Most window air conditioners come with an accordion style flap attached to the sides to fill the open space.
How to properly seal a window ac unit.
Adjust the ac unit s window vent panel to extend across the width of the opening.
Narrow or hard to reach gaps measure the length of gaps that are 1 8 inch thick or smaller.
Measure the width of the windowsill and use a pencil to mark.
Lower the window sash until it rests on top of the vent panel.
Flashing tape is the first line of defense.
Tear off a length of rope caulk to match.
Smooth the caulk and wipe away.
Before installing a window ac open the window as far as it goes remove the screen and clean the windowsill glass and window frame.
Then lift the window and place the seal under the lip of the window.
Re close the window tightly.
Seal around the window with flashing tape lapping the top piece over the sides.
Press the caulk into the gap.
2 position the end of the weatherstripping at one end.
Then fold down the house wrap at the top and cover the diagonal slits at the top with house wrap tape.
If the gap is deep you may need to press two pieces into the gap to fill it completely.
Open the window where the portable air conditioner will be located.
Cut foam weather stripping to length and attach to the window sash and frame.