There isn’t one single “best” option, but a few common solutions work well depending on the size of the gap and your window type:

• High-density foam weatherstripping tape: Self-stick foam is great for sealing perimeter gaps. Choose thickness to match your gap.
• Non-adhesive foam strips: These compress easily and are useful when you prefer a removable seal (often used with glue points).
• Insulated side panels: Upgrading the side fillers helps reduce drafts and heat gain around the unit.
• Clear window sealing tape: Helpful for tiny seams where air sneaks through.
• Indoor AC covers (off-season): Use when the unit is off to curb winter drafts.

The right mix depends on your window style and climate, and results can vary.

1. Measure the gaps: Note the perimeter and side openings to pick suitable tape thickness and width.
2. Prep the surfaces: Clean and dry the window frame and sash so adhesives bond better.
3. Apply foam tape: Run it along contact points where the sash meets the unit and around the perimeter; press firmly.
4. Seal the sides: Add insulated side panels or firm foam inserts; tape seams neatly.
5. Close small seams: Use clear window sealing tape where you see light or feel drafts.
6. Winter step: Once the unit is off, add an indoor AC cover to reduce drafts.

Avoid blocking vents or drains, follow your unit’s manual, and test for leaks; effectiveness may vary.

Pick foam tape based on the gap you need to fill and how much compression you want:

• Thickness: Choose a thickness slightly larger than the gap so it compresses to a snug seal.
• Width: Match the contact surface; wider tape covers uneven areas better.
• Density: Higher-density foam can resist air leaks and rebound after compression.
• Adhesive type: Self-stick is convenient; non-adhesive strips with glue points suit temporary installs.
• Length: Measure the full perimeter and add extra for corners.
• Temp rating: Check adhesive performance for hot summers or cold winters.

Most foam tapes can be trimmed with scissors for a custom fit.

You can reduce some noise, though full soundproofing isn’t typical for window units.

• Seal rattles: Foam weatherstripping can lessen vibration and air leaks that amplify sound.
• Insulate sides: Firmer, insulated side panels may dampen noise transfer around the unit.
• Stabilize the unit: Level and secure the installation to prevent buzzing or rattling.
• Maintenance: A clean filter and coils can help the unit run more quietly.
• Limit outside noise: Seal small exterior gaps to reduce traffic or street sound.

Don’t block vents or cover the unit while operating. Results depend on your window, building materials, and the AC’s condition.

1. Unplug and inspect: Decide whether to remove the unit or keep it in place.
2. If it stays in: Install an indoor AC cover to help reduce drafts during the off-season.
3. Seal perimeter gaps: Add foam weatherstripping around the sash and frame; tape side panel seams.
4. Extra barrier: Apply clear window insulation film over the opening for added protection.
5. Check and adjust: Look for light or feel for air movement; reinforce as needed.

Don’t run the unit while covered, and follow your AC’s manual for any seasonal guidance. Availability and performance vary by home and climate.