Variables for Energy-Efficient Roofs

Market roof with air handlers

Market roof with air handlers

Editor’s note: This article first appeared in the July/August 2015 issue of Business Energy.

Roof material choice is one area of building envelope design where significant efficiency can be found. Energy-efficient roofs have come a long way in recent years. Cost savings can be realized, and service life can be greatly extended with careful selection of a modern energy efficient roof.

A white roof is just one of many variables in roofing, according to Ryan Shinn, manager, Western Group Marketing, CentiMark Corporation, based out of Carrollton, TX. “You have to look at the thickness of the installation on the roofing system, and the type of lighting that will affect the efficiency of the roof. Also, the ambient temperature and climate. Then, the type of building can radically affect the direction you want to go with your design and materials.”

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As research continues for longer lasting materials, recent breakthroughs have led to new plasticizers that are used in Poly Vinyl Chloride (PVC) roofing, and these allow PVC to resist UV radiation. Shinn says, “PVC roofing is big in chemical manufacturing industries and certain food processing because it resists chemical degradation.”

PVC makes for a thermoplastic roof system that is white, and a highly reflective membrane. These roofs provide strong weathering characteristics, along with puncture and tear resistance. Sheets are welded together using hot air, and these types of roof systems are lightweight, and well suited for second-generation (roof-over) applications.

“We also have better inspection techniques, such as infrared tools, to detect hotspots and areas where water is entering the building through the roof,” adds Shinn. “You want your roof system to be as energy neutral as possible to prevent uneven heating or cooling.”

Roofing materials are also going green, literally. For example, the Findlay Teller Apartments in Bronx, NY, recently installed a living green roof manufactured by Xero Flor America (XFA) based in Durham, NC. The 9,825-square-foot Xero Flor green roof system includes lightweight, pre-vegetated mats that were delivered with well-developed, mature plants. The Xero Flor vegetated mats were rolled out like sod for easy installation. All told, XFA has supplied nearly 90 green roof installations in the New York City area covering more than 600,000 square feet.

Green roofs have gained in popularity in progressive cities like New York, according to Clayton Rugh, XFA Manager and Technical Director. “The green building industry has grown dramatically over the past 10 years through increased technical awareness by the design and construction community,” says Rugh. “Consequently, New York, and many major US cities—such as Washington DC, Philadelphia, Seattle, Portland, and Chicago—have become thriving green roof markets.”

Driving green roof adoption nationwide are the many sustainable environmental and economic benefits. “LEED certification is one of the strongest incentives,” says Rugh. “Green roofs provide or contribute as many as 24 LEED points through thermal protection, stormwater management, water reuse opportunities, and other benefits.”

Additional LEED credits can be obtained from use of native flora, local sourcing, and used of recycled and renewable content. Rugh notes “Xero Flor has a strong LEED position because our production fields and component

suppliers are located near major metropolitan areas, so offer local sourcing for most American projects. In addition, Xero Flor America green roof materials are 100% US manufactured with a very high percentage of recycled content in our products.”

Aside from sustainably sourced products, how do green roofs affect building energy performance? “Green roof provide thermal protection through three different processes,” says Rugh. “First, it’s a lighter colored surface, so it remains cooler than a dark-colored membrane. Also, a vegetative roof dissipates heat load by evaporating water from leaves and stems. These processes combine to enhance building air-conditioning efficiency by reduced thermal loading through the roof structure. Moreover, the green roof assembly acts as a protective covering to prolong the life of a roofing membrane that would otherwise be exposed to solar UV radiation and extreme heat-cold cycles.” BE_bug_web

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