14. Seal Out Air Leaks Around Outlet and Light-Switch Covers
No, you may not squirt spray foam into an electrical box. The foam can lock in heat from the wires, creating a fire hazard. Instead, with the power off and the cover plate removed, caulk the seam where the electrical box meets the back of the wallboard or plaster, says energy auditor Paul Scheckel, author of The Homeowner's Energy Handbook. Then get a foam gasket, sold for pennies at home centers, and place it around the receptacle before reinstalling the cover plate.