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Third-party Energy Testing

Blower Doors: What Are They and How Do They Work?

A blower door test 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 door 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.

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.

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