CFR 5: Reflective Membranes and the Heat Island Effect
In this installment, the GAF ProBlog continues a series called Commercial Roofing Fundamentals. As an introduction to commercial roofing, the series provides an overview of some of the key concepts that are driving industry decision-making.
Reflective Membranes and the Heat Island Effect
While reflective roofs can assist in improving energy efficiency, they may also help to lower urban heat island effects. It’s been found that reflecting the sun’s energy up and away from rooftops in urban environments can also help to lower ambient temperatures slightly.
Due to this phenomenon, some cities have mandated cool roofs while their associated states have not. As a result, it’s important to check with local building officials to find the requirements for a specific location.
How Cool are Reflective Roofs?
The examples below show membrane temperatures measured mid-summer, when the ambient air temperature was 89°F. Typically, due to its dark surface, EPDM is used as a reference non-reflective membrane.
As shown here, highly reflective roof materials such as TPO and PVC may lower roof temperatures by around 45°F. According to the EPA, installing a cool roof reduces roof temperatures, increases the comfort of occupants, and lowers energy demand. EPA recommends installing cool roofs as one of a handful of strategies to combat the Heat Island Effect, along with planting trees and vegetation, green roofs, cool pavement and smart growth strategies.