What To Put Around Window AC Unit: Best Insulation, Sealing, and Aesthetic Solutions for Improved Comfort

Installing a window AC unit is one of the fastest ways to cool a room, but what you put around it plays a critical role in energy efficiency, comfort, and appearance. From insulation and sealing to decorative enhancements, this guide covers proven methods, materials, and tips for what to put around your window AC unit. Improve comfort, save on energy bills, and keep pests and water out—all while maintaining an attractive window area.

Why It Matters: Problems With Poor Installation

A poorly installed window AC can cause:

• Energy Loss: Air leaks force the unit to work harder, increasing costs.
• Water Leaks and Mold: Improper sealing lets in rain and humidity, leading to damage.
• Pest Intrusion: Gaps become an entry point for insects and rodents.
• Noisy Operation: Vibrations increase if not stabilized or insulated well.
• Poor Appearance: Exposed gaps or makeshift shims reduce curb appeal.

Best Materials To Use Around A Window AC Unit

Selecting the right materials ensures better sealing, insulation, and appearance. Below are the most popular and effective materials for window air conditioner installation.

Insulation Foam Strips

Self-adhesive foam insulation strips are an industry favorite for sealing minor gaps around window AC frames. These create a tight air seal and are simple to cut and install.

Expandable Insulation Panels

Most window AC units come with accordion-style plastic side panels. Upgrade to insulated panels (made from foam core or similar) for better thermal and noise performance.

Weatherstripping Tape

Weatherstripping tape, often made of EPDM rubber or vinyl, is ideal for sealing sash gaps or uneven window frames where foam cannot reach.

Spray Foam Sealants

Minimal expanding spray foam can seal large or irregular gaps between an AC chassis and window frame. Use with caution—too much can distort delicate frames.

Plywood Or Plexiglass Sheets

For windows that are taller or wider than your AC, cut-to-fit sheets can close large areas above/below or next to the unit. Paint or wrap for a neater finish. Plexiglass allows some light while blocking weather.

Decorative Curtains Or Covers

Indoors, simple drapes or custom covers can hide side panels, insulation, and cords, especially off-season.

Outdoor Caulk

Exterior-grade silicone or latex caulk is essential for weatherproofing the outside edges of the AC and fill board, keeping out rain, insects, and drafts.

Step-By-Step: How To Seal And Insulate Around Window AC Unit

Installing and sealing a window air conditioner properly is critical for safety and performance. Here’s a concise rundown of the process:

1. Mount The AC Securely: Make sure the unit sits level and securely in the window, following the manufacturer’s guidance. Most units require side brackets or L-brackets for support.
2. Add Insulation Foam: Place self-adhesive foam weatherstripping along all contact surfaces, including the window sash, frame, and between the unit and the sash.
3. Install Side Panels: If included, extend and lock the unit’s side panels. For extra insulation, add foam-backed panels or consider upgrading to insulated rigid boards.
4. Fill Large Gaps: Measure upper or lower gaps not covered by the AC body. Cut plywood or plexiglass to fit. Insulate around the perimeter with foam or weatherstrip, and seal the mating surfaces with caulk.
5. Spray-Foam As Needed: For uneven surfaces or larger holes, carefully apply expanding foam—avoid inside living spaces if possible. Trim any excess after curing.
6. Seal Exterior Joints: On the outside, use weatherproof caulk to seal the window perimeter, edges of panels/boards, and any other visible cracks.
7. Add Indoor Coverings: Use fabric skirts, drapes, or decorative trims on the inside for cleaner aesthetics and additional draft control.

Best Practices For Every Season

Cooling Season: Maximize Efficiency

During the summer, focus on airtight sealing and insulation to keep cool air inside and hot air out. Regularly check seals for gaps or deterioration, and replace materials as needed for peak unit performance.

Off-Season: Protection And Storage

If the unit will remain in the window, consider a heavy-duty insulated AC cover on both sides. This keeps cold drafts out and extends the life of your AC. If removing the unit, clean it and store it in a dry, sheltered area to prevent damage.

Rain And Storms

After severe weather, inspect the sealant, panels, and insulation for water intrusion. Repair or replace materials promptly to prevent mold or property damage.

Common Mistakes To Avoid When Installing Materials Around Window AC Units

• Using Old Towels Or Tape: These provide poor insulation, look unsightly, and can foster mold or pests.
• Neglecting Exterior Caulking: Skipping this step invites water leaks and pest intrusion.
• Blocking Drainage Holes: Never seal or block the AC’s drainage paths on the exterior side—this can cause water backup and serious damage.
• Overusing Expanding Foam: Too much foam expands to deform window sashes or damage walls. Use sparingly and trim after curing.
• Removing Window Stops: Avoid removing key window stops or tracks, which could prevent safe window operation.
• Not Leveling The AC: Always ensure the AC is slightly tilted outward to allow condensation to drain outside.

