Air leakage, or infiltration, occurs when outside air enters a house uncontrollably through cracks and openings. Properly sealing such cracks and openings in your home can significantly reduce heating and cooling costs, improve building durability, and create a healthier indoor environment. Air pressure imbalances in the house can exacerbate these problems. Leaks in ducts can pressurize or depressurize the house. To restore normal pressure, air will force its way through cracks and holes around doors, around windows, and in walls, floors, and ceilings. Infiltration is one of the biggest and most preventable energy wastes in the home.
It is unwise to rely on air leakage for ventilation because it can't be controlled. During cold or windy weather, too much air may enter the house. When it's warmer and less windy, not enough air may enter. Air infiltration also can contribute to problems with moisture control. Moldy and dusty air can enter a leaky house through such areas as attics or foundations. This air in the house could cause health problems.
Besides infiltration through faulty ductwork, infiltration can also occur around windows, doors, and envelope penetrations such as plumbing and light fixtures, electrical wiring, and venting. If your house has a fireplace, it can be the biggest infiltration problem. Consult a professional on how to keep your fireplace infiltration to a minimum.