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

If you are going to have a greenhouse that you need to use in colder temps, please think about installing a simple geothermal system (dig down into the ground, insert some plastic tubing that will vent into the greenhouse) and let the temperature of the earth maintain stasis inside. You can also put any large water containers around the outside or in the center of the inside, painted black to collect more heat during the day. Extending and improving the function of your greenhouses will become a necessity in the coming years. Google "geothermal heat for greenhouses" - you'll get a zillion hits. While you're at it, Google "permaculture". You'll need that knowledge for the future as well. When this country reaches 9 billion population (we are at 7.5 now), we will top out our ability to feed everyone. You should know how to grow your own and hopefully have some left over for others.

ok, so i figured id go ahead and give anot so brief review of this thing got it fast. real fast. like 4 days, so that was pretty awesome. started putting it together in the garage on a friday(cant do that with a big one-HA!) and immediately considered returning it. the instructions didnt have any text. all pictures and numbers. huge PITA to get it going, but i perservered with the help of a few rfosty beverages. saturday, reinvigorated by decent weather, i move the semi assembled pieces to their final location. south side of the garage. 45 minutes later, i seriously considered picking it up over my head and throwing it across the yard. few beverages later(in case you havent noticed i measure everything in beer hours) its assembled and in place and still in one piece. im somewhat pleased with it. fast forward several days, im not so pleased. not because of it, but because of its location. crap for sun there. looking at alternate locations. im guessing i need at least 4-6 hours of sun? filtered sun ok? petunias are growing there now, so i presume thats enough sun... in summary im not displeased with this thing, but i wouldnt get another. in the end, for the same amount of money i could have a 6x8 HFGH, but as mentioned earlier, no realistic place to put it. it does have pretty good room considering, for new plants waiting to be planted, and maybe some cool season container crops like carrots, lettuce, etc. a little vent on top, sliding door. its not made for a 6ft tall 185lb man though. i do feel pretty buff when steeping into it, so maybe as an esteem booster i can recoup some of the cost. also, once again im convinced that the only thing China ever designed and built worth a crap was a big wall. the opinions of this poster do not reflect the opinions of anyone else. on earth. no matter what their affiliation. pics out later. thanks again guys for the advice, and info.

We have a 11 x 16 home attached all glass greenhouse and we're in zone 4-5, so we're pretty close to your situation. In winter, on a sunny day our GH will be warmer than outside temps, but without sun or at night an unheated GH will be only a few degrees warmer than outside temps. The GH does protect our plants from wind & snow but on most winter nights roots will freeze. If you're willing to pull your plants in every night or cloudy day and run them out on sunny days you may find some beneft. You may also have some benefit in late March or early Nov to extend the season, but unheated means unheated and your temps on most days (and nights) won't wary much from outdoor temps. We gave in after one season and added an electric heater and a propane heater as well as the fans to circulate air and heat, covered out GH in winter with a solar pool cover and we now keep tropical plants in the GH year-round. In summer, while we do have 4 passive vents, it's still pretty hard to avoid the need for energy to run vent & circulation fans. I'm sure there's probably a way to use no power at all in a GH, but there will certainly be compromises especially at the peak of each season. I can't imagine July in my GH without fans or January without heat. At a minimum, I'd invest in a cheap thermometer that records highs and lows in your GH so you can at least see what temps you'll be dealing with. As an example...two seasona ago we hit -15F outside for 2 days. The unheated GH hit -9F. Last season we hit -19F for close to three days and our heated/solar pool covered GH never dipped below 58F (and that was with the propane heater set VERY low). Good luck and please do report back how it works out.