Decorative And Functional Enhancements

Indoor Window Surrounds and Trims

Use slim wood moldings or vinyl tracks to conceal foam insulation and side panels for a neat, built-in appearance. Paint or stain to blend with interior decor.

Window Films

Applying insulating window film around the AC unit area boosts efficiency, reduces condensation, and adds UV protection.

Outdoor Covers And Hoods

An external AC hood or awning above the unit can reduce sun and rain exposure, improve cooling efficiency, and extend the appliance’s lifespan.

Magnetic Draft Stoppers

These removable, magnetic fabric or rubber stoppers can seal small leaks around the AC in winter, while staying easy to remove when using the unit.

Window AC Unit Safety And Air Flow Considerations

Proper sealing shouldn’t mean blocking air flow or creating hazards. Always:

• Keep Air Intake And Exhaust Vents Clear: Do not obstruct with insulation or panels.
• Retain Emergency Egress: If the window AC is installed in a bedroom, ensure you can still use the window as an emergency exit if local codes require.
• Secure The Unit: Use recommended brackets and stoppers so the unit cannot fall or shift when the window is opened slightly.

Alternatives To Traditional Materials For Eco-Friendly Homes

For environmentally conscious homeowners, there are several sustainable options:

• Recycled Foam Insulation: Available in strips or panels for effective, eco-friendly sealing.
• Natural Fiber Insulation: Wool or cotton batts, treated for moisture resistance, can be cut and tucked around the unit.
• Low-VOC Caulks And Adhesives: Reduce indoor air pollution while weatherproofing.

Answering Frequently Asked Questions On What To Put Around Window AC Units

What Can I Use If The AC Side Panels Don’t Fit?

Cut-to-fit foam board or rigid insulation panels can be trimmed to size and installed in place of ill-fitting side panels. Secure in place with double-sided tape or adhesive, and seal edges with caulk or foam strips.

How Do I Prevent Bugs From Getting In Around My AC?

Thoroughly seal all interior and exterior gaps with foam, weatherstripping, and caulk. Inspect the installation annually. For persistent pest issues, place fine-mesh screen behind side panels or panels ventilated for the AC chassis.

Can I Use Blankets Or Plastic Sheeting?

These are only suitable as a temporary or emergency fix. For a permanent and safe solution, use foam, insulated panels, and proper caulking materials designed specifically for window installations.

Cost Estimates For Insulating And Sealing Around A Window AC Unit

Material	Typical Cost (USD)	Covers
Insulation Foam Strip Roll	$5 – $12	One average window AC
Upgraded Side Panels (2-pack)	$15 – $40	Most window AC models
Plywood or Plexiglass Sheet	$12 – $35	One large window or gap
Spray Foam Sealant (can)	$6 – $10	Multiple gaps
Weatherproof Exterior Caulk (tube)	$4 – $8	One to two window units
Decorative Indoor Cover or Curtain	$10 – $40	One room
Ready-Made Winter AC Cover	$18 – $50	One standard window AC

Differentiating By Window Frame And AC Type

The ideal solution depends on frame material, window size, and AC type. For vinyl or metal windows, avoid harsh adhesives or expand-and-contract materials. For wood frames, check for rot or warping before sealing. Oversized or irregular AC units may need custom-cut panels or professional installation to ensure safety and performance.

Choosing Solutions For Apartments Or Rented Properties

If you rent, focus on removable and damage-free solutions: use foam strips, draft stoppers, and pressure-fit insulation. Consult your landlord before using permanent caulk, drilling brackets, or adding structural supports to windows or exterior walls.

Maintenance And Inspection Tips

At least once quarterly, inspect all materials put around the window AC:

• Replace deteriorated foam or weatherstripping showing gaps or mold.
• Check caulk lines for peeling or cracks and reapply as needed.
• Wipe down inside surfaces to remove moisture or dust buildup.
• Realign shifting panels or boards after opening or closing the window.

Conclusion: Making The Most Of Your Window AC Installation

By thoughtfully selecting what to put around your window AC unit—using caulk, insulation, fit panels, and decorative touches—you’ll maximize comfort, cut down energy bills, enhance safety, and keep your window looking its best. Prioritize both indoor convenience and outdoor weatherproofing for all-seasons performance.