How To Seal Window Air Conditioner Jun 2026

Rigid foam boards or insulated side panels offer much better thermal resistance than the standard plastic accordion "wings".

For an airtight finish, use specialized tape. Do not use standard duct tape, as it leaves a sticky residue and degrades in the sun. how to seal window air conditioner

When sealing a window AC, the materials you choose matter as much as the method. Rigid foam boards or insulated side panels offer

Best for: Side gaps smaller than 6 inches. how to seal window air conditioner

The gap between the top of the AC and the lower window sash is the biggest air leak.

Use the provided hardware to secure the panels to the window sash.