Tennis,
You do not want to mount the fans in the roof of your greenhouse as maintenance would be a pain.
One of the best designs I saw in a greenhouse had roof vents like many greenhouse, but had several swamp coolers around the base with the fans blowing the air in over the pads. They had two thermostats one to turn on the fans for ventilation and another to turn on the water flowing through the pads. They had excessive capacity for their greenhouse to make sure it stayed as cool as possible in the summer. The roof vents were controlled by same thermostat as turned on the fans.
I agree the standard of having the cooling pads on one end and the vents on the other is not the best idea. I did it in my greenhouse and I have been trying to redo it in recent years to something to allow more air flow over the plants. I also use misting over my plants to both provide cooling and additional humidity. We have less humidity here in Iowa than you do in Ohio. One thing I have added to my greenhouse is standard roof top cyclone vents. I found they help pull out the heat on very warm days. They are also there incase of a power failure to vent the greenhouse.
Good luck with the greenhouse are you sure 24 x 12 is large enough. My greenhouse is 14 x 32, too big in 1984 and too small in 2004.
Tom
At 1:24 AM -0500 3/30/05, tennis wrote:
As I enter the final stages in what seems to be an endless period of planning for a new greenhouse, I am attempting to finalize such design details as air flow/venting and heating, etc. I would like to hear from anyone knowledgeable and experienced in this area. It has occurred to me the most effective way to vent an overwarm 24' x 12' greenhouse in the summer here in Ohio would be to put the venting fans venting through the peak roof of the GH as near the center of the structure as possible, and have vents all around the edges, at floor level and bench level.
Sort of the 'whole house attic exhaust fan' idea. Of course, steps would have to be taken to keep the rain off, but other than that, any reasons why this wouldn't be the best method for venting heat, and having air flow over all of the plants in the GH? I will have three levels of plants (floor, bench, and above-bench shelf + hanging) and the normal 'vent at one end, fans at other', at bench height just doesn't seem to fit. I had planned on a wetwall for cooling, but have decided misters in front of intake vents would be as good and easier to manage, which enables the vents to be spread out as well.
Tennis Maynard
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