Installation Guide: What to Know Before You Cut a Hole in the Wall

Installing a through-the-wall air conditioner can be a smart move for homeowners like Samantha—someone who values clean aesthetics, energy efficiency, and a clutter-free living space. But let’s be honest: once you cut into an exterior wall, there’s no turning back. You want to do it right the first time.

This guide walks you through:

• 📍 Planning your install location

• 🔌 Electrical requirements

• 🧱 Wall construction, framing & waterproofing

• 🧰 Tools, materials, and permits

• 🧼 Finishing the job cleanly

Whether you're considering DIY or hiring a pro, here’s everything you need to know before making the first cut.

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📍 Step 1: Choose the Right Location

You can’t just pick any wall in your home for a through-the-wall AC. It must be:

• An exterior wall

• Clear of wiring, plumbing, or structural load points

• Accessible to a power source

✅ Ideal Wall Features:

• Near a dedicated electrical circuit

• At least 24–36 inches off the floor for airflow

• Out of direct sunlight (saves energy)

• Inside a room under 700 sq. ft., unless you're installing multiple units

Samantha’s Tip: “I almost put mine behind the sofa, but realized it would block airflow. I moved it above my console table instead—it looks built-in and works better!”

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🧱 Step 2: Understand Your Wall Construction

Before you cut, know what you're cutting into. Wall thickness and structure vary by home age and materials.

Common Types:

• Wood-framed wall (most common): 2×4 or 2×6 studs, drywall inside, siding outside

• Masonry/brick wall: Needs specialty cutting tools and anchoring

• Concrete block: Tough but doable with rotary hammers and anchor sleeves

Measure Wall Depth

Standard wall sleeves are made for 5"–7.5" thick walls.
If your wall is too thin or too deep, you may need to shim or trim the sleeve or unit.

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🔌 Step 3: Electrical Requirements

Not all through-the-wall ACs plug into the same outlet. Many use 230V, which is not standard in most homes.

Check Your Unit:

• BTU rating: 5,000–8,000 BTU units may use 115V

• 10,000–14,000 BTU units typically require 230V

• Heat function? That often bumps the amperage

If You Don’t Have the Right Outlet:

• Hire a licensed electrician to:

  • Run a dedicated 230V line

  • Install a matching receptacle and breaker

🔗 Energy.gov on Electrical Load Basics

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📦 Step 4: Choose the Right Wall Sleeve

A wall sleeve is a metal box that holds the AC unit in place and protects the wall cavity. It must be installed before inserting the AC chassis.

Sleeve Considerations:

• Most through-the-wall ACs use a standard 26-inch wide sleeve

• Some units (like GE or Friedrich) require brand-specific sleeves

• Make sure the sleeve:

  • Matches unit size and depth

  • Has proper drainage and insulation

  • Is weather-sealed on the outside

🔗 ENERGY STAR Certified Wall AC Units

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🪚 Step 5: Cut the Wall (Safely)

Once you’re sure of your location and sleeve, it’s time to prepare for the actual wall cut.

Tools You’ll Need:

• Stud finder

• Level and framing square

• Reciprocating saw (Sawzall)

• Circular saw (for exterior siding)

• Drill with wood and masonry bits

• Hammer and nails or framing screws

Framing Tips:

1. Mark your cut with pencil and level.

2. Remove drywall and insulation inside the outline.

3. Cut two studs and frame a rough opening using:

   • Header above the hole to support the load

   • Jack studs and sill plate to reinforce the opening

4. Use pressure-treated wood for the sill to resist moisture.

🔗 Green Building Advisor on Window Flashing

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💦 Step 6: Weatherproof the Opening

This is not optional. Improper flashing leads to mold, leaks, and damage over time.

Steps to Seal It Right:

• Install the wall sleeve at a slight downward angle (1/4" drop toward outside)

• Wrap exterior edges of the sleeve with flashing tape

• Apply silicone caulk around all exterior seams

• Ensure drain holes face outward

Optional: use low-expansion spray foam to seal small air gaps inside wall cavity

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🧰 Step 7: Insert the Unit

Now that the sleeve is level and sealed, slide in the AC chassis.
Secure with the mounting brackets or screws provided by the manufacturer.

Final Checks:

• Plug in the unit (or connect to hardwired power)

• Turn it on and check:

  • Airflow direction

  • Thermostat control

  • Condensation drainage from rear vent

• Listen for excessive vibration—if so, add padding or check sleeve alignment

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🧼 Step 8: Finishing Touches

The last step is polishing the install—inside and out.

Interior:

• Use a trim kit or finishing bezel for a clean look

• Touch up drywall with joint compound and paint

• Clean debris and dust from the room

Exterior:

• Reinstall or trim siding

• Paint any exterior framing

• Add a weatherproof AC cover if not using year-round

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⚖️ DIY vs. Professional Installation

Samantha’s Story: “I did most of it myself but hired an electrician for the 230V line. The framing was a fun challenge, and I love how professional it looks.”

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📋 Permits, Code & HOA Considerations

Before you cut:

• Check local building codes for wall penetrations and electrical work

• Get permits if required (especially in cities or condos)

• Ask your HOA or property manager if modifications are allowed

• Some historical homes or townhomes may restrict exterior changes

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🛠️ Tools & Materials Checklist

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🛍️ Recommended Products from The Furnace Outlet

• ✅ Through-the-wall AC Unit (choose by BTU and voltage)

• ✅ Wall Sleeve (standard or brand-specific)

• ✅ Trim Kit or Grille

• ✅ Weatherproof Cover (for winterizing)

• ✅ Install Kit (optional tools or brackets)

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🧾 Final Pre-Cut Checklist

✅ Selected the correct BTU size
✅ Measured wall depth and checked framing
✅ Verified electrical needs (115V vs 230V)
✅ Bought matching wall sleeve
✅ Gathered tools and safety gear
✅ Reviewed permit and HOA rules
✅ Confirmed drainage plan and caulking supplies

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💬 Final Thoughts from Samantha

“If you take the time to prep everything—location, framing, sealing, and electrical—the install really isn’t scary. My wall unit looks built-in, works quietly, and hasn’t leaked a drop. Worth every bit of effort.”

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In the next topic we will know more about: Wall Sleeves Explained: What They Are, Why They Matter & How to Pick the Right One