More Best Practices
I’ve been on a few energy audits and assessments where the homes were built or remodeled in the late 1990s and early 2000s. Electricians working in those times were installing the traditional recessed light fixtures, also known as recessed cans or pot lights. Generally, this type of lighting fixture doesn’t have any issues when installed inside the air and thermal boundaries of the building envelope. But it can be problematic when the can lights end up displacing insulation and interrupting the continuity of the air control layer. In this post, I’ll discuss the challenges with this type of lighting and share ways to improve the performance of a home that has existing recessed cans.
Recessed lighting was first used in commercial contexts in the 1940s. It quickly transitioned to the residential market and is still widely used. Today’s can lights are required to have labeling that identifies whether they can be in direct contact with insulation; this rating is denoted “IC” for insulation contact, and a label will be found on the fixture housing. Non-IC-rated recessed light fixtures are required to maintain a 3-in. clearance to all insulation. IC-rated fixtures contain a temperature sensor or thermal overload that will interrupt power to the light bulb should the temperature rise above a safe level.
The traditional recessed light fixture has some sort of mounting bracket, like the one in the above photo. Often these brackets are adjustable so that they can be installed in 16- or 24-in.-center framing. They also contain a junction box, where the household wiring is terminated. Junction boxes are required by code to remain accessible. This is accomplished in a…
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4 Comments
Sealing existing can lights and building foam boxes brought to mind a recent discovery of mine. In a different life I am a sculptor working mostly in clay. I have investigated using various derivatives of papier-mâché. I stumbled across a mache product used by taxidermists. The exact proportions of materials is not easily ascertained but they seem to be IMHO less than half paper pulp, less than half plaster and maybe a small amount of glue. It’s mixed with water and applied like sticky plaster. It’s quite strong when dry. It will fill voids quite well. Find it at mckenzietaxidermy.com
I’m in climate zone 7 (Tahoe). I’ve replaced all of my incandescent can lights with airtight LED assemblies. Is that sufficient? Should I also cover the cans with Tenmat covers? (Belt and suspenders and huge PIA) Or will the AT LEDs with maybe some caulk be sufficient to stop air exfiltration to my attic?
The airtight LED trim should help. One way to know for sure is to test. A blower door test is preferred, but you may be able to create a big enough negative pressure in the home by turning on all your exhausting equipment (dryer, bathroom, kitchen exhaust fans, a box fan in a window pushing air out, etc...) to detect air leaking in through the fixture. Be aware that using this method can backdraft natural exhausting heating equipment. I also don't recommend performing the test if there is a fire in a fireplace or woodstove. If you have access to a thermal imaging camera, this can also help "see" any air leaks while the home is under negative pressure. The cameras work best if there is a 10°-20°F temperature differential between inside and out.
Thanks Randy. I ran two bath fans and a kitchen fan and took some photos with FLIR. Prob not sufficient pressure, and amateur equipment.
The airtight LED retrofits didn't look horrible to me (but I don't really know what 'good' looks like!) I was surprised to see some of the lights had cold spots *next to* the light and not *around* the light; not sure why. Some walls and corners showed up as MUCH colder than the lights. In general, lights that also had tenmat covers looked a little better than those I know I haven't gotten to yet. I don't have an airtight LED to compare to an old bulb but I suppose I could uninstall an LED to see the difference.
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