Replies

1. 
   4Lorn2 | Nov 25, 2003 05:26am | #1

   I assume your asking because the recess cans are either old, allowing too much air out or, most probably non-IC, Insulation Contact, fixtures. You could do what many do. That is build an enclosure of some type and insulate around, or in some cases risking overheating, over this encasement. Results, efficiency and risks with this strategy are variable.

   My preference, as an electrician, is to tear out, usually more like pushing up, the recessed cans and replace them with IC rated old work cans. Especially ones that will seal to the existing ceiling. Sometimes you don't even need to take out the existing surrounds as the new cans will work in the old mounts. With a little planning and luck the entire job can be done from below the ceiling working through the same hole the old cans sat in.

   The advantages are that you get a sealed fixture that you can safely bury in insulation and still sleep soundly, a new and effective thermal overload in case something goes wrong like someone over lamping the fixture and vastly improved energy efficiency for a minimal cost. All for far less time and trouble than engineering enclosures and messing around installing them.

   These old  work units are relatively cheap, something like $16 each. Sometimes less. Stay away from the Chinese cheapies. Get a major brand name even if you need to go to a supply house to get them.

2. 
   gdavis62 | Nov 25, 2003 05:43am | #2

   If you are able, box 'em in with sheetrock, and seal the joints.  You will be doing some crawling around in the attic to do so.  Restack insulation up the sides and over the tops of the boxes.

1. 
   OracleDesign | Jan 02, 2004 06:40am | #3

   I don’t know if you came to any conclusions, but I can tell you what I did with new construction. I took used Halo 6" IC "Air Tight" cans. I use quotations because they are not air tight. They just have fewer perforations than non-air tight cans. I don’t know how they can call them air tight. I then used HVAC mastic and completely sealed all joints, rivets, holes, & voids. This includes packing sealant into the wire entry into the can. These were placed with R-38 high density cellulose directly over them with no cycling or overheating. I am not using any high wattage lamps over 100 W. Additionally, after installation, I foam sealed the can to the drywall hole and trimmed the excess away before installing the trims. Now they are air tight. I hope this helps.

1. 
   4Lorn2 | Jan 03, 2004 03:25am | #4

   I think you have the right idea but I'm not sure I would be using mastic to seal the holes. Or spray foam as this stuff, especially the foam, is fairly heat sensitive and flammable. 

   My preference would be a high quality, contractor grade at least, foil tape for holes in the can itself. For sealing any can to ceiling gap I would lean toward foil tape if the ceiling was smooth and either silicone or a fire code, intumescent, caulk if the ceiling wouldn't accept tape smoothly. This caulk, the firecode, has come out in latex versions and gone down in price to the point that it is scarcely more expensive than any decent quality caulk.

1. 
   OracleDesign | Jan 04, 2004 07:59pm | #5

   Actually, you are correct. I did use foil tape for any holes larger than about a sixteenth of an inch. However, the mastic worked great for all of the seams, rivets, etc. I did try using several different sealants to seal the can to the drywall with very limited success. The reason being was that almost nothing would provide a good seal to the cut edge of the drywall where the can dropped trough the ceiling. The foam worked great, but I was careful that none, or rather very little was left exposed. I used a rotozip to cut the holes very tight to the can so the was generally less than an eighth of an inch of gap. I did not attempt to use Fire Sealant.