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....


  1. yay for you daddy kasper!!!!! : ) your house will be nice and cold when we get there ; ) Can’t wait to see you!!!
    Love and miss you,

  2. Wheee!! =:) Oh yes, or at least, I hope so (that the house will be nice and cold for you guys!!) =:) I can’t wait to see you guys too!! Definitely love and miss you guys and am looking forward to watching you get knocked over by some wavies!! =;)

  3. A very nice looking job.

    This would also work on traditional wood windows.

    Does the window seal nicely on the new 2×4 ? I looks like it does.

    You might need to add a vinyl channel on top of the 2×4 if you get drafts coming in during cold weather.

    Best Regards

    Adrian D


  4. Hi Adrian! =:) Thanks!! And yes, you’re absolutely right–this would work with traditional wood windows just as well. Yes, it seals perfectly, and what I’ve done is to put some self-adhesive 1/2″ trim on the top and bottom of the 2×4, which eliminates any draft. And I take the air conditioner units out during the winter too… =:)

  5. Thanks for posting the photos and approach. I used 2x4s on my vinyl windows beneath the AC unit, with 4x4s beneath on the outside roof. Thinking of a different, more elegant approach. Question: with the 2×4 above the unit, you didn’t need any support beneath the unit when in the window? Thanks!

  6. Hey Barry! I’ve been using this set up for the past 2 years (this will be year #3, and I could not be more pleased with it. You don’t need any support underneath the air conditioner, from my experience. I was worried about that too, but the 2×4 is more than strong enough to hold up the weight of the air conditioners, from what I’ve seen. I don’t know that the air conditioner is at the same exact level that you’d get from the expensive metal mounting brackets, but we’ve not had any problems with the air conditioners since I’ve been using this approach. I guess it might be good to replace the 2×4’s every couple of years or so, for safety’s sake, but I haven’t had to yet, and the one’s I’ve been using aren’t showing any signs of wear. =:) Also, I actually saw this idea on the ‘net from someone else, but I don’t think I saved the URL.

    Hope this helps! I’d love to see photos of how yours turn out! =:)

  7. Hi Jason! I documented our installation, which used your approach as inspiration and adjusted as necessary. I setup a page with the explanation and photos. So far, so good – the things works well and cools the room nicely. It also looks better than expected, thanks to your tip on the white paint. –Barry

  8. Hey Barry! Wow, that looks really, really nice!! A couple of comments…. I read that the bottom part of the window frame was not made to support the weight of the air conditioner and that I should support it with wood as you have done, but I’ve just been resting the a/c unit on the bottom of the vinyl window frame and thus far, I haven’t seen any problems yet. But I do like what you’ve done. Do you have any other pictures of this–maybe bigger and zoomed in on just this bottom frame not inserted in the window yet? I’d like to see exactly what you did here.

    Also, I really like the idea of using 2 1×4’s instead of 1 2×4 as I’ve done, but I’m not really clear on exactly how you did it. Are the 1×4’s in 2 separate vertical side channels of the window frame? Are the 2 1×4’s screwed together? How did you get them into the window channels? That’s one of the most annoying parts that I’ve found–getting the 2×4 to be just wide enough to still rest in the channels but not wide enough to prevent me from putting it in at an angle so I can slide it into the channels. Do you think you could explain this part a bit more and take some pictures?

    Thanks very much for letting me know of your work and for the credit! =:) I like what you’ve done!!!

  9. Hi. I have been searching and searching for a way to mount our window air conditioner in our new vinyl windows. This has inspired me as we did not want to spend all the extra $$ on central air or ductless air. I would also like to see a more close up picture of the bottom of that frame that you made.

  10. I too like Karen have been searching to put in a window not central air. I would love to see more detailed pictures from Barry for the do it yourself challanged but willing to try.

  11. With your way you can remove the air conditioner for the winter and close the window. Barry’s way looks permanent(wood across the area where the bottom window goes when it closes and locks). How have you secured the air conditioner to the window so that it can not be removed by burglars but can be removed by you for the winter? (adhesive, screws or ?????)

