Energy saving idea?

What would be the problem with ducting cool air from under a house to the attic in warmer months to help with cooling, and just the opposite in the winter to help with heating?
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woudln't Your floor would get cold from the cold attic air, cooling the air above it, and forcing your furnace to run more often?
Once you cyled the air completly once, the radiant heating from the earth would take a while to warm the air under the house again, more likely it would be the heat escaping thru the floor that would be warming the air under the house, so I think the net benifit would be little to none, ...
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I'd be concerned about the quality of air from under the house. Mold spores could cause problems.
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Edwin Pawlowski wrote:

Interesting - wouldn't they also cause problems under the house?
How about a filter, or a heat exchanger made with some ductwork?
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Sure, mold is a growing problem in homes.
OTOH, bringing in fresh air may help the problem. The filter and heat exchanger would help.
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interesting idea.. i like it.
randy

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John Harlow a crit :

Depends what "under a house" means. Is the house elevated? Is the house on a concrete foundation? etc etc..
Do you mean taking cool air from an existing cavity or laying a couple of pipes under the house and getting air from there? If its the second, it's reasonably common (it's called a Canadian Well here in France). If it's the first, it would depend on the air temperature, the thermal mass's capacity and fan running costs (cold air won't rise on its own...)
Mel
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Melodie de l'Epine wrote:

I'm thinking of the somewhat typical house here in the US (like mine of course ;) with a small crawl space over dirt.

I am thinking about moving the air from the existing cavites using a blower. It seems to me, for the price of running a couple hundred watt blower, there could be substantial energy savings at least in the summer months.
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John Harlow wrote:

I doubt if you would gain all that much and you may have some moisture issues. Cool moist air is not comfortable.
You would gain some, but you just don't have enough area to transfer enough heat (in or out) with just the basement walls. Right now it cools the basement well, but you don't have much air exchange. In addition a lot of the cooling is due to evaporation from the walls. That just adds to the humidity.
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
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On Thu, 02 Dec 2004 17:41:55 GMT, "Joseph Meehan"

Joe, I'm not endorsing the original posters idea. "from under a house" ?
But I have a disagreement with this statement.
" Cool moist air is not comfortable".
In the dry west swamp coolers work well.
Most folks around here have basements where an attic fan & windows open in the basement provide some relief. But practical ? I'd agree probably no.

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26 + 6 = 1 It's Irish Math
wrote:

Very true, but then the cool air will not be most, it will only be less dry. :-)

--
Joseph Meehan



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John Harlow wrote:

For this to be remotely feasible, you'd have to have woefully inadequate insulation. In that case, the obvious solution would be to insulate.
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Good point, but there are attics and there are attics. If the attic is the unoccupied space above the rooms and the insulation is between the joists, you are correct. If the attic is the livable space above the second floor and the insulation is in the ceiling, the idea would work to some degree.
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A couple hundred watt blower? How much air do you think you're going to move from below the house into the attic with that? If you figure out how much energy it will take to run an air handler capable of moving the volume of air it takes to significantly reduce the attic temp, I'm sure you'll find it doesn't make economic sense. You'll likely be spending more on energy than you save. That's certainly true if the attic is properly insulated and ventilated, and if it's not, there your money is better spent just fixing that.
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Chet Hayes wrote:

It's only a matter of time. A low 'cubic foot per minute' fan will just take a bit longer to do the job. As cold air is heavier per cubic foot, he just has to overcome the density difference caused by the temperature variation and whatever resistance to flow may be in the ducting. Large ducts = less resistance.
A one or two ampere motor (approx. 100 to 200 watts) can deliver/remove a lot more energy in heated air that it uses up. That's just a guess for an average bathroom fan motor.
all in my humble opinion, of course..
mike
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A bathroom fan motor would never push hot air down ten feet or cold up ten feet.

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Would you have any evidence for this article of faith?
Nick
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Bathroom fans have a hard time pushing 55 cfm through a 3-4" pipe 20 horizontal feet. They are made to vent smells and humid air horizontally only.
Do the research and think!
wrote:

ten
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Awww. Do they complain?

You might do this and find that the density difference between hot and cold air in houses creates a negligible pressure difference compared to the static pressure rating of the fan or the friction loss of a long duct.
Nick
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Gymy Bob wrote:

I respectfully disagree. I stand by my statement that it would only be a matter of longer time. The amount of air will vary a bit per time period, but it WILL keep moving.
================================== A fan is a "constant volume" device where the transported volume is the same, no matter air temperature and density, if all other things are equal. Only the mass flow through the fan varies with air temperature and air density.
http://www.hvac-toolbox.com/37_144.html ==================================
mike
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