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Commercial Roofs, Energy Savings, and Reflective White Roofs
There has been a fair amount of publicity lately on the topic of white roofs and energy savings. First, let's make it clear that there are significant differences between white spray foam roofing and reflective white roofs. Energy Star doesn't clarify this enough for many consumers. A reflective white roof may at a glance appear to be the most cost-effective solution, but simply painting a black tar roof white does nothing to affect the R-value, an important element of the energy-saving roof equation. Spray foam roofing does increase the R-value and thermal emittance, both of which indicate greater insulation and a reduction in BTUs expended per square foot.
A second factor frequently expressed by many armchair experts is that "if I'm in a northern state and my area of the country doesn't get much snow, then I will gain more in winter heat buildup from a black roof than I will save in summer cooling costs with a white roof." This is a common misconception. For a moment, let's ignore the serious problems associated with high heat and the breakdown of roofing and building components, and let's also ignore the more rapid aging of components generally found in a non-insulated roofing structure. The fact is that a spray foam roof is the cost-effective solution even at far northern latitudes.
For the moment, let's forget about spray foam roofs and simply address the issue of highly reflective white roofs. In this case, even as far north as Minneapolis Minnesota, with all other factors being the same, a low-emittance, low R-value, highly reflective roof will result in approximately the same heating and cooling load overall as a low-emittance, low R-value, black roof. South of Minneapolis, even as short as distance as Rochester MN, highly reflective roofs save energy hands down over black roofs. The Department of Energy has an excellent Cool Roof Calculator that illustrates this.
If you live further north in areas such as North Dakota or northern Wisconsin, white roofing makes even more sense, since there is a reasonable chance that your building will experience snow cover during most of the coldest days.
Even factoring in the average annual reduction in reflectance of 1.5%, buildings further south in Omaha Nebraska or St Louis Missouri will likely have well over a decade before their reflectance decreases enough to warrant a cleaning to stay ahead of black roofs.
However as we mentioned earlier, spray foam roofing is not spray paint roofing. In our prior example we referenced low-emittance, low R-value roofs. Spray foam roofing on the other hand provides a high R-value AND high thermal emittance. Because of this much greater level of insulation, your building will require fewer BTUs per square foot even at northern latitudes.
What are some examples of solar reflectance levels of various roofing materials? Here are a few examples (remember, the higher the number the better):
| Roofing Type | Reflectance* | |
Spray Foam Roofing | 0.83 | |
White Paint | 0.80 | |
Whitewashed galvanized roofing | 0.78 | |
Stainless Steel | 0.55 | |
New galvanized sheet metal | 0.35 | |
Oxidized galvanized sheet | 0.20 | |
Roofing tar and gravel | 0.17 | |
Dark Asphalt | 0.08 | |
Black paint | 0.06 | |
*Numbers are approximate |
So, what is the percent of heat loss through a commercial ceiling? According to the Department of Energy 2008 Building Energy Data Book, approximately 12% of the total heating energy load is lost through the roof. This highlights how important your roof can be in controlling facility costs, but is still only a fraction of the overall energy costs associated with your roof. In fact, the EPA in conjunction with Lawrence Berkeley National Labs states that "Individual buildings could get as high as a 50 percent energy savings with cool roofs."
In addition to the benefits mentioned above, spray foam roofs provide an Energy Star approved monolithic seal over your entire roof deck that is leak free, lightweight, weather resistant, with strong adhesion and wind uplift resistance. Polyurethane foam has a history of over 35 years as a maintainable roofing medium. For most of this time, since 1987, Kohls Foam Systems has been a leading expert in spray foam roofing applications. This in-depth expertise has been recognized with national awards and the focus of many articles in industry publications.
Contact us today at 612-708-4111 and see how we can save you energy, save you money, and install the best roof your building will ever have!
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