the window on top of it to hold it in place. after that you simply need to seal off the open space around the unit in order to keep bugs out of your home and to keep the cool air from escaping.
another major reason to consider a window-mounted unit is the low price of the majority of the units on the market. in most cases, even the largest window-mounted units are only going to cost several hundred dollars. this is a fantastic advantage as it will allow you to buy a window-mounted unit for every room in your house and still likely save money versus buying a central air system.
a 