There isn't a great amount of literature on this subject it seems. I have an air conditioner, the manual assumes that you have a vertical sliding window, but I have one that slides horizontal, so how do I install the unit?

  • 1
    When I had mine, I had a window company build me a window that fit in above the A/C. A couple of 2 inch wide aluminum strips and silicon complete the job. At the time (over 20 years ago) it cost me around $75.00.
    – lqlarry
    Commented May 21, 2012 at 0:18
  • 3
    This Answer might help. Just tilt your head while looking at the images.
    – Tester101
    Commented May 21, 2012 at 16:10
  • @Tester101 my neck was hurting so I just turned my monitor sideways... Seriously a good -answer- comment.
    – lqlarry
    Commented May 22, 2012 at 0:06

3 Answers 3


Most window units are designed for double hung windows. If you want to place it in a casement window (or a sliding window) you really should use a unit designed specifically for that. Here's an example:

enter image description here


However, anything can be hacked. If you build a proper bracket/shelf, and then enclose the top part (plexiglass, for instance) you can probably use what you have (provided it fits, of course).


Most of the ones I've seen are install like this with a timber frame made to sit into the window frame then put the air-conditioner inside of the frame and box it out with plywood, but this looks like a much neater installation where the frame is made from c channel with a perspex panel above the airconditioner.

Perspex panel

It would probably depended on how long you intend to have the air-conditioner install in the window, as to which option you would go with.


Rolling portable units solve all such problems, The only thing that needs fit in the window, sash or slider, is the adapter for the flex duct (similar to a dryer duct) that takes the place of the AC's sitting inside the window or wall. Such units also have the advantage of portability: set them up quickly where ever needed or using whichever window is most convenient. As for casements--assuming that were all you had, the non-crank pane would need to be removed and modified to receive the duct adapter. The inside portable units also offer the advantage of easy cleaning and servicing; and an greater efficiency viz-a-viz a window/wall unit exposed to direct sun and hot outdoor temperatures; and cooling capacity which is not governed by window opening size. They are also much easier to find than vertical window units.

  • The OP said that they already have the AC.
    – Niall C.
    Commented Oct 23, 2012 at 14:20
  • Yes, I see. And apparently it is not new so it could not be exchanged. But, still (especially if well used) selling it and switcing to floor unit might be worth considering. Vertical AC units for slider can be hard to find usually sell for full list, nor for normal (discount); the time and expense of replacing with a sash window or building in a wall opening, depending on skill level, might not compare favorably with the price (and long term convenience) of a floor unit. So the post in question could be deemed as one solution to the problem. Thanks for the comment nevertheless.
    – Lex
    Commented Oct 25, 2012 at 4:13

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