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.

Barbie, your orchids are probably in shock from going from extremely humid Florida to extremely DRY Arizona. You are going to have to do something in your greenhouse to simulate the humidity that almost all orchids need, which is about 50-75%. In a small greenhouse like yours, a small misting system would be extremely beneficial to your plants, especially in the summer. I don't think you need an expensive humidifier at this point. A misting system set up to span the length of your greenhouse, put on a timer to mist for 5-10 minutes every 3-4 hours, will help greatly. Misting also helps to lower the temperature in summer. There is even one called the Arizona Mist System which I believe was designed for folks in dry climates like AZ and NM to have outdoors poolside to moisten the air when sitting out on the deck. These are commonly used in small greenhouses by hobbyists. Of course you will need excellent ventilation in the summer, so fans are also a must, in a 6 x 10 house a couple of hanging oscillating fans or a couple of box fans installed up in the "attic" to draw in fresh air and push out hot stagnant air is key. I know your dilemma, I am also a Floridian with an orchid collection of close to 400 plants, and am used to having all my Vandas, Catts, Dends, Phals, Gongorias etc just hanging out under the breezeway and in the trees where a lot of the time the rain water them for me in Spring, Summer and Fall but in winter I have to move them all into the greenhouse and give them more than benign neglect. My greenhouse is much larger than yours (over 1700 sq ft) but it is also in full sun, and in Florida you know what that means. I have measured temperatures in the upper reaches of the "attic" in Spring and Summer at 110-125F before, so I had to add more fans to combat that (It already had two 36" slant box exhaust fans and 4 oscillating fans...I had to add 4 box fans!). Instead of a mist system I use an overhead sprinkler system, and it creates an actual rainforest environment.

I just put together a small greenhouse (plastic cover) for my plumeria and was wondering if there are any tips I need to know when using one. I'm in Phoenix but it's been below freezing the last 3 nights so I'm hoping the greenhouse will help.

I'm in the Kalamazoo area. Brad-during the first week of school I build a succulent garden with my students. We talk about how plants are like children. We all come to the classroom with different root systems, and we all have different needs. We talk about what is good for all people and how we all want to be treated. I keep the garden in front of a window all year and the students love watering it and watching it grow. It's a fun activity for building community. I also have a hamster because some children never get to have the opportunity to care for a pet. It always amazes me how kids love taking care of plants. We were just laughing on Friday about how H. Chelsea seems to be growing before our eyes. It's going to be another week of 90+ degrees in Michigan with no air conditioning in our school. My plants will be happy, but my students will be miserable. I keep reminding them to look on the bright side. We aren't in the path of a hurricane. We haven't had an earthquake, and we rarely have tornadoes. Blessings to all our friends who have a lot more than hot days to deal with.