Casement Window Kits that Actually Fit
Custom-built inserts for portable air conditioners – engineered for crank-out windows where standard kits fail.
- Perfect-Fit Guarantee: Measured to your window. Free remake if it’s not exact.
- Designed for Casement Windows: Built specifically for crank-out windows, not retrofitted.
- Fast, Simple Install: Most setups take under 10 minutes.
Trusted By 10,000+ Homeowners Nationwide
Finally, A Casement Window Solution that Doesn’t Involve Duct Tape
Measure Once. That’s It.
We guide you through a simple measurement process so your insert is built to your exact casement window. No estimating. No “close enough.”
We Custom-Build the Insert
Your casement window insert is manufactured to spec, engineered specifically for portable air conditioners and crank-out windows where standard kits fail.
Install, Seal, and Finally Cool the Room
Installation takes minutes. The insert seals cleanly, vents hot air outside, and looks like it belongs in a finished home – not a garage experiment.
A Purpose-Built AC Solution for Casement Windows
Cool Air, Contained
Hot air goes out. Cold air stays in.
Clean, Finished Look
No eyesore. No blocked light. No DIY regret.
Your AC, Actually Working
Better sealing means better performance and less strain on the unit.
Built for Casement Windows. Not Adapted.
Standard portable AC kits are designed for sliding windows. Casement windows are different, which is why most solutions fail.
Our inserts are custom-manufactured to your exact window dimensions and engineered specifically for crank-out casement windows. The result is a tight seal, clean appearance, and a setup that works the way it should – without permanent modifications.
This is a complete solution, not a workaround.
Works With Your AC
Compatible with single-hose, dual-hose, and hose-in-hose portable air conditioners.
Fast, Simple Install
Most installs take 5–10 minutes with a secure, durable connection.
Designed for Casement Windows
Purpose-built for crank-out windows where standard kits don’t fit.
Keeps Natural Light
Clear inserts preserve daylight while sealing far better than makeshift fixes.
Custom AC Window Kits for Casement Windows
- Built to Be Removed and Reused – Designed for seasonal use, our inserts install cleanly and remove just as easily. Store it when summer ends or move it to another room without damaging your window.
- Makes Your Portable AC Work the Way It Should – A tight seal means less hot air leaking back in and far better cooling efficiency, without permanent modifications or expensive HVAC installs.
- Stops Hot Air From Sneaking Back Inside – Our sealed inserts block outdoor air infiltration, keeping indoor temperatures stable and reducing strain on your AC unit.
Built for the Problems Standard Kits Ignore
Martinson Manufacturing designs precision venting solutions for situations where mass-produced products fail.
Founded by engineer Joe Martinson, the company focuses on one thing: solving real venting problems cleanly, correctly, and without compromise. Casement windows are one of those problems.
Portable air conditioners aren’t designed for crank-out windows. Most homeowners are left improvising with cardboard, tape, or poorly fitting panels. Martinson Manufacturing builds custom inserts made to exact window dimensions, engineered for proper sealing, and designed to install without permanent modifications.
This is a purpose-built solution for homeowners who want the problem handled right the first time.
Choose Your Window to Get Started
Why Martinson Manufacturing Is Different
Expertly Packaged
Protected for Shipping
Unmatched Service
Real Human Support
Easy Process
Measure. Order. Install.
Perfect Fit Guarantee
Free Remake if Needed
Experience Real Relief with a Properly Sealed AC Window
Put an end to hot air leaks, noisy setups, and constant frustration with a clean, custom-built solution designed to keep your home cool and comfortable season after season.
Our window inserts are made to your exact dimensions, seal tightly inside the frame, and vent hot air outside where it
belongs.
No cardboard, no tape, no permanent modifications – just a setup that works the way it should and looks right in your home.
What life looks like after installing it
- Comfort
- Clean setup
- No hacks
- No frustration
- Better sleep
- Lower energy bills
The Smart Way to Stay Cool
- Easy to Remove Anytime
- Energy Efficient Sealing
- Perfect Fit Guarantee
- Comfortable Indoor Cooling
- Crystal-Clear Visibility
- Simple Installation
- No Damage, No Hassle
- Built for Real Homes
- Free Shipping on Most Orders
- Works With Your AC
- Fast Production Times
- Secure, Protective Packaging
Perfect Fit Guarantee
If your window insert doesn’t fit your window perfectly, we’ll remake it for you free of charge.
Seriously.
Even if it was your fault.
Just email us at info@martinsonmanufacturing.com and let us know what needs adjusting, “make the width ½ inch shorter,” “tighten the height,” whatever it takes. We’ll cut a new one and ship it out the next business day.
We’re not in the business of leaving you stuck with something that doesn’t work.
The Most Complete Portable AC Window Solution
Martinson Manufacturing builds custom window inserts designed to seal properly, vent efficiently, and work with portable air conditioners the way they were meant to. No generic panels. No makeshift fixes. Just a solution that fits and performs.
Each insert is made to your exact window dimensions and engineered to eliminate air leaks that reduce cooling efficiency. Installation is fast, clean, and requires no permanent modifications to your home.
- Works With Any Window Type
- Install and Cool in 5–10 Minutes
- Single Hose, Dual Hose, Hose-in-Hose Compatible
Whether you’re cooling a single room or solving a seasonal comfort issue, our inserts provide a clean, reliable setup that looks right and works consistently. It’s a complete solution designed for real homes and real use.
Custom-Fit Portable AC Window Panels
We design and manufacture made-to-order window panels that seal properly, vent hot air outside, and work with portable air conditioners across multiple window styles.
Select your window type below to build an insert sized to your exact opening. Installation is fast, clean, and requires no permanent modifications.
Choose Your Window to Get Started
Build a custom insert designed to fit, seal, and perform correctly for your specific window type.
The Casement Window Solution
Perfect Fit Guarantee
Free remakes if it's not exact
Fast Production
Most orders ship in 3 days
Free Shipping
No surprises at checkout
The Most Complete Portable AC Window Solution
Martinson Manufacturing builds custom window inserts designed to seal properly, vent efficiently, and work with portable air conditioners the way they were meant to. No generic panels. No makeshift fixes. Just a solution that fits and performs.
Each insert is made to your exact window dimensions and engineered to eliminate air leaks that reduce cooling efficiency. Installation is fast, clean, and requires no permanent modifications to your home.
- Works With Any Window Type
- Install and Cool in 5–10 Minutes
- Single Hose, Dual Hose, Hose-in-Hose Compatible
Whether you’re cooling a single room or solving a seasonal comfort issue, our inserts provide a clean, reliable setup that looks right and works consistently. It’s a complete solution designed for real homes and real use.
Built to Seal. Made to Fit.
Leak Resistant
Designed to seal tightly so hot air stays out.
Perfect Fit
Made to your exact window dimensions.
Fast Setup
Most installs take 5–10 minutes.
AC Compatible
Works with single-hose and dual-hose units.
Real Support
Clear measuring help and answers when needed.
Frequently Asked Questions
