Gary's right, I'm in Florida too, and cold is nada. Heat however is a BIG deal. I use a combo of fans, shade cloth and misters to cool the GH in summer. I spent last summer tweaking and tinkering, but all in all, it worked well. My phals thrived in the GH over summer. Intermediates did well for me also. So I think I had pretty good control over the midday heat. But alas, it is my nature to always try and make it better, so I have some more things I'm going to try out this summer where heat is concerned. More tweaking and tinkering...;0) I placed my GH in full morning sun and I am shaded (dappled) by tall trees by 1:00/1:30pm or so. My heat problem is then over for the day. I'm REALLY glad I did not place the GH in full day sun. The arbor built on the south wall of my GH serves as a shade house in summer also where I hang dens and catts. I water overhead (auto sprinkler system) early in the morning, then fans (also automated) comes on to dry the foliage. My exhaust fan comes on at 85 degrees and misters come on at 90 degrees and go off at 85 degrees. So at midday, the system holds the GH at around 85-90 degrees. An osolating fan mounted high in the GH runs 24/7/365. The air is never still. I grew in the yard for years and between the bugs and squirrels and running around all over the place trying to remember where everything was, I decided on a greenhouse where everything is in one place and very easy to care for. I LOVE my GH!! My best advice to you is to try and visit GH's in your area to see how they are managed. That's what I did, and it really saved me a lot of mistakes (like not placing the GH in full day sun ;0). If you would like to have a look around my GH, click on "My Page" and then on the link (photobucket). Good Luck!! Pat...

Poetmama you can grow many things at 50-90. The size of your g/h is also important. The larger the area, the easier it is to maintain a more even temp. In a very small area, the temps change rapidly. On gray ugly winter days your heat will run constantly. On days with sun, the temps can go quite high. The colder outside, the longer it takes for the sun to heat it up. Yesterday here in zone 6a with the sun out and the outside temp at 20, the heat ran until 10 and was back on by 5:15. In the summer you will need a shade cloth over the structure to prevent the temps from going to 120. With a 50% aluminet shade cloth, you can keep the inside temps to the outside temps. In your zone the shade cloth will be removed around mid-Sept/early Oct and put back on mid-March-ish. I have a vent wall/swamp cooler so am not familiar with other cooling methods. There are some from misting to portable swamp coolers plus vents, fans, etc. As others have said, interior fans are a must, winter and summer. Stagnant air for any plant material in a closed environment is an invitation for disease problems. All of my recommendations assume your g/h is located with no trees or other structures producing shade. If you are going to attempt Phals at 50 degrees, I recommend they be mounted. Phals are warm growers and prefer to never go below 65, but do fine at 60 but a potted Phal at 50 won't be happy with cold roots. There are cool growing Phals but they are species and you have to love the unique blooms to grow them. They are not the "glamorous" tall cascading spiked Phals. Most Lycaste would love those temps except for some warming growing ones. They are not the most common ones. You have winter and summer blooming types so can have various bloom times. Most Masdies will love your winter temps and will do fine for you if your temps get cool over night during the summer. They are true shade growers. More from Nick's list - most Bulbos are warm growers - there are a few that like cool and dryer winters. Be sure and check their temp requirements. Again for warm growers, mounted would be better than potted in a cool g/h. Pescatoreas would be happy to keep your Masdies company in the shade. Other suggestions not on Nick's list would be Sudamerlycaste (Ida) and Sarcos. Most Vandas are warm growing but there are a couple of cool-er growing ones. There is a greenhouse forum here on the Garden Web and they can also offer recommendations regarding your set up. Any particular orchid that catches your fancy is or has been grown by someone on this forum. Good luck! Brooke

I'm weighing here only because Nathan's suggestion MIGHT work but only if you carefully consider a number of things. He is often the one to suggest low tech solutions (of which there is nothing wrong) BUT....any solution high OR low tech is a balance of a number of factors. "Cutting a bigger hole" only has a chance of working IF you also incorporate something to allow "make up air" to enter the gh through low placed intakes (shutters or vents) AND the "bigger hole" has some kind of heat sensitive device to get it to open when you need it to open. Of course, you'd also need to incorporate intakes for a "higher tech" exhaust fan as well. You should also IMHO consider what you plan to put in there. I have orchids in my gh (moderate tech at this point..moving toward higher tech)...I'm only an orchid newbie but while many can tolerate mid 90's, they sure don't thrive above the mid 80's. Finally, I'd also suggest you seriously consider(as in honest with yourself - no one else will know) how much attention you REALLY will pay to the gh day after day after day. Obviously the lowest tech solution is to go out each day (as needed) and open the door and manually open the roof vents and manually check the inside temp and then, when the sun lowers (or sets) and go back out and manually close the door and vents etc. Forget to open it up just one day when it's bright out and your orchids are steam wilted greens. Next step up would be non-electric powered vent opening devices, next above that and you are into thermostat controlled shutters and vents fans, misting systems etc. BTW, NONE of these approaches are bullet proof. I go off to work each day confident that the shutters will respond to the thermostat and the vent fan will kick in 4 degrees later. But if someone takes out a power pole and the gh sits for as little as an hour with no electricity in the mid day sun, well there is very good chane that I've got wilted greens for dinner too.

cuestaroble--That solar powered fan sounds very interesting and something I'm going to look into. Actually in my zone 3 heating is more of a problem than excessive heat and I my system for heating works just fine. I only use the greenhouse for 2 months in spring to start garden plants and flowers. I also have a light set up in my basement and a pop up put up and take down cold frame for my excess hardy plants. The lights come into play early in the season and the cold frame late in the season. My greenhouse is small because I designed it that way to save on heating. I only wanted to heat the space for plants not excess space. It has a slanted roof that is 6 1/2 foot tall at the back sloping to 4 1/2 feet in the front. It has a 30 inch shelf running around the 3 sunny sides and a pull out shelf low to the ground under the east side shelf for shady flowers like impatiens. This only leaves me a 3 x 3 1/2 space in the middle which is enough space for me and only me to work.. The sun does heat it up fast which is what I wanted but such a small space requires some venting to cool it off on warm sunny days. Right now I have a small oscillating fan on the south side blowing towards the door on the north that I will have to start using soon.