Re: Insulation in clean attic
I can't answer for the type of insulation to use or whether or not you need a vapor barrier.
As for the light fixtures, if it's just a light mounted to a junction box, all you have to do is caulk or use a can of spray foam around the junction box to seal any air gaps. The insulation can come in contact with junction boxes.
If it's a recessed fixture ("can light"), check to see if it is "IC" rated. That stands "Insulation Contact" which means you won't have to build a box around it -- all you have to do is caulk or foam any air gaps between it and the ceiling.
If the recessed fixture is not "IC" rated, then you'll either have to replace it with a fixture that is, or build a box around it. I'd recommend a sheet metal box (wood might get too hot); be sure to seal the seams of the box and also seal it to the ceiling material. If you're handy, you might find it beneficial to just replace them with IC-rated LED fixtures.
There are two reasons for sealing air gaps: first, it helps the efficiency of your home by preventing the loss of conditioned air. Second, it prevents humid air from the living space getting into the insulation where it can condense (the top layer of insulation will be colder than the heated space), degrade the insulation value (due to water's heat-conductive properties), and contribute to mold growth.
TIP: If you have any junction boxes with covers accessible to the attic, tie a ribbon to it and staple the other end of the ribbon to a rafter. That way, after it's covered up with insulation, you can find it again.
Last edited by Fencepost; 04-07-2014 at 12:50 AM.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.