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After installing window air conditioning units in various spaces, I've learned how to get window sealing right.
Over 50 AC installations later, I've picked up a few tricks for sealing window air conditioners to ensure optimal energy efficiency and avoid potential mishaps.
In this guide, I'll share an insider's take on installation criteria for different window seal options, their perks, performance shortcomings, and best practices.
Quick glance - My recommendations
HOOMEE 300cm
Gulrear Seal Plates
Loviga Window Seal
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Window seal kit options for room air conditioners
With the right tools and expert hacks, I've found it easy to install an air conditioner seal for any type of window.
Here's a lowdown on the most common window seals and my thoughts based on extensive installation experience.
HOOMEE 300CM
Editor's Choice
4.7
Overall Score
Easy to install
5.0
Durability
4.5
Sturdiness
4.5
Functionality
5.0
Type
Fabric
Hose
Single / Dual
Length
118"
Width
16.93"
Who is the HOOMEE 300CM best for?
The HOOMEE 300CM is best for all kinds of situations and for windows like casement windows.
What you like
What you won't
Portable air conditioners often pose unique installation hurdles, especially when I want to achieve a tight seal.
I use casement window seals to address this snag since they offer a customizable barrier between the window frame and the air conditioner exhaust hose.
Since most casement window seals are made of a flexible polymer foam, this ensures tight compressions against the window sash and frame when closed.
I often apply a thin strip of silicone caulking to vinyl casement windows, where the seal compresses against the hollow chambers to prevent air leakage.
I also use two different window seals when installing a portable air conditioner with separate air intake and exhaust hoses.
One is for the main AC chassis, while the other slimmer seal is for the exhaust hose vent alone.
I prefer using the HOOMEE 300CM window seal for portable air conditioners since the length gives me more than enough material to create a seamless seal around large casement openings.
Thanks to its pliable polymer construction, the wide side compresses tightly against the window frame, while the narrow section easily cinches down on the casement sash.
I'm impressed that HOOMEE included two zippers—one for the main AC hose and another for the less common dual-hose exhaust setups.
I also prefer the adhesive hook tape mounting system, as it locks the window frame and sash in place and prevents air gaps from the seal shifting over time.
Performance-wise, I find the HOOMEE seal exceptional at preventing hot air infiltration, which has boosted the cooling capacity of portable AC units.
Gulrear Seal Plates
Best For Dual Hose Portable ACs
4.7
Overall Score
Easy to install
4.25
Durability
5.0
Sturdiness
5.0
Functionality
4.75
Type
Plates
Hose
Dual
Length
60"
Width
7"
Who is the Gulrear Seal Plates best for?
The Gulrear Seal Plates is best for those looking for sturdy seal plates for their dual hose portable AC.
What you like
What you won't
When installing dual hose portable air conditioner units, I'll need a provision for two separate openings–one for drawing in fresh, cold air and another to expel the hot exhaust air.
I fancy how this boosts efficiency without recycling warm exhaust air back into the room.
Dual seal plates are designed with this in mind, as they come in two pre-cut panel sections to accommodate both intake and exhaust connections.
The holes have built-in grommets, gaskets, or compression channels, allowing for tight seals around each hose's exterior once inserted.
On the exterior sides, the plates use heavy-duty adhesive taping, velcro edges, or even screw-mounted bracketing to securely lock them on the mounting surface—whether it's a window frame, panel, or exterior wall.
Dual hose plates make venting these units straightforward with no guesswork. My work is made easier during installation since this airtight mounting prevents hot air infiltration or leaks between the interior and exterior vents.
I don't need complicated panel cutting, sealing, or rigging— I just cut two appropriately sized holes, insert the hoses, lock the plate in place, and everything's vented!
I like that Gulrear designed their kit for dual hose portable ACs with separate 5.9" exhaust and 5" intake hose outlets.
I don't have to wrestle with one-size-fits-all panels during installation since the multi-piece telescoping window panels allow me to adjust the overall length from 25" up to 60", achieving a tight fit on any size horizontal or vertical sliding window.
The seamless card slot grooves that interlock the inner and outer panel sections also help me eliminate potential air gaps that traditional overlapping panel setups often suffer from around the edges.
I'm particularly impressed with the oval-shaped exhaust vent adapter included in the kit.
