buildings that comply with the following shall be exempt from the building thermal envelope provisions of this code:
- Are separate buildings with floor area not more than 500 square feet (50 m2).
- Are intended to house electronic equipment with installed equipment power totaling not less than 7 watts per square foot (75 W/m2) and not intended for human occupancy.
- 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).
- Have an average wall and roof U-factor less than 0.200 in Climate Zones 1 through 5 and less than 0.120 in Climate Zones 6 through 8.
- Comply with the roof solar reflectance and thermal emittance provisions for Climate Zone 1.
Building thermal envelope opaque assemblies shall meet the requirements of Sections C402.2 and C402.4 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 in framing cavities, where required, and for continuous insulation, where required, shall be not less than that specified in Table C402.1.3, based on the climate zone specified in Chapter 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. The thermal resistance or R-value of the insulating material installed continuously within or on the below-grade exterior walls of the building envelope required in accordance with Table C402.1.3 shall extend to a depth of not less than 10 feet (3048 mm) below the outside finished ground level, or to the level of the lowest floor of the conditioned space enclosed by the below grade wall, whichever is less. Opaque swinging doors shall comply with Table C402.1.4 and opaque nonswinging doors shall comply with Table C402.1.3.
TABLE C402.1.3
OPAQUE THERMAL ENVELOPE INSULATION COMPONENT MINIMUM REQUIREMENTS, R-VALUE METHODa
| CLIMATE ZONE | 1 | 2 | 3 | 4 EXCEPT MARINE | 5 AND MARINE 4 | 6 | 7 | 8 | ||||||||
| All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | |
| Roofs | ||||||||||||||||
| Insulation entirely above roof deck | R-20ci | R-25ci | R-25ci | R-25ci | R-25ci | R-25ci | R-30ci | R-30ci | R-30ci | R-30ci | R-30ci | R-30ci | R-35ci | R-35ci | R-35ci | R-35ci |
| Metal buildingsb | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-19 + R-11 LS | R-25 + R-11 LS | R-25 + R-11 LS | R-30 + R-11 LS | R-30 + R-11 LS | R-30 + R-11 LS | R-30 + R-11 LS |
| Attic and other | R-38 | R-38 | R-38 | R-38 | R-38 | R-38 | R-38 | R-38 | R-38 | R-49 | R-49 | R-49 | R-49 | R-49 | R-49 | R-49 |
| Walls, above grade | ||||||||||||||||
| Mass | R-5.7cic | R-5.7cic | R-5.7cic | R-7.6ci | R-7.6ci | R-9.5ci | R-9.5ci | R-11.4ci | R-11.4ci | R-13.3ci | R-13.3ci | R-15.2ci | R-15.2ci | R-15.2ci | R-25ci | R-25ci |
| Metal building | R-13+ R-6.5ci | R-13 + R-6.5ci | R13 + R-6.5ci | R-13 + R-13ci | R-13 + R-6.5ci | R-13 + R-13ci | R-13 + R-13ci | R-13 + R-13ci | R-13 + R-13ci | R-13 + R-13ci | R-13 + R-13ci | R-13 + R-13ci | R-13 + R-13ci | R-13 + R-19.5ci | R-13 + R-13ci | R-13 + R-19.5ci |
| Metal framed | R-13 + R-5ci | R-13 + R-5ci | R-13 + R-5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-7.5ci | R-13 + R-15.6ci | R-13 + R-7.5ci | R-13 + R17.5ci |
| Wood framed and other | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-3.8ci or R-20 | R-13 + R-7.5ci or R-20 + R-3.8ci | R-13 + R-7.5ci or R-20 + R-3.8ci | R-13 + R-7.5ci or R-20 + R-3.8ci | R-13 + R-7.5ci or R-20 + R-3.8ci | R-13 + R-7.5ci or R-20 + R-3.8ci | R13 + R-15.6ci or R-20 + R-10ci | R13 + R-15.6ci or R-20 + R-10ci |
