Here’s the deal:
Every portable air conditioner needs to be vented. Either out of the window or sliding door. The gap the exhaust hose of the portable air conditioner creates needs to be sealed.
To seal a gap, you can get a universal window seal for portable AC units; further on, you will find the 3 most popular AC window seal kits for portable air conditioners you can install yourself (DIY) and 1 slider door seal kit.
Here is how an installed window seal on a portable air conditioner looks like:

German engineers use the word ‘luftdicht’ to describe the complete sealing of the window or sliding for the gap. ‘Airtight’ is the appropriate translation in English.
The fact is that a portable air conditioner will be less effective if the window gap is not sealed. Without the AC window seal, you’re basically running a portable air conditioner with an open window. That will reduce the effectiveness of portable AC units by as much as 78%.

How do you seal a portable air conditioner window?
Simple. You just use the appropriate window seal kit for a portable air conditioner. Kits are rather easy to install; you can check the best DIY window seals for all kinds of AC units here:
Skip To List Of 3+1 Best Window Seals For Portable AC Venting
There are few things you need to be careful when choosing the right window seal kit. Not all window kits are universal (depends on window dimensions and type), and for crank windows and sliding doors you will need specialized kits; ie. sliding door kits for portable air conditioners.
Let’s cover the basics about choosing these window kits for portable AC units before we look at the kits themselves:
Types Of Windows You Can Use To Vent Portable Air Conditioner
There are 20+ types of windows. The best window seal kits for portable AC units are the ones that are universal. For example, #1 HOOMEE kits (check comparison table below) are completely universal; you can choose between 4 different dimensions and even a sliding door kit.
Here are the 7 most common window types you can install universal window seal AC on:
- Double-hung windows.
- Single-hung windows.
- Casement windows. By the way, you even have casement window air conditioners, specifically designed for this type of window.
- Slider windows; very similar to sliding doors.
- Awning windows.
- Hopper windows.
- Skylight windows.
Most people hung the exhaust hose of their portable AC unit out of double-hung windows. That also means that pretty much every good window sealing kit for portable AC units can be installed on double-hung windows.
For other less common types of windows, like slider, awning, and skylight windows, you should get the universal seal kit.
If you have a double-hose portable air conditioner, you should get the universal window kit for dual-hose portable AC units:

The key thing you need to measure before you buy the kit, however, is the window size:
Window Dimensions
Most sealing kits will fit most of the windows. But not all. To avoid dealing with sealing kit returns, do measure the window prior to ordering the kit.
#2 Airly kit, for example, will support any window that has an up to 158″ perimeter:

#1 HOOMEE kits are available in several sizes; you should choose the size of an anti-air leakage window sealing kit that best fits your window’s dimensions.
First, you need to measure all the window dimensions. Then, you add them all up, as shown here:

When you have that A+B+C+D perimeter total, you can choose a kit for your specific window size.
HOOMEE kits are available in these dimensions:
- Window 300CM; for maximum window perimeter of up to 118 inches.
- Window 400CM; for maximum window perimeter of up to 157 inches.
- Window 500CM; for maximum window perimeter of up to 196 inches.
- Window 560CM; for maximum window perimeter of up to 220 inches.
For sliding door seal kits, you don’t have to do these calculations. You usually get a sliding door seal bracket; check #4 gulrear sliding door seal for more information.
How To Install A Universal Window Seal On A Portable Air Conditioner?
Here’s the DIY part. With every kit, you will get step-by-step instructions on how exactly to install the window seal. You can see one good example here:
Let’s breakdown how most universal DIY window seal kits for portable AC units are installed:
- Adhesive fastener tape is attached to the window. This forms the basis for the window seal kit.
- Paste the adhesive fastener tape along the window frame.
- Cut off all the tape that sticks out.
- Create the full frame by connecting the tapes from the A, B, C, D sides of the windows.
- Grab the window seal AC. Fasten it on the tape; the best way to do it is by starting from the middle of each window dimension.
- Align the window seal on the static and dynamic parts of the window.
- Unzip the seal to make the room for the portable AC unit’s exhaust hose.
- Insert the exhaust hose (or two hoses in case of dual-hose portable AC units) and zip the lock tightly.
Complete installation of the window seal kit shouldn’t take more than 15 minutes.
Installing a sliding door kit usually follows the step-by-step instructions for bracket installation. You have all the instructions in the manual that comes with the sliding door seal kit. Here are all the parts that you get, for example, with the #4 gulrear sliding door seal kit:

With all that in mind, let’s look at the best window and sliding door seals for venting portable air conditioners:
Best AC Window Seal Kits For Portable Air Conditioners
- HOOMEE: Best Universal Window Seal For Portable Air Conditioners (Most Popular, Versatile)
- Airly: Cheapest Air Conditioner Window Seal For Less Than $25
- tBesme: Best AC Window Seal Bracket For Vertically And Horizontally Sliding Windows
- gulrear: Best Sliding Door Window Seal For Portable AC Units
Window Seal For AC: | #1 HOOMEE Window Seal (5 Sizes) | #2 Airly Window Seal (1 Size) | #3 tBesme Window Bracket (2 Sizes) | #4 gulrear Sliding Door Seal |
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Window Size: | 118″ to 220″ | Up to 158″ | 26″ to 47″ (Bracket) | 87″+ |
Models Available: | 4 Window Models | 1 Window Model | 2 Window Models | 2 Door Models |
Door Model? | Yes | No | No | Yes |
Installation Difficulty: | Very Easy | Very Easy | Easy | Easy |
Price: | $$$$ | $$ | $$$$ | $$$$ |
Average Rating: | ![]() |
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Availability: | Check Price | Check Price | Check Price | Check Price |
1. HOOMEE: Best Universal Window Seal For Portable Air Conditioners (Most Popular, Versatile)

