johnnyq, I'm not much help, since I've been shamelessly kicking the can down the road for years now. Made it through the last two winters with a layer of 6 mil greenhouse plastic sheeting over my own badly damaged polycarbonate roof. We've replaced the roof panels once already, and I only get about three years in the HFGH panels before small holes start showing up in the outside layer of the roof poly panels (even with shadecloth in place all year.) I'm lucky we didn't have a wet heavy snow this winter, or we would have been out there rigging up emergency interior bracing! All of my wall panels are still original, and are now about ten years old. They've finally yellowed and developed small holes too, so I'm looking at a sizeable investment to replace all the roof and wall panels. To be honest I'm doing some soul searching about keeping the greenhouse, but I probably will go ahead with the replacement, since all is fine except for the panels. And I'm not sure I want to give up the hobby quite yet. My plan is to buy 4mm twinwall poly elsewhere (not Harbor Freight, as I'm just getting too old to deal with the work of replacing the roof so often.) Last time I checked, FarmTek seemed to be my best source price wise. Did you mean that HF is offering 6mm panels with a warranty now? One (potential?) heads up is there might be a slight glitch with getting 6mm thick panels to slip into the aluminum framing at the roof peak - as you know the panels slide into a channel up there - and there has been past discussion that anything thicker than 4mm might not slide into the channel easily. I don't know if this is a problem with the kits that are newer than mine, though, and it might not be an insurmountable problem. Maybe others will chime in with panel replacement updates.

Harbor Freight did not suggest this. Lets just say that Harbor Freights Tech support was, um Harbor Freight... I have to admit it was nice, they Cross shipped me new ones, which performed the same as the old ones. I found an overseas manufacturer of similar "budget vents", I think they were called Thermofor, who was very helpfull, and gave me a suggestion. I unscrewed the endcap that has the adjustment screw, and press the plunger till the seal almost comes out, then the oil will start to leak if you press softly on the plunger (If I pressed hard the seal comes all the way out, and you get a big mess ;) then close the whole thing and test. THrough trial and error, I now have all five of my HF openers opening between 65 and 75 degrees. Gato, I am not sure why mine did not work, and yours did, I am only 1300 feet higher than you, but I had a Total of ten from HF (The first five and the second five). Even at 38 degrees they were open five inches under load before I modified them ;) I would not recomend that anyone else try this, because I am sure it voids the warranty. (I tried it on just one first, then got bolder and tried the rest. I did spill all the oil out of one, and I replaced the oil with Cooking oil, even this one is now working ;) so I guess I will have to wait and see if opening them is gonna cause any long term ill effects.

I'll second the recommendation for the clear solar pool cover. Have you tried a search yet? There have been quite a few threads on insulating/heating that should contain a lot of helpful information for you. I'm in USDA Zone 7 in coastal New Jersey, used the following last winter and was very pleased: 1. Above-mentioned solar pool cover; 2. Water-filled containers (tubs, milk jugs, soda bottles) for thermal mass; 3. Weatherstripping on panels and caulk in all gaps in the frame; 4. 1" thick foam board insulation on the north wall and north 1/3 of the east and west walls. This year I will be adding insulation around the perimeter of the foundation, since I felt drafts there last year. I did keep the GH at a minimum temp of about 50 degrees, but was very satisfied with lettuce and herbs through winter, a small but very tasty supply of cherry tomatoes from the one plant I overwintered (production was very light December & January, since I did not use supplemental light) and about March or April some snow peas. I didn't calculate the cost of operating the heater, the electric company really messed up our readings the prior year, so I didn't have a baseline, but our electric bills were not uncomfortably high (certainly lower than our summer bills with the A/C!), so I felt that the benefits of the GH far outweighed the cost. Don't mean to stray off topic, but the falling leaves usually precipitate a similar fall in my mood, since they bring to mind the cold, dreary months that are so near. This year, however, going into my first autumn with the greenhouse, I noticed I was, instead, excited as I prepared for another season of GH gardening. What a difference! There are a few folks who've used heated cable - try that search feature. If I happen to find any discussions, I'll post a link for you. Diane

I suspect that you won't get a lot more growth season, though it depends on what you are growing (e.g., cold season crops vs. tomatoes). I just used a greenhouse heating calculator to get a rough idea of what you can expect as far as heating requirements, and it looks like, if it is zero outside, the heater going at full blast will keep the inside at about 35F. Obviously, when it is warmer outside, it will be roughly that much warmer inside the greenhouse, but do you really want to be using a huge amount of energy to keep the greenhouse at a temperature that will allow you to actively grow? I live in a much milder climate than you, and I also use a 1500W space heater, but my goal is to protect sensitive plants, not to try to grow tomatoes that will cost me $20 apiece due to energy costs. I'm not trying to discourage you...just sharing my experience: I had high hopes my first winter until I realized what was practical and affordable.