To install a window AC, open the bottom sash fully, balance the unit in the window with the bottom flange against the outside of the frame, close the sash, lock the sash in place, and expand the wings. Add insulation and weatherstripping to prevent heat infiltration.Continue Reading
Unlock the window, and push the bottom sash so it is fully open. Remove any screens from the window.
Place the unit in the open window, balancing it on the sill. Enlist the aid of a helper, and lift the unit, placing it so the bottom flange is against the frame on the outside of the window.
While your helper balances the unit on the sill, close the sash so the top bracket rests against the inside of the sash. Have the helper release the unit so the window holds it in place.
Prevent accidental opening of the window by inserting screws through the top flange into the bottom of the window sash. Pre-drill the holes to prevent splitting the wood.
Expand the accordion wings on either side of the unit to seal the opening around the unit.
Cut foam core insulation to fit over the expansion wings, and attach it in place. Cut soft foam weatherstripping to the width of the window, and tuck it in the opening between the two sashes.