Custom Weatherization, LLC is a quickly growing company. It was established in 2006 and has been providing energy efficiency services to both residential and commercial properties ever since!

Blower Door Overview

A Draft Test
A blower door test consists of a frame that is installed in an exterior doorway of your home and covered with a durable nylon panel. A large powerful fan is then placed over the panel and a pressure gauge (called a manometer) is attached using hoses. Together, it is a diagnostic tool that measures how much air moves through your house per minute. In other words, blower door testing is a test used to determine how air-tight your home is. By depressurizing the house, we can determine where there are air leaks in your home that allow unconditioned exterior air into the home.
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How Does It Work?

Once our certified auditor sets the house up to be tested. He or she will turn the fan on, which will begin to depressurize your home. This causes the inside of your home to be at a lower pressure than outside. As this process occurs, the lower pressure is immediately replaced with outside air through seams, gaps, cracks, electrical bypasses, plumbing bypasses and any other place where air may be able to move freely. As the blower door test is running, you may walk around and feel where air is moving throughout your home. Once the auditor has recorded the results of the test and taken notes of drafty areas, he or she will then recommend areas to be sealed by our qualified technicians, giving you a more efficient home.

Why have a Blower Door Test performed

Identify Air Leakage

Understand how much air is moving through your home. Know where it is coming from.

Improve indoor Air Quality

Understand the results to create a plan for better indoor air quality.

Prevent Mold & Rot

Identify leaky areas that may contribute to unwanted moisture and mold issues.

Cut Energy Cost

Find opportunities to reduce excess air infiltration.
  • Why Conduct a Blower Door Test
  • Understanding the Numbers
  • Why choose us?
  • BPI Certified


Exterior air leakage, whether infiltration or exfiltration, has an effect on our health and may have an effect on your comfort. Unsealed cracks or gaps in the pressure boundary or air barrier can be responsible for several problems. These openings are the cause of hot or cold air entering the home. This air movement also brings along moisture, bugs, dust and other potentially harmful contaminants. These air leaks allow for unwanted drafts as well as conditioned air (heat or cool) to escape the building or dwelling. Air leakage may have a negative impact on the health & safety and comfort level of the occupants while increasing energy usage. 

It is important to conduct a Blower Door Test to identify the leakage areas. This tool will allow our certified team to determine where the uncontrolled leakage is and to recommend the best, most cost effective approach to effectively seal the unwanted leaks.  


A Blower Door Test simply measures how airtight your home or building is, at 50 pascals (50pa). A pascal is a unit of minute air pressure. The Blower Door measures air and is recorded as cubic feet per minute (CFM). We can use the measured CFM to calculate the air exchanges per hour (ACH50). ACH50 indicates how many times outside air replaces or is exchanged with the full volume of indoor air under the testing conditions of 50pa. ACH50 is one of the most common ways to measure or compare air leakage in a home or building.

In addition to testing the home as a whole, we are able to complete what's called zonal testing. A zonal test determines how connected a particular area of the home is connected to the outside. The most common areas to have a zonal test are the attics, knee-wall areas, overhangs, garages, basements and crawl-spaces. Bedrooms, bonus  rooms, sunrooms and additions are great zones to test as well. The test doesn't measure how much air leakage there is but rather measures the connection between the inside and outside by measuring pressure difference. An attic space is considered to be an unconditioned, outside space. When testing this zone we would expect to read -50pa. This would indicate that the attic has a 100% connection to the outside. Suppose that same test was performed and the results read -35pa. This would indicate that the attic has 70% connected to the outside, leaving a 30% connection to the inside. While this test doesn't measure total air leakage, it is a great method to assist the technician with what air sealing measures to recommend.


Our knowledgeable and certified team is why we can guarantee our customers a satisfying experience. We will not leave you without a thorough understanding of your test and results. Any questions will be answered until understood, making it a positive experience for everyone involved.


Our team consists of qualified individuals. Blower Door Test are conducted by professionals who are BPI (Building Performance Institute) certified. 

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