I have a barrel of water in my greenhouse, which is covered with black plastic. When there is sun, it heats up and releases the heat at night. Of course, we've had no sun for days now so the next few nights will be a trial. The water also helps regulate overheating as it is cool in the morning when the sun starts heating the greenhouse up. I'm not sure how the water compares to these walls, but it is MUCH less labor intensive and could even be used like water barrels to store rainwater.

Your biggest enemy in our climate is TOO MUCH heat. You have to have an easy way to vent the green house. I have to remember to open it on the morning and close it around 4:00. I would love a greenhouse with automatic vents.

I have a little plastic greenhouse, no room for a compost bin. I have researched other heating methods. Supposedly an oil lamp will keep a greenhouse above freezing. Some people use Christmas tree lights.

We have considered something like this up against the south side of the house. The rock there gets very warm. Maybe too warm most days.

Dawn will have much more to say, and some of the other people who have more experience with green houses.

Thanks for sharing your experience. I'd imagine it can get precarious. I think the only solution is to build a smaller scale model or two and monitor the temperature and conditions for a few seasons. I'm assuming location of the wall matters. Not sure I'm willing to do all that.

Right now, I'm really pissed about the quakes and locals reactions.

bon

I have many containers of water in my greenhouse holding water. They help keep the greenhouse warm at night, but they aren't a miracle solution. They also take up tons of space, but I have them underneath tables where I probably wouldn't have plants anyway since the plants sit on top of the tables in order to have full access to light. The greenhouse still drops below freezing occasionally in winter. Of course, I could put a greenhouse heater out there in it, but I never have, since I really don't want to spend money heating another building. Thus, my greenhouse is a passive solar structure, and it does exactly what I wanted it to do when we built it----it allows me to overwinter a few plants that would perish if left outdoors all winter, and it gives me a place to raise seedlings in late winter/spring. By the time I move tomato and pepper and other seedlings out to the greenhouse in late winter, the nights generally have warmed up enough that the greenhouse stays above freezing, even if only just barely above freezing.

As Amy said, excess heat is much more of an issue, even in winter, than excess cold. The fabled "greenhouse effect" can drive up the temperatures in the greenhouse to crazy-high temperatures on a sunny winter morning, and it doesn't take long. I try to remember to always get my greenhouse doors and/or 4 vents (how many I open in the morning depends on the temperatures, how cold the overnight low was, etc.) open by 9 a.m. in winter. If I don't, the greenhouse can hit 140 degrees by 10 a.m. on a sunny day. Sounds crazy, doesn't it, but it is true....and I have 50% Aluminet shade cloth on it. Without the shade cloth, it gets too hot even more quickly. I leave the shade cloth on it year-round. We stay so sunny in general in winter, and often very warm down here in southcentral OK (our highest temperature this month that I can remember was 77 degrees and that was last Saturday) so I spend more time trying to keep the greenhouse cool in winter than worrying about keeping it warm.

Keep in mind that the smaller a greenhouse is, the more prone it is to overheat and the more quickly it will overheat. It is almost impossible to keep small greenhouses cool enough without paying an extreme amount of attention to it daily....so if you build a small-scale model, it really will not predict how a larger Chinese greenhouse would function because size makes a huge difference in how quickly a greenhouse warms up or cools down.

The solid north wall on the Chinese greenhouses serves as a heat sink, which sounds great for winter nights and likely is why you don't see Chinese-style greenhouses in use here. However, it also means you would struggle mightily in winter to keep it from being too hot all day long. I do line up more containers of water along the north wall of my greenhouse to help keep it warmer in winter, but they don't hold heat like a solid masonry wall would.

Really, the Aluminet shade cloth probably gets more credit for the greenhouse staying warm at night that the containers of water. Before we bought the shadecloth (and this is only true of Aluminet, not other shadecloths made of non-metallic threads), even having large containers of water didn't make much difference in terms of nighttime low temperatures. I mean garbage-can sized containers of water only kept the greenhouse ever-so-slightly warmer at night, and I mean just a couple of degrees and not enough to justify filling the whole north wall with large containers of water because they take up tons of space. I chose Aluminet precisely because I saw repeated mentions of the fact that its metallic nature not only deflected sunlight and kept the greenhouse cooler but also would help hold some existing heat inside the greenhouse at night and have found that to be true. My greenhouse at night with aluminet stays warmer than it did without aluminet.