| Walls, below grade | ||||||||||||||||
| Below-grade walld | NR | NR | NR | NR | NR | NR | R-7.5ci | R-7.5ci | R-7.5ci | R-7.5ci | R-7.5ci | R-7.5ci | R-10ci | R-10ci | R-10ci | R-12.5ci |
| Floors | ||||||||||||||||
| Masse | NR | NR | R-6.3ci | R-8.3ci | R-10ci | R-10ci | R-10ci | R-10.4ci | R-10ci | R-12.5ci | R-12.5ci | R-12.5ci | R-15ci | R-16.7ci | R-15ci | R-16.7ci |
| Joist/framing | NR | NR | R-30 | R-30 | R-30 | R-30 | R-30 | R-30 | R-30 | R-30 | R-30 | R-30f | R-30f | R-30f | R-30f | R-30f |
| Slab-on-grade floors | ||||||||||||||||
| Unheated slabs | NR | NR | NR | NR | NR | NR | R-10 for 24″ below | R-10 for 24″ below | R-10 for 24″ below | R-10 for 24″ below | R-10 for 24″ below | R-15 for 24″ below | R-15 for 24″ below | R-15 for 24″ below | R-15 for 24″ below | R-20 for 24″ below |
| Heated slabs | R-7.5 for 12″ below | R-7.5 for 12″ below | R-7.5 for 12″ below | R-7.5 for 12″ below | R-10 for 24″ below | R-10 for 24″ below | R-15 for 24″ below | R-15 for 24″ below | R-15 for 36″ below | R-15 for 36″ below | R-15 for 36″ below | R-20 for 48″ below | R-20 for 24″ below | R-20 for 48″ below | R-20 for 48″ below | R-20 for 48″ below |
| Opaque doors | ||||||||||||||||
| Nonswinging | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | R-4.75 | 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.
- Assembly descriptions can be found in ANSI/ASHRAE/IESNA Appendix A.
- Where using R-value compliance method, a thermal spacer block shall be provided, otherwise use the U-factor compliance method in Table C402.1.4.
- R-5.7ci is allowed to be substituted with concrete block walls complying with ASTM C 90, ungrouted or partially grouted at 32 inches or less on center vertically and 48 inches or less on center horizontally, with ungrouted cores filled with materials having a maximum thermal conductivity of 0.44 Btu-in/h-f2 °F.
- Where heated slabs are below grade, below-grade walls shall comply with the exterior insulation requirements for heated slabs.
“Mass floors” shall include floors weighing not less than:
- 35 pounds per square foot of floor surface area; or
- 25 pounds per square foot of floor surface area where the material weight is not more than 120 pounds per cubic foot.
- Steel floor joist systems shall be insulated to R-38.
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 C-factor for the below-grade exterior walls of the building envelope, as required in accordance with Table C402.1.4, shall extend to a depth of 10 feet (3048 mm) below the outside finished ground level, or to the level of the lowest floor, whichever is less. Opaque swinging doors shall comply with Table C402.1.4 and opaque non-swinging doors shall comply with Table C402.1.3.
TABLE C402.1.4
OPAQUE THERMAL ENVELOPE ASSEMBLY MAXIMUM REQUIREMENTS, U-FACTOR METHODa, b
| CLIMATE ZONE | 1 | 2 | 3 | 4 EXCEPT MARINE | 5 AND MARINE 4 | 6 | 7 | 8 | ||||||||
| All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | All other | Group R | |
| Roofs | ||||||||||||||||
| Insulation entirely above roof deck | U-0.048 | U-0.039 | U-0.039 | U-0.039 | U-0.039 | U-0.039 | U-0.032 | U-0.032 | U-0.032 | U-0.032 | U-0.032 | U-0.032 | U-0.028 | U-0.028 | U-0.028 | U-0.028 |
| Metal buildings | U-0.044 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.031 | U-0.031 | U-0.029 | U-0.029 | U-0.029 | U-0.029 |
