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Air sealing retrofit LED — airtight, IC-rated non-can lighting

rhl_ | Posted in Energy Efficiency and Durability on

Hi, we had some recessed lights in one of our bathrooms. They were non IC rated can style lights, that had large holes into the unconditioned attic space. I was having trouble getting dimmable LEDS in them, so I started replacing them with these retrofit led lights. See the attached photo. These are “airtight” and IC rated. There is no can. I know that they aren’t really airtight. Attached is a photo from within the attic of the attic floor where a recessed light lives.  I want to take a ~16″ wide rectangular piece of rigid foam (I have some polyiso lying around), cut a small hole for the electrical connector to the box (white cord shown in photo), and secure/air seal the rigid foam to the attic floor. Ideally this would make that penetration airtight.

Is there anything wrong with this? Will it work? Is there any reason to believe the LED light will stop working? Is this a fire risk? moisture risk?
I’ve had trouble uploading photos here, so instead you may find the photos here:

air seal this light fixture?

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  1. TimTuckerCom | | #1

    From an electrical perspective, I believe the junction for the 120V AC wiring needs to remain accessible -- either by including the box shown within your sealed off area so you can get to it by removing the light from below or by ensuring you can still get to it from the attic side (covered by removable insulation is OK).

    Personally, I'd be hesitant to have the white wire be the transition period between the sealed / attic area just because the AC -> DC converter is likely to be the part that fails first for a light like that.

    1. Trevor_Lambert | | #2

      It would be fairly trivial to pull the white cable through the sealant to install a new driver. It would have to be done from the attic in any case.

  2. rhl_ | | #3

    That box is surely not able to fit through that hole. they do make extension cords for the white wire, so the box can be attic accessible -- the light fixture "removable" from below. infact, the rigid would help here, so if we packed the cavity with cellulose, removing the light fixture in the future (even removing the insulation) wouldn't interfere with the cellulose.

  3. Expert Member
    BILL WICHERS | | #4

    Yes, the junction box needs to be accessible per code. But the code doesn’t say it has to be “easily” accessible. Since you obviously have attic access to the top of the fixture to take that pic, you have “access” to the junction box to satisfy electric codes.

    I’d just box the light the usual way, but with a smaller box. I’d use maybe 3/4” or 1” thick polyiso sheet. Leave a little air space around the light itself and you should be ok. I would make the insulation tight to the light fixture. Leave the ballast box outside the box if you want.

    You have very little blown-in insulation in your attic. You would do well to add a bunch more, and make sure all the wood framing in the ceiling is covered. It looks like you might need baffles at the eaves too.


  4. KeithH | | #5

    First, I'm just a DIYer. YMMV.

    Personally, I don't think making foam boxes for your can lights is a great idea from a fire perspective. I'd consider an alternative that is less flammable (especially less meltable when it burns). Some options to consider: mineral wool hats, glued together fiberglass faced gypsum box or fire rated paper gypsum board, mineral wool board insulation, framing lumber across that area (backfill with mineral wool or fiberglass) with a screwed on plywood lid for future access, just to brain storm a few things. You could also pass the driver through an air barrier (like the plywood lid) and foam the wiring hole) which would leave the driver on the surface of the attic.

    Another alternative you don't discuss is dumping all those lights with their detached drivers, putting in standard airtight cans with an airtight led lamp. Drivers are attached to the bulb then, you won't need to leave access in the attic, you'll have a metal barrier between your cellulose and the stuff that might burn (led driver and bulb). Yes airtight cans aren't and neither are the lamps but are they good enough?

    You also should be aware that if you bury that wire in cellulose, it might be downrated for amperage. If it is just serving some led can lights, it is probably ok but if that's a large general circuit, you might have a problem burying the wire. Consult with your electrician. If that's the case, you might need to bring the wire up to the roof rafters and come down to each appliance/fixture.

    1. Expert Member
      BILL WICHERS | | #9

      NM (romex) wire restricts you to using the ampacity in the 60 degree column of the conductor ampacity table. It’s assumed that NM wire may be covered in insulation so it’s already allowed some extra thermal margin by that rule (NM wire is actually 90 degree capable insulation, but downrated by code to 60 degrees for ampacity purposes).

      I agree that using a “real” IC-AT can light is probably preferable to the little clip-in lights. If those flip-in lights ever fail, you probably won’t be able to get a matching replacement. With a real cab light, you can swap out the bulb or get new LED trim. Note that the “airtight” rating of the AT can lights is often fairly optimistic so you still want to do the box-over air sealing trick.


  5. rhl_ | | #6

    I wasn't planning on making a "box" i was planning on just sticking the polyiso right on the attic floor, with exactly one sheet of polyiso. This will leave a small airspace however, since (as is shown) the light is not flush to the attic floor, the 4" cutout extends maybe 1/8" or 1/4" above the top of the light fixture. I could cutout maybe a 1/2" deep by 4" diameter round section of the 1" polyiso to make a slightly larger airspace.

    I agree we dont have adequate attic insulation. Also what we do have is approaching 50 years old. We aren't rushing to throw insulation until we first add AC (sized by manual J/engineer for the future insulation), and update the electrical. Then we have a contractor ready to give us *a lot* of insulation. But this is off topic.

  6. KeithH | | #7

    Well, if it was my house and I was going to put in R-60 cellulose, I'd dump those lights when I did and move the drivers into the conditioned space. Or if you love the lights, I'd pigttail the drivers up to the rafters. I don't know what your climate is but I bet your manufacturer doesn't even spec those drivers for attic temperatures.

    I'd also have the wire jump up to the rafters. It sucks to dig in cellulose. I'd also be sure to build up the floor and deck the attic floor for a 4' perimeter around my access point. It also sucks to climb into an attic that just has an insulation dam. You can't sit down, you can't put tools anywhere, you inevitably get insulation in the house.

    If you have all this future work planned and aren't going to backfill with insulation, I'm not I'd do anything to cover your lights up. Seems like a ton of unfun work that could be made irrelevant during your planned attic insulation project.

    But if you do, consider a premade hat. Something like this:

    To summarize, IMHO:
    - Unless a knowledgeable electrician told me I could, I wouldn't bury my homerun wire in insulation and especially not my drivers. Either relocate or change the lighting setup.
    - I'd check the operating temperature range on those drivers.
    - I wouldn't use foam board in contact with warm/hot electrical for any purpose.
    - Consider a mineral wool hat instead of foam board if you want to air seal your cans individually.

  7. jberger | | #8

    Just another idea I used in my last house. I was in a similar situation and decided to air seal from the interior drywall side instead of dealing with the hats, foam, etc.

    It was just a simple tight drywall approach and it appeared to work with the images from a thermal camera.

    Maybe it didn't work as well as a perfectly sealed system, but it did make a noticeable difference in the smoke test and was dead simple to implement. Just some caulk on the inside of the trim ring and popped it in place.

  8. jberks | | #10

    If airtightness is the goal, a simple round vapour barrier light enclosure would do. Just caulk it to the top side of the drywall.

  9. redbera | | #11

    What about simply gluing/caulking the baffle of the LED fixture to the bathroom ceiling to deal with airflow? Would be a little hard to change out upon inevitable failure, but they're supposed to last 10-15 years. Seems worth it to me.

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