Horizontal Window Opener (on timer)

I have a fan on timer in my garage, but I would also like to open the 36" x 24" window during the day to let the warm air in. This doesn't even need to be Arduino, but does anyone have an idea of the easiest way to do this? Somewhat similar to the Chicken coop question, but different enough.

These things are available for greenhouse temperature control, perhaps you could adapt something? Are there any security concerns with having large windows open while it's unoccupied? Turning on a ventilation fan would probably be easier and safer since it'd just need a thermostatic switch.

I thought of that. But the greenhouse windows seem to always only be temperature related. =dumb and not programmable. The window isn't very large--it's just a typical window and it faces my courtyard. Worst case scenario--I can use a HUGE garage door opener--but that doesn't seem elegant!!!

Below is a setup where a relay is energized to operate a motor in one direction. When the relay is deenergized the motor operates in the other direction. Limit switches stop the motor in each direction, and the diodes allow the motor to start in the opposite direction when one of the limit switches is open.