I had a new gas hot air furnace installed in my attic. The
installer/contractor sealed any obvious leaks in the 25 year old duct system
in my attic. My ceilings are well insulated.
Today, the outside temp is 55, in the garage (nonheated, non insulated) it
is 60, in the house it is 72 and in the attic the temp is 70.
Seems to me, the attic should be just about the same temp, maybe a tad
higher, than the garage.
How can I find out where my ducts are leaking? Can I do a "smoke test"
myself? Any suggestions?
Another thing to think about is whether your furnace has a pilot light.
With the (relatively) small volume of the attic, the pilot can make a
difference, especially if there's not much wind to help ventilate the
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You can perform a homemade version of a *blower door test* that will
show whether you have any significant leakage in the supply duct system.
This might be the first order of business, since your method of
determination of leakage above is a bit ambiguous. Solar heating can go
a long way in a well insulated attic. At the conditions that you gave
your attic temp may be normal. On cold days heat radiates up into the
attic, from the space, and on hot days heat radiates down into the space
from the attic. It follows that at some moderate ambient temp the space
and attic temps will be equal.
To see if you really have a duct leakage issue: On a calm day just crack
one window open a few inches, making sure all other windows, outside
doors, and other openings are closed. Turn on only the indoor blower
of your furnace. Observe differences in air movement through the cracked
window with and without the blower running. The difference in air volume
through the cracked window should be close to the air leaking from the
ductwork. This will depend upon the cumulative size of any and all
other structural air leaks. Because of this a wider opening in the
window will produce a more accurate measurement, but at the same time
will make it more difficult to check air volume changes since the
velocity of the air moving through the window will be reduced as the
opening is increased. If you notice a definite change in air flow
through the window between blower on and blower off, then you have duct
leakage worthy of concern. If the change is so low that you are unsure
whether there even is a change, then you probably don't have leakage
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