Everything you need to know about blower door tests

by | Sep 8, 2022 | Performance

Blower door tests are a quick and easy way to find out the airtightness of your home and therefore how leaky or thermally efficient your house is.

This post will explain what a blower door test is, how it works, and how to book yourself in for one.

Table of Content

  • What is a blower door test?
  • How does a blower door test work?
  • Who is a blower door test for?
  • What is a good blower door test result?
  • Blower door test equipment
  • Blower door test cost
  • How to find a blower door test near me


A blower door test is a method of testing the airtightness of a structure. It involves measuring the amount of pressure inside and outside a building, before and after introducing an external source of forced-air ventilation. The difference between these two figures is called the “air infiltration rate,” or AIR.

The purpose of this test is to determine whether there are significant leaks in your home’s envelope, meaning the walls, ceiling, floor, windows and doors. Leaks can be caused by gaps in insulation, holes around pipes, inadequate weatherstripping, cracks on chimneys or skylights, open spaces between framing studs, cracks in plasterboard or around electrical switches… The list goes on and on.

The more sealed and airtight a home is, the less air will move in it. So with the blower door test, we are finding out how well-sealed a house, or how leaky, it is. 


The blower door test is performed by placing a fan-like device (known as a “blower”) in an exterior doorway. A technician then turns on the fan to a pressure difference of 50 pascal. This number has been chosen so blower door tests are comparable to each other, as you will never be able to fully replicate the same conditions without having the same starting point.

The technician then closes all windows and doors and the active blower door will force air into your home through all possible leaks. This form of blower door testing is called depressuration, and is our preferred way of testing when using a thermal camera in addition to the blower door. The drawing in of air creates a temperature difference on all surfaces inside the home, which will be picked up by the thermal camera.

If  you don’t have a thermal camera, you would probably opt for the actual pressurisation of the home, meaning air is forced out of the home through all potential leaks. You could use a smoking device to make these leaks more visible.

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By pressurising the home, the fan then measures how much air is being removed from the home in order to keep the inside at the pressure of 50 Pascal. How much air is being moved is measured in air changes per hour, ACH. This unit measures the number of times the total air volume in a space is completely removed and replaced within one hour.


Blower door tests are for homeowners who want to understand how their home is performing as far as energy efficiency goes. You should get a blower door test if you’re interested in improving the thermal performance and comfort of your home, as well as the inside air quality.

Additionally, those who are considering purchasing a new home will find that having the test performed before making any decisions about purchasing can help them make a more informed decision.

Finally, many builders and tradespeople are only just starting on their journey to energy efficient building, or are simply not familiar with airtightness details and the ins and outs of blower door testing. Booking a blower door test demonstration often is the first step to understanding these details better – and will certainly assist with improving a home’s performance.

Are you interested in booking a blower door test demonstration for your team on site? Send us a message now and we are happy to bring our testing equipment and answer all the questions you might have!


This is a highly debatable topic, as there are unfortunately no minimum airtightness requirements set by the National Construction Code (NCC) yet. However, in order to get passive house certification, the house needs to achieve a result of 0.6 ACH or lower.

Now, the average Australian home probably has an air leakage rate of 15-25 ACH, judging from our experience, which is why we believe getting a result that is below 10 ACH is already a win.

And if you don’t get a result you are happy with, there is no reason to panic. A blower door test is a great way to start a renovation to improve the energy efficiency of a home. After all, it helps you identify those dreaded air leaks that are affecting the thermal performance of your home, so identifying the areas you should focus on in your renos is saving you a heap of work to figure that out yourself.

Something the NCC does address though is that if your home is so airtight that you get a result of 5 ACH or lower, you must include mechanical ventilation to ensure continuous good air quality in the home. So keep that in mind when aiming for a result that is lower than that. 


The blower door test requires specific and specialised equipment. The most important piece of equipment that you need is the blower door itself. It will include:

  • A fan to draw air through an opening in the house and out through a hose attached to it
  • An electronic pressure sensor, which measures how much air flows through your house

We at Outlier also use thermal cameras to identify potential thermal bridging on top of the air leakage inspection, but this is not a mandatory part of a blower door test kit.

Our blower door test kit is from Retrotec, and is sold in Australia by Energy Conservation Technologies. Here’s their website

Fun fact: As most of the blower door test kits consist of a bright red blower door, it is also referred to as “the red door of truth”, as it will undoubtedly shine some light on the weak points in your home.


The cost of a blower door test can vary greatly depending on the size of your home, type of test and location. In general, smaller homes will be cheaper than larger ones. A simple blower door test in a single-family house will usually cost anywhere from $200-$300; while a complex test (that is, one involving multiple buildings) may cost more than $1,000.

We offer blower door testing including thermal imagery and the creation of a thorough energy leakage port from $580.

You can learn more about our air leakage and insulation inspection here


Blower door testing is an essential part of buying or selling a home because it allows buyers to determine if they are getting what they are paying for when it comes to insulation levels in their new or old homes. The best way to ensure that buyers have an accurate idea of how much heat loss their homes experience, which can affect heating bills over time; this makes them better equipped when making decisions about potential purchases or sales—even if they aren’t planning on selling anytime soon!

As of right now, there aren’t many providers of blower door tests active in Victoria. Outlier Studio is one of only a handful of professionals who are offering this service, so if you are looking to have a blower door test done please contact us to book an appointment!

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