Window Size: | 118″ to 220″ |
Models Available: | 4 Window Models |
Door Model? | Yes |
Installation Difficulty: | Very Easy |
Window Types: | Universal Kit, Casement Windows, Top-Hung Roof Top Windows |
Price: | $$$$ |
Rating: | ![]() |
Most portable AC unit owners go with HOOMEE. HOOMEE offers universal window seal kits for portable AC units; they are very easy to install, have an appealing design, and cost only up to $30 a piece.
HOOMEE offers 4 models, and an additional model for sliding door venting. The A+B+C+D window dimensions can be used as an explanation of how to properly size a window seal for a portable air conditioner. HOOMEE offers these window seal kits:
- Window 300CM; window perimeter of up to 118 inches.
- Window 400CM; window perimeter of up to 157 inches.
- Window 500CM; window perimeter of up to 196 inches.
- Window 560CM; window perimeter of up to 220 inches.
- 36″ x 83″ screen door seal.
In short, they have everything. All of the window units will fit any window type, from single and double-hung windows, to casement windows, and so on.
On top of that, these universal window seal kits are also appropriate for dual-hose portable air conditioners.
All in all, HOOMEE kits are the go-to choice for most homeowners. These are the best window seal for portable AC kits, and you even have the additional screen door kit:
2. Airly: Cheapest Air Conditioner Window Seal For Less Than $25

Window Size: | Up to 158″ |
Models Available: | 1 Window Model |
Door Model? | No |
Installation Difficulty: | Very Easy |
Window Types: | Universal Kit |
Price: | $$$$ |
Rating: | ![]() |
If you can’t really figure out what kind of window you have and tally up all the window dimensions, but would still like to install a window seal, the Airly is the most recommended choice. This is the universal window seal kit that will fit windows up to 158″ maximum perimeter.
Because it fits almost 100% of windows, it’s massively produced, and therefore has a lower price. With below the $25 price tag, Airly is the cheapest DIY AC window seal for portable air conditioners.
Pretty much everybody will find installation very easy. With the purchase, you get the step-by-step manual on how to properly install Airly window seal. Basically, it’s an easy and cheap solution for sealing the gap that the portable AC exhaust hose creates in the window:
3. tBesme: Best AC Window Seal Bracket For Vertically And Horizontally Sliding Windows

Window Size: | 26″ to 47″ (Bracket) |
Models Available: | 2 Window Models |
Door Model? | No |
Installation Difficulty: | Easy |
Window Types: | Vertical Windows, Horizontal Sliding Windows |
Price: | $$$$ |
Rating: | ![]() |
tBesme offers the bracket window seal. While most window seals are made out of flexible polyester, these advanced user-friendly window seals are made as brackets.
The bracket actually looks nicer on the window and it’s equally easy to install as universal kits. However, the parts themselves do cost more, and therefore the bracket window seals are pricier.
tBesme offers the best PVC bracket window seals. Based on the diameter of the portable AC unit’s exhaust hose, you have two models:
- tBesme seal bracket for 5.1″ diameter hoses.
- tBesme seal bracket for 5.9″ diameter hoses.
Before you buy the tBesme, measure the diameter of the exhaust hose in order to choose the right model:
4. gulrear: Best Sliding Door Window Seal For Portable AC Units

Window Size: | 87″+ |
Models Available: | 2 Door Models |
Door Model? | Yes |
Installation Difficulty: | Easy |
Window Types: | All Sliding Doors |
Price: | $$$$ |
Rating: | ![]() |
Window seals for sliding doors are a kind of new thing. Even 5 years ago, you couldn’t buy one. The bracket design enabled producers to create a portable air conditioner seal that can fit sliding and screen windows. Of those, gulrear sliding door seal kit has the best reputation.
gulrear seal is installed along the sliding window. In the packet, you get all the necessary parts to assemble the kit yourself. You have to tape the bracket to the sliding window, and it holds surprisingly well.
In such a way, you can great an airtight seal even if you vent a portable air conditioner through a sliding window. All in all, gulrear is the most universal and best sliding door seal for portable AC units:
This is basically how you can use the window seal kits to seal all the open spaces in the window through which you vent a portable air conditioner. You can also check the ventless portable air conditioners that need no window venting.
Can you vent it out a flood vent which is about 14”by 8” ? It would be like a basement or a garage with no windows.
Does anybody have an answer to this question? Please email me.
Hello Joann, portable AC vent size is about 6″. Dimensions-wise, you can vent it out of a 14″x8″ flood vent. Just make sure that that flood vent leads outdoors (you don’t want the hot air being recirculated within the house).