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Staying Cool on Roofs… It’s Not all that Black & White

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Team Attire. Are light colors really cooler than dark colors?

The dog days of summer are upon us and in most parts of the United States, it’s hot out there. Roofing professionals have it tough sometimes. While modern technology, such as mobile apps for performing roof measurements and estimates remotely can greatly reduce the number of times a roofing contractor needs to be under the sun, they still have to get out there (and get up there) to do inspections, repairs, replacement and new construction. This often requires hours on a roof with no shade and only the protection of their work attire. So, what’s the best approach to a roofing company’s uniform color, whether a simple t-shirt or a full ensemble? What will best ward off the relentless, pounding hot rays of the sun? It’s not all black or white. In fact, it’s sort of complicated!

Let’s start to explore this conundrum by starting in the animal kingdom. Many animals inhabiting hot desert environments exhibit black fur or feathers. Common vultures are primarily black in color despite the hot climates they inhabit and the open, sun-drenched areas in which they scavenge. According to research summarized in Nature, the international journal of science, experiments prove that white feathers actually allow more penetration of short-wave radiation to the skin. More heat flows inward through white plumage than through black. Goat herds of the Sinai desert are largely dominated by black specimens, too. Scientists hypothesize that radiative heat load at skin level and the risk of heat stress can be reduced by donning dark colors. These examples sort of fly in the face of our preconception that black clothes make you hot in hot weather.

Similar reasoning about dark colors reducing heat stress has been applied to understanding why the inhabitants of the Sanai desert, the Bedouins, often wear black robes. As we all know, heat rises. Wearing black can be an effective way to keep from overheating if clothing is worn loosely as in this picture of a young Bedouin girl with her baby goats (black goats, incidentally). Black indeed absorbs heat but the space between the black cloak and the girl’s body (thanks to the loose-fitting) creates a kind of chimney effect moving the heat upwards and out through the top of the garment. This cooling principle wouldn’t work if she was wearing a form-fitting black shirt, however. Get it? Yes, maybe it seems far-fetched but black garb is, in fact, common in the traditional Bedouin wardrobe. Surely there’s a reason they sport black when the average summer temperature hovers around 97° Fahrenheit.

As you ponder this idea of a cloak serving to vent hot air like a chimney, think of basic roof design. Roofs use vents in the same way to give pent up hot air an escape outlet. If heat is trapped due to poor ventilation it would compromise living conditions in the home or building. The same is true with living things. That’s why vented clothing is popular among roofers. Loose-fitting shirts like those made by Columbia, Patagonia, and ExOfficio are designed with slits on either side and open panels to the back. Heat from outside and heat emitted from the body due to strenuous motion can escape through the slits openings in the shirts.

The question of whether white is better than black for keeping cool has a valid comparison in roofing materials. More than half of the sunlight reaching the earth is invisible to the human eye, and this invisible sunlight heats the roof. Roofing professionals may be familiar with the term thermal emittance or emissivity. In warm and sunny climates highly emissive roof products can help keep a home or building cooler by releasing the remaining heat absorbed from the sun. Although white roofing material tends to be effective in reflecting back sunlight and thus heat, colored roofing materials can also be made to reflect sunlight. According to CertainTeed a manufacturer of roof shingles, “Historically, cool roofs have been either white or some other lighter shade color. However, that dynamic has changed in recent years with the development of residential cool roof products like Landmark Solaris® and Presidential Solaris® that can achieve EnergyStar® qualified levels of solar reflectivity even in dark, rich hues.”

Play it Safe. Wear light colors!

Despite the competing theories out there, when it comes to team attire it’s probably best to play it safe and go with light colors to beat the heat in spring and summer, especially for roofing professionals who have to get that much closer to the Sun than the rest of us surface dwellers. Unless you need to rush off to herd sheep in the Sania desert after completing your roof job, don’t wear a thick black cloak. It would draw too much unwanted attention anyway. Also, you might want to ignore what the team at iRoofing decided to choose as their team t-shirt color. Keep in mind, they’re just software engineers who spend all their time inside an office kept at a constant 68°F to ensure all the office computers don’t overheat.

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