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TomC[_2_]

wrote in
:

My Guess....furnace in the basement? Does it happen all the time or
only when the ac/furnace blower is running?

It's pretty much happening all the time. I do have the HRV running
most of the time. But even with that shut off I still feel draft.
The basement is about 75% underground with 8' tall cement walls. The
rear of the house is above ground and about 10 feet on either side
are also semi-above ground. It has to be coming from the HRV or dryer
vent.

My basement is very similar to yours and I experience drafts
under/around the basement door also. It's most noticable when the
ac/furnace is running. I have two hvac registers in the basement, but no
returns. On a windy cold day the drafts are most noticable even when the
blower is not running. I have a fresh air intake for the furnace and a
gas fired hot water heater in the basement that is vented to the
outside. Also, my garage is at the exposed end of the basement but
seperated by block walls. My theory is that there's enough fresh air
from the mentioned openings to create a positive pressure in the
basement and the air has to find a way out and takes the least resistant
route which is under the basement door. Even though the house is well
insulated there's enough openings on the upper level via bathroom
exhausts, kitchen exhaust, and fireplace that it creates enough lower
pressure for the draft to occur. FWIW.