Overnight Temp for CAM Orchids

[Clawhammer]

Hello everyone.

I grow inside and control my temperature with an air conditioner, the lights take care of the heat, so I have total control over the temperature in my environment.

During the summer I have to cool the room overnight with the A/C. I set the unit's timer to make the room 67 degrees for 6 hours.

Question, what is the temperature that cattleya and other CAM orchids begin to open their stomata? Do I need to go to 67 degrees?

Also, does the length of time that the stomata are open have much of an effect on growth rate?

I am trying to balance the cost of running the AC vs maximizing growth.