Its elliptical design reserves more space to create a completely sealed connection, even on window frames with exterior grooves or trim pieces.
Loviga Window Seal
Fabric Seal for Sliding Windows
4.6
Overall Score
Easy to install
5.0
Durability
4.5
Sturdiness
4.5
Functionality
4.5
Type
Fabric
Hose
Single
Length
60"
Width
10"
Who is the Loviga Window Seal best for?
The Loviga Window Seal is best those who want an easy to install seal kit for a single hose portable AC.
What you like
What you won't
Unlike casement seals that bend and compress, sliding window seals must split apart in the middle to allow those window sashes to glide when opened or closed.
Installing the gaskets helps me create an airtight interior/exterior separation.
Those two gasket pieces interlock in the center using a zipper, velcro, or grooved channel design.
This sealed connection in the middle allows the sashes to slide when you want to open the window.
What I find handy is using a seal kit that perfectly matches your window dimensions and AC chassis size. This ensures those gaskets can compress fully on all four sides to prevent hot air infiltration.
One of the biggest perks of sliding window seals in my books is how easy they are to install compared to other options like shrink-wrap plastic films.
With most kits I've used, it's as simple as pressing those adhesive-backed gaskets right into the window tracks on both sides.
I don't have to struggle with complex measuring, cutting panels to size, or dealing with a mess of tape residue.
Those peel-and-stick gaskets allow for an extremely quick setup that can still be easily removed come fall when AC season is over.
I also find these seals practical because they preserve the window's full functionality.
Rather than permanently removing the sashes or blocking the sliding path open, the seal travels with the window as you open and close it normally.
The Loviga air conditioner window seal is one of my dependable options for sliding windows, as it uses an adjustable drawstring closure system instead of the traditional zipper design.
During installation, I can achieve a gap-free air leakage seal around the exhaust pipe or hoses.
Loviga was thoughtful about using a waterproof, heat-insulating white fabric material.
Since the reflective surface reflects sunlight, I've noticed portable air conditioner units record more efficient cooling performance than paneling, which absorbs outdoor heat radiation.
I also find its heavy-duty velcro and adhesive more reliable in securing the panel. Installation is literally a 5-minute job since I don't do any drilling.
Instead, I just press the adhesive velcro strip to the window frame, drape the panel over it, poke the exhaust pipe through the hole, tighten the drawstring, and secure the pipe with the included velcro ties.
tBesme Seal Plates
Best Telescoping Seal Plates
4.6
Overall Score
Easy to install
4.5
Durability
4.75
Sturdiness
4.75
Functionality
4.5
Type
Plates
Hose
Single
Length
48"
Width
5.9"
Who is the tBesme Seal Plates best for?
The tBesme Seal Plates is best for all kinds of situations and for windows like casement windows.
What you like
What you won't
I find seal plates somewhat fault-safe when installing a single-plate air conditioner, as they ensure optimal efficiency by preventing cool air from escaping.
Seal plates are easy to install since I don't need a zip and adhesive fastener during installation. I won't cut panels to size or try to rig up a custom venting solution.
When installing a single hose AC, a gap between the window sash and the frame may appear, and seal plates help me bridge this gap.
Since the pre-cut opening in the fixed plate allows the AC exhaust hose to vent hot air outside, it won't mix with the cool air being pumped into the room.
I would opt for this seal plate from tBesme if I'm installing a smaller single-hose portable air conditioner due to its versatility—it virtually fits any 5-inch exhaust hose from major AC brands.
The use of rigid PVC construction is also a plus for me since thicker material should hold up well to seasons of user and sunshine exposure without cracking or warping.
I also find tBesme's telescoping side rails quite innovative as they can extend the overall width from 45cm to a very generous 122cm maximum length.
This adjustability helps me achieve a tight fit on all sizes of sliding windows during installation while eliminating those pesky exterior air gaps.
Its flush mounting design without protruding plastic ridges means a cleaner lower profile, preventing snagging hazards around the window opening.
Comparing seal kits for portable AC units
Preview | Name | Rating | Purpose | Price |
|---|---|---|---|---|
HOOMEE | 4.7 | Window Seal For Casement Windows | ||
Gulrear | 4.7 | Seal Plates For Dual Hose Portable ACs | ||
Loviga | 4.6 | Window Seal For Sliding Windows | ||
tBesme | 4.6 | Seal Plates For Single Hose Portable ACs |
What I look for when choosing a window seal kit
What kind of window do you have?
