Blower Door Test
by High Plains Architects
April 16, 2018
We have had several Blower Door Tests performed to determine if there were any significant leaks where cold in the winter or heat in the summer could infiltrate into the house. We felt that our house was very well insulated and holes had been sealed to prevent such an occurrence but how do we know for sure? That’s where the Blower Door Test comes into play. First, it is necessary to close all the windows and doors except one. Then a big fan is placed in the one open doorway and sealed tightly to the edges of the doorframe. The fan is turned on to either push air into or suck air out from the house to pressurize/depressurize it in order to determine where any leaks might be located. The first couple of times we performed this test, we discovered that we, indeed, had some areas that we had neglected to seal well. Randy made note and took care of those leaks. Then, on April 16, 2018, when we had our most recent Blower Door Test, we got the results Randy was hoping for: .038CFM (cubic feet per minute)/SF and .67ACH (air changes per hour). Randy was thrilled and, as a result, I was thrilled also! I’d like to say I knew the significance of those results but I didn’t have a clue. So, it was a teaching moment. According to our Passive House Consultant, the reading on the airflow manometer at the time of the test is divided by the square footage of the envelope of the house to determine the leakage in CFM/SF envelope area. Our reading averaged 327.5 CFM. Then that number is divided by the square footage of the envelope area which in our case is 8,571 SF. The American standard for Passivhaus –a tough standard to achieve - is a maximum of 0.05 CFM/SF envelope area. In addition, current building codes allow a maximum of 5.0 ACH. This is calculated by dividing the reading on the airflow manometer by the net volume (not the gross volume and there is a difference) multiplied by 60 seconds in an hour. Therefore, our average reading of 327.5 CFM was divided by our net volume of 29,273 CF times 60 seconds/hour. The results are below.
Maximum Cubic Feet Minute/SF envelope area STANDARD: 0.05 OUR HOUSE: 0.038
Maximum Air Changes per Hour STANDARD: 5.00 OUR HOUSE: 0.67
So, if I’m interpreting our results correctly, our house is exceedingly air-tight. Wahoo!!! And, we now have the information we need to complete our submission for Passive House Certification.