Thermostat to overide, US version?

I've been searching all night trying to find a DIY on a thermostatic fan controller. I'm looking to have a constant low setting on a fan dimmer switch until a thermostat kicks in, pumping the fan to full power. Once the desired temp is reached the fan goes back down to its constant low setting. Blah blah blah... found a few different diagrams online but all used thermostats from the UK. This seems like the best setup, http://www.uk420.com/boards/index.php?showtopic=55189 but I would be using a 24v thermostat, so I would need a transformer, would I also need a relay? Does anyone have a diagram or link that could help me out? Thanks guys, I seldom post because the answers are always there, but I've really been searching for hours on this one and my ass is numb. Bowl and bed... Ben and Jerry's?

https://www.rollitup.org/attachments/grow-room-design-setup/64476d1201982801-connecting-thermostat-fan-room-ventilation-diagram.jpg another good diagram but doesn't incorporate the dimmer switch.

Al has one on his al B fuct thread in the hydro ponic section
spent 15 minutes trying to find it for ya. Can't remember what page it's on
I'll do some more looking for ya, because I will be doing mine soon also like this.
You wire a tstat and a speed controller in parallel to your fans. Have the controller set on low
and it will run the fans on the lower setting. Once the tstat kicks in, it will over ride the controller because electricity follows the path of least resistance. This is beyond my scope on how to get better detailed for you. But it might get you started. I'll do some more looking for you here in a bit.

Many Thanks, thats what I've been searching for! Only how do I go about wiring the transformer to the thermostat (since I'll be using a 24v thermostat and the fan is 120v). Thanks for all the help.

your tstat and speed controller aren't 120v?

sadly not, its a 24v... just scrap it and go with a 120v u think?

ya I would keep it simple as you can. I know some devices run on low voltage and can control 120 vac devices but unless you totally know what you are doing, I would stick to the 2 devices and wiring them together