Okay, I looked at the link. I thought the 'votive candle' for heating was a good idea until I saw the specs for plastic windows. Glass windows, sure. But with polycarb windows I'd suggest a lantern instead. Preferrably with a vent doohicky to catch the hot exhaust and lead it outside. A candle would produce soot and would need to be as far as possible from the plastic or it would discolor and maybe melt. And of course plants need SOME oxygen, so using up the O2 inside the box might be a bad idea. As for construction, it looks reasonable. It should be placed in a sunny location. I have been thinking of making Mittlidier boxes. Mini-hoophouses with hinged bases so you can lift them up to get to the plants.

Swanzeyguy, I remember seeing it done in Northern Germany, but not sure "how" it was done. The man had a greenhouse/green grocer operation going all winter. Fresh lettuce mostly...but lettuce is less cold hardy than the cabbage family. He had berms of soil built up in a field with the cold frames facing south...other than that, I can't say. I suspected that he might be using hot manure buried under the soil in the bottom of the frames. My grandfather told me that was how they built them for starting early season plants...he grew up in Illinois. Chinese veggies, lettuce, cabbage, spinach, kale, etc. needs less light. If you can keep the soil temp at 55 to 60 degrees, it doesn't take much cover to keep them from freezing. We use hot water lines under beds in an unheated greenhouse. Only need to run the hot water when it really gets cold... then on a bad night, toss some floating row cover over the lettuce, spinach, etc. It traps the warm air rising from the soil. Only loss has been leaves that touch the plastic on the sides of the greenhouse. The beds are built right up against the outside cement block foundation. We did line it with some 1 inch styrofoam. Square bales of hay would be better, but haven't needed it. I have used hay bales to build a raised cold frame, but not in country as cold as you deal with. Works great for winter propagation of woody plants...keeps cutting bottoms warm for rooting while the tops stay cold, so they will stay dormant.

Okay, my area has recently been moved to zone 6 from zone 5 (ah, global warming...). But you are in zone 7, and I can confidently say that you are really over-thinking (and over-engineering) this. I have to deal with a lot of sunlight during the winter, so overheating is a major consideration. Eliot Coleman tried heavy row covers as the inside layer (high tunnel with greenhouse plastic as his outside layer) and found the heavy row cover fabric blocked light from his growing plants. He's in Maine, lots of clouds in the winter, and fruther north than I am in New Mexico. So I went with the heavy row cover fabric as my outer layer on low tunnels (10 ft pvc pipes bent over 3 ft wide rows), and light row covers over 5 ft arches of concrete re-mesh as my inner layer. At Thanksgiving I spread 6 inches of leaves over the plants (carrots, radishes, and turnips). Last week I harvested some of all 3, and although a few radish leaves at the edges were frosted, the roots were fine. Kale (and cabbage and Brussels sprouts, if I were growing them this year) is in a bed protected from deer by re-mesh arches and mulched with 6 inches of leaves, but otherwise is not protected (deer LOVE cabbage-family plants). Likewise spinach and miner's lettuce are not under row covers, but are mulched with pine straw. When temps get down to the low teens and singles I'll pull a row cover over them, too. I don't have any lettuce or chard in the winter garden this year, but have had it in the past. Put them in with the turnips and radishes, as they are more tender than spinach or kale. In zone 7 they should last all winter. I used to give up on lettuce around Thanksgiving, but have found that deep mulch keeps the mature lettuce around for a bit longer even in my simple tunnel. I was also advised to just pull my Thanksgiving lettuce up by the roots, cut the lettuce about an inch above the crown, and then replant the roots in a pot on my kitchen windowsill. I never have the patience to wait until it grows a whole head, but I have a few leaves to put in sandwiches every week for a couple of months. Keep it simple, keep it cheap, keep it fun. Catherine

That house here would run approx. $300,000. I'm kinda shocked at the price....but I know it's very different around the country. How exactly do you 'know' that it's priced below current value? 15 years is not old at all for a house. I can't possibly see the windows need replacing now. If the seals are bad....just replace the seals....maybe 500 bucks at most. Painting?....wrong colours for you or just dirty paint now? I wouldn't think the entire house would need painting. Maybe a few rooms? This is not that expensive(a 12x12 room here would run approx. $300 bucks). Roof?....again...15 years is not that much..why does it need replacing? Hail damage? Still....this would only run approx. 5 grand for shingle replacement(at least here...sounds like everything is less in TX). Is the house in a nice neighborhood and good schools? I can't see replacing faucets...sinks...counter tops....etc when they are only 15 yrs old! Exactly what do you 'need' to upgrade inside? I couldn't even 'build' a house that size at cost for that price here! It sounds like a heck of a deal. The market is going to change several years down the road....I think it would be a good investment for the future IMO.