I think hoop-style or high-tunnel style greenhouses are the best option for us here in Oklahoma because our weather fluctuates so much that we need their flexibility. The only people I know of in my county (and I'm sure there's others I have no idea have greenhouses as I certainly don't know everyone here) who went to the trouble and expense to build a glass greenhouse.....well, baseball-sized hail got it. We haven't had any hail here bigger than ping pong balls since we built our hoophouse-style greenhouse and they bounced right off of it. After seeing a photo of the glass greenhouse in the northern part of our county after it was shattered by baseball-sized hail a few years ago, I promptly gave up on my dream of someday building a greenhouse made of recycled windows. Between the hail and the wind, the hot winters, etc., I don't think glass greenhouses are very practical here, and am perfectly content with the greenhouse I had.

Because the greenhouse heats up so much on sunny days, it is tricky to grow lettuce in it for winter. The same heat buildup I don't mind too much in winter because the citrus trees and tomato/pepper plants love it in February or March also means the lettuce can get too hot and bolt. In a perfect world, I would have two greenhouses---one to keep warmer for the plants that need it, and one to keep cold for cool-season crops in winter. I could achieve the same thing with cool-season crops (and, some years, I have) in the ground in winter under low tunnels if I wanted to, but honestly, at the end of a long late winter through late autumn growing and canning season, I usually am too exhausted to care about growing greens through winter. I think the exhaustion stems more from canning 600-800 jars of food a year plus dehydrating and freezing the rest much more than from the act of gardening itself. Believe me, by the time the first hard freeze gets the garden, I am ready for a break from it all. I just enjoy the break from the garden for a couple of months and buy organic greens at CostCo during that time.

There have been years I have kept winter greens alive in the garden without even using row covers, and that tended to work out pretty well, although occasionally a night with temperatures in the teens will cause some freeze damage. I don't think we've even made it into the teens yet this year so if I had planted a full garden of winter greens, they'd be doing great if they hadn't rotted off at the soil line in all this rain (we are at more than 200% of our usual annual rainfall now). Instead, I opted to leave my tomatoes, peppers and watermelons in the garden and still was harvesting them in November. It was the latest in the year we've ever had watermelon plants producing ripe melons, and it was awesome.

Every year is different though, and maybe in some years when the garden didn't produce well and I wasn't canning, freezing and dehydrating like a maniac, then I would be hungry to have a winter garden and keep it going all winter......and I'd still rather have the plants in the ground under low tunnels (you can pull back the tops pretty easily on warm days) than in a greenhouse that I know will get too hot on 99% of winter days. The 1% of the time it doesn't get too hot is when we have clouds for days on end with no sunlight and the water-filled containers slowly lose their heat accumulation. I think the containers filled with water make a huge difference for me in my greenhouse because we have more sunshine than clouds. I don't know if they would help as much in a part of our state with more persistently cloudy/rainy/snowy winter all winter long or if they'd work well enough in more northern parts of the state that get a lot colder than we do.

I wanted a greenhouse forever and am happy we built ours, but it isn't the winter solution to a gardener's need to grow plants because it is such a battle to keep it from getting too hot. I already fight the heat all summer long outdoors and, frankly, don't feel real inspired to have to fight the heat inside the greenhouse all winter long. That probably explains why I don't grow a lot in the winter greenhouse---it just has overwintering citrus plants, and a few containers of ornamentals that are frost-tender in it. None of them mind the heat, but if I was trying to have lettuce and other winter greens in it, I'd be worried every day about them getting too hot and bolting....so I had to choose. I cannot keep winter greens as cool as they need to be in the greenhouse at the same time I'm keeping citrus plants and brugmansias as warm as they need to be. By the time I am moving tomato, pepper and other seedlings from the indoor light shelf to the greenhouse, it is at least February, and the brugs already have been moved back outdoors. The citrus still stays warm enough once the tomatoes and peppers are out in the greenhouse, but I move those trees out onto the patio as early as possible so they can soak up all the heat and sun from it too----partly just to make room for all the seedlings. Greenhouse management is very time-consuming in a highly variable climate like ours where your wintertime high can be 77 degrees one day, and then your low temperature can be in the 20s less than 24 hours later. It keeps you on your toes trying to keep the greenhouse warm enough every night and cool enough every day, and you certainly cannot go out of town for a week without having someone else checking your greenhouse day and night every single day and night so it can be opened or closed as needed to keep it warm or cool as needed.

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