Seal around the window with flashing tape lapping the top piece over the sides.
How to properly seal a window ac unit.
Press the caulk into the gap.
Adjust the ac unit s window vent panel to extend across the width of the opening.
Step 3 examine the sash.
Measure the width of the windowsill and use a pencil to mark.
Re close the window tightly.
To fix this purchase some air conditioner foam seal at your local hardware store if there isn t any with your unit.
If the gap is deep you may need to press two pieces into the gap to fill it completely.
Then lift the window and place the seal under the lip of the window.
Tear off a length of rope caulk to match.
Cut foam weather stripping to length and attach to the window sash and frame.
Smooth the caulk and wipe away.
Ask a helper to hold the air conditioner unit in place while you raise the bottom window sash up enough so that you can access the bottom edge.
Flashing tape is the first line of defense.
Open the window where the portable air conditioner will be located.
Most window air conditioners come with an accordion style flap attached to the sides to fill the open space.
Narrow or hard to reach gaps measure the length of gaps that are 1 8 inch thick or smaller.
Lower the window sash until it rests on top of the vent panel.