[welchfarm]

I have had better luck using small ceramic heaters on a thermostat.

inside fans moving air help. Exhaust fans will come on if you produce to much heat when the sun comes up there goes the heat you just produced at night

[AutumnRidge]

By doubling the layers of Greenhouse film and adding an inflation fan to expand the layers 3 – 5 inches apart will save you approx. 45 to 50% on heat loss. Use infrared film and you can save another 15 to 20% on heat loss especially on Clear cold nights. If you have questions feel free to ask. I use to be a Greenhouse construction and managment consultant.

[AlphaDelta]

I’d love to hear more. I assume the fan is inside the structure, so warmed air is circulating? We tend to have warm Winters (South Texas), but like right now are below 20°f. By Wednesday we’ll be back in the 70s. I’m gone a lot, so need to automate as much as I can afford. Thanks for any input!

[RedDutchessFarm]

The formula for calculating btu’s needed to heat a greenhouse is:

Total number of square feet of exterior of greenhouse(roof, sidewalls, endwalls)

Multiplied by:

the number of degrees you want to maintain between outside temperature and inside temperature

Multiplied by: 1.14 for single layer plastic. -or- .73 for double layer inflated plastic

Example:

2500 square feet of exterior area X 60 degrees (if it’s 0 outside you can keep it 60 inside) X 1.14 for single layer plastic equals:

171,000 btu’s

X .73 for double layer inflated equals:

109,500 btu’s

A huge difference between single layer and double layer inflated!