  12. Hey Jan! =:) Yep, mine is trivially simple to remove during the winter and store the a/c’s in the basement. Also, I have screwed the top of the a/c unity into the 2×4 that holds it in place. there is nothing holding the bottom of the window onto the top of the 2×4 underneath it, but there’s only about 4 inches of room for a burglar to get through if they absolutely wanted to, and my a/c units are at least 10 feet off of the ground. And I live in a forest. If someone was determined to burgle me, there would be far easier ways of breaking into my house to find me waiting for them with a shotgun. =:)

  13. Jason, I hope you see this because it’s such a fabulous idea, but I have a few questions. Maybe there are some steps left out that are probably self-explanatory for the handy but I’m getting lost from the chisel out step. Exactly what is that being attached to?

    I love the idea so much! But I’m just having a hard time understanding how you are able to attach this from above.

    We were told we void the contract with the vinyl window comp. if we damage or put holes in the frame. We would LOVE to find a way to use our window air conditioner. Security isn’t really a concern (second floor).

    Thanks for any help with more steps for this project for the challenged!

  14. Hi Carol! =:)

    So, the 2×4 fits in the grooves in the side of the window frame, and the air conditioner rests against the 2×4. So, the first problem is that the depth (not length) 2×4 is too thick to fit inside the window channels as it is. That’s why I notched the ends of the 2×4–to a thickness that would allow the 2×4 to fit into the window channels. The second problem is that you have to cut the 2×4 down length-wise so that it is long enough to fit horizontally in between the window channels and overlap enough inside them to have good strength still, but you have to make it short enough so that you can put the 2×4 into the window frame at an angle and then slide it in place so that it’s perfectly horizontal. I’m not sure if I explained that clearly enough. If not, just let me know and I’ll put up some more explanatory pictures.

    FWIW, if I was going to do this over again and hadn’t already cut the 2×4’s down to size, I’d use 1×4’s like @Barry suggested and showed here: http://joycemajor.com/household/air-conditioner-in-vinyl-window.html

    HTH! =:)

  15. Thank you so much for the prompt response and input. Can you tell that I’m eager to have a darn air conditioner in my bedroom?

    We just got the vinly windows at Home Depot and according to them if you put any screws in or damage the frame with an air conditioner you void the warranty. Wish I would have known that before purchasing the windows.

    Thanks so much!

  16. Thanks for the detailed instructions. I impetuously screwed in 4 a/c window units to our new vinyl windows last night before finding out it might not be a good idea. They seem to be holding all right. They are not anywhere near where they could let argon gas escape. Why is this a problem (besides possible voiding the warranty, which would be a problem)?

  17. Hey Mark! I think the biggest problem is that the vinyl window frames are just not built to have screws put into them (they’re not solid vinyl and screw holes strip really easily), and they are nowhere near as stable as wooden windows, nor do they support the weight of the A/C windows without bowing.

  18. This was really helpful, thanks alot.

  19. Hey Jason, thanks so much, I’ve been trying to figure out a way to do this! My only question, and maybe you already answered it and I just didn’t catch it in reading everything, is this: do you have a formula for arriving at the cut length of the 2×4, as far as being long enough to fit securely in the track, but short enough to allow angling it and slinding it INTO the tracks? That sort of trial and error scenario is the part thet makes me NUTS in a project like this, lol, and I don’t want to mess up and cut the thing too short! Thanks!

  20. I’ve got a SLIDING/Horizontal Vinyl Window. Seems almost impossible to get my air conditioner installed. I already had a portable one, but once the temperature is above 90 Degrees it’s not that effective.

    So I’ve got my new air conditioner just sitting here.

  21. Hey Jim. Sorry for the delayed response. =:( I’m guessing you probably have already figured this out by now. To answer your question, I forget exactly how I figured the right length of the 2×4. I think it was just trial and error for the first one and then after that, I used the measurement that I arrived at. It should be pretty easy to arrive at the right length by just looking at the length of the diagonal line of the 2×4 and making sure that’s equal to the width of the inside channel of the vinyl window frame.

