White Flat Roofs: Energy Use and Environmental Advantages

On a hot, sunny day in Montgomery County, black flat roofs are often as much as 90 degrees hotter than the surrounding air temperature. When that heat transfers down to the building below, cooling costs rise, often dramatically. There are also environmental costs to this heat absorption. The energy used to cool the structure is often produced at coal-fired power plants responsible for excess carbon emissions.

The Cool Roofing Solution

In response, so-called “cool roofs” are gaining traction across the country. In fact, in the western United States, cool roofs have grown in popularity to the point that they represent about two-thirds of all roofing and re-roofing installations.

So, should you change your black flat roof into a white one? At BRAX Roofing, we see important reasons to consider durable white roofing materials like GAF’s white EverGuard Extreme TPO and GACO’s white silicone coatings.

It’s reasonable to wonder why the added cooling costs associated with black roofs are not offset by heat absorption on cold winter days. Why don’t black roofs help as much in the winter as they do in the summer? Since hot air rises, any heat transferred to the building from a black roof tends to remain mostly in the upper reaches of the structure, where it does not benefit the occupants as much.

Also, any heat absorption in the winter is minimized by shorter days and lower sun angles. Finally, don’t forget that, in the winter, a black flat roof is often covered by snow for days or weeks at a time. When snow turns that black roof white, the potential for beneficial heat absorption is eliminated.

Study Compares Flat Roofs

A report entitled “Economic Comparison of White, Green, and Flat Black Roofs in the United States” compares white, black, and green roofs. It appeared in the March 2014 issue of Energy and Buildings, an international journal devoted to energy use and efficiency. For the study, researchers analyzed 22 American flat roof projects. In each instance, project managers considered two or more types of flat roofs. Researchers conducted a thorough analysis of the 50-year costs of black, white, and green roofs. Green roofs include vegetated varieties and those with rooftop gardens.

The researchers at the Lawrence Berkeley National Laboratory provided conclusive evidence of the energy savings possible with white flat roofs. They looked at whether black, white and even green (vegetated) flat roofs were the most cost-effective over a 50-year period. Arthur Rosenfeld, a co-author of the study, is a Distinguished Scientist Emeritus at Berkeley Lab and a previous commissioner of the California Energy Commission. In 2012, he received the National Medal of Technology and Innovation from President Obama for his pioneering work in energy efficiency.

Efficiency of White Roofs

Researchers suggest that, strictly in terms of energy efficiency and climate change, white roofs offer advantages over both green and black roofs. Rosenfeld asserts that “white roofs are three times more cost-effective at countering climate change than green roofs.” The contrast between white and black flat roofs was even more significant. In fact, Rosenfeld suggested that the energy savings provided by white roofs are so substantial that contractors and property owners should phase out traditional black roofs over time.

Flat Roof Manufacturers

• Mule hide
• GAF
• Firestone
• Carlyle
• Polyglass

Flat Roofing Materials

• TPO
• EPDM
• PVC
• Rolled Bit
• Torch down
• Tar

For a more in-depth description and run down on the materials, please feel free to click the material name, and it will take you to the material page.

Since white roof reflectivity is so beneficial, it is important that the white roofing products employed retain most of this reflectivity over time. There are numerous manufacturers.

At BRAX Roofing, we are always looking for roofing products that will simultaneously cut energy costs and reduce carbon emissions. We’d welcome the opportunity to evaluate your roofing requirements. Please contact us today for a no-cost, no-obligation estimate.