ORNL roof and attic design proves efficient in summer and winter
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.
OAK RIDGE, Tenn., Sep. 10, 2012 — 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 ventilation system that pulls air from the underbelly of the attic into an inclined air space above the roof.
“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 computer simulations.
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 design 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.
Funding was provided by the DOE Office of Energy Efficiency and Renewable Energy and Billy Ellis Roofing under a User Agreement. UT-Battelle manages ORNL for DOE’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/.
UT-Battelle manages ORNL for the Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/.
In Sweden keeping heat in during winter is the main problem, not keeping heat out. Good insulation could become useful summertime too. Latest summer was the worst for ages, with only half a dozen “real summerdays” local weather service says.
–Ahrvid
Ps. Hackers hacking away at Jo Nova again? It this moment I only get “This account has been suspended” when trying to connect.
Brilliant
Saving energy is good. It’s what I believed since I was 20 years old.
just leave the carbon, the politics, the tree rings, Al Gore, Mann, Gleik and the Polar bears out of it.
and let me go back to growing potatoes and other stuff
and Hansen.Please no more Hansen
Long time reader, and very occasional poster. Had to comment on this as it is not totally new, just a variation on a ventilated ridge system.
My house in rural Australia has a large verandah completely surrounding the house. Under the verandah, all the way around is a vent feeding into the cavity between insulation and the corrugated steel roof. All along the ridge of the roof is a ventilation cowling. Cooler air is drawn in from the vent under the verandah, and convects up the underside of the roofing, venting out at the top.
It’s effectiveness is clear inside the house on 100 degree plus days, and of course the fact that it requires regular cleaning of dust buildup from the mesh covering the inlet vent!
Something old is new again!
I seem to remember this passive double-layer roof ventilation system from my years in southern Spain. Not quite as sophisticated, of course, and executed in concrete, but I think the basic idea is the same.
This is not brain surgery. It’s common sense.
Now will someone be getting a patent on the “new” idea? I hope not.
I seriously doubt it could be done for the cost they estimate on any but the smallest of homes with plain roofs. Maybe a 1000sqft house could be done for $2000. You can’t even get asphalt shingles replaced on a standard 1800sqft house for under $5000. And I’d want a engineering evaluation of the additional weight and resulting stresses during a heavy snow. Btw, this design would not shed snow very well without additional heat being added somehow.
Have they tested this in heavy snow climes?
Why does the green cult not spend some of their billions on developing useful energy efficient suggestions like this instead of wasting it like they do on activism, propaganda and hate speech?
As Tim Wainwright says this sort of roof design is common in Australia and has been so for 100 years especially in the tropics, Our own house in Sydney has solar panels on the north (sunny) slope and they act as a cooling sub0surface airflow channel which keeps the house 10 degrees cooler in hot weather in addition to the effects of 6 inch roof insulation and 6 inch sub attic floor insulation. We do not seem to have much in the way of winters in Sydney but summers used to be very hot.
It is good to see people devoting themselves to practical cost-saving ideas that are useful to peoplerather than pursuing anti-social scams like CAGW and Carbon trading.
Quote: Poorly sealed HVAC ducts leak conditioned air into an attic, which typically costs homeowners $100 to $300 per year based on ORNL computer simulations.
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 design for about $2,000 and save $100 a year./Quote
Does this make sense to anyone? I don’t see why anyone would spend $8K to seal the attic and essentially air condition it. Why not fix the leaking ducts?
This solution seem more about moving hot air out of an attic to keep it from radiating heat back into the living area of the home. I’m very interested because I am about to begin the design phase on a new home.
just checked Jo Nova – also getting the account suspended message…
Pittzer says:
September 12, 2012 at 2:50 pm
Does this make sense to anyone? I don’t see why anyone would spend $8K to seal the attic and essentially air condition it.
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Yes it does make sense.
Think “GOVERNMENT SUBSIDIES” via stimulus spending.
(remember the insulation boondoggle associated with the last porkulus bill??)
http://www.foxnews.com/politics/2011/04/14/obamas-5-billion-weatherizing-program-wastes-stimulus-funds-auditors/
Greenies will promote it
Even I have thought of a double decked roof with flow through ventilation design. Common sense for the Texas heat and we rarely get any snow or ice where I am.
I have ridge vents on my house, which were billed as a way to allow passive airflow and let
heat out of the top vent. Problem is, this only happens when the wind blows, which it never does during a typical Florida day. My attic gets to over 140 degrees, and since the morons ran the duct work thru the attic , the air in the ducts heats up while sitting for the next AC cycle and even during steady state conditions, gains 8+ degrees travelling from the source to the room vents. It is impossible to adequately cool this house. If the building codes had any intelligence, they would require interior ductwork – note that any airduct leakage in this case is irrelevant- the leakage is to interior space. Blown in insulation protects me from any transfer of heat from attic to my interior. Note that even if this newfangled roof manages to keep attic temps close to outside ambient temps, that would still have attic ductwork running thru 90 degree plus temperatures, rather than the 70 degree temps on the interior if located there. Moral of the story – put ductwork within the interior conditioned space, where it belongs. That would save far more energy than anything anyone can do with a roof.
