HVACopediaVentilation & air changes
cfm for people or air changes, ACH from airflow, blower-door ACH50.
More airflow & ducts calculators
Airflow & heating outputcfm, temperature rise, output and cooling airflowStatic pressure & friction rateAvailable static pressure and the friction rate for duct designRound duct sizeDuct diameter from the airflow and the friction rateRound ⇄ rectangular ductEquivalent sizes with the same frictionFan lawsWhat happens to pressure and power when the airflow changesPsychrometricsWet-bulb, humidity, dew point, grains and enthalpy from two readings
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Calculation aids and reference figures for licensed technicians. Always follow the manufacturer’s data plate and manual for the exact model, and local codes. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Pressures are typical saturation values and change with load and airflow.