Remember back in science class when you learned about the physical properties of visible light? Namely the fact that dark surfaces tend to heat up in the sun, while lighter surfaces stay cooler? In case you need a little refresher, that happens because black colors absorb all the wavelengths of light, while white surfaces reflect them.
Given that principle, wouldn’t it make sense to ditch the dark-colored shingles on your roof? After all, they’re probably just absorbing heat and making your home’s AC work harder, right? Well, the answer is actually a little bit more complicated than that. Let’s take a look at the pros and cons of white roof surfaces, to help you decide whether or not this feature is right for you.
The Cool Roof Controversy
Certain energy professionals may recommend what’s known as a “cool roof”—a surface painted white, or made from a light-colored material—to homeowners looking to reduce their energy consumption. Generally, they reserve this recommendation for homeowners living in particularly hot climates—areas with hot days and problematic cooling costs. Those in the north may actually benefit from the additional heat gain from dark-colored roofs. So a cool roof only makes sense for homes located in hot climates, where excess solar radiation is a problem.
Cool roofs gained popularity as an innovative energy-cutting initiative sometime in the last few years. Since black surfaces absorb heat, proponents argue, they increase the urban heat island effect. That means they raise surrounding temperatures in dense metropolitan areas, which in turn increases the need for AC and other cooling measures. If roofs were painted white, on the other hand, the effect would be lessened.
However, while this measure may have some positive results for individual homes looking to save energy, in the long run, some evidence shows that if we painted all our roofs white, it might be damaging to the environment. A Stanford study, for instance, concluded that white roofs might actually have the opposite of the intended effect. Their modeling showed that an increase in white surfaces could reduce the overall cloudiness of the area, which would allow more sunlight and heat in the surrounding city. That heat, in turn, could increase global warming, reversing the energy-saving benefits of the light-colored roof.
What Are the Benefits of Light-Colored Roofs?
While researchers still need to do additional studies to decide how cool roofs affect cities en masse, if you opt for a lighter colored roof on your home, you’ll definitely see some immediate advantages. Here’s a sampling of some of those benefits:
- According to the Department of Energy, a light-colored roof may reduce surface temperatures by up to 50 degrees. The cooler your roof stays, the better its chance of lasting through its full lifespan.
- Cool roofs limit the amount of heat transferred into your home’s interiors, meaning you need less AC.
- The less AC you use, the more you save on your utilities. For instance, some homeowners have reported that their energy bills dropped by more than $100 a month after they installed a cool roof.
What Is a Cool Roof Made Out Of?
While you can always opt to install lighter colored shingles during a reroof, many homeowners also choose to retrofit their roofs using cool roof coatings. These products consist of silicone, acrylic, or polymer liquids that look and feel like a very thick paint. Unlike light-colored shingles, they are specially formulated to reflect light and heat. Typically, they contain UV resistant materials that protect your roof from sun damage. Some may even feature water protection that keeps rain from pooling on your roof’s surface.
Before painting your roof with a cool roof coating, make sure to give it a thorough cleaning with a pressure washer. This will ensure you don’t mix in dirt or grit present that will counteract the heat-reducing benefits. This is also a great time to check for loose, broken, or missing shingles, as well. Make sure to take care of any damage you see before you start to paint. You can also hire a roofer or painter to do the work for you.
When Is a Cool Roof Appropriate?
As previously mentioned, cool roofs demonstrate the greatest benefits in very hot climates, where air conditioning costs are high. However, if you live in a subtropical or other humid area, it’s possible that a cool roof could increase the presence of mold and algae, since the surface won’t be hot enough to deter this growth. In turn, that algae can cause damage to your roof over time. In colder climates, a lighter-colored roof may also collect condensation, which can also harm your roof.
All in all, it’s worth weighing the risks and benefits of a cool roof before you opt to install one on your home—because educating yourself about your energy consumption is always a cool idea.