Thermostat help please...

[Tortlover]

I am in the process of building a cabin/shed for my exotics (6' x12') to house my APH and torts during the not so good weather and I want to install a couple of extractor fans for the summer as the Hogs will stay in there all year round.

I am a little stuck about how to get the fans running on a thermostat as thermostats kick in when it gets below a certain temp...I need something that will kick in when it gets above a certain temp....am I being dumb for not being able to think of how to do this??

Any help or suggestions will be appreciated??

Thanks