I am refinishing my basement into a 1BR apartment and I happen to have an easy access to intake outside fresh air and fan it into the apartment. I was planning to have one of those standing AC units so I had put a 4" vent outlet on the outside of the bedroom, same as for a dryer. The plans changed so I went with central air but still have the outlet in the wall that could be used, with some degree of easy adaptation (to remove the flap that prevents inflow).

My question is, does it make sense to fan fresh air into a basement living space, of course controlled with a switch? Will it significantly improve the quality of air breathed inside? It would be like fan assisted ventilation.

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    "Make up air" is usually a good idea and normaly drawn in by the furnace (there needs to be a filter prior to the furnace). By using some of the draw of the furnace you wont need an additional fan plus the entire house will recieve the fresh air. If you just want the air in the basement that is a good idea also but be aware if your basement has HVAC vents the air from a secondary blower may reduce the furnace/AC to the basement while the fan is blowing.
    – Ed Beal
    Feb 23, 2016 at 0:28

1 Answer 1


I think it's a bad idea. I understand the intent & initially it sounds good, but it's a basement. If anything you really would only want it to exhaust air & you absolutely wouldn't want to introduce humid outdoor air into the basement. You might even have a Radon problem that this would be better used for.

If you can't use it for Radon, Bath or Kitchen exhaust venting, then plug it up with foam or fiber insulation until a future use can be determined. You could also use the hole as natural light by making your own Sola-tube type of setup.

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