If you have a flat roof, then you may be paying too much to keep your building cool. This is because the most common roofing material for flat roofs is asphalt. While asphalt roofing is inexpensive as opposed to other roofing materials, it can increase your utility costs because it will absorb the UV rays of the sun, convert them to heat, and conduct that heat into your building. Thus, if you have an asphalt roof, you should look for a roof coating that will improve on the weaknesses of asphalt.
One of the most important things to look for in a roof coating is its color. Black roofing materials, such as asphalt tar, get their color from the fact that they absorb all or most of the sun's rays. The more of the sun's energy that a material absorbs, the hotter it gets. Asphalt roofing, whether it be shingles or flat roofing, can reach temperatures well over 150˚. White roof coatings, on the other hand, get their color by reflecting the sun's rays away from your building. Because they absorb less of the sun's energy, white roof coatings will keep your building cooler and reduce your cooling costs by up to 20%.
A second factor to consider when choosing a roof coating is how emissive it is. Emissivity is a measure of whether a material retains heat. If you have a material that holds onto the heat it absorbs, it can easily conduct that heat into the building below. Asphalt roofing, for example, can release heat into your roof deck for hours after the sun goes down. An emissive material, on the other hand, will release what heat it does absorb, and while some of that heat will go into the building below, most will go back into the atmosphere. Some materials are naturally emissive, but those that are not can be treated with an emissive coating.
If you are worried about paying to much to keep your building cool, you may be loathe to add the cost of a roof coating to your already strapped budget. On the other hand, as long as you save more money than you stand to spend on the financing costs of purchasing a low energy roof coating, you will still come out ahead. And, once you pay off your roof coating, you will be able to enjoy pure savings. Thus, an energy efficient roof coating is worth the cost.