I wasn't thinking I would need to spend more then $75 on heaters...lol. Is $400 the minimum I need for an adequate one? I was thinking all I needed was one or two small ajustible ones that would heat the whole gh. What about cooling? Someone mentioned misters... Are those expensive?

I used a misting fan. It worked well and was about $100.00 years and years ago. This is why you need to figure out what you want to do with the structure and how big before you go on. I bought my latest one used from my neighbor. It was 200.00. It cost $600.00 + to skin it with the inflator. Add the heater etc. Wiring and box...Water... Or maybe your'e McGyver and can do it by scavenging.

Did you see Charles picture? He uses that to start seeds and do cuttings in the summer (I assume). Then he stores his gardening supplies in it as a "head house." So, decide what you want to do first, then explore your options. There are lots of variables as Jerry and Roberta said (and my genius husband just said we have all given you good advise, believe him).

That $75 heater might be barely adequate for a 4' x 6' lean-to against a house, down to maybe 35 deg F for a few hours. And in the moist environment of the GH, last a few months if you are lucky (if it doesn't short out and burn the place down first). Use the calculator to determine the thermal output that you need (in the US it'll probably give you the value in BTUs) and compare with the rated output of the heater you're looking at. You'll find that for any GH big enough to walk into, in any but the most mild climtaes, you need a whole lot more than that little heater. And it needs to be robust enough to work SAFELY in a moist environment. (Same for cheap fans... electricity and water do not play nicely together) The fogger that I use is also in the $400-$500 range. It also needs to survive a damp environment without self-destructing, potentially also with hard water depending on where you live.

¿Que?

I haven't yet had a night that is at all below 0 C, and yet mmy heaters are running sometimes for 12 hours to keep everything from going below 11C.

That is two 1Kw oil rads a 2Kw heaterwith fan, and a fan that does a small amount of heating.

4 Kw for 12 hours. Our Dec. Jan and Feb electric bills are way up, and that's using poly carb twinwall sheets.

Had I the money I would have done what I saw a Koi breeder in Japan do. His koi house had two twinwall layers and a space between those. At night he would blow polystyrene beads into that space, filling it completely, and then in the morning they would be blown back into the reservoir.

I sure wanted that twin wall, but we couldn't get the semi into the backyard and the delivery cost was almost as much as the product.

I've also seen greenhouse "bubble wrap"that you can hang and next year I might try that. Bottom line, Neon, figure out what you want first, visit growers in your area, ask them questions.

Ouchie!

Heating is likely the biggest cost of operating a greenhouse in your area. My 14' x 18' Turner GH, with 8 mm twinwall carbonate, in Bucks County PA, averaged about $3000 a winter for propane use.

Forget those average lows; find out the lowest lows that have ever occurred, and buy a heater capable of heating your greenhouse under those conditions.

Great advise, Ray! It's an expensive hobby for sure. I just noticed my greenhouse window is leaking...Ouchie is right!

Ok. Thanks guys. Happy Holidays!

I'm embarrassed to say I forgot all about the Hobby Greenhouse Association, even though a friend is the past President. On their FAQ page they have a download link for a Before You Buy Guide.

https://www.hobbygreenhouse.org/