Window fans with thermostats are available at Sears, Home Depot and Wal-Mart, as of 2015. Most models feature twin fans that reverse to bring air in or push air out of the house.
The Bionaire model BW2100 sold at Sears includes a programmable digital thermostat and three speed settings. The unit fits into most double-hung windows, and it includes an extender screen. The Lasko model 2138 available at Home Depot is designed for windows that are 25 to 35 inches wide, although the unit also operates on a tabletop. The Jarden Home Environment Holmes fan model HAWF2041 available at Wal-Mart features a slim design that doesn't require removal of the window screen.