A blower door test is one of the most useful tools available for understanding how air moves through a home. By temporarily using a calibrated fan to create a small pressure difference between the inside and outside of the building, the test helps identify how much air is leaking through the building envelope and can help locate areas where improvements may be needed.

For homeowners, the process is generally straightforward. The testing equipment is installed in an exterior doorway, the home is placed into the proper testing condition, and measurements are taken to evaluate air leakage. Depending on the purpose of the test, the results may be used for energy-efficiency evaluations, new-construction testing, diagnostic work, weatherization projects, or to better understand comfort concerns within the home.

What should I do before the test?

Most of the preparation involves making sure the home can be placed into a consistent testing condition. This may include making sure windows and exterior doors can be closed properly, ensuring areas of the home are accessible, securing pets, and identifying heating, ventilation, fireplace, or other equipment that may need special consideration during testing.

Every home is a little different. A newer home may require very little preparation, while an older home, a home under construction, or a property with multiple heating or ventilation systems may require a few additional steps.

To make the process easier, we created the preparation tool below. Answer the questions about your home and it will generate a personalized checklist based on your responses.

Why does preparation matter?

A blower door test is most useful when the building is tested under controlled and repeatable conditions. Proper preparation helps the tester obtain an accurate measurement and reduces the chance that an open window, operating fan, inaccessible area, or other condition affects the results.

It also helps the appointment move more efficiently. When common preparation items are handled before the tester arrives, more of the appointment can be spent performing the test, reviewing the home, and discussing the results.

Don’t worry if you are unsure

You do not need to be an expert on your heating system, ventilation equipment, fireplace, or building construction before scheduling a blower door test.

If you are unsure how to answer one of the questions below, simply choose “Not sure.” The checklist will identify the item so it can be discussed with the tester.

As a general rule, homeowners should not make unfamiliar adjustments to boilers, furnaces, water heaters, dampers, ventilation controls, or other mechanical equipment solely for the purpose of preparing for a test. When in doubt, leave the equipment as it normally operates and ask the testing professional for guidance.

Use the preparation tool below to see what, if anything, should be completed before your blower door test.