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The Blower Door Test

One of the advantages of working at MWA is our team’s ability to collaborate internally – across four distinct service lines. The blower door test provides an ideal opportunity for our Commissioning engineers and Test & Balance technicians to work together, each bringing their unique skillsets and experiences to a project. Alexis, from our Commissioning team, and Dave, from our Test & Balance crew, recently traveled to Louisville, Kentucky to conduct a blower door test for a medical research facility. The client had asked us to assess the enclosure leakage rate for one of its laboratory cold rooms.

MWA uses a calibrated blower door testing system to determine the airtightness (or leakage rate) of an entire building or specified zone within a building. It’s important that both the blower door test fan and pressure gauge are calibrated. Uncalibrated blower doors can only detect leaks; they cannot measure how much air is leaking or how effective air sealing methods are.

The blower door test works by blowing air into or out of a building or enclosed space, creating a slight pressure difference between inside and outside. This pressure difference forces air through any holes or gaps in the enclosure. The tighter the building or space (i.e. the less holes or gaps in the enclosure), the less air required for the blower door fan to create a change in pressure.

A blower door test could be used as a diagnostic tool for several reasons, including:

  • To reduce energy consumption
  • To avoid moisture problems
  • To avoid drafts from outside air leaking in
  • To determine how much ventilation is needed to provide acceptable indoor air quality
  • To access the rate of air leakage for critical spaces like hospital rooms (ensuring pollutants are not coming in to clean spaces) or laboratory cold rooms (helping maintain temperature-controlled spaces)

MWA’s typical procedure for evaluating enclosure leakage rates involves the following steps:

  • Obtain floor plan drawings in order to calculate the Total Surface Area of the space to be tested. This is necessary to determine how many fans will be needed.
  • Once onsite, carefully assess the space.
  • Disable any air systems (like energy recovery units, exhaust fans, dampers, etc.).
  • Prepare the space by blocking all openings affecting the test. This includes sealing all penetrations, doors, floor drains, toilets, etc. using an adhesive plastic.
  • Notify facility personnel to ensure all doors and windows remain shut throughout the test.
  • Mount the blower door frame, flexible panel, and variable-speed fans into the doorway.
  • Pressurize and depressurize the space gradually to +/- 50-75 pascal or maximum possible pressure allowable by the available blower door. The achievable pressure will depend on the leakage condition of the room.
  • Use a handheld controller linked to analytical software to instantly collect and evaluate the air leakage data.

Following the test for the laboratory cold room, Alexis and Dave worked together to assess the data and deliver a detailed report to the client which included an executive summary, air leakage data from multiple different pressure readings, and general site observations. The test demonstrated that the space did, in fact, meet the specified air tightness criteria for laboratory cold rooms. If the space had failed to meet the requirement, MWA would have returned to perform an IR thermographic scan to locate the sources of leakage. Whether you’re trying to reduce energy costs, fix moisture problems, improve indoor air quality, or meet an air leakage rate criteria, the blower door test is a powerful diagnostic tool.