I have a small powder room that doesn't have a register/vent so it gets a bit cold compared to the rest of the house. I could install a new duct line split off from the main but there is a wall/floor register right on the other side running in the wall cavity in a 2x4 wall. I'm wondering if I can just cut out the back of the rectangular duct and install a baffle to split the air to two registers and then fine tune with how open the registers are. Or is there a premade solution for this? I found some split return air ducts for equalizing are between rooms but not this specific setup

split register

2 Answers 2


My parents' house has one place with vents that look exactly like that - the duct has two vents, one on each side, and there is a baffle inside such that you cannot look through the vent and see the other room. The baffle extends about 1-2 inches past the edge of the registers.

I spent some time trying to find a pre-made part (or even a picture of someone having done this), but I can't find one.

  • I actually used this to my advantage when running network cable between the two rooms. I was able to remove the cover on one side and reach in to pass the cable over the baffle and into the other room. NOTE: for safety, this should use plenum-rated cable.
    – Moshe Katz
    Nov 27, 2020 at 6:27
  • good idea on extending the baffle down past the edges
    – redlude97
    Nov 27, 2020 at 18:46

This was a common practice in very old houses especially when running heat ducts to a 2nd floor. The only problem is that the room needing the most heat may not heat properly. The fitting you are asking about were called double stack head duct fittings or a similar name and are still available. Myself, I would buy a 4" hole saw and drill a 4" hole in the plaster/drywall and through the back side of that supply duct. Then seal the newly cut hole and install a 4" plastic sewer fitting or similar fitting into that hole. You could go to a big box store to match a sewer fitting or vent fitting with a correctly sized hole saw. (hope this helps).

  • You say "sewer fitting" I'm seeing a plastic floor drain which is pretty ugly. I'm sure that's not what you're talking about, is it? Could you maybe supply an example pic of what you're talking about?
    – FreeMan
    Nov 28, 2020 at 12:59
  • I used the "sewer fitting " as an example of what you could use which would fit in the newly cut cut hole.. The size of the hole and the covering would be up to @redlude97. Oh ya; since I am not computer literate I have no idea how to post a picture. my bad
    – d.george
    Nov 29, 2020 at 12:18
  • You've got 8k rep and never posted a pic here? That's most impressive!
    – FreeMan
    Nov 29, 2020 at 14:02

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