Is a Blower Door Test required on a renovation or addition?

The short answer is yes. A Blower Door Test is technically required on certain renovations and additions for residential construction. The determining factor is the scope of the project and whether or not the building inspector is enforcing it. Unfortunately, the code does not give any clear alternatives for the test, other than what is defined for new construction homes.


We are finding a lot of inspectors throughout West Michigan requiring a Blower Door Test for a project undergoing an addition. Technically the code requires a test on the entire structure, with the addition, at the end of the project. The problem with this path is the entire house will have to pass the Blower Door Test threshold for new construction, which is 4.00 ACH50 or lower. This can be very difficult if the existing structure is old and/or poorly insulated/air sealed. See our recent blog post on reasons a Blower Door Test will fail.

Some inspectors here in West Michigan have been allowing an alternative path. This substitute route allows you to run a Blower Door Test on the structure prior to starting any work. This gives us a baseline result for how air-tight the home is. Once the project is finished, we run a second Blower Door Test and compare it to the first result. As long as the home is equal to or tighter than the initial test, it’s considered passing.

The second option is by far the best. We have not seen a project fail when it has taken this course. On the other hand, most projects fail the first option. There are two downsides to the second avenue. One, it’s not techincally defined in the Michigan Energy Code and two, it costs more due to the fact that you have to pay for two tests.


It gets a little more challenging for renovations. We are finding some building inspectors not requiring a Blower Door Test for a renovation that does not include an addition as part of the work scope. Some inspectors are requiring a test if a certain percentage of the structure is taken down to the studs. Fortunately we are seeing some inspectors allowing for the second option that we described above.


Whether you are doing a renovation or addition, we highly recommend talking to the building inspector prior to pulling permits and get their Blower Door Test requirement in writing. We are finding most building inspectors are not providing this information at the permit stage. In a lot of cases the inspector mentions the test requirement at the end of the project and at that point your options become much more limited.

Please call us if you have any questions about the process. We would be happy to help you! 616-419-8558

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