Kasperian Moving Parts

kinda like Batman, but with a wife and 3 kids

Double-Hung Vinyl Windows and Air Conditioners


The final product

Or, possibly titled “How to hang that pesky, 50-pound window air conditioner unit in those purty little vinyl windows that you can’t stick screws into.”

We have beautiful, wonderful double-hung vinyl windows, yay us. They’re very pretty, very functional, operate very smoothly, etc., etc. HOWEVER, they do NOT play nicely with window-unit air conditioners (you can’t screw the air conditioner into the vinyl window parts). So after getting a brilliant idea from a newsgroup post, and not willing to pay $40 for a metal air conditioner brace that I can’t really use anyway (again, vinyl window sill), I set out to make my own air conditioner brace out of a 2×4, some white paint, and a little sweat. Turned out purty nice too, I must say.

I was really pleased with the final outcome of this little product. What started out as a crazy idea with me looking (to my bride, at any rate, who pointed it out several times) like I was just trying to not pay $40 for an air conditioner brace turned out to be a really nice solution. First, I didn’t have to drill any holes into the nice vinyl window frames or sill (they wouldn’t have held anyway). Second, the air conditioner is MUCH more stable by mounting it from above to the window sill than below to the frame. And third, there is no way this air conditioner is going anywhere, unless the entire window frame decides to exit my house. =:)

Here’s some pictures of the process. I hope this helps someone else!

Don’t screw into the vinyl window sill or frame!!
The vinyl window frame has a channel that the window slides up and down in. I cut a 2×4 to fit into this channel. Step 1 was measuring where my cuts would be on the 2×4 with a paint stirrer I had lying around. I wanted the 2×4 to fit inside the channel with the rest of the 2×4 sitting against the frame.
I set the depth on my circular saw to match the offset from the edge of the 2×4 to the channel. I did this twice, once per side of the 2×4.
I drew lines on the 2×4 showing where I wanted to cut and then chisel.
Another view… the lines where I wanted to cut with the circular saw, to the depth I wanted, and then chisel out the rest.
Here I’ve cut the depth to the channel from both sides of the 2×4.
Another view, having cut to the depth of the channel offset from each side of the 2×4. Note that I had to change the circular saw depth for each cut.
Double-checking my work before chiseling the rest out. Making sure that the 2×4 will fit into the channels. Left side looks good.
Right side looks good too.
The goal here was to clear out the rest of the wood between the top and the channel we cut on the 4 corners of the 2×4. Using a chisel here was pretty easy, assuming you have someone who can hold the 2×4, since you’re going into the grain of the wood and then just pulling the chunk out.
Next I painted the 2×4’s with some glossy white paint I had laying around to match the white trim on the windows.
The hardest part here is being patient. We had 3 windows that needed A/C units, so I did 3 2×4’s and painted them all at once.
Here’s the finished product. Painted, dried, installed. The trick to installing the 2×4 is that you have to insert the 2×4 at an angle and then rotate it into place in the channels. So I raised both windows up to the top, obviously did not have the A/C unit in place yet. Then, put the 2×4 into the channels, at a 45 angle, and then slide the top end down and the bottom end up until they’re fitted in the channel and the 2×4 is sitting flat.
Left and right side of the expandable A/C curtain have to come up a bit higher than they normally would to rest on top of the window frame at the bottom and screw into the bottom of the 2×4 at the top. It felt a little weird doing it this way, but in practice, it worked well for 10 years for us and never caused damage to our A/C units.
I also opted to drill a new hole into the top of the A/C unit frame to get it to sink more solidly into the 2×4. Your mileage may vary greatly here and I’m sure there’s other ways of doing it, but I wanted to make sure it was solid.
And there’s the finished product. If you look carefully, you can see that the left and right edges of the expandable curtains sit at a bit of an angle rather than perfectly straight, but this never caused a problem for us.
This unit was in our front-facing living room. As you can see, I drilled 2 new holes at the top of the A/C frame and used some heavy duty wood screws to anchor the A/C to the 2×4. I wanted to make sure if anyone tried to break in, they’d have to remove the entire window frame to get in.
I also added a bit of cut white PVC pipe at the top of the window to make sure nobody could raise the window frame and get in that way. If you’re not dealing with vinyl windows, you usually screw the top of the A/C unit into the bottom of the window frame, which secures it a bit. Since you can’t do that with vinyl window frames, I locked the frames in place with this white PVC pipe, which you can’t even see from the inside of the house, and which blends in nicely with the white window frame from the outside.

Author: Jason 'vanRijn' Kasper

My name is Jason 'vanRijn' Kasper. I am the ring leader of the amazing Kasper family. I am unashamedly a Christian Nerd. These are our stories....


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