    James: Sorry, but I’m not sure how you’d get an A/C unit into a horizontal vinyl window. =:/ I’d probably look at the inside A/C units that just have a small hose that runs out to the window instead of trying to mount an A/C unit in the window frame itself. =:(

  22. Thank you for posting this work around. We have AC in our rental home, but the duct is destroyed leading to the master bedroom. I finally gave up and bought a window unit, but didn’t want to screw it into the landlords vinyl windows. You Flicker photos were so very appreciated.

  23. Thanks for the feedback, Bex! So glad this was helpful! =:)

  24. Wow! Smart. But, is this considered a permanent installation? I would like to remove it for the winter…I guess it wouldn’t be that hard.

  25. Yeah, it’s totally non-permanent. I take mine out every fall.

  26. Got an email notification that there was a new post in this thread today. Made me laugh since I’d just brought the 2x4s from last year (yeah, got lucky & figured the length right the FIRST time!) out of the basement…to finally prime & paint them for this year (it was too hot to waste time on that last year). Temp today unexpectedly hit 90…maybe I’ll paint them when I REMOVE them in the fall!

    I have 3 different types of vinyl windows here, frames all protrude 1″+ above the wood sill, so I use commercial steel a/c support brackets as well, to avoid the unit sitting on the vinyl frame. One of the window styles is especially weird (RAISED bed between bottom sash & screen), so with the bracket in place the a/c sits slightly above the frame. Last year I sealed gap with white duct tape (anything in a pinch), but today I built up the sill with 2 2x4s cut to window width, and everything fits great. It also adds a bit more security, which is good since I’m on the first floor of a house in the City.

    Thanks again, Jason, your great idea, and sharing it with us, was a lifesaver after I replaced the wood windows!

  27. Hey Jim! So glad to hear it helped! =:)

  28. Thank you for this, took quite a bit of google-fu to come up with the right word salad for a window AC bracket with flush exterior windows. Just did this today with a quick notching of a 2×4 and it worked brilliantly. Considered a 1×4 but liked the stability in my vinyl windows better with the notching. You sir win the internet!

  29. LOL! Thanks! Glad to hear this helped! =:) FWIW, this year, I’m buying all new portable A/C units which will alleviate this problem as well as the whole back- breaking lugging the window units up 2 flights of stairs to boot!

  30. We did the portables when we were apartment bound, had a Royal Sovereign model with dual hoses that did great. I recommend dual hose models otherwise you will be having to drain the AC a lot when humidity is up. And remember to put the plug back in the drain after winter if you have a single hose model (our other one, a Kenmore) otherwise you’ll be ready to blame the pets for peeing the carpet 🙂

  31. I have been meaning to do something like this, but really have no power tools at all so have been trying to come up with something else. I found some 11/16″ MDF boards that fit nicely in the slot that I was going to use, but am now getting paranoid that they might not be strong enough to hold the air conditioner. From prior experience, I know that people tend to underestimate the strength of wood, so would like your opinion as to whether this would be a good option or if I should try to find a handyman to do this more like your mock up.

  32. How are the portable AC units working for you? Two years ago I bought a portable unit for our bedroom because I didn’t think the vinyl replacement window should have a window AC unit. Our 1870’s house has central air, but upstairs doesn’t cool off to well. I bought an LG for a little less than $300. It cools well. I like that it’s easy to put away in the fall (basically, I just roll it to a closet). The problem we are having is that the stupid thing sets off an alarm that the fluid chamber needs to be emptied. . . about every hour. Yeah, it’s lovely at night being woken up every hour or less. Not sure if Illinois is just too humid for this unit? But even when I empty it, a few minutes later it’s going off again that it needs to be emptied. Today I read some reviews of this unit, and it seems to be an issue. (There’s that hindsight thing showing up to bite us in the backside!) So now I’m looking at a window unit…which led me to your tutorial. I just looked at our windows again and it would seem that ours would require more complicated notching (and I can see that being an issue with the hubby). So my question is, what if we don’t notch? And just make it fit snug against the sides as best we can. Also thought that the smaller piece of wood underneath like Barry mentioned is something we would do too.

