Cabinets and Heating Vents

When a new cabinet covers an existing heating or cooling register, warm air needs a new path. Here are tips on installing toe-kick vents for those situations. August 8, 2006

We have been in business for a little over two years. We have concentrated mainly on building furniture, but lately have been getting a few cabinet jobs. I have been building furniture and cabinets as an employee for other businesses for 15 years. Now that I bear the full responsibility for the work that I do, I have begun to question some of the techniques I have learned through the years. On our last cabinet job, we had to install a cabinet above an A/C heating vent, so I did it the way that I've always done it. I cut a hole in the toe kick, covered it with a vent and installed the cabinet. Should there be ducting running from the floor vent to the toe kick vent, or is it okay to just let the toe kick and cabinet bottom act as ducting?

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor A:
Honestly, I've never had to run HVAC ducting under a cabinet before. In our neck of the woods, it's a self-contained hot water/blower unit. I'm not sure just letting the hot air find its way out the bottom of the cabinet is a good method.

From contributor K:
There are 4-5 ways to do everything in this business! I guess if the bottom of the cabinet were sealed all the way around, that would help prevent air leakage, but would also contribute to the cabinet going through continuous hot/cold cycles (expansion/contraction), which, depending on how your cabinet is constructed, could be a problem.

Ideally, if the cabinet over the vent is at the end of a run or a vanity, it's best to duct it out the side as opposed to the toe-kick, so the doors above it are not exposed to constant heating/cooling cycles, thus, prone to checking. However, if that is not the case, then toe-kick it is!

That said, the best way to do it in either case, in my opinion, is to duct it out to the side or toe-kick, caulk around the ducting in the toe-kick where it meets the wood (this avoids backdraft into the toe-kick area), and then install the vent grate (matching material if you like). This will allow maximum ventilation to the outside of the box, and depending on how strong the air flow is, will also minimize the effects on the above doors/drawer fronts.

From contributor F:

When you do your site measuring, document exactly where the floor duct lies in relation to your cabinetry. Then when you build the toe kick assembly that is in that area, box it in under the cabinet by leaving a 2" or 3" clearance from the duct. I think that does a good enough job of directing the air flow into the room. I don't caulk or otherwise try to seal it off. I have done quite a few and never had troubles with the cabinet or its doors.

From contributor C:
We always leave the finished base off in these situations. We build the cabinet with a sub base. At installation we cut out the sub base where the vent is, then the HVAC guy installs a 90 degree bend 1/2 outside the sub base. Install the finished base with the grille cut out and then apply the grille. You should never allow the cabinet to carry air, hot or cold. I have never seen base heat to damage doors or cabinetry in this situation.

From contributor B:
Contributor C has got it. I usually cut the opening in the kick myself. Most builders prefer a 3" X 10"-10 1/2" hole, coming up 1/2" off the floor. Vents are 4" X 12" and that cutout leaves plenty of meat to screw the vent to.

From contributor D:
To simply put a grill over a hole in the toe kick and let the HVAC system inflate the area dramatically reduces the air flow. The air will find its way out, but using duct work to take the air to the grill will help retain its pressure. Most kitchens that I've seen have too little air moving into them anyway, and reducing it further never seemed like a good idea to me. The previous post that recommended the 90 degree turn and extending the duct through the opening 1/2" and covering it with a grill is the best way to handle it, in my opinion. Parts are readily available at HVAC supply houses or from an HVAC installer and aren't that expensive. If you install it yourself, be sure to count your fingers when you're done. Ductwork is some kinda sharp!

From contributor I:
I do mine exactly like contributor F described. 10 years, never had a problem.

From contributor O:
Most people don't, but I typically build a box under the cabinet to channel the air through a 2 1/4" x 12" register hole that I try to keep high enough to run base shoe under. This helps the air flow by not heating up the entire cabinet. I even will try and center the vent on the cabinet.

From contributor T:
I share contributor O's method and have been doing so for quite some time . The 2 1/4 x 12 vent (floor register) works well and comes in white or brown . I centre to either cabinet or door and also cut the opening as high under the toe as possible . Cut the opening for the vent tight. It is not held in by screws!