Posted By jdebree on 29 Sep 2013 08:19 AM
I'm using a number of recessed LED cans (horrors!) I have a test model in my barn that stays on 24/7, and it is only slightly warm- you can barely feel it. Here in SC, the climate is so mild I don't think they will be an issue. Snow is rare, and melts in a matter of hours anyway. I used 'air-tight, insulation contact' cans, but they aren't very tight. It appears that the only real seal is the gasket on the bezel. I plan to built boxes out of foil-lined foam to go over each can to reduce the effect of thin spots in the insulation. Does anyone know if I can safely seal the cans themselves? There is a pretty big gap in places that could be sealed with aluminum tape. Or can you spray foam on them when the ceiling is flashed prior to cellulose?

In SC you don't have to worry about ice dams creating roof leaks that back up, soaking the wall's cavity insulation and causing staining/dripping through the gypsum, which is what I predict will happen if he sticks with R38s with thin-spots where the can lights go. (It's a slow motion movie with a predicable ending, it's been run SO many times before.)

The gaskets are kind of a joke, as is the air-tightness. Sealing the fixtures better with FSK tape works, and caulking the fixture to the gypsum with acoustic sealant or fire-stop 1-part foam works too.  I wouldn't spray-foam the whole can though- in 25 years when it comes time to replace that LED that eventually failed a foamed-in-place fixture would be a nightmare to replace.

My LED's are a retrofit in a conventional ICAT can. You just twist them to remove from below. I'm more worried about the safety aspect of foaming a can, especially if some future owner decides to go incandescent. I'm planning to have the ceiling flashed w/foam before piling on cellulose. Should I have them flash the cans, or avoid them?

Posted By ultimatehomestead on 17 Sep 2013 10:32 PM
 
It has vaulted ceilings which I know isn't the best for insulating but the Mrs. won on this choice.

Good read about vaulted ceilings using fiberglass batts:

Cathedral Ceiling Ice Dams


"...a cathedral ceiling framed with 2x12s and insulated with fiberglass batts to R-38 "with no regard to air sealing." The result? Nasty ice dams where two sections of roof intersect..."

jdebree - the cans should be filled with rock wool which will protect the foam. Also they should have thermal protection which shuts down the light if the can interior gets to hot.

Are you install a vapour barrier on the ceiling or just the foam?

Are you installing vapour hats on the fixtures? Heres a pic for those unfamiliar with them. http://www.house-improvements.com/vapor-barrier-poly-installation

Recessed lights in a cathedral ceiling are an energy disaster...  Best you can do is find the lowest-profile LED fixture that you can

I agree. Consider low voltage surface mounted LEDs for a ceiling. No gaps in the insulation and only a small hole needed for the wire.

First off, I have to admit that I was wrong about the type of ceiling I'll have. I actually have a vaulted ceiling which I am told is different than a cathedral ceiling. Hopefully this will allow me to have even more insulation in the ceiling. I have been looking for a deal on led fixtures and hopefully I'll be able to sneak those in my budget as well. With the ridiculously bad weather we are having here I am almost 2 months behind schedule and falling further behind every day. I have updated my build blog for those who are following it.

What about building high-efficiency Styrofoam insulation into the walls as they are built?