Mechanical ventilation
Powered exhaust and HAF fans for existing structures—size both tools on this page and combine into one quote.
2 tools on this page
Choose a sizing tool
Each option opens a different calculator on this page. Your quote list can include more than one.
Exhaust fan sizing
Structure
Eave / gutter height (ventilation model)
Approximate floor area: 2,880 sq ft
What drives the number
This tool uses the same ventilation sizing approach as our greenhouse configurators: your dimensions set how much air we target moving, then we pick a practical fan count and catalog fans that can deliver that duty. Exact coefficients and pricing tables stay on our servers—what you see here is the outcome, not a spec sheet to copy.
- Inputs — width, length, sidewall height, and how many connected houses (bays) you run.
- Airflow target — a CFM requirement derived from those dimensions, with a length-based adjustment for how far air moves from inlet to fan (longer houses need more margin).
- Layout & price — fans per bay stay within catalog limits; very small houses may use one fan per bay when two would be oversized. We then match fans and accessories for a conservative website total.
Estimates are for planning only. Final fan selection, electrical, and installation depend on site review.
Understanding the results
Mechanical ventilation uses powered fans when passive venting alone is not enough—or when you want predictable air exchange or mixing. That includes gutter-connected houses, cold frames, seasonal tunnels, and single-bay structures.
Exhaust fans remove warm, humid air and support pad-and-fan cooling. HAF fans push air along the house so it mixes instead of stratifying.
Both calculators use the same engineering rules as our greenhouse configurators. You get indicative CFM, fan counts, and pricing for your entered dimensions; our team still confirms details before any formal quote.
Equipment overview
Switch between exhaust and HAF tools above. Exhaust sizing uses house width, length, sidewall height, and bays. HAF sizing uses floor dimensions and bays for circulation layout. Add each result to your quote list to combine with heaters, evaporative cooling, or other equipment.
Frequently asked questions
When do I need exhaust fans versus HAF fans?
Do these calculators work for cold frames?
Can I add both exhaust and HAF to one quote?
Request a quote
Use Add to quote list on each tool, then open the bar at the top of the site for one combined request.
Request a quote