Air Turnover Rate Calculator
Understanding Air Turnover Rate
Air Turnover Rate (ATR), often expressed as Air Changes per Hour (ACH), is a crucial metric in HVAC (Heating, Ventilation, and Air Conditioning) and building design. It quantifies how many times the entire volume of air within a defined space is replaced by fresh or conditioned air within a one-hour period. A higher ATR generally indicates better ventilation, which is vital for maintaining indoor air quality, controlling humidity, and ensuring occupant comfort and safety.
The calculation is straightforward. You need two primary pieces of information:
- Room Volume: This is the total cubic space of the room or building, typically measured in cubic feet (ft³) or cubic meters (m³).
- Airflow Rate: This is the rate at which air is supplied to or exhausted from the space. For this calculator, we use Cubic Feet per Minute (CFM).
The formula used is:
Air Turnover Rate (ACH) = (Airflow Rate (CFM) × 60 minutes/hour) / Room Volume (ft³)
This calculation helps determine if the ventilation system is adequately sized for the space. For instance, in cleanrooms, operating rooms, or laboratories, a high ACH is essential to minimize contamination. In residential settings, adequate ACH ensures that pollutants are removed and fresh air is circulated, contributing to a healthier living environment.
Example:
Consider a room with a volume of 1200 cubic feet (ft³). If your ventilation system provides an airflow rate of 600 CFM, the Air Turnover Rate would be calculated as follows:
ATR = (600 CFM × 60 minutes/hour) / 1200 ft³
ATR = 36000 / 1200
ATR = 30 Air Changes per Hour (ACH)
This means the entire volume of air in the room is replaced 30 times every hour.