| Attic and other | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.021 | U-0.021 | U-0.021 | U-0.021 | U-0.021 | U-0.021 | U-0.021 |
| Walls, above grade | ||||||||||||||||
| Mass | U-0.151 | U-0.151 | U-0.151 | U-0.123 | U-0.123 | U-0.104 | U-0.104 | U-0.090 | U-0.090 | U-0.080 | U-0.080 | U-0.071 | U-0.071 | U-0.061 | U-0.061 | U-0.061 |
| Metal building | U-0.079 | U-0.079 | U-0.079 | U-0.079 | U-0.079 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.039 | U-0.052 | U-0.039 |
| Metal framed | U-0.077 | U-0.077 | U-0.077 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.057 | U-0.064 | U-0.052 | U-0.045 | U-0.045 |
| Wood framed and other c | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.051 | U-0.051 | U-0.051 | U-0.051 | U-0.036 | U-0.036 |
| Walls, below grade | ||||||||||||||||
| Below-grade wallc | C-1.140e | C-1.140e | C-1.140e | C-1.140e | C-1.140e | C-1.140e | C-0.119 | C-0.119 | C-0.119 | C-0.119 | C-0.119 | C-0.119 | C-0.092 | C-0.092 | C-0.092 | C-0.092 |
| Floors | ||||||||||||||||
| Massd | U-0.322e | U-0.322e | U-0.107 | U-0.087 | U-0.076 | U-0.076 | U-0.076 | U-0.074 | U-0.074 | U-0.064 | U-0.064 | U-0.057 | U-0.055 | U-0.051 | U-0.055 | U-0.051 |
| Joist/framing | U-0.066e | U-0.066e | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 |
| Slab-on-grade floors | ||||||||||||||||
| Unheated slabs | F-0.73e | F-0.73e | F-0.73e | F-0.73e | F-0.73e | F-0.73e | F-0.54 | F-0.54 | F-0.54 | F-0.54 | F-0.54 | F-0.52 | F-0.40 | F-0.40 | F-0.40 | F-0.40 |
| Heated slabsf | F-0.70 | F-0.70 | F-0.70 | F-0.70 | F-0.70 | F-0.70 | F-0.65 | F-0.65 | F-0.65 | F-0.65 | F-0.58 | F-0.58 | F-0.55 | F-0.55 | F-0.55 | F-0.55 |
| Opaque doors | ||||||||||||||||
| Swinging | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 |
For SI: 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.
- Use of Opaque assembly U-factors, C-factors, and F-factors from ANSI/ASHRAE/IESNA 90.1 Appendix A shall be permitted, provided the construction, excluding the cladding system on walls, complies with the appropriate construction details from ANSI/ASHRAE/ISNEA 90.1 Appendix A.
- 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 to or subtracted from the original tested design.
- Where heated slabs are below grade, below-grade walls shall comply with the F-factor requirements for heated slabs.
“Mass floors” shall include floors weighing not less than:
- 35 pounds per square foot of floor surface area; or
- 25 pounds per square foot of floor surface area where the material weight is not more than 120 pounds per cubic foot.
- These C-, F- and U-factors are based on assemblies that are not required to contain insulation.
- Evidence of compliance with the F -factors indicated in the table for heated slabs shall be demonstrated by the application of the unheated slab F-factors and R-values derived from ASHRAE 90.1 Appendix A.
U-factors of walls with cold-formed steel studs shall be permitted to be determined in accordance with 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 |
Building envelope values and fenestration areas determined in accordance with Equation 4-2 shall be permitted in lieu of compliance with the U-, F- and C-factors in Tables C402.1.3 and C402.1.4 and the maximum allowable fenestration areas in Section C402.4.1.
