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  • Writer's pictureCertified Energy Raters

What is a Blower Door Test?

So what is a Blower Door test and why would I need one?

Blower Door Test

A Blower Door test is a diagnostic tool used to measure the air leakage of a building envelope. Here's a breakdown of its purpose and benefits:


  • Quantify Air Leakage: The primary function of a blower door test is to determine how much air is escaping or entering your home unintentionally. This leakage can occur through cracks, gaps, and other imperfections in the building envelope, which is the barrier separating the conditioned interior from the outside environment.

  • Identify Leaks: The test not only measures the amount of leakage but can also help pinpoint the location of these leaks. This is often done with smoke or infrared cameras that can visualize drafts and identify specific areas where air is passing through.


  • Improved Energy Efficiency: Uncontrolled air leakage can significantly impact your home's energy efficiency. By identifying and sealing leaks, you can prevent conditioned air from escaping in the winter and hot outside air from entering in the summer. This can lead to substantial savings on your heating and cooling bills.

  • Enhanced Comfort: A drafty home can be uncomfortable to live in. Sealing leaks can help maintain consistent temperatures throughout your home and eliminate drafts, creating a more comfortable living environment.

  • Better Indoor Air Quality: Excessive air leakage can allow pollutants like dust, pollen, and even moisture to enter your home. Sealing leaks can improve indoor air quality and create a healthier living environment.

  • Reduced Noise Pollution: Leaks can also act as pathways for unwanted noise from outside to permeate your home. Addressing these leaks can contribute to a quieter and more peaceful living space.

  • Verification During Construction: Blower door tests are often performed during the construction phase of new homes to ensure proper building envelope air-sealing practices are followed. This helps to meet energy code requirements and ensure the home's intended energy performance.

The Blower Door Test Process

  • Door Installation: A large, inflatable fabric panel is installed into a doorway of your home, creating a temporary seal.

  • Fan Activation: A powerful fan is mounted within the fabric panel. This fan draws air out of the house, depressurizing the interior.

  • Pressure Measurement: Specialized gauges measure the pressure difference between the inside and outside of your home.

  • Leak Detection (Optional): During the test, smoke pens or infrared cameras can be used to identify specific locations where air leakage is occurring.

  • Data Analysis: Once the test is complete, the collected data is used to calculate a value that represents your home's air leakage rate. This is often expressed as a metric called ACH (Air Changes per Hour). A lower ACH signifies a tighter building envelope and less air leakage.

Interpreting the Results of a Blower Door Test

The ACH rating is compared to benchmarks established for your climate zone. Here's a general guideline:

  • Excellent: ACH <= 3

  • Good: ACH 3 - 5

  • Fair: ACH 5 - 7

  • Poor: ACH > 7

However, it's important to note that ACH is just one factor influencing your home's energy efficiency. Other factors like insulation levels and HVAC system efficiency also play a role.

Applications of Blower Door Tests

  • Pre- and Post-renovation Assessments: A blower door test can be conducted before and after air sealing upgrades to quantify the improvements made.

  • New Home Verification: Builders often use blower door tests to ensure new homes meet energy code requirements for air leakage.

  • Troubleshooting Comfort Issues: Drafts and uneven temperatures can be signs of excessive air leakage. A blower door test can help identify the culprit.

  • Improving Indoor Air Quality: Sealing leaks can minimize the infiltration of pollutants and allergens from outside.

By understanding the purpose and benefits of blower door tests, you can make informed decisions about improving the comfort, efficiency, and overall health of your home. Overall, a blower door test is a valuable tool for homeowners and builders alike. It can help identify and address air leakage issues, leading to a more energy-efficient, comfortable, and healthy home.


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