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Blower Door Testing

Accurately Measure Your Home’s Air Leakage

RetroFoam of the Carolinas Blower Door Test Setup

What is Blower Door Testing?

Whether it is coming in or going out, warm air is always on the move. It naturally moves through cracks, gaps, and holes and affects indoor air quality (IAQ). 

Remember your parent(s) yelling to the heavens, “I’m not paying to heat/cool the outside!!!” Sorry dad, you are. The blower door test tells you just how much air is leaking out and being replaced by outside air.

A blower door test by RetroFoam of the Carolinas provides a measurable comparison of a homes air changes per hour compared to industry standards.  We perform blower door testing on homes that we insulate with either spray or injection foam prior to and after the installation. 

How is a blower door test performed?

  1. All exterior openings to the home are closed and locked. This includes windows, doors, dampers. The only door not closed is the one where the test will be performed.
  2. A path for airflow is created by keeping interior doors open. Any room that is serviced by the HVAC system directly or indirectly must be left open. 
  3. Turn off all gas appliances, electrical appliances, HVAC, bath fans, or other ventilation devices.
  4. Set up the blower door to an exterior door and take an outside pressure reading.
  5. Turn on the fan and test for leaks.

How does a Blower Door Test work?

The blower door test is performed by using a powerful fan that pulls the air out of the home. The indoor pressure is lowered which forces the higher-pressured air from outside to come in through any openings. A device called a manometer is used to calculate the amount of air leakage by giving a measurement that shows  air changes per hour (ACH). During the test the technician will walk around the home and take note of any areas where leaks can be heard or felt. 

What is an acceptable ACH score?

Most state building codes require a home to have a ACH50 (Air Changes per Hour) score of less than or equal to five. Simply put, your home should only exchange air 5 times in one-hour. 

The following are basic guidelines for ACH50 results:

  • ACH50 results less than 5.0 — The house is tight and meets industry standards
  • ACH50 results between 5.0 and 10.0 — Moderate tightness
  • ACH50 results above 10.0 — A very leaky house

In older, existing homes, building scientists suggest that a target improvement is to cut air infiltration from the original ACH50 by 20-30%.

Get your free in-home estimate

Call RetroFoam of the Carolinas to speak with a member of our concierge service and set up a free in-home estimate.

Our project manager will visit with you to discuss ways to better insulate your home and cut down on the air leakage. While we love insulating the whole house, from top to bottom, many of our customers take it a step at a time, starting with the walls and our injection foam or the attics with spray foam.

Once our crews perform the blower door test you can speak with one of our concierge to understand the importance of the test results and determine what other steps can be taken to better improve your home’s energy efficiency.