where:
| A | = | Sum of the (UA Dif) values for each distinct assembly type of the building thermal envelope, other than slabs on grade and below-grade walls. | ||
| UA Dif | = | UA Proposed - UA Table. | ||
| UA Proposed | = | Proposed U-value • Area. | ||
| UA Table | = | (U-factor from Table C402.1.3 or Table C402.1.4) • Area. | ||
| B | = | Sum of the (FL Dif) values for each distinct slab-on- grade perimeter condition of the building thermal envelope. | ||
| FL Dif | = | FL Proposed - FL Table. | ||
| FL Proposed | = | Proposed F-value • Perimeter length. | ||
| FL Table | = | (F-factor specified in Table C402.1.4) • Perimeter length. | ||
| C | = | Sum of the (CA Dif) values for each distinct below- grade wall assembly type of the building thermal envelope. | ||
| CA Dif | = | CA Proposed - CA Table. | ||
| CA Proposed | = | Proposed C-value • Area. | ||
| CA Table | = | (Maximum allowable C-factor specified in Table C402.1.4) • Area. | ||
Where the proposed vertical glazing area is less than or equal to the maximum vertical glazing area allowed by Section C402.4.1, the value of D (Excess Vertical Glazing Value) shall be zero. Otherwise:
| D | = | (DA • UV) - (DA • U Wall), but not less than zero. | ||
| DA | = | (Proposed Vertical Glazing Area) - (Vertical Glazing Area allowed by Section C402.4.1). | ||
| UA Wall | = | Sum of the (UA Proposed) values for each opaque assembly of the exterior wall. | ||
| U Wall | = | Area-weighted average U-value of all above-grade wall assemblies. | ||
| UAV | = | Sum of the (UA Proposed) values for each vertical glazing assembly. | ||
| UV | = | UAV/total vertical glazing area. | ||
Where the proposed skylight area is less than or equal to the skylight area allowed by Section C402.4.1, the value of E (Excess Skylight Value) shall be zero. Otherwise:
| E | = | (EA • US) - (EA • U Roof), but not less than zero. | ||
| EA | = | (Proposed Skylight Area) - (Allowable Skylight Area as specified in Section C402.4.1). | ||
| U Roof | = | Area-weighted average U-value of all roof assemblies. | ||
| UAS | = | Sum of the (UA Proposed) values for each skylight assembly. | ||
| US | = | UAS/total skylight area. | ||
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. Skylight curbs shall be insulated to the level of roofs with insulation entirely above deck or R-5, whichever is less.
Exceptions:
- 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.
- Where tapered insulation is used with insulation entirely above deck, the R-value where the insulation thickness varies 1 inch (25 mm) or less from the minimum thickness of tapered insulation shall comply with the R-value specified in Table C402.1.3.
- Unit skylight curbs included as a component of a skylight listed and labeled in accordance with NFRC 100 shall not be required to be insulated.
Insulation installed on a suspended ceiling with removable ceiling tiles shall not be considered part of the minimum thermal resistance of the roof insulation.
The minimum thermal resistance (R-value) of materials installed in the wall cavity between 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 shall not be used in determining compliance with Table C402.1.3.
“Mass walls” shall include walls:
- Weighing not less than 35 psf (170 kg/m2) of wall surface area.
- Weighing not less than 25 psf (120 kg/m2) of wall surface area where the material weight is not more than 120 pcf (1900 kg/m3).
- Having a heat capacity exceeding 7 Btu/ft2 • °F (144 kJ/m2 • K).
- Having 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 thermal properties (component R-values or assembly U-, C- 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.
Exceptions:
- 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 to the top of all perimeter floor framing or floor assembly members.
- Insulation applied to the underside of concrete floor slabs shall be permitted an airspace 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 not less than of 10 inches (254 mm) of soil.
Exception: Where the slab-on-grade floor is greater than 24 inches (61 mm) below the finished exterior grade, perimeter insulation is not required.
Radiant heating system panels, and their associated components that are installed in interior or exterior assemblies shall be insulated with a minimum of R-3.5 (0.62 m2/K • W) 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 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 C402.2.5.
Low-sloped roofs directly above cooled conditioned spaces in Climate Zones 1, 2 and 3 shall comply with one or more of the options in Table C402.3.
Exceptions: The following roofs and portions of roofs are exempt from the requirements of Table C402.3:
Portions of the roof that include or are covered by the following:
- 1.1. Photovoltaic systems or components.
- 1.2. Solar air or water-heating systems or components.
- 1.3. Roof gardens or landscaped roofs.
- 1.4. Above-roof decks or walkways.
- 1.5. Skylights.
- 1.6. HVAC systems and components, and other opaque objects mounted above the roof.
- Portions of the roof shaded during the peak sun angle on the summer solstice by permanent features of the building or by permanent features of adjacent buildings.
- Portions of roofs that are ballasted with a minimum stone ballast of 17 pounds per square foot [74 kg/m2] or 23 psf [117 kg/m2] pavers.
- Roofs where not less than 75 percent of the roof area complies with one or more of the exceptions to this section.
