The air exchange rate, often measured in air changes per hour (ACH), describes how many times indoor air is replaced with outdoor air in an hour. It affects indoor air quality, moisture control, comfort, and energy use. Too little exchange can trap pollutants, while too much can waste heating or cooling energy.
/ˈɛər ɪkˈstʃeɪndʒ reɪt/
The air exchange rate, often measured in air changes per hour (ACH), describes how many times indoor air is replaced with outdoor air in an hour. It affects indoor air quality, moisture control, comfort, and energy use. Too little exchange can trap pollutants, while too much can waste heating or cooling energy.
What is a good air exchange rate for a home?
There isn’t one universal ACH for every home. The ideal rate depends on home size, occupancy, and how tightly sealed the building is.
Source: The Cooling Company
Balanced ACH supports healthy air without wasting energy.
Balanced ventilation systems help maintain healthy air exchange without wasting heating or cooling energy, especially in well-sealed homes.
Have your ventilation system inspected periodically to keep air exchange at healthy, efficient levels.
“Have your ventilation system inspected periodically to keep air exchange at healthy, efficient levels.”
Modern energy-efficient buildings often need mechanical ventilation because natural air exchange rates are lower.
Can a home be too tightly sealed?
Yes. A very tight building envelope can reduce natural air exchange, which may require mechanical ventilation to maintain air quality.
How do I measure air exchange rate?
A professional can use blower-door testing and ventilation measurements to estimate ACH for your home.
Do I need a ventilator to improve air exchange?
Not always, but well-sealed homes often benefit from ERVs or HRVs to bring in fresh air efficiently.
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