A: Most window air conditioners are designed to fit in windows where the bottom sash — the movable framed glass section — slides up and down. These windows are called double-hung or single-hung, depending on whether the top sash also moves or is fixed.
Either way, the procedure for installing the air conditioner is the same, and manufacturers typically give pretty clear instructions:
- Heavy units come with a support bracket that extends outside but usually can be installed from inside; lighter-weight units skip the bracket and are held in place by pressing against window parts.
- Installers open the window and lift the air conditioner into the opening. They position it so the bottom edge of the unit fits against the outside lip of the window stool (a trim piece across the bottom that many people refer to as the sill, although technically that word refers just to the exterior, slanted piece at the bottom of the window.)
- Then they lower the sash and tilt the unit so the bottom of the sash fits into a flange at the top of the air conditioner. The air conditioner tilts downward from the house on the exterior, which helps it shed rain. But probably even more important, it creates pressure pushing inward against the stool at the bottom and outward against the sash at the top. That holds the unit in place, although manufacturers also tell people to add a few screws to keep everything from moving.
- Most new units come with extendible pieces and strips of foam to fill in gaps on the sides.
With sliding windows or with casement windows, which crank open, installing an air conditioner gets more complicated. Relatively few units are designed for installation in these windows. Searching the Home Depot website for window air conditioners, for example, turns up more than 140 models, but only two are designed for casement or sideways-sliding windows.
The air conditioners themselves are probably not all that different, although they have more of a vertical look. The big difference is that they come with various attachments that make it easy to support a unit when there is no top sash to lower and to fill in the space above the unit with something that’s more attractive than the plywood you resorted to.
However, if you already have an air conditioner, you can probably rig up suitable add-on components on your own. To see what type of things you can add, start by reading the installation instructions for a unit such as Frigidaire’s 10,000 BTU Slider Casement Window Air Conditioner ($639 at Frigidaire.com).
Here are some suggestions to guide you.
- For starters, you will probably need a support bracket if you don’t already have one. Make sure it’s rated for the weight of your unit. The Turbro ACS-100 universal window air conditioner support bracket ($38.88 at Home Depot) supports up to 100 pounds, more than sturdy enough for the Frigidaire model, which weighs 72 pounds. The bracket manufacturer notes that it might not be as easy to install on plastic or metal windows, but if your old house has wooden window frames, it should be easy. It was designed to work with Frigidaire models, as well as some from other manufacturers. Securing the air conditioner to the bracket should hold it in place.
- To fill the gap above the air conditioner, the Frigidaire kit includes a plastic frame with a slot for a plastic insert. You should be able to duplicate a frame made from strips of wood or plastic molding. Make the frame as wide as the window, but give it “legs” that extend down alongside the air conditioner, which will help hold it in place. Use smaller pieces of molding to create a lip above the air conditioner, and fit piece of clear plastic into that area so that you can see out of the window above the air conditioner.
- For the plastic, you can get acrylic or polycarbonate. Acrylic, often referred to as Plexiglas, a brand, costs less than polycarbonate (a.k.a. Lexan, a brand). Polycarbonate is less likely to break and doesn’t scratch as easily, but it’s more likely to yellow over time. For your purposes, either probably would work just fine.
- Use strips of foam, rather than caulk, to fill gaps between the frame you make and the window opening in your house. It will make it much easier to remove the setup come winter.
- Consider getting a side panel kit with accordion-type panels that you can extend to fill the gaps on the sides of the air conditioner, such as a Maxclimate kit ($39.99 on Amazon).
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