I recently discovered moisture in my attic and the mold inspector recommended sealing all the canned lights in our house. We have about 30 in vaulted ceilings where there is no attic access.

Any tips on how to seal the fans from below?

For reference. House in in Seattle, built in 2008. Canned lights are IC air tite halo models. I was surprised that they leak air as they are air tite. But I can imagine given its not sealed like our bathroom recessed lights and closet recessed lights that have a glass cover and gasket.

If I take the baffle off the unit is metal and there are some screws and such.

Do I just caulk the can to the Sheetrock around the opening and then form or tape the crevices using duct tape?

  • How much moisture were you having in the attic - just "some" or "a lot"? Are you sure the moisture is coming from your light cans? Is your roof ventilation adequate?
    – Mark
    Jan 6, 2015 at 5:36
  • Yah, moisture from sealing cans seems suspect to me as well.
    – Ariel
    Jan 6, 2015 at 10:29
  • Light to moderate moisture. We are getting ridge vents installed in the attic. Jan 12, 2015 at 18:57
  • Removing the moisture will be essential to your health. Mar 3, 2016 at 1:30

2 Answers 2


Your best option is to caulk the can's rim to the ceiling drywall and then replace the bulb with a drop-in LED replacement. These things are self-contained units that seal off the air leakage paths themselves, and you can caulk them to the housing too for extra assurance.


I would not use caulk but rather some self-stick very thin foam tape. Cut the tape into 5 pieces (5 lines, since it doesn't come in a circle, make a hexagon with it) and tape to the can. Then press onto the ceiling.

But get the thinnest, and softest (least dense) tape you can find.

  • 1
    What's wrong with caulk? I found that my recessed cans have an accessory available which is a plastic gasket with adhesive that seals the can to the sheet rock and covers up the only holes in the can for adjustment to flush the can to the ceiling. Jan 12, 2015 at 18:58
  • 2
    I would not want to install the can in a way that makes it hard to remove. I'd also worry about the heat from the bulb drying out and cracking the caulk.
    – Ariel
    Jan 12, 2015 at 19:06
  • In my experience heat is much more likely to degrade foam tape than caulk, especially if the caulk is silicone-based. Foam tape just crumbles after a few years.
    – isherwood
    Dec 3, 2015 at 22:09

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