Installing a Window Air Conditioner in a Tilt Window

A window AC unit.

It can be difficult to install a window air conditioner in a tilt window, also known as a casement or crank window. These windows do not slide out, but instead a portion of the window lifts up, making it difficult to fit the outside part of the window air conditioner. However, it is possible, and there are two ways to do this.

Installing a Window Air Conditioner

For anyone wondering how to install a window air conditioner in a tilt window, you need to first establish the kind of tilt window you have.

Half Tilt

The most important thing to do is to check that the window you have chosen is suitable for use with a window air conditioner. Check that the window frame is firm and without cracks or signs of rot. If either of those signs are there, the frame may not be able to support the air conditioner unit. Check that the hinge in the tilt window is in good condition.

At this point, you will need to remove the portion of the window that does not tilt and replace it with a balsa wood panel. This will reduce the amount of light available to you, but you can drill a suitable hole through the wood and fix the window air conditioning unit together.

Prime the balsa wood, and then paint it with long-wearing paint. Insert in the opening. Slide the window air conditioner sleeve into the plywood and fix it. You may wish to add wooden spindle supports here.

Attach the sleeve to the plywood with screws, and seal around the rim of the air conditioner. Caulk around the edges of the plywood where the wood and the window air conditioner touch.

Vertical Tilt

Another type of window is the vertical tilt window, where the whole window moves.

Lift the window all the way out, and screw in the metal support bracket, as per the owner’s manual. Ensure that the bracket is straight, and then lift the window air conditioner onto the bracket.

Close the window and note where the window touches the AC. Weatherstripping should be placed in any area touched by the unit. If the window and the window air conditioner do not touch, extend the side panels.

Caulk the edges of the window frame, sealing the areas where the window air conditioner meets the window. This prevents cool air from leaking out.

Another Alternative

Modern suppliers of window air conditioners have created models specifically designed for tilt windows. These units are modified so that a homeowner can easily attach the outside part to a tilt or sash window without having to replace the glass. These devices come with careful "how to" installation instructions, which should be read carefully before installing.

If in any doubt, it is cheaper to hire an expert and pay the full price for their skills, rather than risk damaging the window frame and having to call in someone to sort out the mess.