  33. Hi Lisa! The portable AC units are working great for us so far. I bought 3 14,000 BTU portable Whynter units from Amazon (http://is.gd/glGOOz) and I had another 12,000 BTU Commercial Cool unit I bought from Walmart. The Whynter portables are dual-hose, which are supposed to be the best way of doing portable units since they isolate the motor-cooling from the room-cooling airflow paths and should prevent hot air being pulled into the house by the portable A/C unit to replace the air being pumped outside with the one-hose model. The Whynter units are also evaporative or auto-draining which theoretically should mean that we won’t have to empty the fluid chambers ever. The Whynter units were a little pricey ($500 a piece), but we have Amazon Prime, so shipping and handling was free for 2-day delivery.

    Thus far, I’m very happy with the units we bought. Summer came early for us this year and we’ve used them for a couple of weeks already, even though the weather has cooled down again, and they worked very well for us. I’m even more happy about not having to lug 4 80+ pound window units up 2 flights of stairs to install them this summer. And if they continue to work as well as they have thus far, I’ll be ecstatic about not having to remove the 80+-pound window units at the end of the summer and haul them back down 2 flights of stairs. So I won’t be able to really answer how they’ve worked for us until probably next year, but thus far, I’m very pleased.

    As far as the notch goes, I don’t know that it really matters whether you notch a 2×4 or use a single piece of wood that is wide enough to fit in the notch without cutting it. My concern would be the amount of weight being exerted against the middle of the board by the air conditioner. With a 2×4, that’s not a concern. With a 3/4″ piece of plywood or something, I’m not sure. I’m thinking it might be okay, but maybe just watch it and make sure it’s not bowing outwards.

    Anyway, I’m curious to see how this works out for you, so I’d love to see pictures and hear how it goes. Good luck and happy cooling! =:)

  34. Gah, I’m sorry, Joleen, I totally missed your comment! It sounds like you’re thinking of doing the same kind of thing as Lisa. And honestly, I don’t know how well a thinner wood would hold up with the weight of the air conditioner. The problem as I see it is that the majority of the weight is going to be concentrated towards the center of the wood board. With a 2×4, the advantage is that that weight is more evenly distributed across the board until it reaches the window channels because the 2×4 is 1.5″ thick–thick enough to stand on and not bend the wood. With a piece of plywood or MDF, that force is going to have a greater effect in the center of the wood, I believe, since MDF/plywood is generally 3/4″ thick (half as thick as a 2×4). I’d be worried about the wood bending enough to the point that it falls out of the window channels or breaks entirely.

    Another thought is that you’re going to have to get the wood in place by angling it in. With a 2×4, that’s not a big deal because the height of the wood is only 3.5″ (so the diagonal line between 2 opposite corners isn’t going to be much greater than the length of the wood). I would think that to make up for the lack of thickness of plywood or MDF, you’d want to use a taller piece of wood, which is going to mean you’re going to have a tougher time angling it in place. The problem is that the diagonal line between two opposite corners is going to be longer with a taller piece of wood.

    Hm. I could have sworn I saw somebody who said they used a 1×4 instead of 2×4 wood, which would be similar to what you were suggesting with the MDF or plywood (which should be roughly 3/4″ thick). But I can’t find it now.

    Anyway, I’m very curious to see how you ladies made out and how things turned out for you if you used thinner wood than 2×4’s. =:) Hope everything is well with you! Please be safe! Air conditioners are heavy and can seriously injure, if not kill, anything they fall on.

  35. Hi Jason,

    Thanks for the idea–worked perfectly on three units that I installed in vinyl replacement windows!


