Greenhouse Exhaust Fan Sizing

Exhaust Fan cfm (cubic ft. per minute) Calculator --
Buy fans from mfg! Call Future Products 877-374-3267.
Adequate ventilation essential to cool greenhouse, sunroom or pool enclosure.
• For freestanding structure exhaust fan sizing use formula (width x length x Ave. height) to get cfm (cubic ft. per minute) of fan required.
• Attached greenhouse/sunroom exhaust fans are sized by taking 7 cfm for every sq. ft. of south facing glazing. Include roof & wall area in total.
Locate fan on wall away from prevailing winds, usually at peak of end wall. Position shutters/louvers low on opposite wall.
Discuss inlet shutter or louver sizing and control options with Future Products.

Freestanding Structure Fan formula (width x length x Ave. height) for cfm.

A.

ft.

Enter the width of the structure

B.

ft.

Enter length of the structure

C.

ft.

Enter the average height of the structure.
The average height most often determined by adding side wall height to ridge height and dividing by 2. For structures with different height side walls just do your best to determine the "average" height. Close estimates are fine.

D.

cfm of Fan. Optimal fan size in Cubic Feet per Minute.

Attached (lean-to) greenhouse/sunroom exhaust fans sized by taking 7 cfm (multiplier) for every sq. ft. of south facing glazing (polycarbonate, glass, etc.). Include roof & wall area in total. Position fan high in end wall.

A.

Enter sq. ft. of south facing glazing (polycarb, glass, etc.).

B.

Enter Multiplier. Not an exact science. Use common sense.
For situations with full southern exposure enter 7.
-If colored poly, trees overhead, not facing south, figure can be as low as 4.
Even a north facing roof, on June 21st, will get hot inside. Play with different multipliers. See how these figures fit with available fans.

C.

cfm of Fan. Optimal fan size in Cubic Feet per Minute.

Freestanding Structure Fan formula (width x length x Ave. height) for cfm.
A.	ft.	Enter the width of the structure
B.	ft.	Enter length of the structure
C.	ft.	Enter the average height of the structure. The average height most often determined by adding side wall height to ridge height and dividing by 2. For structures with different height side walls just do your best to determine the "average" height. Close estimates are fine.
D.	cfm of Fan. Optimal fan size in Cubic Feet per Minute.

Attached (lean-to) greenhouse/sunroom exhaust fans sized by taking 7 cfm (multiplier) for every sq. ft. of south facing glazing (polycarbonate, glass, etc.). Include roof & wall area in total. Position fan high in end wall.
A.	Enter sq. ft. of south facing glazing (polycarb, glass, etc.).
B.		Enter Multiplier. Not an exact science. Use common sense. For situations with full southern exposure enter 7. -If colored poly, trees overhead, not facing south, figure can be as low as 4. Even a north facing roof, on June 21st, will get hot inside. Play with different multipliers. See how these figures fit with available fans.
C.	cfm of Fan. Optimal fan size in Cubic Feet per Minute.