"John Harlow" wrote in message
...
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?

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, ...

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?

"John Harlow" wrote in message

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?


I'd be concerned about the quality of air from under the house. Mold spores
could cause problems.

Edwin Pawlowski wrote:
"John Harlow" wrote in message

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?


I'd be concerned about the quality of air from under the house. Mold
spores could cause problems.

Interesting - wouldn't they also cause problems under the house?

How about a filter, or a heat exchanger made with some ductwork?

"John Harlow" wrote in message

Interesting - wouldn't they also cause problems under the house?

How about a filter, or a heat exchanger made with some ductwork?

Sure, mold is a growing problem in homes.

OTOH, bringing in fresh air may help the problem. The filter and heat
exchanger would help.

interesting idea.. i like it.

randy

"John Harlow" wrote in message
...
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?

John Harlow a écrit :
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?




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

John Harlow wrote:
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?

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

John Harlow wrote:
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?


For this to be remotely feasible, you'd have to have woefully inadequate
insulation. In that case, the obvious solution would be to insulate.

"Robert Barr" wrote in message

For this to be remotely feasible, you'd have to have woefully inadequate
insulation. In that case, the obvious solution would be to insulate.

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.

Melodie de l'Epine wrote:
John Harlow a écrit :
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?




Depends what "under a house" means. Is the house elevated? Is the
house on a concrete foundation? etc etc..

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


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...)

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.

26 + 6 = 1 It's Irish Math
"3rd eye" wrote in message
...
On Thu, 02 Dec 2004 17:41:55 GMT, "Joseph Meehan"
wrote:

John Harlow wrote:
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?

I doubt if you would gain all that much and you may have some moisture
issues.

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.


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


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.






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

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.

Chet Hayes wrote:

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?

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

Gymy Bob wrote:

A bathroom fan motor would never push hot air down ten feet or cold up ten
feet.

Would you have any evidence for this article of faith?

Nick

Gymy Bob wrote:

A bathroom fan motor would never push hot air down ten feet or cold up ten
feet.


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

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 in message
...
Gymy Bob wrote:

A bathroom fan motor would never push hot air down ten feet or cold up
ten
feet.

Would you have any evidence for this article of faith?

Nick

Gymy Bob wrote:

Bathroom fans have a hard time pushing 55 cfm through a 3-4" pipe 20
horizontal feet.

Awww. Do they complain?

Do the research and think!

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