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I have followed the blogs on the heat loss problems of ceiling can lights

I have followed the blogs on the heat loss problems of ceiling can lights. If one replaces the PAR30 incandescent with an ECOSMART LED and caulk the rim of the LED trim with silicone, the entire unit should be air tight, since the light itself is a closed

Asked by Jack Pladziewicz
Posted Jun 27, 2014 3:21 PM ET
Edited Jun 27, 2014 4:24 PM ET


8 Answers

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It looks like you may have had a question, but that you stopped mid-sentence. So I'm not sure what your question is.

LED conversion kits cut down on air leakage through recessed can lights, but they don't eliminate the leakage. For more information on this issue, see Recessed Can Lights.

In that article, I wrote:

"Another way to cut down on air leakage through a can—especially one installed in a cathedral ceiling—is with an LED conversion kit. These kits include airtight compartments that can be inserted to replace an existing fixture’s can and lamp trim. Examples of LED conversion kits include the Cree LR6 LED conversion kit (about $130) and the Cooper All Pro LED conversion kit (about $80)."

Answered by Martin Holladay
Posted Jun 28, 2014 6:11 AM ET
Edited Jun 28, 2014 6:13 AM ET.


Thanks Martin. This was my question and I have read the article you reference. I still do not see how a retro kit is needed. If one seals the rim of the CREE LED to the sheetrock with silicone or other suitable caulk and assuming the CREE LED is itself airtight - which it appears to be - the recessed can should be completely isolated from the room and be air tight. It would be the equivalent to sealing a plastic disk over the can opening. Insulation value is of course a different matter.

Answered by Jack Pladziewicz
Posted Jun 28, 2014 6:28 PM ET


JAck: i've disasembled quite a few LR6 and CR6 and the front light compartment is pretty much hermetic.

So if you caulk the finish rim to the wall paint you should theoretically get a viable seal.
Use clear silicone and use a pretty large bead of it, and hold the can through the day with extensible broom/paint roller stick on a sponge or something smoochy.

This only solves the air leakage problem.

Then run buy some aerogel to fix the insulation problem! mouahahah :p $$$$

Answered by Jin Kazama
Posted Jun 29, 2014 1:16 AM ET


Clear silicone that squeezes out of the joist will interfere with your paint job. That said, a conscientious installer can probably make this type of light fixture close to airtight.

I hesitate to recommend the method widely, because most installers are likely to be less conscientious than you probably are.

Answered by Martin Holladay
Posted Jun 29, 2014 6:00 AM ET


I really don't think air sealing either the Cree CR6 or 4 and the LR6 or 4 would be as much of a problem as Martin thinks. I've installed the cans for the 4" version in several rooms, with several rooms to go. The brackets that stick out of the Crees that are meant to hold them inside the cans are really ingeniously made. They hold the lights very tight to the can and to the ceiling. There is little to no slop involved. They act almost like an infinitely fine ratchet mechanism where the light mechanism can be pushed in as tightly as you could want to the ceiling. Turning the light in one direction releases the tension and it will then just fall out. It cannot happen on its own. It is really genius the way they designed such a simple latching mechanism.

But don't take my word for it Martin. Buy a standard can and a Cree and see for yourself. It should be very possible to not use any caulk whatsoever, just appropriate weather stripping that is very carefully placed under the lip. In about a year I should be at a point of blower door testing and I should have definitive results that I will report if it hasn't already been verified by you or someone else.

Answered by Eric Habegger
Posted Jul 11, 2014 6:58 PM ET
Edited Jul 11, 2014 7:15 PM ET.


Thanks for your report. I'll have to try them out.

Answered by Martin Holladay
Posted Jul 11, 2014 7:25 PM ET


No problem. I should make one tiny qualification to what I just reported. If you have a textured ceiling that is textured right up to the cans themselves then weather stripping alone probably won't do it. It would still be worth a try though. But you certainly wouldn't need mop handles to keep the lights up if you wanted to let some caulking dry. They are very tight and secure.

In the case of a textured surface what I would do is install the lights temporarily and then tape around the perimeter of the lip of the Crees. Then remove the light and use the tape as a guide to fill in the texture with compound until its smooth. When its dry then just use weather stripping. It will be much easier to remove the light this way for troubleshooting rather than using caulking, which will stop the turning motion that releases the Crees.

Answered by Eric Habegger
Posted Jul 11, 2014 7:59 PM ET


Martin, Jin and Eric - Thank you for your thoughtful answers and input.

I did a simple test to check the air tightness of the CR6. I placed it in a small plastic bucket of just the right size to allow the unit to fit inside as it would in a ceiling can, yet for the CR6 trim to rest on the bucket rim, the way it would fit against a ceiling can. I then sealed the CR6 trim to the plastic bucket rim with duct tape. I had pre-drilled a hole in the bucket to take a hose from a small vacuum. I then over-layed a piece of "cling wrap" over the face of the CR6 so that it clings to the face of the trim edge. If the CR6 is airtight the cling wrap should not pucker as a vacuum is applied to the inside of the bucket; if the CR6 allows any air through the unit the cling wrap should pucker as the vacuum applied to the inside of the bucket and the backside of the CR6 draws air through the unit into the vacuum. The result was that the cling wrap only puckered very slightly and slowly over time indicating that the CR6 is indeed very nearly airtight itself. This experiment simply confirms what we thought about the CR6 unit. So if one seals the CR6 to the ceiling in a typical ceiling can installation by whatever means (caulk, two-sided tape, weather strip, etc) the room side of the unit should be very nearly airtight from the attic space.

I believe the approach that Eric suggests for producing a smooth surface by filling the texture under the CR6 trim should provide a pretty good fit, and cut air infiltration significantly, although it will of course not make the connection airtight - that would require a tiny bit of caulk (or even paint) between the CR6 trim edge and the ceiling surface. It would not take much to complete this seal - possibly 1/8" bead of caulk at the edge of the CR6 trim that could relatively easily be popped loose with a putty knife when the CR6 fails, keeping in mind that the new LED lights are rated 35,000-50,000 hours (equivalent to many years of normal use) one would be faced with "breaking" the seal very infrequently.

In sum, I think the CR6 and similar LED lights not only provide an attractive opportunity to greatly reduce energy use for lighting, but also provide a very nearly airtight seal for existing ceiling cans - many of which may be great sources of the convection of warm air into attic spaces causing significant heat loss, ice dams and roof damage. This is one feature of the new LED lights that may be under appreciated.

Answered by Jack Pladziewicz
Posted Jul 12, 2014 12:34 PM ET

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