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5.5.3.1.1 Roof Solar Reflectance and Thermal Emittance
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Roofs in Climate Zones 0 through 3 shall have one of the following:
- A minimum three-year-aged solar reflectance of 0.55 and a minimum three-year-aged thermal emittance of 0.75 when tested in accordance with CRRC-1 Standard.
- A minimum Solar Reflectance Index of 64 when determined in accordance with the Solar Reflectance Index method in ASTM El980 using a convection coefficient of 2.1 Btu/h•ft2•°F, based on three-year-aged solar reflectance and three-year-aged thermal emittance tested in accordance with CRRC-1 Standard.
- Increased roof insulation levels found in Table 5.5.3.1.1.
Table 5.5.3.1.1 Increased Roof Insulation Levels
| Roofs | Nonresidential | Residential | ||
|---|---|---|---|---|
| Opaque Elements | Assembly Maximum | Insulation Min. R-Value | Assembly Maximum | Insulation Min. R-Value |
| Climate Zone 0 | ||||
| Insulation entirely above deck | U-0.027 | R-36 c.i. | U-0.027 | R-36 c.i. |
| Metal buildings | U-0.028 | R-35 | ||
| Climate Zones 1 to 3 | ||||
| Insulation entirely above deck | U-0.030 | R-33 c.i. | U-0.029 | R-34 c.i. |
| Metal buildings | U-0.028 | R-35 | ||
The values for three-year-aged solar reflectance and three-year-aged thermal emittance shall be determined by a laboratory accredited by a nationally recognized accreditation organization and shall be labeled and certified by the manufacturer.
Exceptions to 5.5.3.1.1
- Ballasted roofs with a minimum stone ballast of 17 lb/ft2 or 23 lb/ft2 pavers.
- Vegetative roof systems that contain a minimum thickness of 2.5 in. of growing medium and covering a minimum of 75% of the roof area with durable plantings.
- Roofs where a minimum of 75% of the roof area
- is shaded during the peak sun angle on June 21 by permanent components or features of the building;
- is covered by offset photovoltaic arrays, building-integrated photovoltaic arrays, or solar air or water collectors; or
- is permitted to be interpolated using a combination of 1 and 2 above.
- Steep-sloped roofs.
- Low-sloped metal building roofs in Climate Zones 2 and 3.
- Roofs over ventilated attics, roofs over semiheated spaces, or roofs over conditioned spaces that are not cooled spaces.
- Asphaltic membranes in Climate Zones 2 and 3.
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