ECOsparks Solar Powered Roof Vent

Hi,
How much cold are we talking about? What is the temp. difference between roof space & outside? The Eco vent can have a switch wired to disable it manually or automatically when the temp outside falls below the roof space temp. Or you can get a temp. operated hydraulic damper that closes when the outside temp gets lower.
I could go on forever without knowing the installation circumstances.
I hope these few points give you an idea of what can be achieved.
Keep Well,
Ray King

thanks a million