When it comes to recessed can lighting, “IC” means “insulation contact”. IC-rated cans (usually labeled as “IC-rated” or simply “IC”) are appropriate for attic installations and anywhere else you plan to have insulation touching the can’s housing. Non-IC cans (almost always labeled “Non-IC”) must have an air gap (3″ or more) between the can and the insulation, meaning you’ll have to cut the insulation back from the edge of the can. Putting insulation in contact with a non-IC can is a fire hazard. To put it simple: Don’t do it.
“Non-IC” cans aren’t good for attic installations because you’ll lose a lot of energy through the area around the can. They’re fine for first floors or basements where you typically won’t have insulation between the joists.
If you’re considering cans for an attic installation, we also recommend looking for air tight cans – cans that are reasonably sealed against air leakage to prevent drafts through the ceiling.
What Cans are IC-Rated?
As a general rule, most 5″ and 6″ cans are IC-rated, while most 4″ and smaller cans are not. This is not universally true, however. Smaller diameter can lights can be built with a much larger housing surrounding the can to provide an IC-rating.