For horizontal and vertical sliding windows:
I find these the easiest to tackle when venting air conditioners.
Most seal kits I've fitted, whether it's window panels or plate mounts, are designed to be compatible with horizontal sliders or vertical hung/gliding windows.
For a tight fit, my true and tested trick is finding an adjustable length kit that extends to match your window's dimensions.
For single and double hung windows:
I find hung windows operate similarly to vertical sliders, except that the sashes move up and down instead of side-to-side.
The only snag I've seen with hung windows is ensuring enough clearance below the raised sash to route those hose connections through and mount the venting hardware securely.
For casement windows:
Casement windows can sometimes be taxing during installation as the entire sash rotates outwards.
To dodge this downside, I use a kit with extremely pliable mounting panels and gaskets that can bend and compress against that swinging sash without obstruction.
I've had luck with kits that use polymer gaskets or foam liners built specifically for complex casement geometry.
But getting them installed leak-free definitely requires some patience and precise measurement.
ACLAB note:
Some windows like Casement windows cannot be fitted with regular Window ACs. Hence, portable ACs with a sealing kit is the most likely option.
Related article: Popular casement window ACs reviewed
For slider windows:
Sliders have horizontal sashes, similar to sliding windows, for portable AC venting.
I use an adjustable-length seal kit that matches the window width to vent out their side without much hassle.
For awning windows:
Awning window units are arguably the trickiest to properly seal in my experience since the perpetually protruding lip can really obstruct when trying to make a secure hose connection.
These windows have sashes that hinge outwards from the top to bottom.
For this reason, I have to get creative with customizing kids using adhesive gaskets, insulation panels, and a lot of caulking.
Window seal fabric vs window seal plates
There's no best option, as each venting solution has perks and downsides. Also, it all depends on your specific AC setup and window type.
Window seal fabric at a glance
I'd give fabric window panels high marks for their flexibility and customizable fit, as these adjustable cloth barriers are often made of polymers or synthetic fabric.
Take the HOOMEE window seal, for instance. Thanks to its soft, pliable material, it's my most viable option for irregular window geometries like awnings or casements.
I'd have a nightmare getting a reigned plate mounted securely on such applications.
I also find installing fabric panels relatively painless since I don't need to drill or source for complex mounting hardware. I'm good to go with simple adhesive Velcro strips, tension rods, or snap tracks.
I'd say the fabric panels fall short on their sealing performance.
While the materials can be cinched tightly, I haven't seen zippers and velcro creating as powerful and airtight seals as a plate's integrated rubber gaskets.
Window seal plates at a glance
Since they're made of premium plastics like ABS or aluminum, I've delivered a leak-proof, energy-efficient venting solution with seal plates.
UV-treated materials also withstand years of intense sun and temperature cycling.
Seal plates such as the tBesme window vent kit, with their dense construction combined with thick compression gaskets, help me create a robust insulating barrier during installation.
The low-profile, secure mounting using heavy-duty adhesive strips or screws also gives plates a distinct aesthetic and permanent installation edge over fabric panels.
One notable downside of seal plates is their fixed dimensions and mounting requirements, which make them challenging to install on awnings, casements, or other complex window types.
What material is the seal made of?
The material composition for both window seal fabrics and rigid plates impacts performance.
Here are the different options I've come across 50+ installs later:
Fabric materials:
Rigid seal plate materials:
ACLAB note:
The seal material that I choose for a client depends on their budget, expected longevity needs, and climate exposure.
Do you have a dual hose or a single hose portable AC?
Single hose portable ACs
These have just one air hose that exhausts the hot air inside the room, and the unit expels hot air from the condenser coils.
Since there is only one hose connection point, single-hose kits tend to be more affordable and have a simpler installation process than their dual-hose counterparts.
During installation, I have to vent this exhaust hose out of a window or wall penetration, and the seal kit has just one primary vent opening to accommodate that single exhaust hose.
Most kits I've worked with include an adjustable window panel or plate with a circular/oval opening ringed by thick rubber gaskets or weather stripping.
