Blower Door Tests

Written by The U.S. Department of Energy's Office of EERE
Sat, Mar 06, 2010

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Professional energy auditors use blower door tests to help determine a home's air tightness.

Topic Summary

These are some reasons for establishing the proper building tightness:

Reducing energy consumption due to air leakage
Avoiding moisture condensation problems
Avoiding uncomfortable drafts caused by cold air leaking in from the outdoors
Making sure that the home's air quality is not too contaminated by indoor air pollution.

How They Work

Diagram of a blower door. The parts of the blower door are labeled as follows: exterior door frame (around the outside edge of the door), temporary covering (over the surface of the door), and adjustable frame (just inside the exterior door frame). An air pressure gauge, a small vertical rectangle with three round gauges inside, is alongside of the door. The top gauge is connected by a tube to the temporary covering, and the bottom two gauges are connected to a fan sitting at the bottom of the door. The caption reads: Diagnostic Tools. Testing the airtightness of a home using a special fan called a blower door can help to ensure that air sealing work is effective. Often, energy efficiency incentive programs, such as the DOE/EPA ENERGY STAR® Program, require a blower door test (usually performed in less than an hour) to confirm the tightness of the house.

A blower door is a powerful fan that mounts into the frame of an exterior door. 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. The auditors may use a smoke pencil to detect air leaks. These tests determine the air infiltration rate of a building.

Blower doors consist 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.

There are two types of blower doors: calibrated and uncalibrated. It is important that auditors use a calibrated door. This type of blower door has several gauges that measure the amount of air pulled out of the house by the fan. Uncalibrated blower doors can only locate leaks in homes. They provide no method for determining the overall tightness of a building. The calibrated blower door's data allow the auditor to quantify the amount of air leakage and the effectiveness of any air-sealing job.

Preparing for a Blower Door Test

Take the following steps to prepare your home for a blower door test:

Close windows and open interior doors
Turn down the thermostats on heaters and water heaters
Cover ashes in wood stoves and fireplaces with damp newspapers
Shut fireplace dampers, fireplace doors, and wood stove air intakes

Article source: The U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE). For the most up-to-date information please visit the EERE website.