Over the past 15 years, reflective or “cool” roofs have been promoted as an effective way for building owners to save energy and lower utility costs while reducing a building’s carbon footprint. The belief that white roofs are always the most environmentally friendly and energy-efficient choice is widely accepted. The use of white roofing is even mandated at some state and local government levels. What most people don’t realize is cool roofs are not a quick fix for climate change and may actually increase energy consumption in certain climates.
Cool roofs have contributed to energy savings in warm, southern climates by reducing air-conditioning costs during hot summer months. It makes good financial sense that cool roofs would be popular in these areas. However, in cooler, northern climates where building owners typically spend five times more money on heating buildings than cooling them, a reflective roof can actually increase energy consumption and, therefore, increase carbon emissions.
In addition, another side effect has been based on the fact that lighter has been regarded as better. It has been disregarded that these roofs stay cooler longer, even after the temperatures have dropped. Being such, the reflective roof membranes will fall below dew point and remain below dew point for longer periods of time, as compared to darker roofs, and condensation is more likely to form under the membrane. This condensation is potentially destructive to the roof system, including the deck (deteriorated wood and corroded steel), fasteners and insulation.
Obviously the intention is good by those looking to utilize a reflective roof. However, it is important to note that a reflective roof will never function the same way in a cool climate as it does in a warm climate. This isn’t to say that roofs can’t or shouldn’t be used in places with harsh winters, as long as certain design modifications are carried out (air/vapor barriers, multiple layers insulation, etc.). When this happens, these roofs can perform quite well.
As a building owner, the best way to be prepared is to be educated on the risks involved and know the potential risks. A roof system should be chosen based on building location and use, not on theory that portrays reflective roofing as a universal fix for climate change and energy savings.
