A Polarizing Perspective? Cool Roofs in Northern Climates
White roof or black roof? This simple question has perplexed and even polarized segments of the construction community for much of the last decade. In 2009, then Secretary of Energy Stephen Chu tried to settle the issue by recommending that the roofs of all “flat topped” buildings be painted white, and all new buildings be constructed with reflective roofs.
Chu’s approach only intensified the debate. Much of the ensuing disagreement has focused not so much on whether white roofs should be used at all, but where they should be used, and where dark membranes are a better choice. There is consensus in the roofing community that reflective membranes can save energy in climates zones 1-3. But disagreement persists about the appropriate approach in Zone 4 and north.
ERA’s members manufacture and market both black and white roofing membranes. Their interest is in ensuring that their current and potential customers, as well as code-setting and regulatory groups, have accurate information about their products. With this overriding goal in mind, ERA embarked upon a wide-ranging study of the available research on the choice of black or white roofing membrane. Our focus was on the use of “cool” or reflective roofing in northern, cool-to-cold climates; our goal has been to distill the best science-based thinking on the subject and provide some much-needed clarity in the black-vs-white debate.
The result of our efforts is an exhaustive review of the available research, most of it completed during the last decade. Two issues stand out in study after study: condensation problems with white roofing in cold climates, as well as higher energy costs during the winter months that offset any economies realized during warmer summer months.
You can find the entire White Paper on “Cool Roofs in Northern Climates: Energy Efficiency and Moisture Performance Implications” on this website at http://www.epdmroofs.org/news/articles/2017/01/02/white-paper-cool-roofs-in-northern-climates
The White Paper offers important guidance about the choice of roofing membrane color. Beyond that, it underscores the fact that each building presents a unique set of challenges and options related to the durability of the roofing membrane, the method of attaching the membrane, the choice of insulation, and the use of air barriers and/or vapor retarders. Given the complexity of roofing design, a one-size-fits-all mandate is not a viable approach: only a roofing professional has the expertise to make correct design choices, including that of roofing membrane color, for any individual building project.