What is a Blower Door Test, and why is it important (or possibly even required)?

Blower door tests are not particularly common during a general home inspection (pre-existing homes), but performing this test is required for new construction...and for good reason! As building science (and the applicable energy code requirements) evolve, testing a home for its airtightness has become the new standard. How tight a building envelope is has a direct correlation to how energy efficient the home will be. This is where the blower door test comes into play - which is a combination of a large fan, a cloth and frame that fits snugly in an exterior door, and a manometer for measuring airflow. Most energy codes require a passing test measured in ACH50, or air changes per hour at 50 pascals of pressure. In Montana, the passing requirement is 4 ACH50 or less.

Blower door frame, cloth, fan, and manometer

Passing test at <4 ACH50

Failing test at >4 ACH50

But what is an air change per hour...let alone at 50 pascals of pressure? Air changes per hour represents how frequently the air inside a building is replaced with outside air through various leakage spots. 50 pascals represents a 20 mph wind blowing on each side of the building simultaneously. With a blower door running in conjunction with tools like a thermal camera, we can can see where this air leakage is occurring through the building envelope, or conditioned area of the home. The lower the ACH50, the more airtight the building is and thus, the more energy efficient it will be.

While a building's insulation is very important for energy efficiency, sealing its air leakage areas is critical for the best performance (which means lower utility costs) when heating or cooling the home. A number of air leakage locations commonly exist - especially around attic hatches, electrical fixtures, windows, and exterior doors.

Leakage under exterior door

Leakage around fireplace masonry on exterior wall

Leakage around bathroom fan

Leakage around ceiling can light

Leakage around unsealed attic hatch

Leakage at light switch on exterior wall

Even though blower door tests are not required for existing homes, they are a great way to visualize where air leakage is occuring. This can provide information for an actionable plan to improve the home's energy efficiency, and there may even be a Weatherization Program through the state to help with your home's performance.

Whether you're a builder, buyer, homeowner, or realtor in Montana - resources are available to learn more about blower door tests, qualified providing contractors, and additional home energy efficiency information.

Ready to learn more, or schedule your blower door test in Ravalli or Missoula county? Send me a message or give me a call today! Don't want to miss future blog posts? Click here and subscribe at the top of the page (no spam, I promise)!

-Jonathan

info@cameronhomeinspections.com  

406-306-1331

ASHI # 265859 MTHI # 0452

ICA # 18243

ITC # 273199

*The views and opinions expressed in this blog are those of the author and do not necessarily reflect the official policy or position of any other agency, organization, employer or company.