TABLE C402.3
MINIMUM ROOF REFLECTANCE AND EMITTANCE OPTIONSa
| Three-year aged solar reflectanceb of 0.55 and 3-year aged thermal emittancec of 0.75 | |
| Three-year-aged solar reflectance indexd of 64 | |
- The use of area-weighted averages to comply with these requirements shall be permitted. Materials lacking 3-year-aged tested values for either solar reflectance or thermal emittance shall be assigned both a 3-year-aged solar reflectance in accordance with Section C402.3.1 and a 3-year-aged thermal emittance of 0.90.
- Aged solar reflectance tested in accordance with ASTM C 1549, ASTM E 903 or ASTM E 1918 or CRRC-1 Standard.
- Aged thermal emittance tested in accordance with ASTM C 1371 or ASTM E 408 or CRRC-1 Standard.
- Solar reflectance index (SRI) shall be determined in accordance with ASTM E 1980 using a convection coefficient of 2.1 Btu/h • ft2 • °F (12W/m2 • K). Calculation of aged SRI shall be based on aged tested values of solar reflectance and thermal emittance.
Where an aged solar reflectance required by Section C402.3 is not available, it shall be determined in accordance with Equation 4-3.
where:
| Raged | = | The aged solar reflectance. |
| Rinitial | = | The initial solar reflectance determined in accordance with CRRC-1 Standard. |
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 C405.2.3.1.
TABLE C402.4
BUILDING ENVELOPE FENESTRATION MAXIMUM U-FACTOR AND SHGC REQUIREMENTS
| CLIMATE ZONE | 1 | 2 | 3 | 4 EXCEPT MARINE | 5 AND MARINE 4 | 6 | 7 | 8 | ||||||||
| Vertical fenestration | ||||||||||||||||
| U-factor | ||||||||||||||||
| Fixed fenestration | 0.50 | 0.50 | 0.46 | 0.38 | 0.38 | 0.36 | 0.29 | 0.29 | ||||||||
| Operable fenestration | 0.65 | 0.65 | 0.60 | 0.45 | 0.45 | 0.43 | 0.37 | 0.37 | ||||||||
| Entrance doors | 1.10 | 0.83 | 0.77 | 0.77 | 0.77 | 0.77 | 0.77 | 0.77 | ||||||||
| SHGC | ||||||||||||||||
| Orientationa | SEW | N | SEW | N | SEW | N | SEW | N | SEW | N | SEW | N | SEW | N | SEW | N |
| PF < 0.2 | 0.25 | 0.33 | 0.25 | 0.33 | 0.25 | 0.33 | 0.40 | 0.53 | 0.40 | 0.53 | 0.40 | 0.53 | 0.45 | NR | 0.45 | N |
| 0.2 ≤ PF < 0.5 | 0.30 | 0.37 | 0.30 | 0.37 | 0.30 | 0.37 | 0.48 | 0.58 | 0.48 | 0.58 | 0.48 | 0.58 | NR | NR | NR | NR |
| PF ≥ 0.5 | 0.40 | 0.40 | 0.40 | 0.40 | 0.40 | 0.40 | 0.64 | 0.64 | 0.64 | 0.64 | 0.64 | 0.64 | NR | NR | NR | NR |
| Skylights | ||||||||||||||||
| U-factor | 0.75 | 0.65 | 0.55 | 0.50 | 0.50 | 0.50 | 0.50 | 0.50 | ||||||||
| SHGC | 0.35 | 0.35 | 0.35 | 0.40 | 0.40 | 0.40 | NR | NR | ||||||||
- “N” indicates vertical fenestration oriented within 45 degrees of true north. “SEW” indicates orientations other than “N.” For buildings in the southern hemisphere, reverse south and north. Buildings located at less than 23.5 degrees latitude shall use SEW for all orientations.
In Climate Zones 1 through 6, not more than 40 percent of the gross above-grade wall area shall be permitted to be vertical fenestration, provided all of the following requirements are met:
- In buildings not greater than two stories above grade, not less than 50 percent of the net floor area is within a daylight zone.
- In buildings three or more stories above grade, not less than 25 percent of the net floor area is within a daylight zone.
- Daylight responsive controls complying with Section C405.2.3.1 are installed in daylight zones.
- Visible transmittance (VT) of vertical fenestration is not less than 1.1 times solar heat gain coefficient (SHGC).
