An important part of reducing energy costs in the home is sealing air leaks. When heated or cooled air escapes from your home it has to be replaced by air from the outside. Unconditioned air from the outside has to be conditioned for your home to remain comfortable. If you can keep the conditioned air inside the home longer it will save energy dollars by not having to condition new air. It would be very difficult to stop all the air leakage in your home nor would your want to. For maintaining air quality it is recommended that natural air changes per hour not be less than .35, In other words a little over one-third of the entire volume of air should be replaced with fresh air every hour.
When air sealing you should begin with the largest leaks first. Begin by sealing air leakage into the attic, Attic Hatch or accesses need to be weather stripped and insulated. Most times tradesmen cut or drill holes in framing and do not seal around the object,any plumbing and wiring penetrations should be sealed.Caulking or expanding foam can be enough to seal most of these areas, backer rod can be used to fill larger cracks before caulking. Another problem area in attic are kitchen and bathroom soffits; this is an area where the soffit is framed, then sheetrock is installed around the soffit instead of to the ceiling joists leaving the soffit and often the wall open to the attic. These can be sealed by covering the opening with a fire rated foam board, plywood or sheetrock, then caulking or foaming the edges. Look for dirty spots in the insulation they often indicate holes where air is leaking from inside the house. If you have an attic or whole house fan sealing the shutters will make a big difference. Recessed light fixtures can be another air leakage area,be careful with these, some are not rated to be covered with insulation or sealed. You can use a high temperature silicone sealant where the housing of the light meets the ceiling, then you can build a drywall air seal or box around it leaving clearance around the fixture for ventilation. If you are using Cfls ( Compact Fluorescent Lamps ). in these fixtures heat won’t be as much of an issue.
Duct boots and registers; if in the ceiling or floor can be caulked or foamed at the joint between boot and ceiling or floor.
Bathtubs and showers are another area that needs to be addressed, seal from underneath with expanding foam. The same applies to drain and water line penetrations in kitchens and baths.
Joints in in the foundation, sill plate, plumbing and air conditioner penetrations through foundation walls can usually be sealed with caulk or foam.
After sealing the largest leaks move on to the smaller ones such as doors and windows. If the weatherstripping is bad or not making a good seal it should be replaced. A lit incense stick can be helpful finding minor air leaks by holding it next to a crack, the smoke can tell you if there is air leaking into or out of the structure. Small Leaks can usually be caulked, you can use a colored or clear caulk to make it less obvious on interior surfaces.
Sealing the larger leaks in your home can make a big difference in your utility bills, the smaller ones probably won’t, but sealing them will increase your comfort level and if there are a lot of them they are worth addressing.