Top hats for recessed LED lighting
We’re doing a top-to-bottom remodel on a 50-year old ranch home. We removed all of the attic insulation in this process and lighting will be installed before we re-insulate the attic. The lighting includes several recessed LED downlights. The fixtures are ICAT rated and include gaskets on the trim flanges that – in theory – seal the fixture to the drywall.
Two potential problems:
1. I’m skeptical the minimal gaskets will provide an effective seal.
2. If we need to pull down the fixture for maintenance (e.g. a defective driver, which is connected to the fixture, in the attic), we’ll disrupt the insulation above.
I understand that “top hats” can be installed. Simple covers that go over the fixtures in the attic, cut to pass the wiring through and are foam-sealed to the drywall / light frame / wiring. Rated for the purpose. The commercial products I’ve found so far – made by Tenmat (for example, https://www.tenmatusa.com/insulation-protection-covers/ff130e-recessed-light-draft-stop-cover/) – are pricey at $20 and up. These are round, appropriately named. (
For the fixtures we’re using, a rectangular cover would fit better, providing more room to separate the driver from the fixture. Our insulation contractor says they’ve had good luck making their own boxes using Thermoply, using foil tape to seal the joints. This seems like a good way to go. They can be fabricated to meet the size requirement and I believe Thermoply is an appropriate material from a fire-rating standpoint.
A box could also be made from drywall but harder to work with than Thermoply.
Any experience with this approach or other products / methods you’d recommend?
Thanks in advance.
Doug
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Bummer this wasn’t answered. I have the same question.
Standard GBA practice has been to "box over" can lights with rigid foam when you have access to them from above. XPS can work for this, as can polyiso. 1/2" foil faced polyiso and foil tape on the seams does a good job. You don't need a lot of R value for the box itself if it's going to be buried in loose fill insulation anyway.
Recently I've started to build the boxes with plywood and 2x2s, so that they can be stepped on without being damaged. I got the idea on here from one of the other members that boxes over bathroom fans, but it can work with lights too. All you need is an air sealed box, you can make it out of pretty much any materials you have on hand.
Those pre-made top hats are great for retrofit work, since some of them can be squished through the hole in the drywall so that they can be installed from below. They aren't cheap, but they save on labor.
I usually seal up the cans before installation with some foil tape over the seams and any holes. I don't trust the gaskets either (they're usually not even applied to the can correctly all the way around), but a little rope caulk makes a nice removeable seal if needed. If you air seal the box above, then the can itself doesn't really need to be air tight anymore. I think boxing the lights over is a better way to go, and it allows for pulling the can out (if you use "remodel" type cans) from below without disturbing the attic insulation.
Bill
I haven't used the Tenmat hats but they're the typical "green" solution. I, and the builders I work with, usually make our own from foil-faced polyiso. A few cuts, tape the corners and you're good to go. Just be sure to leave enough space that the fixtures won't overheat.
Thanks, Bill and Michael, for the responses. I had to proceed without your input and ended up building Thermoply boxes as our insulation contractor suggested. It was labor intensive but worth it: the top hats get the job done!
Thermoply cuts nicely with a utility knife and scores well for folding. I used 3M "Venture Tape," a foil tape used for duct sealing, to seal seams, squeegeeing it after application. A lot of custom fitting was required as several of the lights were very tight to framing and wiring adds complexity. Heavy tin snips worked great for that part of the process. I used construction adhesive to adhere the bottom tabs of the box to the drywall and plumbing strap to hold things in place while that cured; left the strapping in place as backup. Finally, I foamed any remaining openings. The boxes were covered with deep loose-fill insulation.
An IR scan with blower door depressurizing the house showed great results - 11 of 12 lights were invisible. The only one that showed some remaining leakage was predictable; it's located very close to the pinch point at the edge of the 4/12 roof framing and was hard to reach for my big frame. To address that leakage, I'll experiment with reinforcing the gasket material on the light fixture inside flange. Or maybe I can drop the light and get a foam gun far enough in the hole to seal the box a bit more from the house side?
I sized the boxes generously so that the driver and light source were well separated (better heat dissipation), and to accommodate a long enough Romex whip for easy servicing of the fixtures.
