The only way to know for sure is to hire an energy specialist or auditor to measure the air tightness of your home using special equipment (e.g. a blower door). On your own, you can perform some simple do-it-yourself checks such as feeling for drafty areas with all the exhaust fans turned on, looking for light shining through cracks, and checking attic spaces for dirty insulation and mold around ductwork. Air leaks waste energy and reduce comfort, so it's a great investment to tighten up excess air leakage.
Dropped ceilings and gaps in all walls and ceilings should be sealed with blocking, expanding foam sealant and/or caulk. Seal window and door leaks with new weatherstripping and door thresholds or sweeps. Select the caulk, weatherstripping, or foam sealant products suited for the temperature, surface material or type, and the location. Read the label directions for application information. Clean surfaces before caulking and weatherstripping. Rope caulk, backer rod, or other materals should be used before caulking any cracks or gaps larger than 1/4-inch. ENERGY STAR® has a good resource for do-it-yourself sealing projects. See the ENERGY STAR web site .
