Adding Automatic Ventilation to a Rion

OK, I have a 8x16 rion and I want to add a better ventilation system. Currently I have 3 auto roof vent that I only use in the summer. I take down the openers and lock the windows shut so the openers will not freeze.

I am thinking of removing the louvered window and replacing it with a 12" exhaust fan. That part is straight forward. I will mount and piece of plywood against the frame and cut a rough opening in the wood to mount the fan. I want this fan to be thermostatic. Is there a need for variably speed too? I ask because I want to start using my greenhouse from Feburary thru early December. I dont want to shock the plants with fast cold air.

The next question is about thermostatic louvers. I want to mount one on the opposite end. There is no real place to do this. I could cut through the PC. The problem is I need to cut a 19" opening in the lower panels to for a 16" fan. That will not leave much along the sides. I could mount two 12" louvers but that doubles the cost and a greater need for electricity.

What have you all done to ventalate your rions?

I do not have a Rion, my GH is home made. All of the fans I have in the GH push the air out. So the air doesn't blow on the plants. I have a number of post here.
I have a 20" in the gable and two 52" paddle fans mounted over head, all pulling away from the plants and all have 3 speeds. I use high. Hope this helps, but everyone is different.

Dwight

You might find this web site helpful
http://www.littlegreenhouse.com/fan-calc.shtml