How To Install A Window Air Conditioner In a Casement Window?

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How To Install A Window Air Conditioner In a Casement Window?

Installing window air conditioning units in casement windows may seem daunting, but it’s not. Of course, it would help if you had the correct equipment, a little know-how, and time to complete the job. Most come with instructions on installation and steps to ensure a proper, safe facility.

Installing a window air conditioner requires all the right tools and materials. First, you must determine the location for placement. That means it needs to be centered on the window sill for most people. You will also need to choose the width of your casement window opening to determine how long your extension cord will be.

This article will help you determine the unit’s right size to fit the existing opening of your casement windows and give some tips for you to consider when installing your new window unit.

What is a Casement Window?

A casement window is a class that opens by swinging outward on a hinge. This window is generally held open using a crank, lever, or cam handle. Because they are opened with a crank mechanism, casement windows can be opened quickly and to any desired width.

Casement windows are suitable for modern homes due to their practicality and versatility. They can be installed on top of other windows and let in light and air rather than different window styles. 

Casement windows have the following benefits:

  • They open wide, allowing you to use airflow with less effort than other types of windows.
  • Because they are opened using a crank, casement windows are easy to use. 
  • They are handy for people with limited mobility or strength, requiring less effort than many other types of windows.
  • Casement windows make it easier to minimize drafts – close the window tightly against its frame when you want to seal it against the weather.

Can You Use a Window Air Conditioner In a Casement Window?

Yes, window air conditioners are designed to fit both casement and double-hung windows.

The frame has side panels on each side of the unit, which can slide back and forth to adapt to the width of the frame so it fits the window’s width. That makes them compatible with casement windows, which have a crank handle that allows you to open and close them.

Some models of air conditioners are available that feature a removable chassis for casement windows. It is designed for windows that do not open out.

Window Air Conditioner Installation In a Casement Window By Yourself

As a do-it-yourselfer, you can save money by installing your window air conditioner in a casement window. Window A/C units can be heavy and must be installed securely to operate safely and efficiently.

With just some essential tools and instructions on installing an A/C unit into a casement window, you can cool your living space down quickly and efficiently.

Here’s everything you need to know about installing an air conditioner in your casement window.

1. Materials You’ll Need

Let’s examine the materials and tools to install your new casement window.

Equipment and Tools

  • Screwdriver
  • Drywall T-square
  • Pencil/Marker
  • Tape Measure
  • Ladder
  • Cutter


  • Selected Casement window A/C unit
  • Wood boards with accurate length and depth
  • Medium-sized particleboard 
  • Heavy Duty Plywood piece 

2. Choose Location

First, you’ll want to choose where to install your window AC unit. It should be a room that needs cooling and doesn’t already have an AC unit in the wall or ceiling. Some parts of your home are better suited for window units than others. 

Find a spot in your window where installing the unit and getting it out again is relatively easy. Some good places are living rooms, garages, or even bedrooms.

Ensure no outlets are in the way unless you use an extension cord. You should also check for adequate clearance around the unit to have enough room for airflow.

3. Choose Unit

Pick one that will fit appropriately in the selected space. Measure the area before selecting, and keep measuring until you’re sure.

Choose an appropriate unit for your room and ensure it will fit inside your window. Next, move the team into position and check if it will do. You may need to eliminate the side panels on the unit or turn the unit sideways. 

Midea 5,000 BTU EasyCool Window Air Conditioner and Fan - Cool up to 150 Sq. Ft. with Easy to Use Mechanical Control and Reusable Filter

Midea 5,000 BTU Window Air Conditioner

If your window is old, you may want to replace the windows before installing a new air-conditioning unit. It can save you money over time, plus the added insulation will help keep the cold air in and restrain hot air from entering your home through cracks in old or damaged windows.

4. Build the Support Base

This can be done by using scrap wood, cinder blocks, or anything else that has enough weight and is stable enough for your needs, as long as it doesn’t block any vents on the side of your home.

Most units over 6,200 BTUs will require this step. The accessible way to do this is with 2x4s and plywood cut to the appropriate size. You can then place the base on top of your windowsill and drill it with 3-inch deck screws or lag bolts.

