Attic Insulation and Can Lights
I need help with some decisions regarding attic insulation in an existing home. The house is a single level rancher built in 1999. There is minimal attic insulation- a 6 inch or less fiberglass mat. The house has recessed ceiling “can” lights, 19 of them. In a recent energy audit, it was found they are a significant source of leakage. The single layer of existing fiberglass mat is just laid over the can fixtures in the attic. I want to blow in cellulose insulation into the attic to R45 or greater. Should I just have it blown over the existing fiberglass mat? I have read fiberglass allows drafting of air; will this still occur since there will still be air gaps around the cans where the mat is laid over them? Once insulator told me I could cut out the mat around each can so the cellulose could fit right around each can that way. Another told me I might have cellulose get into the house if that were done, since the cans are of course not air tight. What is the best way to proceed? I also have a related question about the fixtures themselves. I think they are IC (insulation contact) rated cans but I am not totally sure. I had an electrician on another job look at them and he wasn’t totally sure either. He looked at one both from the attic side and also pulled one out from inside the house but it had been painted over where he said the designation should be. How can I definitely tell that the fixtures are IC rated? Thanks very much, Marion
Replies
Not sure about the IC rating. Is there not even a model number that you can see/find? Even a brand name? I would think an IC rated fixture would also be 'air tight', but not sure why they didn't make them that way.
19 can lights is a lot. Can lights IMO really got oversold. People installed and used them for everything. My last house was really nice, but they overused them there, too.
One option is to make boxes for them like I've seen in new construction. People have made boxes out of various materials including e.g. drywall and Thermax insulation board. Place the box over the fixture and seal it to the ceiling. You'll make provisions for e.g. the wire, and seal it all up. There are probably lots of things you can use for the boxes. You might even be able to buy something designed for it.
Then you can do whatever you want w/ your insulation. Don'te forget to take care of holes in top plates while you are rummaging around up there.
Can lights can be a HUGE source of air leakage and heat loss to an attic. I inspected an expensive home once where the owner couldn't figure out why he had 16" ice dams on his eaves. I looked in the attic and it was like daylight with the recessed lights on ... just from the light leakage through the holes.
Clewless1 has some good insight for you. IC rated and AT (air tight) are independent of each other. AT cans aren't really very air tight anyway, and with a thick layer of dense pack over them IC cans can still overheat. Some insulation contractors put fiberglass batts over the cans before they blow cellulose to give the cans a bit of breathing room, and to protect them from infiltration from the bits of cellulose.
Don't do this unless you are very sure they are IC cans though. I don't know how to tell other than by their labels, and if you compare them to similar size cans from the same mfgr they will have bigger housings.
Leaving the existing fiberglass in place might be ok, but it will crush down and won't add much R value. You'd be better off removing it, sealing any penetrations from wires, ducts, etc., and especially around chimneys, then blowing the cellulose in.
I have 16 cans and they were costing me.
Built boxes over them with plenty of space and foamed them in place. Have also converted to all flourescents so heat should not be a real problem. Had to replace dimmer switches.
Also found and fixed leaks in ductwork and foamed or caulked where all vents were cut into the ceilings.
Our electric usage on our 26 year old house is way less than it was a few years ago.
House was really poorly built in so many ways.
Pete
On the last job we did, we built boxes out of scap OSB and placed around the cans and then blew cellulose over them. The boxes were a pain, but were a quick fix in a pinch. After the fact, the insulation contractor recommended using cheap styrofoam coolers that can be sealed w/ can foam.