Home energy professionals use a blower door as a diagnostic tool to determine how much air is entering or escaping from your home.
Professional energy assessors use blower door tests to help determine a home's airtightness. Our blower door instructional video illustrates how a blower door test is performed, and how your contractor utilizes the diagnostic information provided to identify areas of air leakage in your home, and make energy-saving improvements.
These are some reasons for establishing the proper building tightness:
- Reducing energy consumption from excess air leakage
- Avoiding moisture condensation problems
- Avoiding uncomfortable drafts caused by cold or warm air leaking in from outside
- Controlling outdoor contaminants, pests, and odors from entering your home.
- Determining proper sizing and airflow requirements of heating and cooling equipment.
- Determining whether mechanical ventilation is needed to provide acceptable fresh air and maintain indoor air quality in your home.
Blower Doors: What Are They and How Do They Work?
A blower door is a powerful fan that a trained energy professional temporarily mounts into the frame of an exterior doorway in your home. After calibrating the device, the fan pulls air out of the house, lowering the air pressure inside. The higher outside air pressure then flows in through all unsealed gaps, cracks and openings such as gaps, cracks, or wiring penetrations. If conditions do not allow for lowering the pressure in the home, the fan may also be operated in reverse, with air pressure increased inside the home.
While the blower test is being conducted, the analyst may use an infrared camera to look at the walls, ceilings, and floors, to find specific locations where insulation is missing and air is leaking. The analyst may also use a nontoxic smoke pencil to detect air leaks in your home. These tests determine the air infiltration rate of your home, which is recorded on a laptop or tablet.
The blower door test is conducted as part of the energy assessment of your home. Your contractor may also operate the blower door while performing air sealing (a method known as blower door assisted air sealing), and after to measure and verify the level of air leakage reduction achieved.
Blower doors consist of a frame and flexible panel that fit in a doorway, a variable-speed fan, a digital pressure gauge to measure the pressure differences inside and outside the home, which are connected to a device for measuring airflow, known as a manometer.
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 flowing out of the house through the fan.
Uncalibrated blower doors can only locate leaks in homes. They provide no method for determining the overall tightness of the home.
The calibrated blower door's data allow your contractor to quantify the amount of air leakage prior to installation of air-sealing improvements, and the reduction in leakage achieved after air-sealing is completed.
Preparing for a Blower Door Test
Your home energy professional will perform the blower door test, including a walk-through of your home, setting up the blower door, and conducting the test. The following steps will help prepare your home for a blower door test:
- Plan to do a walk-through of your home with the auditor. Be prepared to point out areas that you know are drafty or difficult to condition comfortably.
- Expect the auditor to request access to all areas of your home including closets, built-in cabinets, attics, crawl spaces, and any unused rooms.
- The auditor will need to close all exterior doors and windows, open all interior doors, and close any fireplace dampers, doors, and woodstove air inlets.
- If you heat with wood, be sure all fires are completely out - not even coals - before the auditor arrives. Remove any ashes from open fireplaces.
- Expect the auditor to set controls on all atmospheric fossil fuel appliances (e.g., furnace, water heater, fireplaces, and stoves) to ensure that they do not fire during the test. The auditor should return them to the original position after the test.
- Expect the test to take up to an hour or more, depending on the complexity of your home.