GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

More recessed lighting questions – best air seal?

dave_naff | Posted in General Questions on

I appreciate all of the thoughts that folks have put into the Q&A elsewhere on the site. A few questions that have come up as I’ve poked around:
1. What’s the best technique for air sealing any of the LED retrofits with the ceiling?
2. What tends to have the greatest impact: filling the prior insulation void created by the can with insulation or simply getting a tight seal around the ceiling?
3. Do any of the junction box insertable LEDs have heat dissipation issues? (presuming the junction box is surrounded by insulation?

Thanks in advance!!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    BILL WICHERS | | #1

    I like to use a bead of rope caulk around the perimeter of the trim ring to seal that ring to the drywall (not to the metal of the can). This is probably as good as you can do for air sealing aside from "boxing over" the entire can light from the attic side.

    The air seal will do more for you than insulating, except perhaps if you have a deep can that pokes all the way through a thin insulation layer. You really shouldn't stuff the can itself full of insulation though -- if you have thin insulation above the can, you should really fix that from above, on the attic side.

    The lights that can go directly into drywall (no recessed can) always make me nervous when installed right up into insulation. I prefer the fixtures that mount into the octagon electrical boxes so that there is at least some level of protection for the light from the insulation. I've never used the clip-in lights that need no can or box behind them, since I have never really trusted those style fixtures.


  2. user-5946022 | | #2

    Can't answer your other questions, and can't even answer #3 fully, but I can share this:
    I used the Nicor Sure Fit (very very thin) J box mount LED's. 8 of them are in Jboxes that protrude into approx 18" of cellulose in a vented attic, so if the J boxes are 2" deep, there is 16" of cellulose above them. Also, each J box in such a location either has a putty pad on the attic side to air seal it, or got sealed from the attic side with spray foam when they foamed the top plate at the perimeter. So far I have had absolutely no issue with Nicor lights related to heat or any other issue with the light part of the fixture (I had an issue on one light with the trim piece staying on, and Nicor promptly sent a replacement light and trim). Highly recommend these. I also finally installed a dimmer to 2 of them, and they also dim well.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |