Blower Door Test Results

 

I am giving the blower door test its own post because I think this will be of interest to people who are interested in monolithic domes. First let me say we were excited to find out our house was a 0.27 ACH50! 

The last few weeks leading up to our final CO inspection were a whirlwind. One of the big surprise steps was a blower door test. We found out about it just chatting with our building department officials maybe 2 or 3 months before the inspection. It came up in general conversation because we constantly ask them questions and ask for their advice. Being owner builders, we have way more inspections than a builder would have (by choice) and we have been working with our inspectors for many years instead of the typical 1 year build. The best advice I can give other owner builders is to ask questions and encourage the building officials to tell you about what they will need to see next and what has to be signed off on before you can get to the next step. Think of them as team members helping to guide you through all the red tape of building your own house. Things will go a lot smoother with that outlook.

There are many things that have come up in this project that we had no way of knowing about without us constantly asking the officials what the next steps were. The officials do not think to offer that info because they are used to builders who already know the steps. We made sure to constantly ask "what do you need to see going forward". It is far easier to do it right the first time than to miss something and have to redo work.

I had heard of blower door tests but never realized it was something that all new construction must pass. I got a few quotes from test companies and realized that our situation was going to be more difficult than the typical test. For this reason I didn't pick the cheapest company but instead picked the one that was actually excited to do the test on an unusual house. He was $50 more than the other quotes. He even researched the construction type to give us the quote. I felt like there wouldn't be any surprise costs because he knew what he was getting into and would be cheaper in the end. A big thing we have learned building this house is that quotes are not what you pay. They are estimates and you will be billed no less than their estimate BUT it can be higher if they spend more time than expected. The test company must do a bunch of calculations to figure out how much air volume is in the home in addition to bringing the test equipment and doing the pressure test. I wanted the person to be ready for a different house and the additional challenges associated with the job. Challenges = money when hiring people to work on the house.

The first challenge was giving him data so he could do his air volume calculations. Luckily between the pattern review document monolithic sent me when they created the airform and the construction documents there was enough info for him to figure out the volume. I still have no idea how he did it but I am the first to admit math is not my strength.

The second challenge was where to attach the fan system. Our doors and windows are all either extra tall (8 ft) or round top. Turns out they make their equipment for more normal size square openings. Lucky for us the company did have one door seal that was just barely tall enough for the 8ft door. He wasn't sure it would fit until he arrived to do the test.

In a test they depressurize your house with all doors, windows and vents shut. Then they measure the pressure based on how much air the fan can pull from the house. This will tell them how much air can leak into the house through areas (gaps, cracks etc) that are not supposed to be open. They then calculate how many total house volumes of air changeover can happen in a specific time frame and give the house a rating.

The lower the number the better the house is sealed. Normal building code for a new construction requires a rating of 3.0 ACH50 (Air Changes per Hour), passive house standard is anything below 0.6 ACH50

 Below is the detailed report submitted to our town.