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3 Simple Casement Window Air Conditioner Solutions

Don't suffer in the heat with crank out windows! These simple, rental friendly solutions will allow you to have a casement window air conditioner this summer!

How to Install a Casement Window Air Conditioner

Our upstairs rooms have casement windows (also known as crank out windows), making an in-window air conditioner impossible to install. We avoided going upstairs altogether on the hottest days! But I've found three simple ways to set up a casement window air conditioner, to keep our upstairs cool all summer long!

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Central air conditioning is pretty rare in Seattle, since our summers are usually 75 degrees with low humidity (to make up for those dreary, rainy winters!) But the last few summers have been creeping into uncomfortable territory, and when you add in wildfire smoke that forces our windows closed, it becomes unbearable!

smokey Seattle skyline
This was our view of Seattle during the worst of the wildfire smoke in 2018!

Our upstairs is just the playroom and the guest room, so most of the time we just avoid going up there when it gets too hot. But with family coming to visit this summer, I started searching for a way to install a vertical window air conditioner to make our guests more comfortable.

What is a Casement Window?

A casement window is a window that operates on a hinge, instead of sliding on a sash. My window cranks outward, which is nice for catching the breeze but doesn't help when the air is still and hot.

casement window

Supposedly, casement windows are more energy efficient and are more soundproof than sliding windows. But I'm not a fan of the design, and plan to switch them out if we ever remodel the upstairs.

Portable Air Conditioners

Portable air conditioners have dropped in price significantly since they first came on the market. Now they're comparable to window units, and way more versatile. I nabbed one of the few left in the store just before our heat wave started!

portable air conditioner unit

Instead of mounting the entire unit in the window, a portable air conditioner rests on the floor and uses a vent pointed outside. It's easy to remove the vent when the weather cools down, so you can open the window instead. Unfortunately, the vent brackets won't work with a casement window! 🙁

portable air conditioner vent bracket

I needed a way to block out the hot air (and bugs) outside while still allowing for venting for the air conditioner. After some research, here are a few good options for how to put a portable air conditioner in a crank window.

Plexiglass Casement Window Air Conditioner

This was my first idea, and it turns out I'm not the only one who thought of this option! I was debating screwing the Plexiglass directly to the window frame, but this video shows how one homeowner replaced his window screen with a custom made Plexiglass insert instead.

This is a great long-term solution, and one that I will probably do at some point once I figure out all the parts. But with the heat wave imminent, I needed something quick and easy!

The downsides to this method are that big acrylic sheets are expensive, and it's difficult to cut a perfect hole for the exhaust vent without cracking. Check out my tips and tricks for cutting Plexiglass if you decide to go this route.

I also had a hard time finding a screen frame that would fit in our windows, and I didn't want to drill permanent holes in our window frame either.

Foam or Plywood Window Insert

This method uses the window vent insert that comes with the portable air conditioner, coupled with a piece of rigid foam or plywood to block the rest of the window. This would also work if you want to install an air conditioner in a sliding window as well. You can see how one homeowner did it in the video below.

This is a fairly cheap and easy solution, but also has its own drawbacks. We only have one window in this room, so blocking off all the sunlight isn't really an option. Plus, a strong gust of wind would knock a foam insert right out! Plywood would require multiple screws to be drilled directly into the window frame.

Fabric Window Seal for Portable Air Conditioners

I stumbled upon this fabric window seal kit on Amazon, and it was cheap enough that I decided to give it a try. This is definitely the most renter friendly option, and a temporary solution that we'll use while I puzzle out the Plexiglass version above.

This casement window air conditioner installation kit comes with a triangular piece of fabric with a zipper down the middle and Velcro along the edges. You also get a roll of adhesive Velcro and large zip ties.

casement window air conditioner fabric window seal kit

How to Install the Fabric Window Seal

The instructions weren't exactly clear, so I thought I would do a quick tutorial on how I installed the fabric window seal. I apologize in advance for the horrible photos. Taking pictures of a window on a sunny day is hard!

Our window frame was filthy, so I removed the screen and gave the entire thing a good cleaning. This will help the adhesive Velcro stick better.

cleaning window frame before installing casement window air conditioner

Apply the Velcro to the window (the part that moves) and the window frame (the part that holds the window in place when closed).

applying adhesive velcro to window frame for casement window air conditioner seal

Find the widest point of the fabric, and attach the narrow side to the moving window frame where it opens. Make sure the zippers will be on the inside where you can actually use them!

fabric window seal for casement window air conditioner

Work your way around the frame, folding the fabric at the corners to make a 90 degree turn. I had a little extra fabric at the ends, but I just tucked them outside.

attaching casement window air conditioner seal to window frame with velcro

Apply the other side of the fabric the same way to the non-moving part of the window.

window seal with zippers in casement window for air conditioner

Then just crank out the window, open the zipper and stick out the vent. I tried to wedge mine between the window and the outside trim so it wouldn't move.

portable air conditioner vent through casement window seal hole

Then close the zipper around the vent, and thread the zip tie through the pull. This keeps the zipper from opening and letting in those pesky bugs!

casement window air conditioner vent zip tied to fabric seal

It's certainly not the most attractive option, but it works! When the weather cools down, I can remove the fabric and put the screen back in about 15 seconds. 🙂 The casement window can still open and close normally, so I can leave the Velcro in place until we need to apply the fabric seal again.

casement window air conditioner with fabric window seal

Now that we have a casement window air conditioner solution in place, we can go upstairs on those hot summer days, and our guests will be so much more comfortable!

Check out these other easy home improvement projects!

William Miller

Tuesday 18th of June 2019

How do Iinstall a portable A/C exhaust out a slider window?


Tuesday 18th of June 2019

A portable air conditioner should come with a plastic opening cover that the exhaust hose fits into. Slide the window closed just enough to hold the plastic cover in place.


Tuesday 18th of June 2019

Don't laugh, but I may use this solution so that I can build an access point for an outdoor cat palace. Thank you!!


Tuesday 18th of June 2019

Ha, that's a great idea! I'd love to see how it turns out!

jen larson

Tuesday 18th of June 2019

Just the info I needed!!!! I have this type of air conditioner and casement windows in my room in the back of the house and double hung in the front of the house- thought I needed to buy a super huge expensive window A/C and hope it would be enough to push through the entire upstairs, now I have options. Thank you Vineta!! :)


Tuesday 18th of June 2019

Glad I could help! We've been debating installing a mini-split upstairs, but it would be so expensive for the few hot days we get around here. The fabric window seal has been working out great!

Wednesday 12th of June 2019

Appreciate this post. Let me try it out.


Tuesday 11th of June 2019

We've used this type of air conditioner for a few years now. I did the acrylic window, and somehow managed to cut a decent circle! The other thing I did, for a screen, is buy a small roll of screen. I cut it to fit the plexi and then I just used hot glue all around the edges and corners, tapped and pressed it down all around, till it was smooth and voila!!! No bugs coming in and the air conditioner is vented!

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