ORNL roof and attic design proves efficient in summer and winter

September 10, 2012 by Emma Macmillan, Oak Ridge National Laboratory
A new roof system field-tested at Oak Ridge National Laboratory improves efficiency using controls for radiation, convection and insulation, including a passive ventilation system that pulls air from the underbelly of the attic into an inclined air space above the roof.

(Phys.org)—A new kind of roof-and-attic system field-tested at the Department of Energy's Oak Ridge National Laboratory keeps homes cool in summer and prevents heat loss in winter, a multi-seasonal efficiency uncommon in roof and attic design.

The system improves efficiency using controls for radiation, convection and insulation, including a passive that pulls air from the underbelly of the attic into an inclined air space above the .

"Heat that would have gone into the house is carried up and out," says Bill Miller of ORNL's Building Envelope Group. "And with a passive ventilation scheme, there are no moving parts, so it's guaranteed to work."

The new roof system design can be retrofitted with almost all roofing products. The heart of the design is a foiled covered polystyrene insulation that fits over and between rafters in new construction or can be attached on top of an existing shingle roof system. Homeowners don't have to remove old shingles, which saves money.

Poorly sealed HVAC ducts leak conditioned air into an attic, which typically costs homeowners $100 to $300 per year based on ORNL .

To address the problem, some homeowners pay $8,000 to seal the attic with spray foam, which can save upwards of $460 a year. For less initial cost and the same number of payback years, homeowners can retrofit the attic with the new for about $2,000 and save $100 a year.

Looking to the future, Miller and colleagues are working on designs with lower initial installation costs, and greater cost-effectiveness overall.

The paper, "Prototype Roof Deck Designed to Self-Regulate Deck Temperature and Reduce Heat Transfer," was published by the National Roofing Contractors Association. Authors on the paper are W. Miller, Stan Atherton and Russell Graves of the University of Tennessee, Knoxville, and Billy Ellis of Billy Ellis Roofing.

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3.4 / 5 (5) Sep 10, 2012
I don't like it - looks to me as though ice dam issues have been made worse.
And spend $2000 so I can save $100 per year??? Maybe ORNL can explain to me how this represents good value, cuz a twenty-year payback does not make financial sense.
5 / 5 (1) Sep 10, 2012
Oh, great. They've reinvented the 1956 Land Rover double roof.

And the crimped aluminum roofover on my retired mom's mobile home.

Hope they don't want a patent.
1 / 5 (1) Sep 10, 2012
It is trivial to retrofit such a design into the interior of a rafter system.

It isn't rocket science.
not rated yet Sep 10, 2012
Ice dam issues would not be worse. As long as the upper layer of the roof is always below freezing, shielded from parasitic heat loss from the house, the snow wouldn't melt, no water means no ice dams.

A 2,000 dollar investment that saves 100 dollars a year is like receiving a 5% return from a savings account that contains 2,000 dollars. The 2,000 dollar will depreciate, but so will the 2,000 in the savings account. Except we call that inflation.

not rated yet Sep 11, 2012
As fitted to Landrover back in 1956, the same priniciple but at least it's being put into practice.
The Station Wagons saw the first expansion of the Land Rover range. Station Wagons were fitted with a "Safari Roof" which consisted of a second roof skin fitted on top of the vehicle. This kept the interior cool in hot weather and reduced condensation in cold weather. Vents fitted in the roof allowed added ventilation to the interior.

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