I am new here. I built a passive solar greenhouse from a plan I found in The Passive Solar Energy Book. All walls are solid except the south face. I poured an 18" high perimeter foundation, put in chicken wire, then large gravel, and bricked the center area. Under the shelves I placed water filled black barrels. I don't know how well this works as I have nothing to compare it to and I assume it depends on your individual climate. However, here, in the foothills of central California we get sun in the winter (T-shirt and jeans OK outside) though it gets cold as soon as the sun goes down. The GH is not finished and has openings at both ends where I plan to put in an exhaust fan and some intake louvers. Even with these unfinished openings it gets very hot. . .this month it was up to 115 degrees. I don't have the electricity ran to it yet, so leave the door open and can keep it between 90-95. I hooked up a weather sensor in the GH and have that linked to my computer and see that it rarely gets below 45 degrees at night even when it is about 30 degrees outside. Again, I am new to this and still learning what I need to know and cannot say how effective the heat sinks are. I plan to put in an exhaust fan, two intake vents (trying to decide whether to have motorized or gravity louvers for the intakes). I will put in a HAF fan system. . looking at one of those rectangle thermostatically controlled window fans with two small fans both reversible and with speed controls and set one one direction and one the other direction to get circular horizontal air flow - these used be about $40 at Lowes. I also had a spare 6" fan in a section of heating duct pipe so I installed that to duct runs to opposite corners of one side of the GH - about 6" up from the floor and then ran it up to a "T" in the center of one shelf and then and blow air into the center of the GH . . even when it is hot in the GH it is considerably cooler under the shelves - really amazingly so. Still experimenting. Everything I have planted has really grown rapidly even with a lot of heat an no fans as of now. At times in the winter it can get down to 20-25 degrees. . . this may happen a few times a season. I will have an electrical thermo controled heater to turn on when it gets that cold. Hopefully I won't ever need to heat it very often. I think my problems will be to keep it cool enough and air circulation.

One thing a GH will allow you to do is alter temperatures, humidity, and light exposure. The link I have added is just a general example of an evaporative cooler. Basically, water is misted through your wall. As far as what to grow, that's not a hard question. What produce do you eat the most of...start with that. What produce is least available locally...grow that. Can you grow anything that can be stored for later use (potatoes, carrots, onions, shallots, etc...) grow that. Of course many of these are not necessarily GH candidates, but hopefully you get the idea. Then there's the germination side of things. You will be able to get heirloom seeds started earlier and in better conditions with a GH. At any rate, think first of your own consumption, then think about things you'd like to show off to friends (e.g. your very own Orchid), and if so inclined, something you could sell at a local market (I have Shiitake and Oyster mushrooms on logs, but they wouldn't do well in your outdoor environment, but could do very well in the controlled GH environment.) Good luck and have fun. Cheers, Russ Here is a link that might be useful: Evaporative Cooling Products

Are you planning to grow enough veggies for four people over the winter in a GH? I'm in zone 6 and unless you add expensive lights, most veggies just "sit there" during the short days of winter. They produce nothing! You'd be better off gardening outdoors all during the warm months and either canning or freezing your harvest for winter meals. That's just my opinion. Others may disagree.

Thank you for the reply. I will inform her about the vapor barrier. I think she is starting to feel better about it.