I have a below ground basement which is always cold unless you turn the
heat on. Even on a warm summer day you need to turn on the heat to
bring it up to a comfortable temperature. It's well insulated, but the
sun doesn't hit any of the wall to warm it up.
As I crawled around in my attic the other day the heat was almost
unbearable. It was 30 degrees outside and must have been 45 in the
attic. I was thinking to myself, why can't this warm attic air be used
to heat the basement? I think all you would need is a vent running
from the attic to the basement with a fan pumping the air through it.
The drawbacks I could see to this system are that there is fiberglass
dust in the attic, the system would only work in the summer, and the
air in the attic seemed to smell funny, although it may have just been
Has anyone ever tried to implement such a system?
we had a local guy try a similar thing last summer. He ran
two 12" pipes from the crawl space (under house) to attic,
to "swap" cool foundation air with hot attic air, to reduce
air conditioning load. And added a 3/4 hp blower. Result:
worked great for about 30 minutes, then the floors started
to get warm ;-) he has good mechanical skills, just needs
the math to work out these things, or nick's phone number!
-larry / dallas
I wonder if you were to get insulated round duct, the kind that has the
spring in it. If you were to run this down to your basement and have a
blower attached at either end. My thought would be to have the blower in the
basement (only due to the hight heat in the attic) I would also build an
enclosure for in the attic, attach the duct to one end of the enclosure and
have the other end fitted for a filter (to remove dust and fibers) I think
this is doable! Great idea too! I have a woodshop in my garage and thinking
about this, maybe this would work for me. Seeing that the heat rises and the
second floor of my garage is heated (its another workshop and rec room up
there) I wonder if I could bring enough warmth down to the shop to make it
Comfort depends on the temperatures, but it will bring down the heated air
and is certainly worth the minimal effort required. . May be just as cheap
to run a second heater though. It certainly won't be free. (except in
It can, altho it may condense water in the basement if its dew point temp
Tdp = (T+460)/(1-(T+460)ln(RH/100)/9621)-460 is higher than the basement
temp. For instance, 70 F and 50% makes Tdp = 530/(1-530ln(0.5)/9621))-460
= 50.5 F, with condensation on 45 F basement walls. Then again, that warms
the walls. With enough airflow, they will warm to the dewpoint and the
condensation will re-evaporate. Without enough airflow, the basement will
gradually become an aquarium. We might avoid this with a "differential
humidistat" that only moves air through the basement when it contains less
absolute moisture than basement air, eg a Smart Vent (tm.)
My basement has a $5 humidistat and a $12 window box fan near the floor
that pushes air up through a duct to the first floor when the RH of the air
near the floor rises to 60%. Yesterday, I washed some clothes and hung them
to dry in the basement. The fan is running this morning, for the first time
this year. T = 65.5 F with RH = 69% on the first floor. The outdoor temp is
51.0, at 6:30 AM. This might be a good time to run a dehumidifier to warm
the house. Or wait till outdoor air warms up later today, and open a window.
If it were hot and humid outdoors, a window AC could help, with additional
net house cooling from the basement.
An attic with a transparent south roof can collect lots of heat,
as in our Soldier's Grove Solar Today story at
This is something I've thought of as well. You would need two ducts,
supply and return, otherwise you'd draw air into the attic from the
outside, which would make the whole thing useless in the winter. Using
a filter over the intake in the attic as someone else mentioned is a
necessity. It must be pleated hepa grade to ensure no attic
contaminants move thru the house. Bigger is better than smaller- lower
resistance, longer maintenance cycle. A bit more $ up front, but can be
vacuumed clean many times with care. Use a fan/blower that's just large
enough to move the air at a reasonable rate. You'll have to figure out
for yourself how to control the on-off cycle. If you have predictable
sun in winter, a photo switch might do, or a timer or ? otherwise.
There should also be a filter on the return in the attic, as there may
be times/conditions when the fan is off that you get air going down
that way. All of this depends on if/how well your attic is ventilated
and other "local" conditions.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.