Many people look forward to selecting paint colors, countertops and appliances when designing their new homes. One other item that they may want to add to the list is how tightly the home is built.


A typical existing home can be very leaky by today’s standards. The metric used to measure the leakiness of a home is air changes per hour (ACH), often measured at 50 Pascal’s (ACH50). In many existing homes this number can approach or even exceed 10 ACH50. For context, the International Energy Conservation Code (IECC), which sets minimum standards with regards to energy efficient construction, requires all new construction to meet certain air leakage requirements. In the 2009 edition the limit was 7 ACH50 (air changes per hour @ 50 pascals), which was then tightened to 5 ACH in the 2012 edition, and again to 3 ACH50 for the most recent 2015 edition. It is widely accepted throughout the industry that anything less than 5 ACH50 is considered to be a tight home.


To measure a home’s air leakage, we use a tool known as a blower door. To conduct a blower door test, a fan is mounted into a frame of an exterior door, which pulls air out of the house thus lowering the air pressure inside. Because the outdoor air pressure is now higher than the air pressure inside the home, the outdoor air is pulled in through all penetrations, crack and openings in the buildings envelope.

To measure the airflow, a manometer is connected to the fan and includes reference hoses inside and outside of the home that monitor airflow and pressure. The manometer measures airflow at cubic feet per minute reading (CFM) measured at 50 Pascal’s. Using this number and the volume of the home, we can calculate the infiltration or leakage rate.

Formula for calculating the ACH on a house using a blower door:

ACH50 = CFM50 x 60 ÷ House volume

Read more on Blower Door Testing and Sealing the Building Envelope (PDF)


“Having a blower door test helped validate the quality and energy efficiency we are getting with our new home. With rising energy costs its great piece of mind that any preventable issues with the home were addressed and we will spend less on heating & cooling as a result.”

– New Homeowner, Ballston Lake, NY




The benefits of having an energy efficiency home with little air leakage are great. Here are some advantages:

  • Lower utility bills
  • Reduced heating and cooling loads
  • Improved comfort
  • Improved indoor air quality
  • Reduce/eliminate moisture problems


If you are a builder or homeowner and are interested in getting a blower door test done on your home, please contact us at 518-377-9410 or

This entry was posted in Energy Code, Energy Efficiency, Energy Savings, Indoor Air Quality, Residential Building. Bookmark the permalink.

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