What is a Blower Door Test For?
Blower Door Tests are used to help determine a building’s airtightness. 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
- Determining how much mechanical ventilation might be needed to provide acceptable indoor air quality.
How does a Blower Door Work?
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 tester may use a smoke gun 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 building, and an airflow manometer and hoses for measuring airflow.
How to prepare for a Blower Door Test?
Take the following steps to prepare the building for a blower door test:
- If you have a stove or fireplace, be sure all fires are completely out – not even coals – before the tester arrives. Remove any ashes from open fireplaces.
- Plan to do a walk-through of the building with the tester. Be prepared to point out areas that you know are drafty or difficult to condition comfortably.
- Expect the tester to request access to all areas of the building including closets, built-in cabinets, attics and any unused rooms.
- The tester will need to close all exterior doors and windows, open all interior doors, and close any fireplace dampers, doors, and stove air inlets.
- Expect the test to take up to two hours or more, depending on the complexity of the building and prevailing weather conditions.