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Blower Door Testing


Test Procedure:

The blower door fan is used to blow air into or out of the building, creating either a positive or negative pressure differential between inside and outside. This pressure difference forces air through all holes and penetrations in the building enclosure. The tighter the building (e.g. fewer holes), the less air is needed from the blower door fan to create a change in building pressure. Typically, only depressurization testing is performed, but both depressurization and pressurization are preferable. Different values for blower door metrics are to be expected for pressurizing and depressurizing, due to the building envelope's response to directional airflow. The smallest fan ring that allows the fan to reach the maximum target indoor/outdoor pressure differential should be used. A multipoint test can be performed either manually or using data acquisition and fan control software products. The manual test consists of adjusting the fan to maintain a series of indoor/outdoor pressure differentials and recording the resulting average fan and indoor/outdoor pressures. Alternatively, a single-point test can be performed, where the blower door fan is ramped up to a reference indoor/outdoor pressure differential and the fan pressure is recorded. Often the blower door hardware converts fan pressure measurements directly to fan airflow values.



- Testing residential and commercial buildings for air tightness.

- Testing buildings at mid-construction to identify and correct any failures in the enclosure.

- Testing buildings for compliance with standards for energy efficiency, such as the IECC and ASHRAE.

- Testing building envelopes and window frames for water tightness and rain penetration.

- NFPA Clean Agent Retention testing (this type of testing is usually described as a door fan test rather than     a blower door test).

- Duct leakage testing of forced air heating/cooling systems - both supply (vents) ducts and return ducts can be tested to determine if and how much they leak air.

To learn more about residential energy savings and the HERS rating index visit the Residential Energy Services Network (RESNET).

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The EnergyStar website is a valuable tool for an in-depth look at all things energy related. --- www.energystar.gov

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