Topic Type
Information

Though not full-system temp management, automatic vent openers are a good option for venting tunnels and greenhouses in no-elec situations. Search around online - most seem to fall within the $50-100 range. We've had good success with them in helping prevent midday high temp extremes.

Forums
Solar Powered Greenhouse Ventilation
Forum comment

I've numbers that say passive venting requires an area 20% of your square footage to be open during the day. So if I have 200 sq ft of growing space, I would have to have 40 sq ft of vents, which is a lot. I think these would be awesome for the air intake portion of the system. Now I just need to figure out the exhaust side of things.