I was in the shower yesterday and said "Oh no, a loose tile!". 5 hours after the shower, I'm here, as the tile was not just "loose" but water had gotten all into the wall and was wet. So at this point I've torn out all the wet parts, but to my surprise, there's an airduct hidden behind the wall, going nowhere (red arrow):

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I stuck a towel into it so debris wouldn't fall in, but here's how it looked after I pulled the drywall off, completely open:

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No way this is supposed to be like this, right? Tell me this was a screwup by the builder and they forgot to close it off?

The furnace is right below the bathroom, and a very short run duct is going to this location. On the opposite side of this wall is the closet... I always wondered why it was so warm in there.

What should be done about this? I could easily remove the ducting from the furnace and seal up the hole if that's the job required.

  • Is there any other heating vents in that room?
    – crip659
    Oct 8, 2023 at 11:55
  • Yes, right by the entry door to the bathroom. It's the master bath, but only something like 6x8' (guessing, didn't measure it).
    – LarryBud
    Oct 8, 2023 at 11:56
  • 3
    You're sure it's not an air intake drawing air from a room above the bathroom?
    – popham
    Oct 8, 2023 at 19:16
  • Are you sure this is a duct? Looks to me like nothing more than a gap that was hidden, and therefore didn't need to be closed. Is there something that the photo doesn't show?
    – MikeB
    Oct 9, 2023 at 8:57
  • Isn't the difference between a vent and a simple void that one goes somewhere and the other doesn't? Oct 9, 2023 at 18:50

1 Answer 1


Look up.

At various points in time it has been considered acceptable in various places to use a stud bay as a duct, without bothering to line it in metal, etc. So you may find a register above this location.

  • 2
    House was built in 1995. So it might be "ducted" to the upper floor using this bay?
    – LarryBud
    Oct 8, 2023 at 11:55
  • 3
    I can see them using the bay as a cold air return, but not a heating duct.
    – crip659
    Oct 8, 2023 at 11:58
  • 9
    Looking at where it goes, I believe you're right, it's a cold air return.
    – LarryBud
    Oct 8, 2023 at 12:02

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