You may already know where some air leakage occurs in your home, such as an under-the-door draft, but you'll need to find the less obvious gaps to properly air seal your home. For a thorough and close measurement of air leakage in your home, hire a qualified expert to conduct an energy audit, particularly a blower door test. A blower door test, which depressurizes a home, can reveal the location of many leaks.
Air Ducts Suffering? Common Obstructions That May Be Affecting Your Ductwork
HVAC systems require unobstructed air ducts to operate properly and efficiently. When the air circulation is out of use or restricted, or when leaks or other problems prevent efficient air travel through the ductwork, your indoor comfort will suffer, your HVAC system legal instrument work harder, and you’ll pay more to energy or cool your home. By watching for and correcting common obstructions in your ductwork, you’ll be able to keep your furnace, air conditioner or heat pump working at their best.
Combustion Air Ducts, Part I: Why Houses Need Them - StarTribune.com
Have you ever noticed a big insulated tube descending down next to the dry land near your chamber or boiler in the basement? If you trace this duct down, you'll find that it connects to an opening at the exterior of the building. This is essentially just a fault in the side of the building that brings in fresh outdoor air. This opening is a unresisting ingestion that provides needed air to the home.