Cool roofs shine as hotter cities turn down the heat

By Emma Richardson. 

ROOFCORP helps contractors navigate updated code requirements for roof coatings.  

Commercial roofs in warm climates like Los Angeles provide unique challenges, as the city is subject to elevated radiation year-round. Additionally, the long cooling season and urban heat island effect can cause roof surface temperatures to climb to 150°F or higher. The intense heat strains HVAC systems, increases energy use and shortens the lifespan of the roof.  

In response, California lawmakers created Title 24 which updates building codes to require minimum solar reflectance and thermal emittance values. Roofing products are tested for compliance by the Cool Roof Rating Council, an independent party. To make adoption more accessible, the Los Angeles Department of Water and Power now offers rebates for qualifying cool roof installations.  

A cool roof uses fluid applied membranes on top of an existing roof system. These membranes are reflective, allowing them to divert heat away from the building back into the atmosphere. This lowers the roof temperature, which in turn reduces the burden on the building’s cooling systems. A product’s cooling capacity is evaluated based on its solar reflectance, which means how much energy is reflected into the atmosphere, and its thermal emittance, meaning the product’s capacity to release heat.  

Choosing the right coating product depends on the condition of the preexisting roof, the climate in question and building owner needs. The three types of coatings available for cool roofs are acrylic, silicone and elastomeric.  

According to ROOFCORP, “Acrylic coatings are water-based, highly reflective and well-suited to high-UV environments like Southern California. They apply easily, dry quickly and deliver strong cool roof energy savings in California’s drier climate zones. Acrylic coatings perform best on roofs with adequate drainage, as prolonged ponding water can reduce their effectiveness over time.”.” 

They continue to explain that silicone coatings are more suited to roofs with poorer drainage because they degrade more slowly when exposed to water. Elastomeric coatings, a thick film flexible enough to accommodate a roof expansion and contraction, work better for older commercial roofs that may have minor movement and wear and tear.  

With more than 40 years of experience in commercial roofing, ROOFCORP is the perfect partner to help contractors navigate cool roof requirements.