Exception: Fenestration that is outside the scope of NFRC 200 is not required to comply with Item 4.
In an enclosed space greater than 2,500 square feet (232 m2) in floor area, directly under a roof with not less than 75 percent of the ceiling area with a ceiling height greater than 15 feet (4572 mm), and used as an office, lobby, atrium, concourse, corridor, storage space, gymnasium/exercise center, convention center, automotive service area, space where manufacturing occurs, nonrefrigerated warehouse, retail store, distribution/sorting area, transportation depot or workshop, the total daylight zone under skylights shall be not less than half the floor area and shall provide one of the following:
- A minimum skylight area to daylight zone under skylights 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.
- A minimum skylight effective aperture of at least 1 percent, determined in accordance with Equation 4-4.
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. |
| Light well depth | = | Measure vertically from the underside of the lowest point of the skylight glazing to the ceiling plane under the skylight. |
Exception: Skylights above daylight zones of enclosed spaces are not required in:
- Buildings in Climate Zones 6 through 8.
- Spaces where the designed general lighting power densities are less than 0.5 W/ft2 (5.4 W/m2).
- 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.
- Spaces where the daylight zone under rooftop monitors is greater than 50 percent of the enclosed space floor area.
- Spaces where the total area minus the area of daylight zones adjacent to vertical fenestration is less than 2,500 square feet (232 m2), and where the lighting is controlled according to Section C405.2.3.
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 D 1003.
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.
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 4-5.
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.
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.
Exception: Air barriers are not required in buildings located in Climate Zone 2B.
The continuous air barrier shall be constructed to comply with the following:
- The air barrier shall be continuous for all assemblies that are the thermal envelope of the building and across the joints and assemblies.
- 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.
- Penetrations of the air barrier shall be caulked, gasketed or otherwise sealed in a manner compatible with the construction materials and location. Joints and seals associated with penetrations shall be sealed in the same manner or taped or covered with moisture vapor-permeable wrapping material. Sealing materials shall be appropriate to the construction materials being sealed and shall be securely installed around the penetration 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.
- Recessed lighting fixtures shall comply with Section C402.5.8. Where similar objects are installed that penetrate the air barrier, provisions shall be made to maintain the integrity of the air barrier.
Materials with an air permeability not greater than 0.004 cfm/ft2 (0.02 L/s • m2) under a pressure differential of 0.3 inch water gauge (75 Pa) when tested in accordance with ASTM E 2178 shall comply with this section. Materials in Items 1 through 16 shall be deemed to comply with this section, provided joints are sealed and materials are installed as air barriers in accordance with the manufacturer’s instructions.
- Plywood with a thickness of not less than 3/8 inch (10 mm).
- Oriented strand board having a thickness of not less than 3/8 inch (10 mm).
- Extruded polystyrene insulation board having a thickness of not less than 1/2 inch (12.7 mm).
- Foil-back polyisocyanurate insulation board having a thickness of not less than 1/2 inch (12.7 mm).
- Closed-cell spray foam a minimum density of 1.5 pcf (2.4 kg/m3) having a thickness of not less than 11/2 inches (38 mm).
- Open-cell spray foam with a density between 0.4 and 1.5 pcf (0.6 and 2.4 kg/m3) and having a thickness of not less than 4.5 inches (113 mm).
- Exterior or interior gypsum board having a thickness of not less than 1/2 inch (12.7 mm).
- Cement board having a thickness of not less than 1/2 inch (12.7 mm).
- Built-up roofing membrane.
- Modified bituminous roof membrane.
- Fully adhered single-ply roof membrane.
- A Portland cement/sand parge, or gypsum plaster having a thickness of not less than 5/8 inch (15.9 mm).
- Cast-in-place and precast concrete.
- Fully grouted concrete block masonry.
- Sheet steel or aluminum.
- Solid or hollow masonry constructed of clay or shale masonry units.
Assemblies of materials and components with an average air leakage not greater than 0.04 cfm/ft2 (0.2 L/s • m2) under a pressure differential of 0.3 inch of water gauge (w.g.)(75 Pa) when tested in accordance with ASTM E 2357, ASTM E 1677 or ASTM E 283 shall comply with this section. Assemblies listed in Items 1 through 3 shall be deemed to comply, provided joints are sealed and the requirements of Section C402.5.1.1 are met.
