How To Install a Window Air Conditioner In Sliding Window?

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How To Install a Window Air Conditioner In Sliding Window?

Horizontal sliding windows (also known as slider windows) are more often used in regions where space is at a premium. They may not be as popular in areas that experience colder weather.

A horizontal slider window design can make installing an air conditioner challenging, but it can be done safely with proper measures.

This article covers everything from the preparation requirements to installing a window air conditioner in a sliding window.

Installing an air conditioner in the sliding window might not be as simple as installing one in a standard frame, but it’s possible. Before starting the project, measure your air conditioner’s width and height. Also, include any vents that might stick out on the sides and the size of the window’s opening.

Can You Put a Window Air Conditioner In a Sliding Window?

Yes, you can put a window air conditioner in a sliding window.

If you want to install an air conditioner in a sliding window, you’ll need to ensure that the unit is adequately secured so it doesn’t fall out when you slide the window open or closed. We recommend retaining rods or some other securing mechanism to do this. 

Window air conditioners are created to fit within a common window space with minimal clearance requirements. The Consumer Product Safety Commission (CPSC) says air conditioners should fit securely within the window opening. There is not more than two inches of space on either side or four inches above or below.

There are two classes of window air conditioners:

Casement/slider units are designed to fit horizontally sliding windows. They come in several sizes; most have slide-out chassis for easy installation and removal. In addition, many have accordion panels on the sides to help you seal the gap between the air conditioner and the window frame—be sure your window is wide enough for the unit you choose so you don’t block the view.

Standard/double-hung units can be installed in vertically opening (aka double-hung) windows. These also come in various sizes but don’t have slide-out chassis. So you’ll need to remove them from the window frame when they’re not in use.

How Difficult is This to Do?

If a window air conditioner is your only option, you can still find a way to make it work in a sliding window.

Whether it’s a small apartment or a rental home, there are numerous reasons why a central air conditioning unit is not an option. Fortunately, window units are an easy and simple fix for any homeowner.

Before beginning the process, pick up an installation kit so your unit fits securely into place and doesn’t move around while in operation.

How Long Does it Take?

You can station a window air conditioner in a sliding window in about an hour and a half.

Read Also: How To Install A Portable Air Conditioner In A Horizontal Sliding Window?

How Much Do Materials Cost?

The total cost of installing a window air conditioner in a sliding window depends on the materials you need to purchase and their prices in your area. This project will set you back $250-$700.

Material costs will depend on the type of unit you choose, how much insulation you need, and whether or not the installation is straightforward or complex.

Items You Will Need To Install a Window AC In Sliding Window

Items You Will Need To Install a Window AC In Sliding Window

Window air conditioners are a tangible way to stay cool during the year’s warmer months. They are also simple and can be installed in many different types of windows, including sliding windows.

You must guarantee you have some essential tools and supplies before getting started. Here’s what you’ll need.

  • Deck screws
  • Saw
  • Screwdriver
  • Plywood Scrap
  • Electric drill
  • AC unit
  • Measuring tape
  • Scissors
  • Wrench
  • Ladder (optional)
  • Window sill
  • Weatherstripping

How To Install a Window AC Unit In a Horizontal Sliding Window

Installing a window AC unit in a horizontal sliding window requires some DIY know-how, but it’s not too complicated.  

Choose a Window

Choose a window that is at least 6 inches larger than the width of your new AC unit. If you want to find the exact size of your unit, look at the label on the side that says “BTU” (British Thermal Unit).

You will notice two numbers, one on top of the other – the maximum number should be ten times larger than the bottom. The top number is how many inches wide your unit is.

Be sure to choose a window that can fully support the weight of the air conditioner. Horizontal sliding windows are recommended, as they provide the most space for the unit and allow you to install and remove it quickly.


MAGZO Adhesive Foam Weather Stripping 1 Inch W X 1 Inch T, Thick Window Air Conditioner Sealer Open Cell High Resilience, Total Length 13 Feet (6.5ft x 2 Rolls)

Thick Window Air Conditioner Sealer

You’ll need to install weather stripping around the sides of your AC unit to prevent warm air from plunging through any gaps between the unit and the window frame. The weatherstripping you choose will depend on the materials used in your window frame.

Apply weatherstripping around the sides of your window frame to ensure no gaps between the frame and the casing. It will keep your unit secure and help stop air leaks that could affect its performance. Just measure your window frame carefully before buying it, so you know how much you’ll need.

Support Brackets 

Qualward Air Conditioner Bracket Window AC Support Brackets - Heavy Duty with 2 Arms, Up to 180 lbs for 12000 to 24000 BTU AC Units

Air Conditioner Bracket Window AC

These brackets will hold your AC securely in place while allowing you to open and close the window without removing it from the frame.

