In the Professional Roofing article titled “Un-Cool Consequences of Cool Roofing,” Samir Ibrahim exposes the truth behind the misconception that reflective roofing is always an effective way for building owners to achieve energy savings and lower their total utility costs, and therefore reduce their building’s carbon footprint. To explain why white roofing is not a universal fix for climate change and achieving total energy savings, Ibrahim couples results from the most recent roofing studies with his 30+ years of roofing systems design experience. The potential side effects of white roofing, and the causes and warning signs of these side effects, and the best ways to avoid the trade-offs associated with reflective roofing are also discussed.
It is essential that roofing professionals and building owners be able to separate fact from the fiction when it comes to a one size fits all perception of ‘cool’ roofing.
The underside of a reflective membrane, the roof insulation and occasionally the roof deck (when combined with lower insulation levels or when using a single layer of insulation) are cooler than their counterparts on a dark-coloured roof. If warm moist air contacts any of these surfaces below the dew point, condensation is formed. Condensation can cause warped insulation that impacts R-value, dripping from a thawing roofing assembly, mold growth within a wet roofing assembly and loss of adhesion to the roof deck which increases the risk of a blow off. All of these issues can cause damage to a building and cost building owners money in repairs. Consultants, architects and contractors should use the information available to design roof systems that will reduce the potential liability for condensation problems. Dark coloured roofs are one way to increase the safety factor against potential condensation.
In fact, most manufacturing companies exclude any damage caused by condensation from their roofing system warranties. Manufacturers have clearly stated that they are not liable for condensation problems.
Despite the promotion of the cool roofing concept beyond where it was originally intended, it is always important to remember that different geographic areas, climates, and weather conditions require different types of roofing systems.
Not only does this belief ignore climate zone, building type and insulation level, it is also based on studies done during the late 1990’s and early 2000’s. The most recent and comprehensive studies like the Ashley-McGraw Architects, PC and CDH Energy Corp study show that reflective roofing does not save energy in certain climates.
It is essential for roofing professionals and building owners to be educated about the unintended consequences of reflective roofing like condensation, and the conditions under which it can become a problem. A roofing system should be chosen based on numerous variables including a proven track record of UV and weather resistance, life cycle analysis, geographic fit, building location and use, and less on the perception that white saves net energy everywhere.