And yet another opinion-
The outside intake to the air return runs the house at a slightly
elevated pressure which makes it less "drafty" (all the drafts are going
out). Disconnected, your house would probably be draftier but cheaper to
heat since you are not forcing air out through cracks. A new well sealed
house might use an air-to-air heat exchanger but with your leaky house
that wouldn't be effective. Having a source for combustion air that
leaves up the flue is also an issue but not so much, as you said, in
your drafty house. My house, drafty type, has a flexible insulated duct
for combustion make-up air with the end bent in a U shape at the end - a
block from cold air just flowing in.
Of course that is only true for the short periods when the furnace
blower is running. What about the rest of the time? And if the
house is so drafty that it's noticeable, the drafts should be fixed.
Disconnected, your house would probably be draftier but cheaper to
Yeah, that's for sure. Plus, by drawing air into the house purposely
to force air out cracks, you are doing exactly that. On a calm day
with no breeze when there would not be much air flow through these
cracks, and hence little energy loss, now you've got a blower creating
Having a raw outside air intake into the return plenum is simply one of
the dumbest things imaginable
A new well sealed
Pay attention to trader. He got it right. Fresh air piped into the
return duct from the outside is a large waste of energy dollars. Its
typical on a rooftop commercial application where required amounts of
air into the building are needed.
If you have an atmospheric burner (open to your basement) many codes
require piping in fresh for combustion. Most just leave the pipe
hanging on the side of the furnace or down at the floor. I prefer to
actually point or connect the pipe to an opening near the burners.
Just make it easily disconnectable for easy service to your furnace.
It does have to be sized properly or it will do no good.
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