Rip a piece of plywood that is the equivalent of width and height as the opening. Place it on top of the windowsill. Slide the air conditioner on top of the plywood, then secure it with screws into either side of your window frame.

5. Install the Support Base on the Windowsill

Measure the width of your window and cut two pieces of lumber to this length. These will be the base pieces or the top and bottom.

Measure the height of your window and cut two pieces of lumber to this length. These will be the sides that are going to support the base pieces. The ends of these side pieces should be cut at 45-degree angles for a mitered joint with the top and bottom base pieces.

Use a level to ensure your base is level, then attach it to the windowsill using wood screws or nails. Next, you create a box inside the window frame that supports your air conditioner unit.

Read Also 

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

How To Install a Window Air Conditioner In Sliding Window?

6. Determine the Center Point

Measure from each side of the windowsill to find its center point. Next, measure half the width of your unit, add 3 inches, and mark this point on each side piece. It will be where you mount your bracket hardware to attach your A/C unit to the window frame.

Position the A/C unit in the window, ensuring it rests on the support base you installed earlier. You’ll need to ensure that the top of the A/C unit is at least four inches above your windowsill before installing.

If you have a metal security screen in front of your window, remove it before sliding the air conditioner. Leave the plastic window guards in place.

7. Position the A/C Unit in the Window

Ensure that the front legs are placed on the window sill and resting on its side, with the back panel pressed against your side of the window frame.

Open the window and establish the air conditioner into the opening. Again, you can have someone help you with this step. Rest the bottom of the air conditioner against the lower window sash, and lean the top against the upper strap.

Position the unit so that its back is about one inch from the front edge of the windowsill to allow for proper drainage, and make sure it’s centered in the window opening.

8. Make Sure the A/C Is in Proper Alignment

Once your unit is settled into place, you’ll want to ensure that it’s in proper alignment. You can open and close your window until the A/C is centered. The open part of the window should sit flush with both sides of the air conditioner unit for proper fit. 

If there are gaps, move the A/C or use shims to correct its position.

You must ensure your air conditioner is appropriately aligned on the sides. You may have difficulty fitting it correctly into place if it is misaligned. To check for alignment, open both windows perpendicular to each other and close them again to work together as a standard window would.

9. Fill the Top Gap

Make sure the window is open at least halfway. Then measure the height of the opening and compare it to the specifications for your air conditioner model. If there is a difference, adjust your bracket accordingly.

Attach the support bracket on the window frame using a hammer and screwdriver. Place the unit inside the window, ensuring its bottom edge is flush against the shelf, and its sides are resting on its frame.

Hold it while you drill screws into each bracket through holes in the air conditioner’s sides. Use foam weatherstripping tape to fill gaps between the unit and the wall so that no outside air can get in or out.

10. Create a Tight Seal

Set your A/C unit at an angle to fit into the window frame and create a tight seal. The bottom of the A/C unit should fit snugly into the bottom of the window frame, and the top should be positioned just above where you want it to end up. 

Press down on the top of the A/C unit to bring it down into the window frame and ensure that the sides fit tightly into their slots.

Make sure the foam weather stripping is in place. If not, add it to the bottom edge of your window frame. The unit should sit on the foam weather stripping to give an airtight seal.

Can You Install a Portable Air Conditioner In a Casement Window?

portable air conditioner in a casement window

Yes, you can install a portable air conditioner in a casement window. 

Installing a portable air conditioner in a casement window is easier than sliding windows.

Since casements are designed to be opened like that, they will stay stable and prevent accidents while keeping your portable AC safe from any damage if you place it on the ground outside.

You’ll also want to ensure that your portable AC is correctly sealed using plywood or Plexiglas.

Can a Window Air Conditioner Be Installed In a Wall Sleeve?

Yes. Wall sleeve installation is usually less complicated than a window installation, and you can use your unit’s slide-out chassis to make the process easier.

Wall sleeves are designed to hold window air conditioners and can be easily installed on a wall or through an exterior wall.

Many window air conditioners can be installed in a slide-out chassis wall sleeve designed to fit into a pre-built hole in the wall. This sleeve type is typically an aftermarket product, so before purchasing a window air conditioner, ensure it has a slide-out chassis.

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