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I am redoing our kitchen, and adding more cabinets. This register ended up behind 2 cabinets. How should I route the duct to 1 or 2 toe kick vents? Do I need duct work under the cabinet, or can I just let it blow into the area under the cabinets and put in toe kick registers to let the air out?

Picture of cabinet with vent partly behind it

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    Do you have access to the duct work below the floor or is it in the wall?
    – JACK
    Sep 22 '21 at 1:10
  • If you can get underneath the floor and the duct is there you can move it. I put ductwork under my cabinets, that worked quite nicely for me. However there was a basement underneath so I was able to do it easily. I took a flat duct, put a round hole in it in the middle, added an adapter and connected the duct to that. Taped it, added two registers and all is working great.
    – Gil
    Sep 22 '21 at 1:11
  • I do have access to the basement. Moving it to come up through the floor under a cabinet is possible. Sep 22 '21 at 18:11
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I faced a similar situation when we added new cabinets to our kitchen. Our vent was in the floor, but, more conveniently, didn't span 2 cabinets.

I simply purchased some rectangular sheet metal ducting, cut a hole in the bottom to allow the air from the floor duct in, and ran it to a hole I cut in the toe kick. I put the vent from the floor duct into the hole in the toe kick. It's served admirably for the last 30 years.

I would suggest that you can do the same, except that you'll have to split the duct lengthwise and put 1/2 into each of 2 cabinets. I see no reason why you couldn't simply attach the duct to the cabinet sides to help ensure that the majority of the air actually makes it to the toe kick instead of leaking out under the cabinet. You'll also have to come up with some sort of custom grill to cover each half as it pokes out from below two neighboring cabinets.

To be honest, you could simply allow the air to blow under the cabinet without any ducting at all, but you will lose all air speed and it will just dribble out of the vent(s) in the toe kick. It will still heat/cool, but it wouldn't be as efficient at getting the air into the living space instead of just being trapped under the floor. This isn't a highly recommended option, but it is an option.

Due to the added complexity of ducting across the two cabinets, you might consider rearranging the cabinets to allow the vent to fall under just one cabinet. Obviously, you've already purchased the cabinetry and have your (spouse's?) heart set on this arrangement, but... it might make your life enough easier to make it worth it. Something to consider.


An option that would involve more work, yet make life easier (ah, the oxymoron...) would be to gain access to the duct work, most likely from below, and reroute it slightly so that it exits the wall or floor a bit to the left or right so that it is below one cabinet instead of split across two.

Since this will be hidden behind cabinetry, you could also tear up the wall/floor a bit to gain access from above to reroute it there. If your house is newer, it's likely that flex duct was used, so there's a chance that there will be enough room to wiggle the duct around to make it come out where you now need it.

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    I don't understand your statement about air speed. That isn't how airflow works. There's not really added resistance to flow with an open undercabinet cavity. If the entrance and exit have similar area, flow rate will be similar. It may not be directed as well, but....
    – isherwood
    Sep 22 '21 at 13:21
  • I said "loose" air speed, not "lose" air speed. "loose" air speed is very bad. ;) (or just a dumb typo). IIUC, the amount of "blow" you feel at the vent will be determined by the speed at which the air moves. When moving through a duct of x" cross section you'll get y speed. Quadruple the size of the duct and you'll quarter (or worse) the speed. Thus it won't feel like it's blowing as much. Of course, I could be totally wrong.
    – FreeMan
    Sep 22 '21 at 13:21
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    I do have access to the basement. I'll have to look at where I could re-route the duct. I think I can run a new duct up through the floor under a cabinet, but I'm not sure if I could move it within the wall to be under one cabinet due to other stuff in the wall. Sep 22 '21 at 17:54
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    I am re-routing the ductwork up through the floor under one of the cabinets. I found a toe kick duct boot at Menards that will do what I need. Sep 26 '21 at 1:27
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You certainly can just use the cabinet base as a duct. Modern code tends to require supply runs to be fully ducted, but that's mostly for efficiency. It was done with cabinet bases for decades with no ill effect. Returns are less strict and are often simply floor or wall cavities.

Since the current duct is split among two cabinets, I'd probably do these things:

  • Cut appropriate openings into the backs of each cabinet to match the wall opening.
  • Cut standard vent grill openings into the bases of each cabinet, spread as wide as is convenient (or directed where heat is needed).
  • Close any openings in the bottom of the cabinet where air would leak. Even just stapled cardboard would do.
  • Place foam tape or some other seal around the wall opening to block any airflow that would escape to other areas.

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