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Closed Cell Foam Insulation around downlights and other heat sources

Concerned_Home_Owner | Posted in General Questions on

A friend recently had a certified contractor install Closed Cell Insulation in his home addition. During the installation, he received multiple opinions regarding whether it should be sprayed directly on his recessed lighting housings. The recessed lights are Juno LED lights in IC rated housings. Since they were IC rated housings the contractor felt it was OK to spray up to and on the housing. However, the architect felt that approach was unsafe and ordered the contractor to cut/scrap away the foam directly around the lights (around 4″) and install Mineral Wool. So now he has Closed Cell insulation everywhere in the addition except around those downlights. Was this a good idea? Also, should this also be considered in the walls directly behind the oven and refrigerator due to their heat? Also, the scrapping of the closed cell insulation was not perfect as there was still some remnants of it stuck to the ceiling joists and housing. Could these remnants present a problem?

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  1. user-2310254 | | #1


    Here's my non-professional opinion based on your description.

    Recessed lights in a cathedral ceiling (assuming that's what your friend has) are a bad idea. I think the homeowner should have kept the closed cell in place to better air seal the lights--although it would have been better to use surface-mounted lights. (Your friend might want to make this change if there is still time). If it's too late to change the lights, it would be a good idea to focus on air sealing them to minimize air movement into the ceiling. New drywall should be installed in an airtight fashion as well.

    But let's see what the professionals advise.

  2. Expert Member
    Akos | | #2

    This should answer your question:

    Overall it is not a good idea to cover over slim LED lights as these or their supply might need be replaced down the road.

    For ceiling my preferred method is a vapor tight electrical box with a surface mount low profile LED light. The electrical box can be covered with SPF without issues and you still have an easily replaceable light.

  3. Expert Member
    BILL WICHERS | | #3

    The thing that makes an “IC” rated fixture IC rated is a thermal switch inside that will shut off the light if the fixture gets too hot. That’s pretty much it.

    You’re probably ok with the closed cell spray foam from a safety perspective, but it’s not a good idea. As Akos points out, the slim fixture with separate power supplies should really not be covered regardless of their rating due to future serviceability needs.

    The most important thing with a cathedral ceiling is air sealing. If you can apply maybe an inch or so of spray foam to the sides and top of the mineral wool around those lights, you’ll seal things and be ok in regards to air sealing.

    If you want to make room for a slim fixture, you can make a insulated cavity by taking some 1” or 1.5” thick XPS sheet (note that 1.5” is the depth of a standard square electrical box), and cutting two squares a few inches bigger in all directions than the fixture and power supply. Cut a round (or square, it doesn’t really matter) hole in the middle of one of those squares. Glue the solid square on top of the one with the hole using some foamboard adhesive. Now you can seal that to the top of the drywall, and you’ll have a sealed and insulated cavity you can use to contain the slim fixture and it’s power supply. You can cut a small notch on one side to run a wire out, then seal that with some canned foam after installation. This method is quick, simple, and cheap. You can use whatever type of insulation you choose over the top of the foam “box” you’ve made.


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