Greenhouse Ventilation Calculator
Exhaust Fan Sizing
Calculate required fan CFM for greenhouse ventilation
Natural Ventilation Sizing
Calculate ridge and side vent areas for passive ventilation
Formula
CFM = Volume x Climate Factor | Intake Vent Area = CFM / 300 | Natural Vent Area = Floor Area x 15-22%
Frequently Asked Questions
How many air exchanges per hour does a greenhouse need?
In summer, greenhouses need 40-60 air exchanges per hour (roughly 1 per minute) to maintain temperatures. In winter, 2-4 exchanges per hour is sufficient to control humidity and CO2 levels. The required CFM equals greenhouse volume times exchanges per minute.
How do I size a greenhouse exhaust fan?
Calculate your greenhouse volume (L x W x H), then multiply by 1.0-1.5 depending on climate. A 12x30x8 ft greenhouse is 2,880 cu ft, requiring about 2,880-4,320 CFM. In hot climates, increase by 25-50%. Place the fan on the leeward end.
Is natural ventilation sufficient for a greenhouse?
Natural ventilation (ridge and side vents) works for mild climates and smaller greenhouses. Vent area should be 15-25% of floor area. For hot climates or commercial operations, powered exhaust fans with evaporative cooling pads are more effective.
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