What is a Blower Door?

Every home has air leaks, but the cumulative total leakage can vary widely based on whether air sealing efforts have been made. To measure the amount of leakage in a home a tool called a blower door is used.

Air leaks can be simple and inexpensive to seal if you can just find them, and that is where the blower door comes in. A blower door is a piece of diagnostic equipment that is used to measure the air leakage in a house, and to see how the house rates on a scale of “leaky” to “tight”. If a house is already tight, air sealing is obviously not required. But if it is too leaky, a blower door test can tell you how serious the leakage is and aid in locating the leaks. Once the leaks are sealed, the blower door can be used to calculate the actual amount of reduction in airflow.


A blower door consists of a frame and flexible panel that fit in a doorway, a variable-speed fan, a pressure gauge to measure the pressure differences inside and outside the home, and an airflow manometer and hoses for measuring airflow. The fan pulls air out of the house, lowering the air pressure inside. The higher outside air pressure then flows in through all unsealed cracks and openings.

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