A powerful fan is mounted in the frame of an exterior door. During a depressurization test, the fan pulls air out of the house, lowering the interior pressure and pulling air in from the outside through unsealed cracks and openings.
Photo courtesy of the Building Performance Institute, Inc.
Anyone thinking of buying a house or building one should consider having a blower door test performed. It will help determine the cost of future energy bills.
The blower door test is a diagnostic tool used to measure the airtightness of a structure. A powerful fan is mounted in a temporary airtight frame of an exterior door. During a depressurization test, the fan pulls air out of the house, lowering the interior pressure and pulling air in from the outside through unsealed cracks and openings. A pressure gauge measures the amount of air pulled out of the house by the fan and coming in through unsealed cracks and openings.
The diagram shows the many leakage points possible in the home.
Diagram courtesy of the Building Performance Institute, Inc.
Results of the test can determine if there are unsealed cracks and openings in the house’s shell that should be sealed. Infrared cameras are used to locate every leak which can then be amended. Properly sealing a house will increase comfort, reduce energy costs, and improve indoor air quality.
This test is required for certain certification programs, including ENERGY STAR and Passive House (Passivhaus). Passive House has the most stringent blower door test requirements, allowing a maximum infiltration of 0.6 air changes per hour (ACH) when measured at 50 Pascals pressure difference. (Pascals are a measure of pressure.) For reference, typical new houses that has not been properly air sealed will test between 4 to 6 ACH @ 50 Pascals, and typical existing houses will test between 8 to 10 ACH @ 50 Pascals. Results below 2.0 ACH @ 50 Pascals may be considered “tight,” while 1.0 ACH @ 50 Pascals is a typical target for high-performance new construction.
A blower door test is being conducted in this newly renovated home in Lakeside, Ohio.
Photo courtesy of Peter Baker
The blower door test is used as one aspect in determining a Home Energy Rating System (HERS), or how energy efficient the house is. The HERS rating system is used across the United States but is required for all homes in California. HERS is a national standard developed by Residential Energy Services Network (RESNET), a not-for-profit association. HERS rates the efficiency of a home compared to a standard house with the same dimensions and climate. A certified rating provider, working under the supervision of RESNET, determines the individual house rating, which is often used in determining eligibility for some programs, such as ENERGY STAR.
Blower Door testing should also be considered when upgrading an existing home or building as well. Home performance contractors will use the results of the tests when conducting audits for making recommendations on improving the energy efficiency and indoor air quality (IAQ). The Building Performance Institute (BPI) certified Energy Auditors and Building Analysts are proficient at conducting this test on existing homes and buildings. More information can be found at the BPI and Home Performance website.
When a home is built very tight with minimal air leaks, a heat recovery ventilator HRV or energy recovery ventilator (ERV) is generally recommended in order to bring fresh air into the house. These units exchange stale heated or cooled interior air with the fresh exterior air without losing the heat or cool.
To find a certified energy auditor close-by check the web site of the RESNET HERS Index or Building Performance Institute, Inc. (BPI)