When we think about how nature can deliver a beating to our commercial roofs, we usually think about rain and wind. But in dry, hot climates, roofs face another of nature's challenges, one that can be just as devastating over time: the sun. Prolonged exposure to hot sun can take a serious toll on commercial roofs, weakening them through thermal shock and UV breakdown, and heating the building beneath them.
Below, we'll talk about what you can do to protect the most vulnerable part of your building from sun damage.
How Hot Can Your Roof Get?
The temperature of a roof under the sun depends on its material and color, as well as the environmental conditions around it. This is because of the way in which solid materials absorb the sun's rays. Sunlight enters the atmosphere as ultraviolet (UV) radiation. Your roof absorbs those UV rays and converts them to infrared radiation, which is re-emitted as heat.
We all know that darker colors absorb more of the sun's rays (that is, in fact, why they're darker), so darker colored roofs will be hotter under the sun. A black roof can be anywhere from 50 to 100 degrees hotter than the ambient temperature, meaning that, on a 90-degree day, your roof could be as hot as 190 degrees. Unpainted metal can be as much as 50 degrees hotter than the surrounding temperature, while a plain white roof can be as much as 30 degrees hotter. Specialized roof coatings, like those produced by the Topps® company, convert those oftentimes to just 2° F. over the outside air temperature.
What Areas Are Most Susceptible to Heat Damage?
Unsurprisingly, the areas of the country most affected by heat damage are the ones known for their hot, dry, sunny climates, especially Texas, New Mexico, Arizona, and Nevada. As anyone who lives in these places knows, summers here can be brutal. Averages hover in the 90s and highs can soar towards 110 degrees. Surprisingly to those outside the Midwest and South, summer temperatures often hover in those temperatures, too.
But it's not simply the heat that puts buildings in some states at risk, it's also the elevation and aridity. Because atmospheric moisture pulls UV radiation out of the air, roofs with less humidity and atmosphere between them and the sun are more exposed to UV radiation. A roof in Las Vegas on a 90-degree day will be more vulnerable, in a shorter period, than a roof in Miami on a 90-degree day, because it is absorbing so much more UV radiation.
The Effects of Extreme Heat on Your Roof
Heat exposure can damage roofs or compromise buildings in a few important ways.
WEAKEND ROOFING MATERIALS
Extreme temperatures can take their toll on roofing components, causing them to crack, curl, break down, and dry, and shorten their lifespan.
Like most materials, when roofs get hot, they expand, and when they cool down, they contract. This constant process of expansion and contraction will compromise their structural integrity, causing them to crack and disintegrate, and pulling apart seams. For metal roofs, fasteners loosen, and seams open up. This is especially a concern in climates where temperatures can fluctuate vastly and quickly between day and night. Or, where cool rains can shower onto hot roofs.
UV rays don't simply damage roofs on account of the heat they cause. They can also alter the molecular structure of some roofing materials, causing oxygen molecules to bind with hydrocarbons in the material, which can lead to brittleness and cracking. Similarly, UV rays attack the original protective finish of other roofs such as metal roofs. That’s when rust develops.
When roofs absorb heat from the sun, they emit much of that heat below them, raising building temperatures. This, in turn, requires you to use more energy to keep your building cool and comfortable.
How to Protect Your Roof from Extreme Heat
As we've shown, roofs take a beating from the sun. However, there are a few things you can do to substantially mitigate that damage.
Inspect Annually for Vulnerabilities and Trouble Spots
You should inspect your roof once a year for signs of sun damage. Check for gaps in seams, and cracking or curling of composites. Any signs of damage should be addressed immediately, and in some cases, you may consider a restoration process to bring your roof back into shape. This process is where a stitch-in-time can save nine. Wait too long, and the option expires.
Making sure that the area beneath your roof is properly ventilated can help to reduce heat and humidity build-up.
Protect Your Roof with a Heat-Resistant Coating System
The single most effective thing you can do to protect your roof from sun and heat damage is to apply a heat-resistant coating to it. These coatings reflect UV radiation away from the roof, so that your roof can't absorb it and turn it into heat.
Metal roofs with a reflective coating can be about 40% cooler than unpainted metal roofs, and the temperature of black roofs can drop as much as 50 degrees F. when a reflective coating is applied. Heat-resistant coatings can protect your roof from thermal shock and UV damage, while also slowing the aging process and lowering cooling costs.
The sun is a formidable foe to your commercial roof. Its rays can bake roofing materials, break down structural components, and cause devastating thermal shock. In places that are especially exposed to the sun, a little preparation can prevent a lot of damage. Applying a heat-resistant coating and inspecting your roof regularly are essential to its health and longevity.