Van life · ventilation
Van ventilation fan CFM calculator.
Convert your van's interior volume and the air changes per hour you want into the airflow a roof fan should deliver.
Inputs
Fan airflow
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How to size a van ventilation fan
CFM = volume in cubic feet x air changes per hour / 60. Cubic feet convert to cubic metres at 0.0283168 (NIST), and 1 CFM is about 1.699 cubic metres per hour.
Worked example. A 14 ft x 6 ft x 6 ft living space is 504 ft3. At 15 air changes an hour: 504 x 15 / 60 = 126 CFM, which is 214 m3/h.
Choosing a fan. The ACH targets in the list are rules of thumb, not published standards. Fan CFM ratings are usually free-air figures, and airflow through a roof vent, screen and filter is lower, so check the fan's own performance data and leave margin.
Safety. A fan is not a carbon monoxide control. If you cook, heat or run any fuel-burning appliance inside the van, follow that appliance's ventilation and venting instructions and fit a working CO alarm.
Frequently asked questions
What CFM fan do I need for a van?
Multiply the interior volume in cubic feet by the air changes per hour you want and divide by 60. A 504 ft3 van at 15 ACH needs about 126 CFM.
How many air changes per hour should a van have?
There is no published standard for vans. 6, 15 and 30 are rules of thumb for light airing, cooking and cooling; choose by how you use the space.
How do I convert CFM to cubic metres per hour?
Multiply CFM by 1.699. 126 CFM is about 214 m3/h.
Can a vent fan protect me from carbon monoxide?
No. Follow the ventilation instructions for any fuel-burning appliance and use a working CO alarm.
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Planning estimate, not professional advice
Results are planning estimates from the numbers you enter. They are not professional, engineering, electrical or safety advice and are not a substitute for the manufacturer's instructions or local code. Never rely on a fan for carbon monoxide safety; follow the instructions for every fuel-burning appliance.