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 C402.2, 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.
- 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 C402.2.
- Unit skylight curbs included as a component of an NFRC 100 rated assembly shall not be required to be insulated.
Low-sloped roofs, with a slope less than 2 units vertical in 12 horizontal, directly above cooled conditioned spaces in Climate Zones 1, 2, and 3 shall comply with one or more of the options in Table C402.2.1.1.
1. Portions of roofs that include or are covered by:
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.
1.6. HVAC systems, components, and other opaque objects mounted above the roof.
2. Portions of roofs shaded during the peak sun angle on the summer solstice by permanent features of the building, or by permanent features of adjacent buildings.
3. Portions of roofs that are ballasted with a minimum stone ballast of 17 pounds per square foot (psf) (74 kg/m2) or 23 psf (117 kg/m2) pavers.
4. Roofs where a minimum of 75 percent of the roof area meets a minimum of one of the exceptions above.
MINIMUM ROOF REFLECTANCE AND EMITTANCE OPTIONSa
|Three-year aged solar reflectanceb of 0.55 and three-year aged |
thermal emittancec of 0.75
|Initial solar reflectanceb of 0.70 and initial thermal emittancec of |
|Three-year-aged solar reflectance indexd of 64|
|Initial solar reflectance indexd of 82|