Blower Door Test

Walls, doors, and windows are part of a home’s thermal “shell.” When outside air is segregated from reaching the inside, warm air remains inside during the cold winter months and cool air stays in during the hot summer months. This type of thermal performance is a key component of any energy-efficient home.

The blower door test is an assessment of how well the shell prevents air from the outside from penetrating the inside. With all planned air intakes sealed (i.e., windows closed and all doors shut) the blower door is installed in the front door of a home. A fan in the blower door slightly depressurizes the home and measures the overall amount of outside air penetrating the home through leaks in the shell. These leaks may be from many sources, such as improper seals around windows, framing, wires, pipes, or recess lighting. A home is more airtight when it has fewer of these leaks. Astute builders can also use the results of a blower door test to accurately determine the size of the HVAC system needed to comfortably maintain home temperatures.