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Community and Q&A

Recessed Lights and Blown-In Cellulose

unremarkab1e | Posted in Green Building Techniques on

Hey everyone!

I plan on using Airtight Self-Gasketing LED downlights in my drywall ceiling, and will have blown in cellulose on top of them.

When it comes time to replace the downlights, when I pull the light down, will the cellulose fall down from the hole in the drywall? Or will the cellulose somewhat settle/clump together and keep its form, and I slip in the new LED puck light?

Or do I need to install some sort of cover (cardboard box taped and sealed around the edges) on top of the puck light?

if anyone has any recommendations for 4” airtight LED down lights 2700-3000k that would be great, so many options out there.

Edit – Does anyone have experience with blower doors or independent testing with these supposed airtight gasketed puck lights? They seem a little too good to be true from an air sealing standpoint.

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  1. Expert Member
    PETER Engle | | #1

    It depends. If the light installs into a standard junction box, then no because the j-box will hold back the cellulose. If this is an all-in-one LED, then yes, some cellulose will fall out when you pull out the fixture because there will be a cable loop above the ceiling that you need to pull out to change the fixture. Some cellulose will come with it, but not too much. The cellulose will clump together and maintain some amount of cavity while you are changing the light. Over time, that cavity will probably settle, so you'll get a bit of cellulose leakage each time the fixture is changed. With 10 year+ ratings on the fixtures, this shouldn't be too much of a problem. No real recommendations for fixtures. They change so often. The major brands seem to have better life span in my experience.

    1. unremarkab1e | | #3

      Thank you for your very helpful response!

      Will weigh the pros/cons of each.

  2. DC_Contrarian_ | | #2

    Note that if you put in a junction box it has to be secured to hold a 50 pound load, whereas an all-in-one can just hang from a hole in the drywall. I don't like the all-in-one fixtures, but there is a certain practicality to being able to put them wherever you feel.

    In my own home I insisted on junction boxes in insulated ceilings, with flush(ish)* LED fixtures. The junction boxes were sealed with caulk after drywall and before painting.

    *(Another downside of junction box fixtures is they don't seem to come as flush to the ceiling as the all-in-one ones do. )

    1. unremarkab1e | | #4

      Thank you your response!

      Will definitely have to consider the increased costs of the junction boxes/labor vs the puck lights.

  3. mordors_eye | | #5

    I just finished doing this in my home, only with loose fill fiberglass. I purchased Lessco Airseal covers. I used excess ZIP liquid flash or other sealants I had on hand to adhere the plastic flange directly to the top of the sheetrock in the attic. I also drilled a small hole into the plastic to push the connecting wire through and then gooped around that hole. I didn't trust the alleged "AT-IC gasket" to do the job by itself. They were like 5 bucks a piece and I used about 20 for the top floor.

    1. unremarkab1e | | #8

      I like the price point of that product. Did you bury the driver under loose fill insulation? It doesn’t seem like it would fit underneath the lessco air seal cover.

      My thorough 5 minute google search makes it seem like the driver should be ventilated or at least easily accessible. So either a cover big enough to fit the driver or extensions and have the driver hanging from a truss piece above the insulation.

      Thanks for your input.

  4. Expert Member
    Akos | | #6

    When I had a blower door test done I was pretty surprised that the slim LEDs leaked no air. Even with an IR camera there was no leak around them. The spring clip on these is pretty strong and as long as you take some care installing it it does seal pretty well. The important detail to get right is the hole size. Almost none of the so called 4" slim LEDs use a 4" hole make sure to measure what it needs, if you make it too big it is hard to get the gasket to seal properly.

    Using a vapor tight octagonal box and mounting the LED on it is the better option. These junction boxes have a gasketed flange that will seal against the drywall. You can get slim LEDs that mount onto these that look the same as the two piece ones. This is one I've used before for this:

    For regular slim LEDs with a separate driver I like to go for high CRI dim to warm units. Budget LEDs provide a greenish light when dimmed low which is not the most flattering lighting. Lot of them also strobe at 120Hz, unfortunately there is no way to find out without installing it and taking a high frame rate video of it with a newer cell phone.

    So far the one that tick all the boxes that I've found (that is high CRI, dim to warm, no strobing) is this one:

    1. unremarkab1e | | #9

      Wow good to know about verifying their air sea with the blower test and IR camera, I was planning on doing the same. Those are definitely premium LEDs!! What did you do about the driver? Did it fit under the octagonal box or under the insulation?

      Thanks for your response!!

  5. user-5946022 | | #7

    I am pleased with the 2700k Nicor Sure Fit j box mount LED fixtures I used.
    Where they are installed in conditioned space under a vented attic, I did a combination of sealing the J boxes with putty pads or spray foam, from the attic side.
    The Nicor fixtures are very flat - they extend less than 1/8" below the gyp, less than many of the clip type. These were easy to get approved by the inspector since the inspector insisted on seeing jboxes at all locations where code requires a light fixture. You can also buy square trim, or round trim, both in various colors, for these fixtures.
    The 2700 are 94 CRI, R9>50, dimmable and can be used in damp locations. The lumens/watt could be better, but all in all, I'm very pleased with them. The trim is all metal, so less likely than plastic to discolor over time. Had a problem with one of the trim pieces for one of the lights, and they promptly sent a replacement with no problem.
    I've got not affiliation with this company other than being a happy customer.

    1. unremarkab1e | | #11

      Thank you for your response!

      The nicor fixtures look nice and I think we’ll be able to fit them into our budget, really appreciate you commenting.

  6. GBA Editor
    Kiley Jacques | | #10

    Mike Guertin answers your question with a video about how to air-seal above the puck light here: How to Air-Seal an Electrical Box in an Attic.

    1. unremarkab1e | | #12

      Appreciate your response and everything you do here Kiley!

      I was really hoping that the blown in cellulose would settle/clump together so that I could change out the LED lights (plug n play) without too much of it falling out of the ceiling. It doesn’t seem that too many people have installed them that way.

      After reading everyone’s responses and research, I think I’ll be going with the tenmat recessed light cover with the LED light and driver within the cover. Then I’ll seal the cover with leftover zip liquid flash or sealant/caulk.

      Appreciate everyone’s help and responses.

  7. greenscrew | | #13

    I'm facing the same dilemma.. what is everyone's thought about the idea of laying a thin piece of fiberglass insulation batt over the light and driver before blowing the cellulose to retain the cellulose in the event of future servicing needs?

    1. Expert Member
      MALCOLM TAYLOR | | #14


      If you are confident in the fixture providing good air-sealing, that's exactly what I was thinking made sense.

    2. unremarkab1e | | #15

      Hmmm interesting idea, I suppose we could blower test prior to insulation installation. If these “air-tight LEDs” do a good job, that fiberglass batt idea seems reasonable.

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