I asked for advice and got it, didn't I? The trouble is, I didn't use it! I went to the Johnny's site and saw the premium model, but like Goldilocks, it was toooooo big. (I measured the footprint of where I want it to go, and even the smaller ones seemed really big.) I went to the other places where posters provided links and looked.... I didn't want to have to drag tables or shelving out and an 8' dimension (eiher way) is too big because there are roses right there with some SERIOUS canes. I only plant to keep it up in March and April, possibly into May, but that would be to keep plants dry rather than warm. Then I looked at some simple little upright ones. I think you could put one flat on each of the three or 4 shelves, but they were tooooo small. A heater would probably burn the plants closest to it. Then I went to Ebay and looked at all theirs and looked and looked and finally decided on a little 4 x 6 with shelves. It is NOT a good one. The plastic is reinforced, but there is no venting. Not real sure that was too bright, but we'll see. There is no anchoring at the bottom so it could also blow over (often times these come with little ground stakes) On the other hand, the price was right and I really just wanted a large germinator. It is a walk in model, so in a pinch I could put a heater in it without melting the plastic. I love wintersowing except for two things: the milk jugs look like hell and now that I am midway into it, people are talking about taking the tops of the jugs when the sun is shining & it's warm out, and then putting them back on when it's cold! I thought you could leave them out there on their own! No way I am babysitting 300 jugs next year! If only it had some vents, I would be really, really happy, but as it is, I just want to see what kinds of temperatures I can expect. As cheap as it was, maybe the reinformced plastic will rip right off the bat and those will be my vents :) Thnaks for all the insight, though. I enjoyed all your posts and collective thinking. Lime

You are right about regulating the temp. It is a bit of a challenge. I have a Hygrotherm (sp) that Santa brought me so I can watch it more carefully while I'm in the house. Where I have lucked out is that my DH is an engineer and while he couldn't care less about the greenhouse or the plants he is interested in the engineering of the heat, lights, electricals and water. He put a thermostat on my electrical baseboard heater and ran the water and the electric. It is probably going to be even more of a challenge this winter to heat because now I'm going to have a long narrow operation. But I'm sure I'll learn a lot too. I'll have to try and arrange things in micro climates. I would like to see some pics of your GH if you have any to share. I am having some problems with my blasted camera so this is the best I've got. Cindy

NO: a tent will NOT store heat. Even permanantly constructed 4 & 6 ML polycarbonate walled GH's won't store much without additional insulation, and why folks in northen climes who want to operate their GH's through winter and can't afford to pay 10X the cost of heating their homes to heat their single pane glass or polycarb GH's, insulate the ground below them, line them with bubble wrap, then bundle them up in solar pool covers. Then, there is water. As one who has had the occassion to haul water buckets out to a barn when a pipe burst in the dead of winter, I can tell you- it's no fun.

Forgot the little decimal. I thought that was a lot. I only used 3 - 1500 watt heaters for my greenhouse. But of course I had solar pool covers, and extra layers of plastic and 7 - 55 gallon rain barrels with water. I had ice on the inside of the windows a few nights. Even in my zone 7, 34 for an outside low temperature is stretching it. And we often have a lower wind chill factor. So for a zone 5 area it can get down to -20 and the greenhouse needs to be above 32 or 34 because that is not enough of a buffer before freezing. So using those figures: 177 Area of greenhouse -20 Outside temperature 38 Inside temperature 1.20 Heat loss factor ------ 12,219 BTU's One 1500 Watt heater produces approx. 5200 BTU's(varies). So that means approx 2 1500 watts and one 750 watt. My three (3) 1500 watt heaters and a ceiling fan cost me $100+/- per month. I can justify that for my 32x37 greenhouse filled with collectible tropicals(AeAe banana, Amorphopallus Titanium(The worlds largest florescent), Rare gingers, citrus, palms, etc). But that would be some expensive tomatoes. And the 3 heaters would take up the space of three pots, plus there would need to be space away from the walls and plants so they don't catch fire. But IMO the heaters would ignite the cover or melt it. Anyone want to try it and report back in the spring??? LOL