Henry Staggs, RRO
May 15, 2020
Arizona gets hot! Just in case you didn't already know that. In the summers here100 degrees can be a relief, and whatever temperature on the ground, it's even hotter on the roof. Oh, and did I mention that the roof is the most exposed part of your building to the sun every day of the year. That heat is absorbed as heat energy into everything at one rate or another, as a matter of fact, that is why thermal image technology works. But that's a different blog article, it matters here only to say that heat beating down on your roof can make to the interior of your building. That heat has to be removed by your air conditioning system which costs you money. We talk for days on all the other benefits of cool roofs, but when the rubber meets the road, the bottom line is the bottom line.
Cool roofs save money! They do more than that, but ultimately what matters to most people is that a cool roof will undoubtedly save you money.
We do not live on an island, or do we? Cities are made of all sorts of materials including a lot of asphalt and concrete both can get hot in the summer months. That heat will actually raise the ambient temperature of the city compared to the rural area nearby. This effect is called the heat island and is what the Environmental Protection Agency (EPA) is concerned with. Why do they care? They are concerned with air quality, and cities tend to have smoggy air. In phoenix on some days, you can see and smell the smog in the air downtown while you are in the downtown area. For every degree above 70, the smog is increased by 3%, and in Arizona, we have a lot of days well above 70 degrees. On a 100 degree day, that put us at 30 degrees above 70. That could increase the smog by 90% yikes!
I addition to the smog factor, it takes more energy to get rid of all that extra heat from inside the buildings. Yes, the energy you are paying for that I talked about at the start of this blog. Not that government is all that concerned with your electric bill, but that they need to help lower the demand that puts stress on the electrical grid. The Department of Energy (DOE) is the government agency that is charged with that job. They are looking at the same heat island effect and cool roofs to help lower the demands during the cooling season, to make sure our power grids stay up and running. None of us want any outages right?
Both of these agencies are looking at the same problem, for different reasons, but still the same heat Island effect problem. They joined together and created a program called Energy Star. This program offers various incentives for building owners to use energy-saving components, including of course the roof. Here is little tid b bit for you, the solar reflectance of a roof is measured based on three years of age under normal conditions. If you have never been to their site, you might want to take a few minutes and check it out. Maybe you'll find a few ways to save some money.
What makes a cool roof cool?
In this business (roof consulting) we love Infrared technology, it lets us see variances in temperature on the infrared spectrum that helps us identify potential problems in a roof system or the entire building envelope for that matter. In short, it works because heat is being absorbed all day and released at night, the IR camera sees the heat being released and that lets us see things we can not otherwise see. The job of the cool roof is to reflect the light off the roof, keeping as much of that heat energy as possible from being absorbed in the first place. The concept is very simple, the less heat the roof takes in, the less heat your air conditioning system has to remove and the lower your electrical demand. The more reflective the roof is, the cooler the roof is.
Lighter colors tend to reflect light better, which is why you see a lot of white or light tan roof coatings. The texture also makes a substantial difference in the reflectivity of a particular surface area. The rougher the texture the less reflective it tends to be, which is offset then by using lighter colors on rougher textured surfaces. Smoother surfaces let you use darker colors and still get some reflective value. Cleanliness matters too, whatever the reflective rate of the roof materials if it is covered with dirt it really does not matter. A dirty cool roof defeats the intended purpose of a cool roof, to begin with.
Rate the roof
I said before that the reflectiveness of the roof is based on a three year age of the roof. But how do we rate the reflectiveness of the roof in the first place? The Cool Roof Rating Council was founded in 1998 for the purpose of finding effective ways to measure and rate cool roofs. They share the same mission of reducing the heat island as do the EPA and DOE. But are not a government agency, the roll is in developing testing methods to make sure that the market has a consistent way of labeling the effectiveness of a cool roof product. You can imagine how confusing it could get if each manufacture made their own rating system up with no consistency what so ever with the other manufacturers.
It gets hot in Arizona, and a cool roof can help you save money. Have questions, give me a call Henry Staggs (480) 265-1613