Yes, the energy and environmental positives are still worth it.
April 4, 2024—The benefits of cool roofs are more or less universally accepted in warmer climates. However, some have questioned the merits of using them in northern regions where temperatures plummet in the fall and winter.
The reason that warm-climate usage of cool PVC (vinyl) roofing is rarely disputed stems from this proven statistic: PVC reflects at least 80% of sunlight away from its surface. This keeps the building (and its surroundings) cooler, reducing the need for air conditioning and helping to reduce haze and ozone that can negatively impact summertime air quality.
But what of cooler climates? The theory goes that, in colder temperatures, it’s desirable to have a darker roof that absorbs and retains the sun’s rays, so it will keep the building warmer.
The U.S. Environmental Protection Agency, citing work by climate scientists Ronnen Levinson and Hashem Akbari, says this so-called “heating penalty” is typically offset by summer cooling energy savings from cool roofs.
Several factors can limit or reduce the heating penalty of cool roofs in winter. The sun’s angle in winter is lower, and days are shorter than in summer, reducing the effect of cool roofs on wintertime energy use. Effective insulation and energy-efficient design can also reduce impacts. Buildings in areas with heavy and long-lasting snow cover would have the lowest heating penalty from cool roofs, since the roofs will be covered with reflective snow for most of the winter.
Simply put, whatever warming gains you might experience in colder months with a dark roof, they still won’t offset the added air conditioning expense of summer. Not to mention the environmental impact of that increased energy usage.
A large national retailer (you might recognize its familiar bullseye logo) builds stores all over the country – in northern and southern states. It uses the same roofing system, PVC roofing membrane over steel, for all of them, regardless of climate. Read the report about results collected at their various locations here: https://vinylroofs.org/wp-content/uploads/2019/10/Cool-Roofs-in-Use-in-Northern-Climates-A-Case-Study.pdf
For more information on PVC roofing, visit https://vinylroofs.org/.
