Recessed lighting has a bad reputation
Hello! I can tell from reading and from my own experience that Recessed Can Lights are a big frowned upon item for use in Green homes. Mainly the fact that they do not seal very well and are far from ‘Air Tight’ even if they say so due to a cheap gasket.
I have seen people use foil-faced poly iso and make boxes to place over the recessed can lights. These boxes can be air sealed without having to make contact with the light fixture.
I’m wondering, if this occurs, does it remediate the bad reputation due to air sealing? If so, has anyone had experience where the box iteself causes the lights to fail prematurely due to what I imagine would be heat build where as before it would seap into the attic?
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I remember reading an article in Fine Homebuilding where someone had actually built and tested a variety of boxes to insulate can lights. He then actually tested them and measured temperatures. My takeaway (admittedly fuzzy now) was that I wouldn't consider foam - too much heat. I'd use something that doesn't burn (say, mineral wool products like Tenmat). And, I'd get rid of the existing light and put in LED replacement lights (e.g., Commercial Electric T65 model available at big box HD) that generate a lot less heat and have a gasketed trim ring. This will give you much better lighting to boot.
Nicholas,
Here is the link to the article by Larry Armanda that Andrew is talking about: Air-Sealing Can Lights Safely. The bottom line is that homemade airtight covers are more dangerous on the old recessed can fixtures -- the ones that aren't airtight or rated for insulation contact -- than on the newer fixtures, and that dangers increase when high-wattage bulbs are used.
For more advice from Fine Homebuilding, see my article on the topic: Recessed Can Lights.
Below, I'm posting an image from Larry Armanda's article.
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Well, I should have clarified that I am talking about modern recessed lights, not older ones. All the modern ones I use and plan on using are LED. I think the highest watts are 11 Watts. They are IC-AT meaning contact is okay and air tight, however the air tight rating comes from two points. The electrician must properly install (meaning also use the foil stickers after they are done wiring) and also make sure the ceiling drywall texture has not ability to interrupt the trim piece which does have a thin film of foam to create that air-tight seal. In my current home abode, the texture on the ceiling is a beautiful sponge swirl that also means highs and lows and I can feel cold air in the winter around the trim piece on a house build just this year. I went in the attic and realized the foil tape pieces that were not properly installed. So sad. But I can also see the trim piece not being able to seal necessarily.
This is why I wonder about the air sealing. If these lights are meant to breathe, installing a air-tight box around them will result in a lot of heat build up over time. I know LED's do not get as hot as incandescent, but I have seen a fair share of LED's get plenty warm. I think they were the earlier designs, but some led bulbs have pretty heavy duty heat sinks on them at the base. The bulb itself is cool to touch, but the base is a different story.
Thoughts? Sounds like I am fine to make boxes, and shouldn't worry about premature bulb or fixture failure as I don't see it mentioned anywhere. Thanks.
Nicholas, I don't think you should worry one iota about overheating a modern LED fixture meant for a standard insulation rated can. There is absolutely no fire danger or lessened service life putting regular insulation like batts or preferably loose fill insulation over it. Like you said, you have to worry about the LED flange to ceiling drywall interface and try to make it airtight. You might have to grind down the texture to do that and then fit a compressible gasket in that area.
Yes, it's a lot of work but it doesn't even compare in the amount of work that would be required to yank the cans and put in the newer low profile units. I think Martin is giving the standard answer of best practices for new construction which is not applicable to your situation using LEDs in insulation rated cans.
If you are not retrofitting, why not use ultra-low-profile LED fixtures in combination with airtight electrical boxes?
Maybe I didn't understand. Are the cans already installed? If not, then do what Steve is suggesting. If they are then do what I suggested in comment 4. The electrical box mounted LEDs are the new, new thing and should be more effective than can mounted lights, of whatever kind.
Nicholas,
You can safely built an airtight enclosure above the top of a recessed can fixture like the one you are describing (a modern "AT" fixture rated for insulation contact). It's a good idea to leave three inches of clearance between the fixture housing and the homemade enclosure box.
Steve & Eric: The ultra low led fixtures I have seen are all in one. They don't also have too many choices for lumens and trim colors where as recessed lights are much more common. Can you link what product you are talking about? I'd check into it.
This is both retrofit and new construction. I have three light situations. Pre-existing can lights that I'd like to improve air tightness, more lights I'd like to add, and in the future a new house I want to build. Currently I could benefit from more lighting being added, and while I'm up there, I'd consider sealing the new lights. Clear as mud?
I would like to see some of the suggested electrical box mounted lights. I'm assuming the box can obviously be sealed easier than a big fixture. I haven't seen them here.
Martin: Okay, good to know. Looks like any fixtures rated at ic are capable of being sealed up.
Nicholas,
Here are links to two GBA articles on the SlimSurface LED fixtures from Philips:
Rethinking Recessed Lighting
Canned Lighting Conundrum
Martin we need an update on the newest technology of recessed lights.. the ultra slim completely enclosed.. furthermore what if you were to caulk the gasket before putting them in place I imagine would help?? perhaps their weakness is the strength of the spring they depend on to hold them in place?
https://www.amazon.com/Amico-Ultra-Thin-2700K-5000K-Selectable-Can-Killer/dp/B087JL1W9M/?_encoding=UTF8&pd_rd_w=fRVkG&content-id=amzn1.sym.35cab78c-35e3-4fc1-aab0-27eaa6c86063%3Aamzn1.symc.e5c80209-769f-4ade-a325-2eaec14b8e0e&pf_rd_p=35cab78c-35e3-4fc1-aab0-27eaa6c86063&pf_rd_r=61ZRY4N5N28JB2AY651E&pd_rd_wg=1nKo5&pd_rd_r=a8213875-e189-4daa-9245-7d4c719a8302&ref_=pd_gw_ci_mcx_mr_hp_atf_m
Michael,
https://www.greenbuildingadvisor.com/article/recessed-lights-and-air-leakage
https://www.greenbuildingadvisor.com/article/rethinking-recessed-lighting
https://www.greenbuildingadvisor.com/article/canned-lighting-conundrum
Actually, the trim rings are not needed with all the new led fixtures for cans. They are all in one units built with flanges right on them. Go to the Cree website for an example. I think we may have been talking at cross purposes if that wasn't clear. You seal the built in flanges to the ceiling drywall. If that isn't satisfactory to you and you want to use external trim rings like the conventional recessed lighting then you will have to do what Martin is suggesting. Personally I would never go that route, but it's your choice.
Nicholas. I was thinking of something like this: https://www.ledwaves.com/collections/pr15-ultra-thin-led-recessed-light
Note that the driver is small enough to be mounted in an airtight box if necessary.
So it seems it boils down to either using AT-IC recessed fixtures and making sure they are properly sealed with caulking or foil tape (not expandable foam due to heat) if I want a recessed light profile, with energy efficiency and to not worry about shortening the lifespan of the LED light itself.
Alternatively, I can use low-profile surface mount LED's instead of can lights. The choices are much more limited here, but I am a simple man so that doesn't negate too much for me. I can see each light needing an electrical box. Shallow mount boxes are nothing but a headache for me if it's a junction. I much rather have a deeper electrical box and just calk the edges to make sure it's sealed and have enough room for wiring and a little room maybe for some heat to dissipate into versus those 1" deep boxes. Even with the deeper box, I see it being a lot less area to a.) seal and b.) take up precious cellulose insulation volume than a typical AT-IC recessed fixture.
A good summary from this topic's question?
Also - Eric, do you have a link to the light you were talking about?