Blower Door Tests

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 auditors may use a smoke pencil to detect air leaks. These tests determine the air infiltration rate of a building.

Several reasons for establishing the proper building tightness are:

  1. to reduce energy consumption due to air leakage;
  2. to avoid moisture condensation problems;
  3. to avoid uncomfortable drafts caused by cold air leaking in from the outdoors; and
  4. to make sure that the home’s air quality is not too contaminated by indoor air pollution.

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 pulled out of the house by the fan. Uncalibrated blower doors can only locate leaks in homes. They provide no method for determining the overall tightness of a building. The calibrated blower door’s data allows the auditor to quantify the amount of air leakage and the effectiveness of any air-sealing job.

Home Energy Audits, EREC Reference Briefs, Office of Energy Efficiency and Renewable Energy, US Department of Energy