Hi Scott,
I grow orchids in a greenhouse here in Southern California and although our winters are milder compared to you guys up north, our summers can be more brutal in the inland regions where I live.
In the winter, I have a heater that is set to keep the greenhouse above 55F. I dont have any plants that require warmer nights than that.
Without the heater, the GH interior could drop down to 40F.
Winter days are not a problem as outside temps rarely exceed 65F and the GH stays under 75F without supplemental cooling.
In the summer, we get very high temperatures and low humidity.
I can only apply so much shading to the greenhouse before I start losing valuable sunlight spectrum.
This is what I use for shading:
Single layer of Aluminet 50% shade fabric on the exterior of the greenhouse.
Single layer of generic 50% shade fabric at select locations on the west side of the greenhouse to protect some of the plants who do not like very bright light.
I also have an exhaust fan that is connected to a thermostat to activate it once the GH hits 80F.
I chose to use the low humidity to my advantage.
I set up an automatic mister with a programmable timer to help cool down the greenhouse and add some humidity.
So in terms of results, this is what I get with the current greenhouse setup.
If at noon, the outside temperature is 100F:
*Shade materials reduce the interior temperature to 95F.
*Exhaust fan and interior circulation fans help further reduce the temperatures down to around 90F.
*When the misters activate, they drop the GH temperature down to around 85F. After the misters stop, the temperature slowly climbs back up to around 90F.
* In the summer, I have the misters scheduled to run for 10 minutes every 30 minutes. So during the day the GH temperature would go through the 85F-90F cycle as the misters activate every 30 minutes.
On very hot days, I go to the greenhouse in the morning and soak everything with a garden hose. This gives the plants extra water and moisture to make it through the heatwave.
The orchids are doing well under this setup, it just needs periodic adjustments and intervention with a garden hose when a heatwave strikes.
However, this greenhouse is not meant for any "cool growing" orchids.
I hope this helps,
John
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