I had a friend in Italy with a south facing study which became too hot in the afternoon. We made up a flat box unit, black-faced and attached it high on the south wall. Then used ducting to effectively connect the box to the cellar with the studio inline. The radiation on the box powered the passive system, drawing cool air from the cellar and through the studio. The cellar was air-leaky which was fortunate but so was the studio which was less fortunate. It worked, but the box needed to be roof-sized. A professional system, linked to a large cellar, underground carpark or purpose-built cut and fill concrete tunnel would take this idea further. The key is getting the driver (the sun-facing convector) the right area/volume for the volume of the building and cool reservoir. It needs to be matt black on the outside and insulated on the house side because, although part of a passive system, it is has to be seen as the driver of the system, required to do a lot more work than the system described above. I think the perfect application for this would be in a purpose-built supermarket with all sun-facing walls acting as convectors and where the cool reservoir is an underground parking/ delivery area. Air is drawn up to ground floor level, across the floor (not rising) and out at or very
near the base of the walls. Then up the convectors. The supermarket entrance would be ten feet up with steps down so as to prevent cool air loss. The cool air would hopefully flow exactly where needed- where people are shopping i.e. 0-6 feet.
A 20 year payback for a retro-fit? Thanks, but no thanks.
I’d love to know how much this would add to the cost of a new roof.
Double layered ventilated roofs are becoming in creasingly common as a high cost custom option on homes in the Houston reas. I wonder how a three layered roof would hold up under strong windstorm stresses?
I wonder how the very high cost of a three-layer system like the ORNL example pays off compared to a two layered solution or just a well ventilated radiant barrier more taditional roof?
sorry…. I think a good solar powered roof vent system might be a nice compromise.
In Washington State wasps and spiders love these crown vents. They quit working when snow covers them but that is just for a few days each year. Same with low-profile stand-off roof vents. Humid air from inside the house is a problem if it gets into the attic space and freezes when the ventilation system quits working. Still – in a new construction it looks promising.
Paper: M$ Doc, 1.0Mb: http://info.ornl.gov/sites/publications/files/Pub30786.docx
Warning: This was given as a link to the paper by Gizmag.
PDF, 3.6Mb: http://www.nrca.net/rp/technical/symposium/pdf/17_miller.pdf
It’s actually a stack of glossy handouts with pics and graphs, a press release kit. But it does have some usable info.
From the paper:
I’ve seen new home construction where attics aren’t even used for storage anymore, there’s a small access door, and electrical wiring is simply laid on top of the joists. Mere residents shouldn’t even be there.
So why not go all the way, and make attics part of the heating system? The attic “floor” is done like a roof, completely sealed away from the rooms, fully insulated. The attic ventilation is closed off by switched vents, heat is allowed to build during the day. Then at night, vents are opened and the stored warmth is used for heating until it is depleted. That’s “winter mode”. To accommodate summer, vents to the exterior are switched open or closed to achieve no more than a maximum allowed temperature.
I’ll also note that in this age of extreme caution, there’s the recommendation to turn water heater temperatures down to as low as 120°F to avoid kids getting scalded. A sealed attic under an uninsulated roof can achieve at least that with bright sunlight, and not just in summer. So stick an appropriate heat exchanger in the attic and use that heat for water heating.
After that, might as well make the attic “floor” extra sturdy, and add some stone or gravel or similar thermal storage mass.
It might save energy but it won’t do anything good to the UHI (maybe greater night day differences).
Cold roof designs like this are fast disappearing in the UK, the days of permeable fibre insulation are numbered. Sealed warm roof designs using composite materials specifically designed for the job is the obvious way to go these days, even for refurbishment. e.g. http://www.celotex.co.uk
It’s actually as simple as adding a layer of foam (panel) insulation on top of the plywood and under (whatever) roofing material you choose, even without the air gap. I have chosen metal roofing due to the tropical nature of our weather and never had a roofing failure. It’s a shocking concept (apparently) to keep the heat out of the attic. Glad to see a proven idea getting some airplay, just realize it can be done more than one way.
The foam panels can be had at retail for less than $1 per square foot, or like I did for may barn, you can grab them for free when a company replaces it’s roof. The biggest problem I found is that the screws for the metal roof are not common in the length required to screw through the foam panels to the decking.
Gerry Parker
All newer houses here in Perth have roof vents. Most are the size and shape of a pineapple and spin as they vent heat from the roof space. A design I assume keeps rain out.
The thing is, I see them gaily spinning away in winter, when daytime temperatures average around 18C and nightime temperatures around 7C, and as people don’t have central heating here, houses get pretty cold. During the day, at least on sunny days, the roof space will be the warmest place in the house and these roof vents are cooling it down.
A means to turn theses vents off in the winter would cost little and generate substantial energy savings.
Its a pet peeve of mine that simple and obvious measures to reduce energy consumption like this are ignored, while billions are spent on boondogles like electric cars and carbon capture.
Looks pretty good to me. Mind you, I say that as someone whose attic “room”, three floors up, has four airbricks facing into the prevailing sou’westerlies and neither heating nor insulation. Pretty much anything looks pretty good compared with that, although it’s almost usable for a couple of weeks twice a year, around the equinoxes. Century-plus-old building standards leave quite a lot to the imagination, like comfort … but hey, if you survived, you got to run the British Empire, which got you out of it and into someone else’s country! Happy days!