Photo Source: Summerhill

• Measures how quickly the air in the home is replaced by outside air
• Expressed as air changes per hour (ACH)
• A blower door is used to perform the test

The lower the air changes the better. It means that heated indoor air will remain in the home longer during the winter, and cooler air will remain in the home longer during the summer. However, moisture and pollutants may also remain in the home longer so it is important to control the quality of the indoor air.

How the blower door works:

• Air from the house is pushed outside with a fan (depressurization), or outside air is pushed into the home(pressurization)
• The fan maintains the air pressure in the home at a certain pressure difference between inside and outside (50 pascals)
• The volume of the air the fan has to move to maintain the pressure lets us know how much air is entering the home through leaks and cracks
• With this information we can determine how air tight the home is