Over the last few years, cool roofs have begun to make their way into the building codes throughout the country.
Cool roofs made its first appearance in building codes in California’s Title 24 in 2005, requiring initial solar reflectance (SR) of 0.70 and initial thermal emittance (TE) of 0.75 on low-sloped commercial buildings throughout the state. Since then, Title 24 has slowly cranked up the reflectivity requirements. The latest round of revisions, for the 2013 code, require an aged SR of 0.63 and an aged TE of 0.75, or an aged solar reflectance index (SRI) of 75. California’s Title 24 now also requires cool roofs on low-sloped residential buildings and on steep-sloped residential and commercial buildings throughout most of the state (SR of 0.2 and TE of 0.75 or SRI of 16).
Both IECC 2012 and ASHRAE 90.1 require cool roofs (aged solar reflectance of 0.55 and aged thermal emittance of 0.75) on low-sloped commercial buildings in climate zones 1 through 3. ASHRAE 90.2 has required cool roofs (initial solar reflectance of 0.65 and initial thermal emittance of 0.70) on low-sloped residential buildings in climate zones 1 through 3 since 2007.
The national above-code standards, or stretch-codes, all also have cool roof requirements.
– ASHRAE 189.1 requires an initial SRI of 78 on low-sloped commercial roofs and an initial SRI of 29 on steep-sloped commercial roofs in climate zones 1 through 3. ASHRAE 189.1 also allows compliance through ENERGY STAR.
– ENERGY STAR defines cool roofs as having an aged SR of 0.50. ENERGY STAR currently does not require a TE rating for its products.
– In order to receive a credit for cool roofs within the LEED system, a building must have an SRI of 78 covering 75% of its roof area, if it has a low-sloped roof, and have an SRI of 29 covering 75% of its roof area, if it is a steep-sloped roof. LEED also has a sustainable sites credit which encourages the use of reflective pavements and hardscapes, as well as the use of vegetation.
– IgCC – The International Green Construction Code has a Heat Island Mitigation section in Chapter 4 (Site Development and Land Use). This section requires that at least 50% of the hard scape be either reflective, shaded or have permeable pavement. It also requires that at least 75% of both steep-sloped and low-sloped roofs meet minimum solar reflectance standards or employ vegetative roofs. The reflectivity requirements are as follows: a minimum aged SRI of 60 for low sloped roofs and a minimum aged SRI of 25 for low-sloped roofs.
Several cities have developed their own cool roof requirements.
– As of January 2012, New York City has required cool roofs on all new and replacement low-sloped roofs. Roofs must have an initial SR of 0.7, an initial TE of 0.75 or an SRI of 78.
– In 2010, Philadelphia passed a law requiring new roofs, or additions on existing buildings to comply with ENERGY STAR’s cool roof ratings.
– In 2013, Washington DC adopted cool roofs into its building code, using the requirements from IECC 2012 (which cover climate zones 1 through 3).
– New York City, Philadelphia, and Washington DC are all in climate zone 4.
Cool roofs certainly have a strong foothold in the national model codes, the national stretch codes and volunteer standards, and even in a growing number of city codes. At GCCA, we are excited it help expand their scope, as appropriate, and expect that the next few years will be exciting ones for cool roofs.
Tags: building efficiency, California