Last month the City of Los Angeles passed amendments to its building code requiring ‘cool roofs’ on all new and refurbished homes. The amendment requires that roofing materials have a minimum solar reflectance, maintained for at least 3 years of aging, and a Cool Roof Rating Council initial or aged thermal emittance of at least a specified value. Exceptions are provided for roof repair, roof partial replacement, and building-integrated photovoltaics.

The Los Angeles ngo Climate Resolve, which has been pushing for this initiative, claims that the ordinance will help Los Angeles:

• become more resilient and healthier on hot days
• reduce heat related hospitalizations
• improve air quality by reducing the formation of ozone
• inoculate against power outages
• reduce homeowners electricity bills
• reduce greenhouse gas emissions
• provide a more pleasant home environment

A cool roof uses material that naturally reflects sunlight as opposed to absorbing the sun’s radiant energy. The result can be more than 50°F cooler on the surface of the roof during a hot summer day and can cool the interiors of buildings by several degrees Fahrenheit, reducing chances of heat-related injuries or deaths.

Climate Resolve states that the ordinance will not be an economic burden for homeowners because the City has expanded its cool roof incentives, making the difference between a cool and hot roof cost neutral.

Details of the City Council action can be found in the staff report at http://clkrep.lacity.org/onlinedocs/2013/13-1214_rpt_atty_12-12-13n.pdf . More about Climate Resolve’s cool roofs campaign is available at http://climateresolve.org/hot-city-cool-roofs/ . Details on cool roof rated products can be found at http://coolroofs.org/product-rating/overview . Note that ratings provide numeric values only, not pass-fail standards, and that these relate only to roofing products in the US market. Ratings may not apply to Canadian products. For reference when interpreting the Cool Roof Rating Council’s ratings, Los Angeles requirements are minimum thermal emittance of 0.75 and minimum 3-year aged solar reflectance of 0.63 for flat and low slope roofs and 0.20 for roofs with a higher slope.