I have a bathroom I'm remodeling, and the current heat vent is attached to a meandering ~10' run of round duct which originates from the trunk of the furnace (located next to this bathroom in the laundry room). The vent needs to be removed because of a change I'm making to cabinets. Can I attach the new vent directly to the supply trunk (which runs right above this room), or is it important that I provide a run of round duct for some reason?

The bathroom is small (6'x11'?), and with the furnace nearby, I imagine putting a supply vent directly onto the supply trunk could result in a lot of hot air coming in due to pressure. Can I solve that by using a small vent?

  • 1
    It's difficult to answer this question definitively, without knowing a lot more about the furnace and the ducting. The best advice I can give, based on the information you've provided, is to install a damper in line with the new duct. This will allow you to make adjustments if they are required, without running all new duct.
    – Tester101
    Jan 12, 2017 at 16:13

1 Answer 1


That should be fine (I've seen it done many times in basements), with a few caveats:

  1. You're right that there will be more flow with that setup than with a length of round duct. Add to that the smaller room you're feeding, and you can see that you'll need to dampen with an adjustable vent.

  2. By doing so you may introduce noise. You have a shorter sound path from the furnace itself, and adding a damper vent will likely cause white noise at that location as well.

  • Thanks. I think I will find a new way to include a run of ductwork of some kind, just to reduce the pressure and reduce the chance of noise. Jan 13, 2017 at 21:44

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