Many people are asking, “What is a blower door test?” On February 8, 2016 the State of Michigan adopted the 2015 Michigan Residential Code. In the newly adopted code, new homes must meet an air change rate (ACH) per hour of 4 or less. So how does this test work and what does it involve?
We begin by creating a pressure difference between the inside and the outside of the house that is comparable to a 22 MPH wind on all sides of the home, at the same time. So unless you are in the eye of a storm an unlikely condition that helps us to visualize air leakage and quantify total building tightness. Let’s project that your house has a floor area of 2400 square feet and a total volume of 19,200 Cubic feet. We measure a cubic foot per hour of 54,000 and divide this by the total house volume yielding an air change rate per hour (ACH) of 2.81. So in essence, we are exhausting 54,000 basketball size pieces of air per hour, and by the laws of physics it has to come back in to the house somewhere. While in this exaggerated condition, a smoke pencil can be used to demonstrate the type of air infiltration that exists. Through this test, we can estimate how much money the homeowner could expect to spend on heating/cooling due to air infiltration alone. I have seen an increasing number of young home buyers investing in the thermal envelope of their home and foregoing aesthetic cost adds. By doing so, these folks invest more in a more tangible return on investment with reduced energy costs and occupant comfort. This excites me as I see people looking to make more long-term commitment to their children, their neighborhoods, and the sustainability of a energy responsible tomorrow.