I'll add photos when I have a chance to download them.
Big picture: recessed lights are still a PITA for insulated ceilings! But we are very happy with the task lighting they provide in the areas where it was otherwise hard to accomplish. (We used Nora Iolites, installed into Nora's new construction frames.)
Doug
Photos: first batch
1 = Wafer light before sealing, easy access
2 = Wafer light before sealing, challenging access in 4/12 roof pitch point
3 = Nora Iolite before sealing
4 = Thermoply box, cut to fit, adapted for adjacent framing
5 = Top hat sizing, using 4" tall box for shorter wafer fixtures
Photos: second batch
6 = Top hat sizing, using 6" tall box for taller Nora Iolite fixtures
7 = Construction adhesive on tabs
8 = Top hat fastened with construction adhesive, held down with plumbing strap and screwed to truss chord on one side
9 = Completed installation with all seams taped (3M Venture Tape); might be overkill but as a quick final step I taped folds where I could reach them
10 = Wafer light in challenging pinch point, completed, spray foamed at gaps
Note: In cutting and scoring, working with Thermoply reminded me of working with tough leather. The Tply sheets came with some pretty good waves in them - i.e. not nearly as flat as desired - providing some challenges in laying things out. But when I cut the top hat blanks and folded the boxes it behaved very well.
For future readers: I just had this done professionally with a good solution. Total of 75 light fixtures, I cut out old non-IC cans and retrofitted LED wafers in holes (6"). quite a few 3" & 4" LED's added. Insulation contractor brought Insullite cardboard boxes, impregnated with fire retardant they say. I didn't want the 12" height penetrating my insulation depth across net 50 ft2, so I cut them down to ca. 5" deep plus 1.5" sealing flaps (made a folding jig, box mods took 1 hour). Boxes @5" depth sized to hold LED driver box and a bit of extra Romex to make future LED swaps easy, they were installed and sealed with can foam prior to the attic receiving 2" closed cell SPF fully across the ceiling plane as air/vapor barrier, with 12" of blown in L77 fiberglass to follow.
Rationale: 1986 ranch, Terrible blower door test results @ 12 ACH sourced to large gaps around central 2 flue fireplace / sheetrock interfaces, many soffits over cabinet uppers and 5 bath vanities with many leaky can lights in soffits and 3 chases, all needing air sealing. 5 bath vent fans, 4 0f not terminated outside shell. Hip roof with very marginal amount of ridge vent => prior mold issues, remediated (paint) by prior owner but vent fans and very leaky ceiling plane as moisture sources not corrected. Mouse infestation. And a great deal of faulty wiring (prior DIY I guess) found, now corrected. Am very glad I had the insulation vac'd out and pull down heavy duty ladder up from garage installed. Great deal of discovered issues now dealt with, new blower door test to follow as soon as basement rim joist cc SPF is completed. CC maybe overkill, but for sure standard air sealing offered by several firms via moving insulation aside to find wiring penetrations would not have been very effective nor found the many (25) wiring hazards.
I don't have pictures but I created my own top hats with a square piece of drywall and four pieces of one and a half inch scraps of rigid foam. I essentially created a picture frame internally with the phone so that there is an inch and a half of space above the surface mount lights.
I've done something similar above ceiling-mounted wireless access points for networks. I use two pieces of 1" or so rigid foam (polyiso is my preference, XPS also works). I cut a hole in one piece using a holesaw for recessed can lights that makes a hole a bit over 6" diameter. I glue a solid piece on top of the one with the hole. I make a small notch in one side of the piece with the hole. I now glue the entire assembly over the top of the access point. The hole allows for some network cable to be coiled up, allowing for a service loop to allow the access point to be removed and replaced in the future if needed. I use canned foam to seal where the cable comes in via the notch in one side. I use this over the Ubiquiti line of ceiling-mounted access points, which are cheap enough to be easy to use in residential installations. Works pretty well to air seal the hole in the ceiling (where the cable goes through), and still allow a way to get a few feet of slack above the ceiling for future service work.
Bill
Figuring small flush mount LED lighting wouldn't get too hot, here is my solution: https://youtu.be/e1KE09Ul7Qg?si=wEAmdLScHM4wMZhY