  36. This idea is absolutely genius!!!!! Worked great for us too. You are awesome!

  37. Jason, I just got new vinyl windows last weekend and need to put an AC window unit in a window upstairs. Its a small unit about 7000 BTU’s. Looking at your photos it looks like you made three pieces of notched 2 by 4’s. However looking at your final assembly photo I can only see one 2 by 4. Where are the other two? Do you have the AC unit setting on a 2 by 4? Is the AC unit setting on your wooden sill trim inside your house or on the vinyl window? My vinyl window has a lip of vinyl material raising up about an 1-1/2″ above my interior wooden sill trim. I’m thinking of attaching wood to my interior wooden sill trim and raising it flush with the window lip to help support the unit and not damage my window.
    My exterior brick molding has been wrapped with PVC coated aluminum.
    Thanks Rick

  38. Hey Rick! Yeah sorry for the confusion, but the pic shows 3 notched 2×4’s because I was installing 3 separate air conditioners. For my particular installation, I felt comfortable resting the bottom of the window units right on the vinyl window sills. The 2×4’s held the top of the A/C units into the window channels and the bottom of the air conditioners just rested in the bottom channel or sill of the vinyl windows. But yeah, it might be a good idea to put some wood underneath the units so they’re not directly resting on the vinyl window frame. HTH!

  39. I’m getting new vinyl windows throughout the house. Was reading the details of the warranty and immediately thought, my A/C units are going to void this thing the first summer. You’ve solved it! Brilliant! And may God bless you for your generosity in going to the trouble of building a tutorial to share with strangers.

  40. Heh. Thanks, Kevin! So glad this was helpful to you!! =:)

  41. Jason, I’m going to give this a try tomorrow. I’ve been looking for a solution and this looks absolutely doable. Very clever, yet simplistic. The pics really help to. I’ve seen a number of DIY frames on the internet, but they all seem kind of complicated to make. Thanks

    p.s. considering you posted this 12 years ago, you’re really getting some mileage on this tip 🙂

  42. Hi Jason,

    I get a 404 error when I try to look at the pictures. From the other comments, it seems that the pictures were available a year ago. Have they been removed? I just bought a very heavy window air conditioner and would like to see how you mounted yours. Thanks!

  43. Hey Becca. Yeah, I took down my flickr account, where all these photos were stored. Let me see if I can find these pictures and make them work again. Thanks for the heads up!

  44. Okay, I found these photos and just uploaded them to my blog. Sorry for the temporarily missing pics! =:)

  45. Your post lives on!

    I’ve learned one thing through the years, I will NEVER have vinyl windows again. I have the two lips over an inch at the bottom where the widow goes when shut, I have the too narrow channel for most brackets.

    I need to install a 14,000 BTU window unit since we burned out our 12K portable unit last year. It died a slow death in the heat when the 90 degree days and nights set in. They just aren’t as robust as the window units.

    So I bought the Ivation window AC bracket, good for 200 pounds. Solid unit, braced by inside frame and bracket arms against the outside of house. The LG AC unit also comes with a sleeve, which should make this a bit easier to install and take out.

    All I need now is a solution for the two rubber feet which brace against the outside of the house (most of the support). I don’t want to permanently dent or even crack the vinyl siding.

  46. Steve: oof sorry to hear that! Yeah Ive had better luck with smaller multiple portable AC units than the big ones. So were you saying that the 2×4 approach wont work for you? It would at least not risk damage to the vinyl siding?

  47. For the purpose of security, where you used a piece of pvc pipe, i have used a spring-loaded curtain rod. This keeps downward pressure on the window which prevents the window from vibrating open while preventing someone from opening it from the outside. Best of all, no measuring or cutting since the rods are adjustable.

  48. Thank you so much for this DIY! I have an elderly dog that suffers in the heat
    and can’t climb the stairs to the second floor AC (mounted in a wood window).
    She’s going to appreciate her new AC and I didn’t have to damage my vinyl windows installing it, win-win!

  49. That looks FANTASTIC!!!!!
    Sadly I am all thumbs and don’t own a circular saw.

    It’s too bad too because from the hardware and descriptions I think I have the same exact vinyl window.

  50. The post that won’t die! Google loves timeless content for sure.

    Thanks for this great tutorial. I’ve got vinyl clad windows too but sadly, they’ve got 1″ high “guard” across the bottom of the window frame. I suppose that it’s there to improve the seal. but it seems to make a window A/C unit a no go for me!

Leave a Reply

Required fields are marked *.


This site uses Akismet to reduce spam. Learn how your comment data is processed.