Absolutely. When it comes to heat-reflective low-slope roofs, just because a membrane looks white doesn’t mean it’s highly energy-efficient. Infra-red radiation (heat) penetrates all the way into a membrane, so even if the top surface is reflecting visible light, the roof could still be absorbing heat into the building.
Many membranes look white only because the top layer or coating is white. If the lower layers of a membrane are grey or black, it can still absorb a lot of heat. This raises costs for cooling in summer, and these costs are never recovered during the winter heating season because of reduced sunlight duration and angle.
The Cool Roof Rating Council (CRRC) independently measures how efficiently a roofing material reflects heat and emits heat. Setting each system’s Solar Reflectivity Index (SRI). A black rubber roof has an SRI of 2 while a white PVC roof will have an SRI as high as 111.
The SRI scores for some roofs that look white can go as low as 30 for a white granular-surfaced modified asphalt roof. That’s less than a third of the energy rating of the white PVC roof.
If reduced cooling costs are important to you, it will pay to consider the SRI when designing or replacing a roof system. For details and explanation please call us and we will help.
