Back in 2012, the International Residential Code (IRC) put forth a revised set of requirements and building code standards as they do every year. 2012 marked a new era in building codes when the airtightness of home came under scrutiny.
What is the airtightness of a home? How is it measured?
Essentially, airtightness is measured to determine how well the house was built to minimize risk of moisture intrusion and provide enhanced stability for energy efficiency.
The airtightness of a home is measured by how drafty the home is—how much air is able to escape through seams, seals, and entryways. It is measured through a special pressurization device hooked up to a machine called a blower door. This test measures the difference between the outside air pressure and air pressure found indoors. The difference is the measurement of airtightness in the home.
How does a blower door test work?
A blower door test is conducted with a unique looking machine that is installed in the entryway of a home, usually the front door. It has a powerful fan that, once turned on, pulls air from inside the home and pushes it outside, essentially creating a vacuum. Scientifically speaking, nature will attempt to fill a vacuum, and it does this in a depressurized home by pushing air through any cracks in the home’s structure.
As the fan runs the air to the outside, an attached device, called a manometer gauges the air pressure inside and out of the home. A comparison of the air pressure and how much the fan has to work to maintain the pressure between the two tells the inspector how well constructed the home is. The pressure is measured in a unit called CMF50.
Understanding the numbers on a manometer can be difficult to explain but the result should be equal to or less than the square footage of a home. Less than is preferable. So, a home that is 2,000 square feet should have a 2,000 CMF50 or less.
The most common times for a blower door test to be conducted is during the building phase of a new home or building. This allows time for builders to reassess their construction and correct any flaws before the completion of the home. A blower door test may be conducted by a building or home inspector when the building is very old, and renovations are being considered.
Acusystem Inspections now offers blower door testing to residential and commercial clients for both new construction and already built structures. Contact us today to learn more about the blower door process or to schedule your inspection and testing.