How To Fit A Standard Air Conditioner In A Horizontal Sliding Window

Posted on: 6 June 2016

If you prefer to save money on home air conditioning, window air conditioners are the solution. Most window air conditioners are made for vertical windows, so they don't come with a bracket, and slider window units can be costly. It is possible to make a mount from plywood for air conditioners without a bracket. Here are some tips to install a window air conditioner in a horizontal slider window.

Prepare to Work

For this project, you need:

  • work gloves
  • safety glasses
  • tape measure
  • pencil
  • Phillips screwdriver or flat-head screwdriver
  • wrench
  • utility knife
  • hammer
  • foam weatherstriping
  • electric drill
  • skill saw
  • nails
  • plywood
  • L-shaped window bracket

Choose a window where the unit can easily reach an outlet, since an extension cord may not supply enough power. Open the window, and check the sill for rot or splintering.

The window must be strong enough to support the weight of the air conditioner. Replace the sill or choose another window if the chosen window shows signs of damage.

Make the Support

Measure the length and height of the air conditioner, and include vents in the measurement. Open the window, and measure the height and width of the opening, but not the frame, to figure how much space will needs to be covered around the unit. Deduct the air conditioner height measurement from the window height, and deduct the air conditioner width from the window width, then use this number for the mount. 

Mark the length and width measurements on the plywood. Use the utility knife to score the lines on the plywood, then cut the lines with the skill saw. Cut two short pieces and two long pieces. 

Drill holes in the boards for nails, and assemble the plywood pieces into a rectangle.Hammer the nails in place.

Install the Air Conditioner

Loosen the screws on the sliding part of the window frame with the screwdriver, and remove the window. Set the window and hardware in a safe place.

Insert and remove the the mount from the window sill to ensure it fits. It should fit tightly against the window frame. Set the mount in the window.

Get an assistant to help you set the unit in the window. Set the unit in the window with a slight tilt toward the outside to allow for proper draining. Drill holes on the inner window sash for the L-bracket, which prevents the window from being opened. Insert the screws, and tighten them. Cut and install foam weatherstripping to fill spaces around the unit.   

Turn on the air conditioner. If the air conditioner doesn't work, you may need to contact air conditioning repair in your area. They should be able to make sure everything has been installed correctly.  


Lowering Your HVAC Expenses

After we purchased our very first home, I realized that I was really struggling with paying for the heating and cooling costs. We were spending much, much more money every month than we thought we were going to, and it was really difficult to figure out what we should do. We thought long and hard about how to minimize our expenses, but we didn't really get anywhere until we talked with an HVAC contractor. He mentioned specific, actionable ways to lower our bill, such as programming our thermostat and using more of our ceiling fans. This blog is all about lowering your bill.

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