how to insulate around a ceiling light can in and attic and loose as little thermal loss/ leakage as possible?
If one uses compact floresent bulbs which do not get as hot as incandesent, how close can you get the insulation next to the light can?
………Terry Nordbye – North Bay Green
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As long as you have specified IC (insulation contact) recessed fixtures, you may safely install fiberglass batts or cellulose directly over the IC can. Most spray-foam installers, however, advise that it isn't a good idea to bury any fixture in spray foam. It's best to build an air-tight box out of rigid foam insulation, with the seams sealed with contractors' tape; the box should be sized so that there is at least an inch of air between the IC fixture and the box. Once this has been installed from the attic side, it's possible to spray foam over the box.
Better yet: don't install any recessed cans in an insulated ceiling.
In the case of a retro and the cans were not direct contact what would you think about making a chicken wire basket/dome around the can and mounding the insulation around it? Other burning question is I would think since compact floresent bulbs don't get as hot as incandesent the problem of close can contact with insulation may not be a problem at all, what do you think?
one thing to consider is that unless the can accepts only pin type CFL's where the efficiency and the clearance requirements go with the life of the fixture, somebody could easily screw in an incandescent bulb creating a possible hazard or a bulb that continually goes out.
As another approach for insulating around the fixture, I have worked with an insulation contractor who sprays foam over a dome shaped mold. When the foam sets up, you remove the mold and you have a cap for the light which then gets foamed in place. Again, this approach only works when you have an accessible attic space.
I agree that the best approach is to avoid installing cans in ceilings that represents the thermal boundary. I have measured as much as 20 Cubic Feet per Minute of airflow through a "sealed" can fixture. Multiply this by the number of cans installed and the leakage quickly adds up to represent a sizeable whole in your envelope. To complete the installation of the sealed recessed can, the drywall should be caulked to the housing and the gasket that comes with the trim kit needs to be installed.
Investigate installing panel led assemblies. They have minimal intrusion into the assembly above, and generate far less heat. Which means most of the problems of heat damage, and fire hazard are eliminated. With the added bonus, that they are far simpler to get a good air seal.
And now that they are commonly available, they are very cost competitive just on initial installation cost, without factoring the longer life, and decreased energy usage.
Randall: You realize you're responding to a thread that ended 8+ years ago, right?