How to seal off an air conditioner in the top of a large window

Question

I recently acquired a new air conditioner, the Midea U, with dreams of a room both quiet and cold. However, when I went to install it, I found that it is too deep for the window I normally put my air conditioner in - the bars on the outside prevent the outside-the-window part from getting too far out the window.

There is a place in my window where the bars are set back, possibly intended for if one wanted to install a large air conditioner (top middle, highlighted on the image below).

However, if I put the air conditioner there, there will be a large gap above and to the left and right of it. I would like this area to be transparent so I can continue having a window, and I would like it to be at least somewhat soundproof, as there is a construction trailer with loud A/C units on it across the street. What can I do to seal off the rest of this area?

I rent, so no irreversible solutions. It's okay if it's expensive if it works well.

Answer 1

Use custom picture frames to fill the larger gaps on the sides of the A/C

Position the A/C to be sandwiched firmly between the top of the window frame and the sash. It looks possible. If there is a gap between the top of the frame and the top of the A/C, try raising the A/C on shims (eg strips of wood placed on the bottom of the metal cage) so the A/C is firmly against the top of the window frame while resting on the cage. Then push the sash up against it. Prop up the sash from underneath with pieces of wood.

Seal top and bottom Then use foam strips (they sell these for just this purpose) to seal the open gaps both top and bottom between the glass of one sash and the frame of the other. If you only seal one gap the inner space becomes very dirty. Forget about the screen. The seal should be formed between the two sashes and the foam strips you place between them.

Seal sides transparently If the A/C has plastic side baffles, remove them. Now you have a small gap on each side of the A/C. Measure them, go to a picture framer, and have them custom-build a pair of frames using a simple square-profile wooden frame and a heavy glass. Screw each of those to the A/C using the holes from the baffles that you removed (you’ll need longer screws). Screw the picture frame to the window frame on the opposite side (the only permanent damage you’ll do). Seal with something non-permanent like white electrician’s tape.

If possible remove and store screen You can't open this window now, so to increase light you can, if possible, remove the screen entirely and store it.

Answer 2

Plexiglas and pipe insulation.

1. Put AC in niche.

2. Measure spaces around it as rectangles.

3. Get plexiglas sheet. Maybe they will cut it at the store for you. Hopefully they will. Or you can cut it which is work. Cut rectangles the size of spaces you need.

4. Get pipe insulation. They are foam tubes cut along one side. They are cheap. Some depicted above.

5. Cut pipe insulation pieces to slide onto the 4 edges of each of your plexiglas rectangles.

6. Push rectangles into place around AC. The pipe insulation will insure a snug fit.

7. Glare balefully through transparent plexiglas. Optional.