Building diagnostics and commissioning is standard procedure at ZED, which includes blower door testing at key stages in the construction process. Blower door testing is a crucial aspect of putting together the building envelope correctly, helping ensure an airtight home. An airtight air barrier not only prevents cold or warm air from getting in, but also moisture, dust, pollen and other contaminants to entering the home.
What does a typical air barrier look like?
We perform blower door tests at multiple points during construction to ensure success. At our Columbia Street Residences project in Cambridge we had to do this initial test without a completed air barrier in the basement but were in range of our target. New Ecology performed the test and found approximate air leakage to be 2.6 ACH50.
How a Blower Test Works
The blower door test is used to quantify the amount of air leakage through a building’s enclosure. A blower door fan is temporarily sealed into an exterior door or window, while all other exterior openings are closed, as well as all mechanical exhaust devices shut off. When the blower door fan is turned on, it creates either a positive or negative pressure differential between inside and outside. This in turn forces air through any penetrations in the building enclosure it can find, which is what the blower door test measures. This air leakage results measurement called ‘air changes per hour,’ or ACH50.
Air Leakage (ACH50)
Air changes per hour (ACH) is calculated using a blower door at a standard pressure difference of 50 pascals (a unit of pressure) between inside the home and outside. A building's ACH50 therefore tells us that at the pressure of 50 pascals, air leaks from the building at a rate of X times the volume of the building per hour. For example, a leaky building might be 15 ACH50, while a high performance building is typically 1 ACH50 or less. The Passive House standard requires 0.6 ACH50 or less.
Architecture: ZeroEnergy Design
Mechanical Design: Ripcord Engineering
General Contractor: Alpha Smart Builders