Common leakage sites houses are spaces around plumbing pipes where they pass through walls or ceilings, and openings around chimneys and electrical boxes. These spaces must be plugged or sealed with materials that will stop air flow, such as sheet metal or silicone caulk around chimneys, and caulk, foam, or rigid insulation board around other openings. Loose or porous insulation will not stop airflow. Caution should be observed when applying insulation in the attics of houses built before 1950, which may have old-style knob and tube wiring. Attics with this type of wiring should be inspected for safety by a licensed electrician before any insulation is applied, to prevent the possibility of electrical fires.
Attics usually have adequate space to allow application of insulation to save energy dollars.
Sealing and insulating heating system ductwork where it passes through unheated parts of the home should be high on any list of priorities for energy conservation. Crawl spaces should have insulation in the floor or the foundation walls or a combination of both. Care should be taken not to separate plumbing pipes from a heat source, to prevent freezing. The ground under a home may be the source of gallons of water evaporating daily into a home. A ground vapor retarder such as a 4-mil plastic sheet can reduce the moisture flow.