Examine the canister for an insulation rating designation. The letters IC stand for “insulation contact,” while ICAT means “insulated ceiling air tight.” Both designations mean that the cans can be in direct contact with insulation and, in the latter case, the can is also sealed against air exchange. ICAT fixtures are the best choice for preventing heat loss.
Spread acrylic latex caulk around the gasket that seals the rim of the canister against the ceiling when you install the fixture. The purpose of the gasket is to reduce airflow -- the caulk makes it more effective.
Fill any gaps around IC- or ICAT-rated cans with fiberglass or cellulose insulation, then cover the cans with enough insulation to reach the top of the ceiling joists.
Keep insulation at least 3 inches from canisters not rated for insulation contact. There are several ways to do this. You can construct a dam by nailing two-by-six or larger lumber between the joists to create a rectangular insulation-free zone around the canister. You can also place a length of metal duct over the canister or a non-flammable cover; the duct must be large enough to create a 3-inch barrier between any part of the light canister and the surrounding insulation. A third option is to install a recessed light cover, following the manufacturer's directions. Covers are available at hardware and lighting stores.
Fill any gaps around the dam or insulation cover with insulation. Add insulation over the top of a commercial recessed cover only if this is specified by the manufacturer. Do not insulate over a dam, duct or other homemade insulation barrier; covering the fixture can create a serious fire hazard.
Things You Will Need
- Acrylic latex caulk
- Fiberglass or cellulose insulation
- Two-by-six lumber
- Rigid metal duct
- Recessed lighting cover
- Seal recessed light covers to the backside of the drywall, as directed by the manufacturer. This creates an air seal for the entire fixture. Common sealants include UL-181 foil tape and fire-rated foam sealant.