Looking at real world examples it seems that the main problem (apart from the difficulties in construction) is the large swing in day/night temps. http://www-unix.oit.umass.edu/~caffery/greenhouse/performance.html They modified the structure and now ""We are very happy with how are greenhouse is performing. The longer term results: we've moderated the temps so that we the greenhouse doesn't get so hot (mostly because we added hens, and they don't like it hot). We still haven't lost any plants--including tomatoes--due to low temps."" http://www.ibiblio.org/london/renewable-energy/solar/Nick.Pine/msg00002.html A very good article on the progression from passive to active to agressive solar heating. Note again the problem with excessive temperature swings. http://www.ibiblio.org/london/renewable-energy/solar/Nick.Pine/msg00028.html ""I've rethought the problem you mentioned, that there may be a daily air temperature variation (delta T) larger than most growers can tolerate, in this solar-heated greenhouse design."" As for SHCS then that system is using the thermal mass of wet dirt. It could just as easily be pipes through water. However, if the SHCS greenhouse also used above ground water storage as well, a hybrid system would have kept the structure at 32F on the times when ""The gross response was such that we could have a 90 deg house when it was 95 outside and a 28 degree house when it was 30 deg below outside with the wind howling away."" That magical 32F. In a "phase change" type of system you would think they would have spotted that important point. The SHCS system emphasises latent heat of vaporisation, not solidification. And, from the world's expert in raising plants in an unheated greenhouse a realisation of the problems that have to be faced I present! http://forums2.gardenweb.com/forums/load/strucs/msg1108354418631.html "" * Posted by: Chris_in_Iowa 4b (My Page) on Thu, Nov 10, 05 at 21:43 I am all for starting seeds and growing them on to transplant size in a minimally heated structure in the spring. If you have minimal or no supplimental heating the biggest problem is it is TOO hot in there during the DAY. I say that because the temptation is to run the greenhouse as hot as you can during the day so as to store up enough energy in there to make it through the sub freezing night. This causes me to have major problems with "leggy" plants, too hot but not the corresponding intensity of light "" The "world's expert" comment was a joke.... :)

It can get real involved, and like yourself, we are looking for answers. Some kinda design where the glazing can be moved according to the seasons, or the glazing being able to be blocked more in the warm months and opened more to the sun in the winter. I can see getting a greenhouse independent of mechanical heating/cooling being more of a design challenge than home builds and pretty involved. Keep in mind in the mining days, air shafts were desinged in below ground mining not only to keep fresh air in, but to help keep the inside temperature between 68-72 degrees. This was done on a local gold mine here where we currently live in the mojave desert by miners in the late 1800's. Non computer aided, uneducated miners who came up with ways of working with the earth without electricity or fossil fuels who lived in cabins built into the earth where they stayed quite comfortable all year round. Plants need light though and that's the difference. We are planning on the greenhouse for use when we move up to the sierra nevadas @ 4500 ft elevation. Gets pretty warm in the summer months, but keeping the greenhouse warm will be the challenge opposite of your concern. I guess we need to keep a researchin' and doing our homework. My wife and I can't get too crazy financially with the project,( I can see where it could), so hopefully some old fashioned, low cost ingenuity will kick in, like the old miners days,( except we have the internet with these cool people/forums)! I'll post some more references as we find them, books, websites, etc.

O.K. Let me rephrase that! I have read on the Growing Spaces forum about some people in the PNW having problems with rain coming in through the open solar vents. I believe that the solution was to have a rain deflector built over the opening. The last that I had time to look, most of the ones located in Oregon were coastal. I'm 30 to 40 miles from the coast as the crow flies. Here is a Google photo link! I'm actually to the right of where they're putting the arrow! The photo isn't really up to date either. I've expanded the ponds and tried to naturalise the watershed back to a more natural state. I've been doing what I can to control erosion! The difference between the basic purpose that they use it for and my needs are the temperature requirements. I don't need to keep it at 80F all winter, but I can't have it dropping below 60F or so. I did originally plan on having a hothouse built inside of a greenhouse from the beginning. That was put on the side for a while and might have to be worked in again. It would be more efficient, as not all of my orchids require constant higher temps. Many of them actually need a variation and/or a seasonal dormancy. I want to have a lot of space. I know how easy it is to outgrow something. I also plan on growing vegetables all winter and will use it to overwinter plants from outside. I have huge pots of lemon grass, citrus, etc. I eat virtually all organic. I was raised that way anyway. I stopped eating all fast food years ago because I got so ill from it. Lately, I have been finding out that there are many things that I'm very allergic to. Virtually everything that has been processed. I always thought that I was sensitive to GM foods. I'm finding out that it's pretty much all glutens and several other common things. The gardens do well all summer, but I want to grow a lot for the winter as well. So, I'm trying to kill as many birds with one stone as possible. One of my primary concerns has also been about earthquakes. I know that it's just a matter of time before we have a big one. I'm not paranoid about them. I've spent my whole life living on the Pacific Ring of Fire around the world. We had a major fire here four years ago. It demonstrated how easily my area would be cut off from the outside. Even the major roads are tenous at best! I like to prepare for the worst and hope for the best. Even if nothing happens in my lifetime, I'll have one hell of a greenhouse!:) Scott Here is a link that might be useful: My location

A good reference book about building greenhouses in our climate is Gardening Under Cover: A Northwest Guide to Solar Greenhouses, Cold Frames, and Cloches by William Head. It discusses siting, styles, and heat sinks. Also shading during summer if you want to use it year round. You need clear for winter use as we have such low lighting to keep things growing. The KCLS has it if you're in King County. I scanned the greenhouse structure page, so email me if you'd like me to share it. It talks about pitch of roof, type of roof & functions. Best wishes & post a photo for us to see. Corrine