Attic heat exchanger?


I've been contemplating methods of obtaining heat from the attic for heating the house during appropriate times of the year. One idea I have is to put a ducted fan in the attic to blow the warm/hot air into the garage as an initial experiment. I can heat the garage to determine the feasibility of the concept.
I'm also thinking that a reversible ventilator would be in order in that it could double as a way to vent hot air from the garage into the attic and out through the roof vents during hot weather. This would even cool the attic somewhat and help the A/C load on the main part of the house.
Anyone have any thougts?
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buffalo ny: garage air due to car exhaust concerns is usually required to be isolated from the home. i would put money into insulating the attic to retain the home's heat. for your complete answers: http://www.buildingscience.com/resources /
Everett M. Greene wrote:

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My brother did something like this and it worked like a champ.
The house was a ranch with attic access from the garage. He just placed a box fan in the opening and had the fan blow downwards into the garage. We're in a 8800 dd climate and he found that it worked best in the spring / fall.
This was done mainly as an experiment, but it did work and I recall that quite a lot of heat was available. If one wanted to do it "right", I would envision a system with a thermostatic switch/thermostat, ducting to pull the heat from the top of attic, to floor level (heat rises), possibly a filter and some kind of high temp cutoff (fire safety). Plus you'd need to think of some kind of return duct as just blowing heat from the attic would result in some pressurization of the house, that air needs to go somewhere...
I'd encourage some experimentation first. (cheap fans and some flexy duct snaking through the house).
Good luck.
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snipped-for-privacy@gmail.com writes:
Thanks to you and the others who replied.

Any suggestions for a source and size for ducted fans?

The garage is already insulated.

I'll look into this.
From: snipped-for-privacy@ece.villanova.edu

I live in the Mojave Desert. I don't need any more heat, especially in July and August :-)
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Well, there's this place: http://www.espenergy.com/in_line_duct_fan.htm
I know nothing about the company at all, but just did a quick search for "in-line duct booster" and they showed up. Looks like they also sell thermostats and dampers too. A six inch duct booster is ~$27. I don't know much about ducted fans, but I think they don't like back pressure, therefore short straight runs with few restrictions may be best. AFA size 6" or 8" I'd guess.
My local Menards (midwest version of HD) has booster fans too. You may want to check around.
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mrfixit341 had written this in response to http://www.thestuccocompany.com/maintenance/Re-Attic-heat-exchanger-181411-.htm : I had the same idea not long ago.A man could run some large flexible duct from the attic and tie it into the air intake.Of course put a shutoff on it for summer.You would also have to put a temp sensor in the attic and have a programmable thermostat with emergency heat setting to run the fan or some kind of relay or 2 thermostats.If the temp in the attis was hot enough on the heat setting it would kick on the fan and heat the house.Or have a seperate fan and thermostat to run it separately.I think you get the idea.Thanks Mark Whitney.Lets make a system and sell it$$$
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Good idea. For more heat, you might replace a south roof with transparent polycarbonate Dynaglas greenhouse roofing material, which comes in 4'x12' corrugated sheets and costs about $1/ft^2 and lasts about 20 years.
You'd also want a return air path and one-way dampers to avoid letting warm air go up into the attic at night. Return air might go up through a ceiling register with a box above it and some heavy plastic film hanging over the screened south wall of the box for a damper. With the transparent roof, the box could also act as a skylight. Supply air could come from a fan below the ceiling that pulls attic air down through a tall duct, with light plastic film hanging over the fan outlet.

That's easier, since warm air rises. You might block the roof vents and add gable vents with doors that open in summertime and close in wintertime.
Nick
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On Tue, 2 Jan 2007 22:39:37 PST, snipped-for-privacy@iwvisp.com (Everett M. Greene) wrote:

IMHO:
IN the winter time, if you have a properly ventulated attic space you should have a 'cold' roof. So effort applied for yoru return can be minimal. I suggest if you want to try to utilize solar heat, cut out the middle step and get professionallly done heat exchangers installed on your roof.
Another idea that came to mind, if you were pumping cold fluid into tubes in your attic, you migght be creating a condensation problem on the tubes that has to be dealt with.
Not a attic, or solar heating expert, just guessing here...
tom @ www.MedJobSite.com
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