HVAC Breaking News

Sept. 3, 2007: New Energy-Efficient Roof System Reduces Heat Transfer, Cuts Utility Bills

September 3, 2007
/ Print / Reprints /
ShareMore
/ Text Size+

OAK RIDGE, Tenn. - Homeowners could see their summer utility bills fall by 8 percent or more with a new roof and attic system being developed at the U.S. Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL).

From an energy efficiency perspective, roof technology has not progressed substantially in hundreds of years, according to ORNL, but that is changing with the use of active thermal mass components, reflective pigments and coatings, subventing, radiant barriers, and other novel techniques being tested by a team led by Bill Miller and Jan Kosny of ORNL's Building Envelopes group. Their prototype roof and attic system works by reducing attic temperatures by about 22°F during a typical summer afternoon and decreasing the amount of heat that gets transferred through the attic floor to the living space.

At the heart of the new roof system is a proprietary inorganic phase change material sandwiched between two reflective surfaces made of aluminum foil. This material is installed as a dynamic thermal barrier between the roof and attic area, creating separate air channels between roof rafters. The configuration is compatible with traditional wood and steel framing technologies. Moreover, the new phase change material overcomes problems that have plagued phase change materials for the past 40 years.

“In the 1970s and 1980s the housing industry made several moderately successful attempts to use phase change materials,” Kosny said. “While these materials enhanced building energy performance, they were in many cases chemically unstable, were subject to corrosion or other durability problems, and suffered from loss of phase change capability.”

Another shortcoming of some previous phase change materials was their susceptibility to fire. Fire is not a problem with the ORNL material, according to Kosny, who noted that ORNL researchers are working with leading manufacturers of phase change material on the development of non-flammable organic material.

In tests at ORNL, phase change materials perform like conventional materials by absorbing heat as the temperature increases. However, as the material melts it continues to absorb large amounts of heat without a significant increase in temperature. Then, as night falls and the ambient temperature around the liquid phase change material decreases, it solidifies again and releases the stored heat to the night sky, Miller said.

With an outside temperature of 92°F, tests at ORNL's Buildings Technology Center show temperatures of conventional attics at 127° vs. attic temperatures of 105° with the Dynamic Attic Heat Exhaust System. Kosny and Miller filed a patent last year for this technology.

“The next generation roof will consist of infrared reflective materials that are dark in color yet reflect light as if they were white,” Miller said. “In addition, radiant barriers and phase change materials will be integrated into a dynamic attic system that reduces utility bills for homeowners. The conservation strategies contribute on a much grander scale by lowering peak demand on utilities, reducing carbon emissions, and ultimately, they could lead to cleaner air.”

If just half of the homeowners in the U.S. made sure they had R30 attic floor insulation and used this roof and attic system, the nation could reduce its Btu demand by about 100 trillion Btu, according to ORNL.

Publication date: 09/03/2007

Did you enjoy this article? Click here to subscribe to The NEWS Magazine

You must login or register in order to post a comment.

Multimedia

Videos

Image Galleries

2014 MCAA Annual Convention

Scenes from the 2014 MCAA Annual Convention in Scottsdale, Ariz.

Podcasts

NEWSmakers: Julian Scadden

Training is an ongoing process. Julian will discuss how you can generate maximum return on time and energy invested training by following a three part process. Listen to this podcast to get expert tips on training, tracking and follow up. 

More Podcasts

THE MAGAZINE

ACHRNEWS

NEWS 04-14-14 cover

2014 April 14

Check out the weekly edition of The NEWS today!

Table Of Contents Subscribe

SERVICE CALLS POLL

Which statement on service calls best applies to your business?
View Results Poll Archive

HVACR INDUSTRY STORE

plumbing-hvac.gif
2014 National Plumbing & HVAC Estimator

Every plumbing and HVAC estimator can use the cost estimates in this practical manual!

More Products

Clear Seas Research

 

Clear Seas ResearchWith access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

DON'T MISS A THING

Magazine image
 
Register today for complete access to ACHRNews.com. Get full access to the latest features, Extra Edition, and more.

STAY CONNECTED

facebook icontwitter iconyoutube iconLinkedIn i con