greenhouse heating and ventilation
 

We have an 8' X15' green house that houses about 50 cattleyas and some odds and ends. I read that their culture requires temperature about 75* in the day and 55* at night. How important is the day/night differential and where do you find a thermostat for a greenhouse that has day/night programability? Also, I read that air circulation is important. Does this mean you run a fan 24/7 or just during the day and set it on a timer? Thanks for your thoughts.
Ed

You have a greenhouse with 50ish Catts and your asking about culture info. I really want to know your background with Orchids. Not to sound condescending of course. As an amature I would say your temps are right on. The day/night diff will take care of it's self with sunlight and temps. As far as air circulation, the more humidity there is the more air movement you should have. GL

Fair question. 40 years ago we had a small green house and a nice collection of orchids, in an environment where day/night temperatures took care of themselves. Career and a move required that we give all that up until a new house, 5 years ago, allowed us, again, to have a green house. We have been slowly collecting orchids since. These orchids fended for themselves until my retirement 6 months ago. I would now like to give them the care they deserve. This means learning by reading and asking questions. When reading about the culture of orchids you constantly run across the comment about the difference between day and night temperature and the need for air circulation. Day/night will not provide this temperature swing in a green house if the outside temperature is 40* or below. The temperature is what the thermostat is set at day and night......unless you put in a programable thermostat. But I can't find that anyone uses these. Why? Same question about air circulation. A programable thermostat and a programable light switch, to turn a fan on and off, do not cost much money at all. Why don't people use them? Or, do they? These were my questions.