I use one similar to this one: http://www.homedepot.com/p/MaxxAir-30-in-Industrial-Heavy-Duty-2-Speed-PRO-Drum-Fan-BF30DDORGPRO/204627482 http://www.homedepot.

I use one similar to this one: http://www.homedepot.com/p/MaxxAir-30-in-Industrial-Heavy-Duty-2-Speed-PRO-Drum-Fan-BF30DDORGPRO/204627482 http://www.homedepot.com/p/MaxxAir-30-in-Industrial-Heavy-Du... I've also used one like this: http://www.homedepot.com/p/HDX-30-in-Pedestal-Fan-SFSC1-750S/202757018 http://www.homedepot.com/p/HDX-30-in-Pedestal-Fan-SFSC1-750S... My neighbor bought a smaller one: http://www.homedepot.com/p/MaxxAir-30-in-Industrial-Heavy-Duty-2-Speed-PRO-Drum-Fan-BF30DDORGPRO/204627482 http://www.homedepot.com/p/MaxxAir-30-in-Industrial-Heavy-Du... The idea is really simple. In our case these are two story homes with balconies. The fan goes on the balcony right outside the sliding glass door. You set it up to exhaust hot air from the house. Open all the windows. That will be your incoming cool air. The windows downstairs are fully open and the upstairs windows only four to six inches. Turn this on as soon as the temperature outside is significantly cooler than inside. There have been days when I've been able to get the house down to 65 degrees in a couple of hours. I've also used the standing fan placed outside a ground level floor window blowing cold air in. Now you open the upstairs windows to push the hot air out. So, you either pressurize your home with cool air or reduce the pressure (by sucking air out) in order to have cool air enter. Not that hard to do. It takes all of five minutes a day to go through the open-windows-turn-on-fans dance and you save hundreds. My next move is to automate this by integrating it into the ducting system as well as providing for a filtered cool air intake path. The best part is that I saved the money I'll need by using this method during the last three summers. That money is going into system that should save me $1,000 to $2,000 per summer when compared to every house in my neighborhood. Nest can't even begin to compare to this performance.