An Overview of Blower Door Tests

20 March 2018

What is a blower door test? Why should you do one? How much does a blower door test cost? 

An Overview of Blower Door Tests


What is a blower door test?

A blower door test is a test that measures how airtight or leaky a home is. During the test, a large fan depressurizes the inside of the home with respect to outside and then measures the air flow through the fan to figure out how much air is being forced through internal leaks to maintain that pressure.. With some calculations we can figure out exactly how much air leaks from your home naturally. It can also be used as a part of a test to pinpoint where your home has the air leaks.

Why should I do a blower door test?

The leakier your home is, the more energy you will use to heat and cool it. More energy used means more money spent. Said a different way, more air leakage = higher energy bills. Estimates by the Department of Energy show that people could save up to 30% on energy bills with some efficiency upgrades to the home.

Homes with a lot of air leaks are also much more at risk for moisture issues like mold and rotting wood. Homes with more air leaks and moisture are often associated with more instances of asthma and other respiratory conditions. So lower air leakage = healthier residents.

Luckily air leaks are a pretty easy fix. Whether you are a DIY-er or would want to bring in professionals, there are a lot of options. But it all starts with knowing how much your home leaks and where it leaks.

How does a blower door work?

1.) All devices that would affect the air flow in the home (HVAC, bathroom fans, etc) are turned off

2.) A blower door is mounted in an external door frame, hoses are connected to measure the air pressure outside, inside, and in the fan assembly, and a manometer is set up to run the whole test

3.) The fan in the door blows air out of the house, depressurizing the home to a set standard with the outside

4.) As air is pulled out of the house, it is naturally replaced by new air. This new air comes through the air leaks in the house. 

5.) By measuring the air flow through the fan (courtesy of the manometer) and plugging it into a formula with the volume and dimensions of the home, the amount of air leakage can be identified

What is a blower door test used for?

The most common use of a blower door test is as a part of code compliance testing in new home construction. Because the air leakage is so important, this test is required by building code. Think of it this way: an air-tight home is a demonstration of a higher quality of construction. So if your home is super leaky, it was probably thrown together and shows that a lot of care wasn’t put into the details.

Blower door tests are also a standard part of energy audits. If you want to figure out how to save money on your utility bills, the inspector should definitely have this as a part of the inspection. A blower door test can help pinpoint exactly where the air leaks are.

How much does a blower door test cost?

A blower door test in Nashville and Middle Tennessee will cost you somewhere between $150 and $400.

It’s not really a DIY kind of task. If you wanted to buy the blower door, fan, and manometer, you’re going to be paying a few thousand dollars. So even if you want to do the air sealing and insulation work yourself, save yourself some money and find a certified professional to conduct the test and inspection.

Who can do blower door tests?

There are a few different certifying authorities for blower door tests. When you’re looking for a contractor to inspect your home and run these tests you want to make sure they are certified by the Building Performance Institute (BPI) or by RESNET as a HERS rater. You can find contractors near you by clicking on the organization name.