A support bracket is essential for keeping your air conditioner in place while you slide it into place on the track of your sliding window. Install the frame at least one foot from the top of the unit to prevent it from sliding out of place when you open or close the window.

Slide out the side panels of your air conditioner unit, then slide them back in until they click into place. Using one hand to hold it up, use your other hand to mark where you’ll need to drill holes for support brackets with a pencil. Be sure there is enough room for your window to open over them when fully installed!

Assemble the AC Unit 

You’ll need to assemble your air conditioner before you can plug it in. Attaching the side panels to the central unit is a simple process. Then, secure them with the two screws included in your kit.

The manufacturer will provide you with a kit and instructions for assembly, so follow them carefully. Once the unit is fully assembled, attach the accordion panels to either side of the air conditioner. These panels are usually foam rubber material, filling gaps between the AC and the window frame.

Read Also: How To Install A Window Air Conditioner In a Casement Window?

Closing the Gap

If your sliding window has a gap where it fits in the frame, you must use insulation strips or weatherproofing foam to close it before installing your AC unit. Closing this gap helps keep outdoor air from entering your home and keeps internal air from leaking outside.

You must also install a window seal or weather stripping around the window frame to close any other gaps to prevent heat exchange through those spaces. Again, this helps maximize your air conditioner’s efficiency, saving you money on energy bills over time.

It will also ensure security when you put it into the window. It also helps direct the airflow into your room instead of letting it out of your window! To close up those gaps, use weatherstripping tape and silicone caulk. 

Place Your Air Conditioner

After you’ve closed off any gaps, place your air conditioner in the window and set it down on a pillow if necessary to eliminate any possible vibrations. Then, slide open both windows about an inch. It will let your air conditioner rest against the frame of your window without sliding back inside your home.

If you have a screen installed in your window, remove it from its tracks, then place it back on once you’ve got everything in place. Make sure that it is balanced on both sides. You want to ensure that it fits inside correctly and that you cannot see any gaps while in place.

Securing the Unit

The last step is to secure the unit. First, you’ll want to screw the stabilizer bracket into the sash. Next, measure and cut the window seal foam. (The foam will be placed around the entire perimeter of the air conditioner.) Finally, press the window seal foam against your window frame, then put your air conditioner back in its spot.

Slide it against a piece of wood cut to fit snugly against your windowsill. Next, use a drill to attach some brackets to the top of the unit. It will keep it from moving around while you’re operating it.

Attach a couple of screws to the bottom of the unit. It will prevent it from falling out when tilting it back and forth to clean off your window sill.

Tips and Safety Considerations When Installing a Window AC Unit In a Horizontal Sliding Window

Installing a Window AC Unit In a Horizontal Sliding Window

When installing a window AC unit in a horizontal sliding window, you will want to use screws to secure it. In addition, you will want to keep the unit tilted slightly upward. It is to prevent condensation from forming. You can place the frame on a few small wooden blocks.

  • After you have installed your unit, you will want to check its level. You can do this with a leveler. If the AC is not level, it will not function properly and may even cause damage to your home.
  • You’ll want to ensure the AC unit is powerful enough to cool your space. Check out the air conditioner’s energy efficiency rating (EER) to do this. A higher EER is better! You’re looking for an EER of 10 or higher.
  • Ensure to take precautions while installing it to prevent it from falling out of the window and injuring someone. Have a friend hold it in place while you secure it with screws. It will help keep you safe and allow you to focus on lining up your screws correctly.

People Also Ask

How Do I Secure an AC in a Horizontal Sliding Window?

You’ll be happy to know that securing your AC unit in a horizontal sliding window is easier than you might think. The key is to install the support brackets, which will help ensure the unit is to both the window frame and the house’s side.

  1. First, ensure they are the right size for your AC unit to install the support brackets.
  2. Next, clean the area where they will be installed (the window frame and house’s side). Again, you’ll want to use a cleaner to remove dirt and debris before proceeding.
  3. Then, ensure that you have wooden screws if your frames are made of wood or vinyl or siding or sheet metal screws if you have metal frames.
  4. Once everything is ready, it’s time to install! Attach securely to the window frame and the house’s side using one bracket on each side.
  5. Add L brackets in front of each frame. It will prevent the window from being opened inadvertently, decreasing the unit’s risk of dropping out the window.

Is it Safe to Have a Window Unit in a Horizontal Sliding Window?

The answer is yes; having a window unit in horizontally sliding windows is safe—as long as you take a few precautions.

Many homeowners are concerned about placing their new AC unit inside a sliding window for fear of scratching or damaging the glass. In most cases, this won’t happen unless you’re not using an in-window support bracket as part of your setup process.

The bracket prevents the weight from sitting directly on top of the glass pane, which keeps it safe from being scratched or damaged by the weight of your new AC unit.

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