How to Air Seal Recessed Can Lights from the Inside

If you have recessed light fixtures in your home you may also have a significant volume of conditioned air escaping into your attic. You can stem the flow of air (and money) by air sealing your light fixtures from the inside with just a roll of painter’s tape, a can of spray foam insulation, and a tube of painter’s caulk.

Even though I already air sealed all my light fixtures from within the attic, I decided to go above and beyond by air sealing the very same fixtures from the inside. At best it’s insurance in the event that I did a poor job from the outside. At worst it’s wasted effort and some slight cost in materials. Since I was already painting the entire ceiling I went for it.

A Liberal Use of Painter’s Tape Permalink

I’d hate to inadvertently get spray foam on my ceiling, so I covered the surrounding area with painter’s tape. Cured spray foam is near impossible to cleanly remove from a surface. Even though I’d have an inch or so of area behind the light trim, I still wanted to spray and distribute the foam as neatly as possible.

Hello Great Stuff, My Old Friend Permalink

I carefully filled the gap between the recessed can light and the ceiling with my can of Window & Door Great Stuff. This both filled the air penetration gap and had the bonus of better securing the can light. These two light fixtures are original to our home, so they’ve been wobbly in-place for more than a half century.

Pull Away the Excess Foam Permalink

Once the spray foam cured I removed the excess along with the painter’s tape. I didn’t worry about doing a clean job of it since my next step was to cover the spray foam with painter’s caulk.

Get Out the Caulk Gun Permalink

I used white latex painter’s caulk to cover the spray foam insulation where it meets the ceiling. Please excuse the amateur hour photo of the caulk tube facing the wrong way with respect to the caulk gun. You’ll want to flip it around when actually using it.

There were a half-dozen holes within the can light housing  that I sealed with clear silicone caulk. This particular tube of sealant was intended to seal gutters and flashing for roofs, but I had some extra left from an earlier project and figured it would work just as well for this purpose.

About Light Bulb Heat and Fire Risk Permalink

As previously mentioned, these recessed light fixtures are old, porous, and from an era when energy efficiency was an after-thought in the building trades. They’re also from a time when the only type of light bulbs were incandescent, which waste a significant amount of the energy by giving off heat as a byproduct of producing light. It was surely better to vent the heat into the attic than the alternative of starting an electrical fire in the housing of the light fixture.

These days, with the ubiquity of ultra-efficient LED bulbs, there’s much less of a worry that a lightbulb would start an electrical fire. With that knowledge we can confidently air seal our recessed lighting fixtures, although as an added precaution be sure to only used enclosure rated LED bulbs.

I also touch upon this topic and insulation rated light fixtures in my post on covering and sealing recessed light fixtures from the attic.

Sealed, Cured, Painted, I’m Yours Permalink

Once the caulk cured I painted over it and the surrounding area with ceiling paint. While not the best seal job upon close inspection, the imperfections are hidden by the trim of the light fixture.

Time to Reassemble the Fixtures Permalink

Before reinstalling the two light fixtures I replaced both their light sockets to mitigate any risk from the old and slightly frayed wiring. This task was surprisingly straightforward and only required a trip to the local big box store to buy the new sockets. You too can do it if there’s any doubt about the difficulty of such a project.

I also removed some ceiling paint from the trim due to the carelessness of a previous paint job. Once I polished the trim I reinstalled the light fixture and admired how nice both fixtures looked with the newly painted ceiling.

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