Greenhouse Air Exchange Planner

How to use this estimate

Airflow is calculated from the turnover value that you enter; the tool does not prescribe an appropriate rate or make safety, heat-stress, humidity, or crop recommendations. Rated fan flow may differ from installed flow because of screens, ducts, wind, and static pressure. The derating is your explicit estimate.

Method

Volume = length × width × average height. Required net CFM = volume × entered turnovers per hour / 60. Estimated installed CFM = rated CFM × (1 - derating). Fan count rounds the required flow upward by that installed flow.

Worked example

A 24 × 12 × 8 ft enclosure is 2,304 cu ft. At a user-entered 20 turnovers/hour it needs 768 net CFM; a 1,200 CFM fan at an estimated 20% derating supplies 960 CFM.

Assumptions and supported inputs

Use measured dimensions and the listed field ranges. Values outside those bounds, missing entries, non-finite numbers, and fractional counts where a whole number is required are rejected. Displayed results are rounded to two decimal places; internal calculations retain full precision. This is a planning estimate, not a substitute for an on-site layout, product instructions, or a qualified trade decision where applicable.

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Northstar Calculators provides this arithmetic for scenario planning. Verify the assumptions and physical fit before buying or building.