🧭 Introduction: Installing a Through-the-Wall AC? Let’s Do This Right!
Hey folks — Mark Callahan here. Installing a through-the-wall AC unit can feel like a big job, especially if it’s your first time. But don’t worry — I’m going to show you every important step so you can tackle it like a pro.
With the right tools, a little patience, and some basic know-how, you’ll get your new unit installed quickly and safely — and it’ll keep you cool for years to come. Ready? Let’s roll up our sleeves and jump in!
(And if you haven’t picked out your AC yet, check out the full selection of through-the-wall air conditioners at The Furnace Outlet to find a unit that suits your space perfectly.)
🔍 Step 1: Gather Your Tools and Materials
Before you cut a hole in the wall, you’ll want to make sure you have everything on hand. Installing a through-the-wall unit is more involved than simply setting up a window AC — so being prepared is key.
Here’s a basic checklist:
✅ Your through-the-wall air conditioner (with wall sleeve)
✅ Level
✅ Measuring tape
✅ Power drill and masonry bits (for brick walls)
✅ Hammer and chisel
✅ Screws and anchors
✅ Shims
✅ Silicone caulk
✅ Insulation foam or weather stripping
✅ Safety glasses, dust mask, and work gloves
And remember — safety first. Be sure to wear your eye protection and follow proper safety procedures every step of the way.
🧮 Step 2: Pick the Right Wall & Confirm Clearances
Not every wall is created equal. Before you touch a drill, inspect the wall where you plan to put your AC. Consider:
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Structural support: Don’t cut into load-bearing walls without consulting a pro.
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Exterior obstructions: Make sure the exterior part of the wall is free of trees, vents, and other obstacles.
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Interior wiring and plumbing: Use a stud finder with live-wire detection to avoid electrical cables or pipes.
It’s also a good idea to check your local building codes for any special requirements. The U.S. Department of Energy has a helpful overview of safe and efficient AC use — check out their AC Energy Saver tips for some great guidance.
📐 Step 3: Measure and Cut the Wall Opening
Here’s where the real work begins. The most common through-the-wall ACs require a hole that matches the wall sleeve’s rough opening — check your unit’s manual for the exact measurements.
✅ Measure twice, cut once.
✅ Trace the outline of the wall sleeve on the interior wall.
✅ Score the drywall with a utility knife and then use a saw or reciprocating saw to cut out the opening.
For masonry or brick walls, you’ll need a power drill and masonry bits to score the perimeter, then use a chisel and hammer to carefully knock out the brick.
💡 Pro Tip: If you’re working with brick or concrete walls, take a look at these masonry demo techniques on The Spruce — see this guide for specifics.
🧰 Step 4: Frame the Opening & Install the Wall Sleeve
Once the hole is cut, it’s time to add a wooden frame — often called “buck framing” — around the inside of the opening. This will support your sleeve and ensure a snug fit.
✅ Use 2x4 or 2x6 lumber to build a box frame that fits the wall sleeve snugly.
✅ Screw the frame into the surrounding studs.
✅ Slide the wall sleeve into place.
Your sleeve must fit level and plumb. Check this with your level before securing with screws.
When the sleeve is installed, seal any gaps between the sleeve and the wall with low-expanding spray foam or weather stripping. You want a tight seal to prevent air leakage — a key part of maximizing energy efficiency.
For a detailed look at wall framing and sealing techniques, check out this article from This Old House that walks you through the basics of framing an AC sleeve.
🧭 Step 5: Slide in the AC Unit and Secure It
With the wall sleeve securely mounted, it’s time to insert your air conditioner.
✅ Slide the AC chassis into the sleeve according to your model’s instructions.
✅ Align the faceplate so it sits flush with the interior wall.
✅ Use the provided screws to secure the unit in place — usually to the sleeve or wall.
Double-check that your unit is slightly tilted toward the exterior (most manuals recommend a slight tilt — around ¼ inch — so that water from the evaporator can drain outside properly).
For help on drain pitch and moisture management, the ASHRAE technical FAQs offer some great insights — see their technical resources for detailed specs.
🔧 Step 6: Seal the Perimeter and Weatherproof
Your unit is installed — great work! But don’t stop yet. Even the best-installed AC unit can let in drafts if you don’t seal up.
✅ Fill any visible gaps around the outside of the unit with weather stripping or spray foam.
✅ Apply a neat bead of exterior silicone caulk around the outside perimeter to prevent water infiltration.
✅ Add insulation panels around the interior trim for an extra energy-saving boost.
When you take the time to seal thoroughly, you help improve performance and reduce energy waste. According to the EPA Energy Star program, properly sealing an AC can improve efficiency by up to 15% — read more on their energy-saving strategies here.
🧽 Step 7: Test It Out & Final Touches
Finally — the fun part. Plug in your AC and test all its features. Adjust the thermostat, cycle through fan speeds, and listen for any vibrations that could indicate improper installation.
✅ Double-check the unit is draining properly outside — water should drip as expected.
✅ Clean up your workspace and admire a job well done!
And remember, periodic maintenance — like cleaning the filter and coils — will help your AC last longer and perform better. Check out this handy article on Family Handyman for AC maintenance tips: Air Conditioner Repair and Maintenance Tips.
🏡 Conclusion: You Did It — Time to Chill!
Installing a through-the-wall air conditioner may seem daunting, but by following this step-by-step guide, you can do it with confidence. Focus on proper framing, a level sleeve, a tight seal, and you’ll have a cool, comfortable space all summer long.
And if you’re still looking for the perfect unit, shop our full range of through-the-wall air conditioners at The Furnace Outlet — where quality and value come standard.
Have questions along the way? Don’t hesitate to reach out — I’m here to help you stay cool.
