Special adaptations for windows when the air conditioner is made for a different type of window?

If you use window-mounted air conditioner units, you may have to make some special adaptations in order to fit the unit into some window types. Air conditioners are not all the same size. Most units come with side extensions that will slide or fold out to cover the gap between the unit and the window frame. Make sure that these completely cover the space. It is best also to cut a piece of foam to cover the area as well, since this will provide an excellent form of insulation. Be sure to caulk around the outside surface of the unit to seal out any air leaks. For some window units, specifically those with tilt-out windows, you may have to build a special shelf outside the window in order to keep the air conditioner unit securely fixed to the window space.