Downlights feature four different types of housing. There is IC (Insulation contact) rated and Non-IC rated for both new constructions and remodels. IC (insulation contact) rated new construction housings should be attached to the ceiling supports before the ceiling surface is installed. IC housings need to be installed wherever insulation will be in direct contact with the housing. Non-IC rated new construction housings are used in the same situations as the IC rated new construction housings, only they require that there isn't contact with insulation and at least 3 inches of space from insulation. IC rated remodel housings are used in existing ceilings where insulation is present and in contact with the fixture. Non-IC rated remodel housings are used for existing ceilings where, ideally, no insulation is present.