My house has been staying cold when I'm not running my wood furnace and using my heat pumps. I discovered cold air blowing through my vents. It's not radiating through, you can actually feel the air blowing with the wind outside. I've eliminated the air coming through the chimney by blocking it off and I still have cold air blowing in. I'm baffled. I know the duct work isn't connected to the outside but I don't understand how it is blowing in. Please help, thanks!
Cold air blowing through vents, furnace not in use?
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Do you have any ductwork outside the conditioned air space? Attic, crawlspace, etc.
jatoxico
Minister of Fire
I used to get get cold air dropping from AC ducts running through my attic. Warm air was rising into the return and cooling then dropping out the vents. It would circulate like that until I began covering the return with plastic sheet.
Not that I can find. I suspected that as well. I asked the previous owners when they remodeled if they left any ductwork open but they said they didn't. I can only look in my basement for the ducts to the first and mid floor, but not the 3rd floor. It's a tri level style home. I'm stumped. I figured there was an open duct somewhere and the wind coming in the attic was blowing down into a duct.
Maybe the home uses open wall cavities for return air? If so, air leakage could be travelling through the walls into the cavities. That almost sounds like a job for a thermal cam to investigate. Measuring temps from the registers and if possible, being able to see anything in the walls. Unfortunately there's been many cases where ducting was sloppy or disconnected. Does the home have outdoor ventilation?
brenndatomu
Minister of Fire
Like a split level ranch?
Those are notorious for some insulation/air sealing issues often times...which if what laynes just said is true about using stud/framing bays for returns (common) then that would explain things...
Fresh air vent? Gas furnace induction air intake? I wouldn’t think these would let in noticeable draft of air, but maybe if it’s windy enough...
I have found this to be the case in my area a lot. Some of the older homes have the returns out at the outside of the rooms in a wall cavity and when the wind blows it will blow cold air to the furnace and out the outlets. Had one house I went to the heat pump couldn't over come the cold air and would run non stop and never warm the house up.
brenndatomu
Minister of Fire
My in-laws had a spec home built about 12 years ago. It shares wall cavities for interior walls as returns. I don't believe it's code now, however one would be surprised.
I don't see any visible returns to the outside/roof. There is a built in cold air return system, but it is all duct work. When I can get a chance with work I'm going to go in the attic and see if the walls are open. Could there be more than one return like you guys are suggesting through the walls? The attic has an open gable end and a turbine vent to airflow through the attics.
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