Greenhouse Heater BTU Calculator

**Surface Area, in square feet, of walls, ends and roof.

**Minimum Outside Temperature

**Minimum desired inside Greenhouse Temperature , in °F

**Heat Loss U-Factor  

These are approx.  representative values:		Loss Value
4-mil polyethylene		1.20
6-mil polyethylene		1.15
6-mil polyethylene - double layer, inflated		0.70
Glass - Single Layer		1.13
Glass - Double Layer		0.50
Acrylic Double Wall		0.54
Fiberglass		1.20
Corrugated Polycarbonate		1.00
Multiwall polycarbonate
	4mm Twinwall	0.70
	6mm Twinwall	0.63
	8mm Twinwall	0.60
	10mm Twinwall	0.56
	10mm Triplewall	0.54
	16mm Triplewall	0.40
	16mm Five-wall	0.33
	25mm Triplewall	0.28
	25mm Five-wall	0.25
Note: U-Factor  ( BTU/hr. - ft2 F) or (1/R-value) 1 divided by the U-value equals the R-value.

**Minimum BTU needed from a gas heater. See our Greenhouse Gas Heaters

**Minimum Kilowatts needed from an electric heater. See Greenhouse our Elec. Heaters