Energy Efficiency - Can Lights
Pierce Homes Energy Program

Another major source of air leakage are can lights placed in ceilings for improved illumination.  Pierce Energy Efficient homes use IC (Insulation Contact) rated can lights, which form an air tight seal between conditioned and non-conditioned spaces.. Non IC rated cans have the equivalent of a 1.5" sq. in. hole in the sheetrock.  Assuming conservatively 50 can lights in a typical home, this would represent a 7" x 10" open hole in the wall of a home, allowing for infiltration of allergens, dust, moisture and other pollutants.