Quick Definition

A blower door is a device for testing the air-tightness of a home, and a blower door test determines the air infiltration rate. A powerful fan is mounted to the frame of an exterior door and pulls air out of the house, lowering the air pressure inside. An air-flow meter measures the amount of outside air that flows into the house through any unsealed cracks or openings. (Yudelson)


In Depth

Blower door tests determine the air infiltration rate of a home – how tight the home is or how much air it leaks. A leaky house makes the HVAC system work harder, and use more energy, to heat and cool the home.

To administer a blower door test, all exterior doors and windows are shut, all interior doors are opened,all dampers are closed and all appliances or fixtures with exhaust are turned off. A flexible panel outfitted with a fan is then installed in an exterior doorway to pressurize and depressurize the house. A manometer measures the fan’s airflow and the pressure differential between the interior and the exterior of the home.

If the house is very tight, mechanical ventilation may be needed to bring in fresh air to the space. If a house is leaky, windows and doors may need to be resealed, cracks may need to be foamed and penetrations for exhaust systems may need to be checked to insure proper sealing.

Our Application

All of our homes undergo blower door testing to ensure maximum energy efficiency. Blower door tests are a factor in the HERS Index score that each of our homes receive. A good blower door test result helps us achieve a lower HERS Index score; the HERS Index score is a factors in LEED Platinum certification for every home we build.

Lessons Learned

In our work, homes built using modular construction have historically scored the worst blower door test scores. Because the modular homes were constructed in an off-site plant, we were not able to oversee their construction and ensure that the insulation and leak prone areas were up to our standards. To date, we have discontinued building modular homes.

Our SIP homes perform better than our wood frame / spray foam insulation homes. SIP houses have fewer cracks and openings to seal, resulting in a tighter home.