Greenhouse Volume & Ventilation Calculator
Calculate greenhouse air volume and the fan capacity required to achieve target air changes per hour for temperature and humidity control.
Results
What is it?
Greenhouse ventilation is sized in air changes per hour (ACH): how many times the entire greenhouse air volume is replaced per hour. For summer cooling, 60 ACH is a common design standard. Fan capacity (m³/min) = volume × ACH / 60. Volume is approximated as length × width × average height.
How to use
Enter the greenhouse dimensions and the target air changes per hour. The calculator returns the greenhouse air volume and the minimum fan capacity in m³/min and m³/hr. Select fans with a combined capacity meeting or exceeding the ventRequired output.
Example scenario
A 30 × 8 m greenhouse with 4 m ridge and 2.5 m sidewall (average height 3.25 m): Volume = 780 m³. At 60 ACH: fan capacity needed = 780 m³/min — split across two 390 m³/min fans. Most commercial greenhouse fans are rated 500–5,000 m³/min.
Pro tip
Locate exhaust fans on the leeward wall and passive inlets on the windward wall to use prevailing winds. In hot climates, evaporative cooling pads combined with fans (fan-and-pad systems) can reduce air temperature by 6–10°C. Control fans with thermostat staging: stage 1 activates at 25°C, stage 2 at 28°C, emergency full ventilation at 30°C.