My basement has two vents from inside to outside. Both are set in-between the main floor joists (see pic) and opens outside, with flaps that opens outwards. The ducts are outside the furnace room. I like to know the purpose of them. Also I'm in the process of remodeling the basement and like to know what to do with them or how to handle them? enter image description here

  • 3
    Can't see anything useful in the picture. A dark square in shadow and some insulation. Where do the ducts go/connect to? If not connected, old dryer vent springs to mind, or basement bathroom vent for a basement bathroom that was planned for but not built (yet.)
    – Ecnerwal
    Commented Nov 15, 2020 at 21:33
  • It does not connect anywhere. It's about 10 inch diameter metal tube that goes from inside to outside. About 18 inches in length. Two of them are there. This basement is not done yet so no bathroom. This bigger than dryer vent. My dryer is on the main flow about 20 feet away from it. Like to add another pic but not sure how to.
    – Nick
    Commented Nov 15, 2020 at 21:41
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    How old is the house??
    – JACK
    Commented Nov 15, 2020 at 21:46
  • less than 12 years old, detached and about 2700sq feet.
    – Nick
    Commented Nov 15, 2020 at 21:49
  • Could these be pressure equalizers in/out sides of the house or to vent out warm air? The flaps out side open outwards.
    – Nick
    Commented Nov 15, 2020 at 21:52

2 Answers 2


Until you said it was only 12 years old, I was going to say coal chutes for an old coal furnace. I had those in an old house built in 1910. The chutes led to a walled area near the furnace chimney (the furnace was long gone but the chimney remained because it formed part of a wall in the kitchen). The walled area was filled with dirt when I bought it, but I excavated the dirt to try to make the space useable and found it to be half full of old coal. I put an ad in the paper and someone bought it from me and removed it.

Any chance your 12 year old home was built on the foundation of a 100+ year old home?

My next guess would be vent fan ducts for a radon extraction system, the flap would be to keep pests from going in but let the air our when the fan runs.


One possibility is that these were the inlet and outlet ducts for a heat recovery ventilator (HRV) that has subsequently been removed. An HRV is a sort of air-to-air heat exchanger that allows you to vent inside air to the outside, while drawing in fresh air from outside. The outgoing air exchanges heat with the incoming air so you get fresh air without needing more heating (in winter), or cooling (in summer). There would also be two missing connections to your furnace ducting.

An HRV is required by modern building codes in many jurisdictions, so it would not be surprising if a 12 year old house didn't originally have one.

If you're in a subdivision of homes built at the same time, check with your neighbors.

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