Ed and Thomas - I can see that ventilation is a science. You two seem to have very large greenhouses. I own a 18 x 11 greenhouse, and I vent with ridge vents. I have two ridge vents, one on either side of the peak of the roof of the greenhouse. They are set to open at 80 and 82 degrees. At the end of February, I begin to notice that the sun has regained some of it's power here in the north country. At this time, on a sunny day, at least one ridge vent will open. That tells me it's time to unroll my light colored 70% shade cloth.
I love my set up. I have 6 awning type windows and a screen door, and in summer, it is never any warmer in the greenhouse than it is outside. I have two ceiling mounted fans, going almost full blast, also. In the fall, about mid November, I will notice that on a sunny day, the vents don't open. So it's time to roll up the shade cloth once again. Simple! Works like a charm. ~Denise, in SE Lower Michigan Ed Merkle wrote: > Thomas, > > All greenhouses should have a way to ventilate excessive heat out. The > best way to do this is with automated exhaust fans and power intake > vents of the proper size. It is usually recommended that the exhaust > fan(s) should be able to make a complete change in the greenhouse air > every 60 to 120 seconds. Your 14 ft x 32 ft greenhouse, if it has a 10 > foot roof, probably holds close to 4,000 cubic feet of space. > Therefore your exhaust fan(s) should have a total exhaust capacity of > about 3,000 to 4,000 cubic feet per minute. Your intake vents should > equal roughly twice the area of your exhaust fan(s). (One 24 inch fan > = 48 inch vent(s).) Most orchid greenhouses should also have an > evaporative cooler or wet pad system to cool and humidify the greenhouse. > > During the winter and transitional seasons when the sun warms the > greenhouse too much on cold days, an exhaust fan and vents are still > necessary. Due to the cold outdoor temperatures, plants should not be > exposed to cold breezes coming in through the intake vents. You can > either move the plants, or provide a second set of vents that does not > open directly onto the plants. Some growers have been known to place a > blower fan (100 to 900 cfm) at roof height, opposite of the intake > vents, and a tube system that pumps the heat down and out, gradually > making a change of air over a longer period of time on those cold > sunny days. > > In addition, an orchid greenhouse should have constant air movement > throughout by using several fans running 24 hours a day. These fans > should constantly mix the air so that temperatures at the roof are not > too different than those near the floor. Even in this kind of > situation you should still be able to find micro-climates for the cool > and warm growing orchids. > > For my own 20 x 50 foot greenhouse here in Nashville, Tennessee, I > have a 10,000 cubic feet per minute exhaust fan set on a thermostat > that turns it on at 78°F. I have a bank of vents that measures 2 x 16 > ft, and two 36 inch vents, that open when the fan comes on. I have a > wet pad (Stuppy) measuring 4 x 16 ft. that runs during warm weather. I > also have four 1500 cfm fans inside the greenhouse that run 24 hours a > day...probably could use a couple more. My object is to provide enough > air movement that the leaves and flowers are constantly moving in a > breeze nearly everywhere in the greenhouse. > > I hope this helps, and I'm sure others may have additional ideas. > > Ed Merkle > Merkle's Orchids > 1008 Maplewood Place > Nashville, Tennessee 37216 > > _________________________________________________________________ > It’s tax season, make sure to follow these few simple tips > http://articles.moneycentral.msn.com/Taxes/PreparationTips/PreparationTips.aspx?icid=HMMartagline > > > > >------------------------------------------------------------------------ > >_______________________________________________ >the OrchidGuide Digest (OGD) >[email protected] >http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com > > _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