With single-hose portable ACs, I aim to achieve an airtight connection around just that one exhaust point while still allowing fresh ambient air to be pulled into the AC's air intake on the other side.
Dual hose portable ACs
Dual hose portables are designed with maximum energy efficiency, using one hose strictly for exhausting hot air.
ACLAB note:
Most of the powerful and large portable ACs are dual hose ACs. Unlike single hose ACs, these do not create a negative pressure inside the room.
In contrast, the other hose is dedicated to continuously drawing in cool air from the outside, which helps separate the air streams.
Before installation, I have to find a seal kit with two separate vent openings and hose attachment points—one oval/circular opening for the exhaust paired with another fresh air intake hole.
This helps me to properly vent both hoses out of the window/wall simultaneously.
Dual opening kits facilitate keeping the intake and exhaust 100% separated for optimal cooling performance and efficiency from the portable AC.
The dual hose design is challenging to install as it has more potential air leakage points.
For this reason, I prefer using seamless plate designs with integrated rubber gaskets over panel styles.
What is the hose size?
Most portable AC manufacturers build their units around standard hose diameters of either 5.0 inches or 5.9 inches.
I've, however, seen some variance depending on the specific model.
For single-hose portable ACs with just one exhaust hose, that diameter measurement determines the minimum size of the circular or oval-shaped vent opening the seal kit needs to have.
I also leave at least 0.5" clearance around the hose circumference for an easier sealed connection.
So, for example, if the single hose portable has a 5.0" exhaust, I'll likely want a seal kit with a minimum 5.5" to 6.0" diameter exhaust vent.
Going any smaller creates a high risk of air leaks around the hose attachment point.
It gets slightly more complicated with dual-hose portable units since I have to account for two different hose sizes—one for the hot air exhaust and another for fresh air intake. These are often mismatched diameters as well.
Many popular dual hose models use a 5.9" exhaust hose paired with a slightly slimmer 5.0" intake hose.
The seal kits must have properly sized vents to create a tight seal around both without mixing air between streams.
How easy is it all to install?
The ease of installation depends on your window setup and whether the seal kit has all the necessary accessories.
Window sealing plates often feature adjustable lengths, making them easy to fit various window sizes.
I recommend buying one with foam insulation strips as they help create a tight seal between the window frame and the sealing panels, preventing air leaks.
As for sealing fabric, some portable air conditioner kits include fabric panels or curtains to insulate further and seal the window opening.
These fabric panels may include features like velcro strips for securely attaching to the window frame or sealing panels, creating a tight seal.
Some fabric panels have zipper openings that allow the exhaust hose to pass through while maintaining a snug fit around it.
FAQs
Can you use a portable AC without a window seal?
While running a portable air conditioner without a proper window seal is possible, I don't recommend going this route. Without it, the hot air will recirculate back into the room, significantly reducing the cooling efficiency and wasting energy.
What happens if the portable AC is not properly sealed?
When not properly sealed, outside air can enter the room through gaps, increasing humidity and heat load. The unit will have to work harder and consume more energy, eventually overheating. Condensation buildup will eventually occur, leading to moisture problems.
Can I use duct tape to seal my window air conditioner?
Duct tape tends to deteriorate over time, losing its adhesive properties, especially in hot conditions. It can also leave behind a sticky residue when removed. I recommend using proper window sealing accessories designed for this purpose.
Can I seal my window air conditioner from the inside only?
Sealing from the inside alone may not create a tight enough seal and could compromise the unit's performance and efficiency.
What type of caulk should I use to seal the air conditioner?
I find silicone caulks durable, flexible, and able to withstand temperature variations. Avoid using latex-based caulks, as they may crack or peel over time due to the heat and moisture exposure from the air conditioner.
Which is the best window seal for your setup?
The best seal kit depends on the window type, AC hose sizes, installation requirements, and accessories to make the installation seamless.
For casement windows, for instance, I'd go with a kit made of flexible polymer like that from HOOMEE, as it compresses tightly against the window frame and sash.
Don't compromise on an improper seal that saps cooling power and wastes energy. Getting it right from the start saves you a massive headache.
My #1 Recommendation
HOOMEE
- Increase cooling performance
- Easy to install (no need for drilling holes)
- Suitable for all portable air conditioners
