When Air-Duct Registers Get in the Way of Crown Moulding

A vent grille near the ceiling interferes with planned crown moulding. Now what do you do? May 26, 2008

I'm installing trim in a 3500 sq ft home. The crown is 6 inch MDF, and right above the flat screen TV is a vent 2 1/2 inches down from the ceiling, blocking my crown.

I went over different options such as:
1. Moving the vent someplace else out of the way, which the client doesn't seemed thrilled about.

2. Building a MDF box that the crown would go around (which is great in some applications except right above a wall mounted flat screen on a 9' ceiling).

3. Installing 1/4 inch MDF where the crown would sit, butt up to the vent so the crown can ride over the face of the vent and cover it a couple of inches (problem with doing that possibly is air would be blowing on the crown, so I would have to put "fillers" on the backside of the crown to stop cold and hot air from causing joints to split). Does anyone have another method around this? If I did the "crown extension" and built it 1/4 inch off the wall to go over the top of the vent, would that affect the joints or anything else later? I glue all joints with Titebond 2 and use 15 gauge 2 1/2 nails in studs.

Forum Responses
(Architectural Woodworking Forum)
From contributor M:
I usually offer 3 options to my clients in this situation:
1. Have a/c vent moved. Usually down is the easiest if there's room. I've done it myself a few times, but an HVAC guy is a better way to go. I do this about 5% of the time.

2. Remove the vent cover/grill and run the crown right over the opening, then buy a new smaller flat (as in no movable flaps in back) cover and just butt it into bottom edge of crown. In most situations the duct work is coming from above and if you take off the existing cover and turn on the system and feel how the air flows out, you'll see that the air is coming out the bottom 1/2 or 2/3 of the opening. So I'm not too concerned with losing airflow, but I'm not an HVAC guy and have never tested the actual loss. I do this 90% of the time.

3. Stop and start crown with mitered returns at cover. This is last resort and only when the client is not picky and it's the easiest solution. Hate it, myself! I only do this about 5% of the time.

Going right over the existing traps it in for good, so down the road...? As far as hot and cold air hitting the back side - not an issue with MDF, just don't put a splice within a couple of feet. If you or the client is concerned, just put some of the adhesive backed aluminum duct tape on the back in that area and there's your insurance. I've never had a callback.

From contributor J:
I've run into this problem with built-ins more than crown, and I usually recommend moving the vent. Short term it can be a pain, but long term they will be much happier, as other solutions will likely leave them regretting their decision years down the road. I'll usually pop the vent and see if it's an easy enough move, and if so I'll offer to do it for them instead of calling in a HVAC guy.

From contributor Y:
In my limited experience, vents up high on a wall are cold air returns. The space between the studs is used as the duct and the air is sucked back to the plenum. All I've done is lower the vent to go just under the crown. Cut the drywall down to accept the new location of the vent.

From the original questioner:
Thanks for your opinions. I feel that it is the best solution to just have a sub move the vent. This is a higher end house ($800k) and I'm hoping to do the rest of the street when I'm done with this one. They're going to have to deal with the pain in the butt short term so I can feel comfortable. Plus you made a good point, and they are picky and pay attention to design details. As for non-picky clients, it's good to know that the MDF should hold up with the ac blowing inside of it with the tape.