Why Are Roofs Not White

The environmental benefits of exposed membrane low slope roofing systems with high solar reflectance and thermal emittance have been established by the cool roof rating council crrc lawrence berkeley national laboratory and others.

Why are roofs not white.

The question is by just how much. Pv cells are dark and so do not reflect much solar radiation into space. Painting roofs white has been like changing lightbulbs one of the well cited easy ways out of climate change. By reflecting more light and heat back to the atmosphere a white roof should act.

Solar panels cool daytime temperatures in a way similar to increasing albedo via white roofs according to a study by scientists at the university of new south wales. The sunlight that bounces off white roofs doesn t all fly out into space. White roofs seem like no brainers in warm climates like phoenix las vegas and miami where they can keep air conditioning bills in check year round. White roofs will stay white.

Unless routine maintenance and power washing is completed a white roof will often dull and look dirty. Because what is the cheapest sloped roofing material. When not drained properly membrane soiling loss of reflectivity and algae growth are likely on reflective roofs. But that is because their business is to capture that energy and convert it into low carbon electricity.

Shingles which are naturally black. States like california even now mandate white roofs on commercial buildings. There s much more to selecting a roof membrane than color but it s not a black and white decision. This problem is especially likely for under insulated cool roofs in cooler climates.

In cooler climates think detroit or toronto the issue is less straightforward. While white roofs may shave electric bills in hot summer months studies suggest they increase winter heating bills. Even white shingles aren t truly white. False white roofs attract and retain dirt easily which quickly diminishes some of the positive aspects of the membrane.