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A blower door test is a method of determining how leaky a building is in terms of air infiltration, or how much cold air leaks into the building during winters and how much warm air leaks out. If the home is being rated from blueprints, the initial rating will assume an infiltration rate. After the home is completed, or for an existing home at the time of the audit, a blower door test is performed to quantify air infiltration and identify where the leaks are located. A blower door is a calibrated, variable speed fan that is temporarily installed into a door opening using an adjustable frame. It has very accurate manometers that measure the amount of air flowing through the fan. A pressure difference of 50 Pascals is created between the inside and outside of the building. This is equivalent to having approximately a twenty mile per hour wind blowing on all sides of the home. It also simulates the "stack effect" in the home (warm air rising). The house is depressurized and any leaks (air infiltration) in the home are accounted for through the air being blown out of the door. By using the volume of the home, the air changes per hour (ACH) is calculated. This number is used, along with the other thermal characteristics of the house, to determine the Energy Rating of the home.
One of the most important systems in your home, though it's hidden beneath your feet and over your head, may be wasting a lot of your energy dollars. Your home's duct system, a branching network of tubes in the walls, floors, and ceilings, carries the air from your home's furnace and central air conditioner to each room. Ducts are made of sheet metal, fiberglass, or other materials.
Unfortunately, many duct systems are poorly insulated or not insulated properly. Ducts that leak heated air into unheated spaces can add hundreds of dollars a year to your heating and cooling bills. Insulating ducts that are in unconditioned spaces is usually very cost effective. If you are buying a new duct system, consider one that comes with insulation already installed.
Sealing your ducts to prevent leaks is even more important if the ducts are located in an unconditioned area such as an attic or vented crawl space. If the supply ducts are leaking, heated or cooled air can be forced out of unsealed joints and lost. In addition, unconditioned air can be drawn into return ducts through unsealed joints. In the summer, hot attic air can be drawn in, increasing the load on the air conditioner. In the winter, your furnace will have to work longer to keep your house comfortable. Either way, your energy losses cost you money.
A duct leakage test on new construction verifies that this important issue is taken care of before the building becomes a home.