- Concrete masonry walls coated with either one application of block filler or two applications of a paint or sealer coating.
- Masonry walls constructed of clay or shale masonry units with a nominal width of 4 inches (102 mm) or more.
- A Portland cement/sand parge, stucco or plaster not less than 1/2 inch (12.7 mm) in thickness.
The air leakage of fenestration assemblies shall meet the provisions of Table C402.5.2. Testing shall be in accordance with the applicable reference test standard in Table C402.5.2 by an accredited, independent testing laboratory and labeled by the manufacturer.
Exceptions:
- Field-fabricated fenestration assemblies that are sealed in accordance with Section C402.5.1.
- Fenestration in buildings that comply with the testing alternative of Section C402.5 are not required to meet the air leakage requirements in Table C402.5.2.
TABLE C402.5.2
MAXIMUM AIR LEAKAGE RATE FOR FENESTRATION ASSEMBLIES
| FENESTRATION ASSEMBLY | MAXIMUM RATE (CFM/FT2) | TEST PROCEDURE |
| Windows | 0.20 a | AAMA/WDMA/CSA 101/I.S.2/A440 or NFRC 400 |
| Sliding doors | 0.20 a | |
| Swinging doors | 0.20 a | |
| Skylights – with condensation weepage openings | 0.30 | |
| Skylights – all other | 0.20 a | |
| Curtain walls | 0.06 | NFRC 400 or ASTM E 283 at 1.57 psf (75 Pa) |
| Storefront glazing | 0.06 | |
| Commercial glazed swinging entrance doors | 1.00 | |
| Revolving doors | 1.00 | |
| Garage doors | 0.40 | ANSI/DASMA 105, NFRC 400, or ASTM E 283 at 1.57 psf(75 Pa) |
| Rolling doors | 1.00 | |
| High-speed doors | 1.30 |
For SI: 1 cubic foot per minute = 0.47 L/s, 1 square foot = 0.093 m2.
- The maximum rate for windows, sliding and swinging doors, and skylights is permitted to be 0.3 cfm per square foot of fenestration or door area when tested in accordance with AAMA/WDMA/CSA101/I.S.2/A440 at 6.24 psf (300 Pa).
In Climate Zones 3 through 8, where open combustion air ducts provide combustion air to open combustion space conditioning fuel-burning appliances, the appliances and combustion air openings shall be located outside of the building thermal envelope or enclosed in a room isolated from inside the thermal envelope. Such rooms shall be sealed and insulated in accordance with the envelope requirements of Table C402.1.3 or C402.1.4, where the walls, floors and ceilings shall meet the minimum of the below-grade wall R-value requirement. The door into the room shall be fully gasketed, and any water lines and ducts in the room insulated in accordance with Section C403. The combustion air duct shall be insulated, where it passes through conditioned space, to a minimum of R-8.
Exceptions:
- Direct vent appliances with both intake and exhaust pipes installed continuous to the outside.
- 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 not within the scope of the fenestration assemblies covered by Section C402.5.2 shall be gasketed, weatherstripped or sealed.
Exceptions:
- Door openings required to comply with Section 716 or 716.5 of the International Building Code.
- Doors and door openings required to comply with UL 1784 by the International Building Code.
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.
Exceptions: Vestibules are not required for the following:
- Buildings in Climate Zones 1 and 2.
- Doors not intended to be used by the public, such as doors to mechanical or electrical equipment rooms, or intended solely for employee use.
- Doors opening directly from a sleeping unit or dwelling unit.
- Doors that open directly from a space less than 3,000 square feet (298 m2) in area.
- Revolving doors.
- Doors used primarily to facilitate vehicular movement or material handling and adjacent personnel doors.
- 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.
Recessed luminaires installed in the building thermal envelope shall be all of the following:
- IC-rated.
- Labeled as having an air leakage rate of not more 2.0 cfm (0.944 L/s) when tested in accordance with ASTM E 283 at a 1.57 psf (75 Pa) pressure differential.
- Sealed with a gasket or caulk between the housing and interior wall or ceiling covering.