05/01/2009

The Black and White on Roofing

Read about the pros and cons of black and white roofing membranes

 

Roofing has recently become more colorful in many ways. For the last 25 years, there have been many new choices concerning roofing, and more are added each year. As those trends continue, there are also a number of new initiatives that take the focus off the primary objective concerning roofing for commercial buildings. While I am currently president at RCI Inc., the content of this article is simply my opinion, and not necessarily the opinion of RCI Inc. members. More information is available at www.rci-online.org. While you’re visiting that site, the RCI technical articles library contains a number of peer-reviewed articles on this topic for further study.

Recently, many studies, mandates, regulations, and recommendations have been offered that speak to the virtues of white reflective, dark, and even stone-covered roof surfaces. The U.S. EPA’s ENERGY STAR® for roofing, as it first began, met my approval. The EPA has done a fine job to date with that program. All of the studies since then have merit, but some serve a specific purpose. One feature offered by highly reflective roof surfaces is the reduction of roof-surface temperatures, which does impact the urban heat island effect. Most of the other roof surfaces can’t offer that environmental benefit.

White (Dirty) Roofs in California

“The main problem with white roofs in Southern California is that they don’t stay white very long. They get dirty and dingy over a short period due to smog, dust, and sediment in the air that ends up on the white roof. The Honda Center in Anaheim, CA, is periodically power washed due to dirt on the white PVC roof, which is highly visible from the ground. This is true of any white, smooth-surfaced roofing product. In areas of the United States where they get a lot more rain consistently throughout the year, the roof has a chance to be cleaned off more frequently. So, unless someone is willing to power wash the roof two or three times a year, a lot of the reflectivity benefits are lost as the roof gets dirtier and dirtier throughout the spring, summer, and fall.”

– Steve Clonts, Vice President, National Roofing Consultants Inc., Pomona, CA

From the perspective of energy savings, ASHRAE and Oak Ridge National Laboratory have taken a reasonable approach concerning the issue of reflective roof surfaces by discussing R-value tradeoff. In many cases and climates, simply adding 1 inch or less of roof insulation (R=0 to R=6) totally offsets any potential savings that could be gained by a reflective surface on roofs. It’s important to note that the added R-value pays back year-round (heating and cooling).

As reflective roof surfaces began to gain in popularity, the potential for errors concerning roof-system selection increased. Roofing materials and systems with limited track records were being chosen based upon surface color only, without much regard for other factors, including longevity. Roofing professionals can sort through the maze of roof systems available to address the specific needs of each building and service exposure. The correct combination of roof-system components will result in the most environmentally sound roof with the best life-cycle and energy performance. There are many discussion points on both sides, but many are simply market posturing, so consider the source as well as the message. Some truly beneficial improvements have resulted from the early initiatives to address the urban heat island effect.

The best approach is neither black nor white; rather, consideration of the goals desired for the roof and understanding that the roof is, first and foremost, a roof. Legislation and incentives concerning the surface color of roofs only restrict building owner choices to save energy and obtain roofing that least impacts the environment. Select the right roof that offers the best performance and meets the long-term needs of the building first, and consider the color as an option.

David R. Hawn is president at RCI Inc., and is a Registered Roof Consultant (RRC).

 

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Our mission is to help our customers manage their buildings' energy costs, improve reliability, and enhance performance while having a positive impact on the environment.
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Mitsubishi Electric’s H2i R2-Series heat pumps provide 100% heating capacity down to 0° F and simultaneous heating and cooling down to -4° F delivering year-round comfort, regardless of climate zone.

 
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