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DIY Installation Guide for 6,000–9,000 BTU Wall ACs: What I Wish I Knew Before Cutting the Wall

If you’re looking to install a 6,000–9,000 BTU wall AC yourself, I’m going to share everything you need to know — and everything I wish I knew before cutting into the wall.

DIY wall AC installation is a project that sounds simple enough, right? You cut a hole in the wall, slide the sleeve in, and pop the unit into place. But here’s the thing: getting it right the first time involves a lot more than just the hole. The details matter.

In this guide, I’m going to take you through framing, sleeve size and support, sealing, insulation, and all the crucial little things I’ve learned after multiple installs. I’ll walk you through the steps, share tips from my own experiences, and help you avoid the most common mistakes.

Along with these installation tips, I’ll also cover how to switch your AC between cooling, heating, and fan modes for the best efficiency and comfort.

And yes — this is all for the most common ACs you’ll find in the Through The Wall Air Conditioners 6,000-9,000 BTUs range.

Let’s dive into it.

1. The Basic Steps for Installing a Wall AC (Without Missing Anything)

Let’s start with the overall process. In my experience, wall AC installs take way longer than you might expect, especially if it’s your first time.

Here’s the overall step-by-step outline:

Step 1: Plan Your AC Placement

Ensure the wall is structurally sound and has room for the sleeve.
The AC should face a room with good airflow and minimal obstructions.

Step 2: Measure and Cut the Hole

Use the unit’s dimensions for the sleeve.
Make sure to level the hole for proper drainage.

Step 3: Frame the Opening

Use wood or metal framing to support the sleeve.
Make sure it’s sturdy enough to hold the weight of the AC unit.

Step 4: Install the Sleeve

Slide the sleeve into the opening.
Make sure it’s aligned and sealed.

Step 5: Insulate and Seal

Insulate around the sleeve to prevent air leaks.
Seal gaps and make sure there’s no water infiltration.

Step 6: Install the AC Unit

Slide the AC into the sleeve.
Secure it and plug it in.

Step 7: Test the AC

Turn it on and check for proper drainage.
Ensure it’s cooling efficiently.

2. The Most Important Step: Planning the AC Placement

Before you even start cutting into your wall, you need to plan where the AC will go. It’s easy to get excited and jump into the project, but trust me — this is where your install can make or break your comfort. UG Nasons

A. Where to Place the AC Unit

First things first: the AC unit must face an open space where air can flow freely.

Avoid placing the unit near corners or behind furniture.
Don’t aim the AC directly at a bed, desk, or seating area.
Ideally, place it near the center of the room for even cooling.

B. Check for Space and Ventilation

Measure your wall thickness — most wall AC units need a minimum depth of 16 inches, but some sleeves require more.
Make sure there’s no studs or wiring in the way.
Check that the AC unit will be level so it can drain correctly.

3. How to Cut the Hole: Measuring, Marking, and Cutting

Once your placement is set, it’s time to cut.

A. Mark Your Measurements Carefully

Using a level, mark the width, height, and depth of the sleeve on the wall.

Tip: Double-check your measurements before cutting. Trust me, I’ve had to patch a few holes because of “close but no cigar” measurements.

B. Cut Through the Wall

Use a reciprocating saw (also known as a “sawzall”) for cutting drywall, wood studs, or brick.
For brick or concrete, you’ll need a masonry blade.

Tip: Start cutting from the inside of the wall to avoid messing up the exterior. It’s always easier to patch a small mistake inside than outside.

C. Test Fit the Sleeve

Before sealing anything, test fit the sleeve to make sure it slides in perfectly. You want it snug but not too tight — allow for a little space to insulate around the sleeve.

4. Framing the Opening: Supporting Your AC

This is where things get a little more technical, but don’t worry, it’s not difficult once you know what you’re doing.

A. Why Framing Is So Important

Framing is crucial because the sleeve will sit on it and support the entire weight of the AC unit. Without proper framing, your AC can tilt, sag, or even fall out — a scenario no one wants.

Tip: Use 2x4 studs for framing the sleeve if the opening is in drywall or wood. If you’re cutting through concrete or brick, you’ll need metal framing.

B. How to Frame the Opening

Cut the studs to fit inside the hole, leaving about ½ inch on all sides for insulation.
Nail or screw the studs into place. You want them to be secure enough to support the weight of the AC.
Check that the framing is level so the AC will sit correctly in the sleeve.

5. Installing the Sleeve: The Key to Efficiency

The sleeve is the foundation of your wall AC install, and getting it right ensures the long-term efficiency of your AC.

A. How to Insert the Sleeve

Once your framing is secure, slide the sleeve into place from the inside of the wall.

Make sure it’s level and flush with the wall.
The front lip of the sleeve should sit flush against the wall while the back of the sleeve should extend slightly out to allow proper drainage.

B. Sealing the Sleeve

Once the sleeve is properly installed, seal the edges around the sleeve to prevent air leaks. Use foam sealant for any gaps between the sleeve and the wall.

This step is crucial. Even small air leaks around the sleeve can dramatically reduce the efficiency of your wall AC.

6. Insulation: The Key to Energy Savings

Insulating the sleeve is one of the most important, yet overlooked, parts of the install. Without proper insulation, your AC will struggle to cool efficiently.

A. What Insulation to Use

I recommend using rigid foam board around the sleeve. It’s easy to cut, easy to install, and provides excellent insulation.

Cut foam board to fit the space between the sleeve and the wall.
Use spray foam insulation to fill any gaps between the foam board and the wall.

B. Why Insulation Matters

Proper insulation helps by:

Preventing air leaks that waste energy.
Protecting against water infiltration (especially in rainy areas).
Keeping the AC’s cold air inside so it doesn’t overwork.

7. Sealing the Edges: Water Protection & Energy Efficiency

Once you’ve insulated, the next step is sealing the gaps and ensuring everything is airtight.

A. How to Seal Around the Sleeve

Use weather-resistant caulk around the outer edges of the sleeve, where it meets the wall. Energy.gov
Be sure to seal the top, sides, and bottom to ensure the sleeve is fully protected.

B. Why Sealing Is So Important

Sealing helps prevent:

Moisture buildup, which can cause rust or mold.
Energy loss, which will keep your electricity bills higher.
Cold air leakage, which reduces the cooling efficiency.

8. Installing the AC Unit: The Final Step

Now that the sleeve is in, it’s time to slide in the unit. This is the easiest part!

A. Insert the AC Unit

Carefully slide the AC unit into the sleeve. Make sure it’s aligned properly, so it doesn’t block the airflow. AHI Carrier

B. Secure the AC

Once the AC is in place, use screws to secure the unit to the sleeve. Make sure the AC is stable and will stay in place.

Tip: Never force the unit into the sleeve. It should slide in smoothly.

9. Testing the AC: Make Sure It Works

Before you finish the job, you need to test the AC to make sure it’s cooling properly and draining correctly.

A. Turn the AC On

Turn the AC on and let it run for 30 minutes. Check for:

Proper cooling
No unusual noises
Good airflow
Adequate drainage

B. Check the Drainage

After running the AC for a bit, check the drainage to make sure it’s working. If water is pooling around the unit, your sleeve might not be level, or the drainage hole might be clogged. Cielo Wigle