Parametric Midea PortaSplit Window Adapter

I originally designed this custom window frame pass-through for my Midea PortaSplit mobile split AC and an older Aubi-style window frame.

Unlike classic mobile AC units with a large exhaust hose, the PortaSplit uses a slim hose bundle connecting indoor and outdoor units.
The downside: the outdoor unit cannot be detached, because the refrigerant line is permanently connected.

🚪 Problem:
The outdoor unit has to go outside — which usually means the window stays open all summer.

Not great… especially if you're not looking to invite the local burglar community. 😅

🔧 The Idea

This insert allows the hose bundle to pass through the window frame while keeping the window fully lockable.

The window can still close and engage the original locking mechanism, so you don’t have to leave it open during summer.

📏 Adaptation Note

The original model  and still here availible model was designed specifically for my setup with an old Aubi Window. But from now on you can generate your own with the Generator below 

🆕 Parametric Generator in the Browser

The first version of this model was very specific to my own window profile.

It worked well for me, but of course many of you have different windows, different dimensions and different frame shapes. That is why there is now a parametric generator as a Streamlit web app.

You can enter your own measurements, check a preview and automatically generate matching 3D-printable parts.

👉 Generator / Web App:  custom-window-adapter-for-ac.streamlit.app

• It runs directly in the browser.
• No CAD software and no local installation required.

The app is still work in progress and definitely not perfect yet.
But it is probably already much better than trying to adapt my very specific window shape to your own window.

I am extremely happy about feedback — especially whether the measurement points are understandable, whether the preview helps, and where you still get stuck during configuration.

If you want to read more about the idea behind this project, the tool itself, and how the generator was built, I wrote a more detailed post on my website:

www-f-l-k.com

⚠️ Important:
Installation requires cutting a slot into the inner window frame.

This typically also cuts through the internal steel reinforcement, which does affect the structural integrity of the frame.

In my case (installation in the lower sill area), this has not caused issues, as this area is not heavily load-bearing and the frame remains fixed in place.

❗ Do not install this in structurally critical areas such as the top (lintel) or the side jambs, as this may lead to damage.

🧩 Modular System

The design follows a simple 3-part concept.

🔩 Base Insert (permanent)
Installed into the frame using screws or silicone.

☀️ Summer Insert
Two-part adapter that holds the PortaSplit hose bundle securely.

❄️ Winter Cover
A blanking plate that seals the opening when the AC is removed.

This keeps the opening clean, closed and reasonably airtight during winter.

💨 Airtightness

Surprisingly good — at least as airtight as an old building allows.

The insert seals the gap quite well and prevents most warm air from entering.

That said… old buildings are rarely perfectly airtight anyway.

❤️ Community Feedback

First of all — thanks for all the interest, downloads and feedback!

I honestly didn’t expect this model to spread that much or even show up in Reddit discussions.
It’s really cool to see that the idea inspired other PortaSplit users to build their own solutions.

After about one year of using this setup, here are answers to the most common questions that came up.

❓ FAQ – After ~1 Year of Use

🪚 Did cutting the window frame cause structural problems?

No issues so far.

However, cutting the slot does partially interrupt the internal steel reinforcement, which means the structural integrity of the frame is affected at that location.

In my case (installation in the lower sill area), this has not caused any practical problems, as this part of the frame is not significantly load-bearing and the window remains laterally fixed within the wall opening.

To add extra support, I also secured the insert with two solid screws into the surrounding masonry.

❗ This should not be done in structurally critical areas (like the lintel or side jambs), where such modifications could lead to damage..

❄️ Does cold air enter during winter?

No noticeable drafts.

During winter the AC unit is removed and stored in the basement.
The passthrough is closed with the blanking plate, which seals the opening well.

In my case this is an older building anyway, so the overall airtightness is mostly limited by the building itself — not the insert.

💰 Why not install a real split AC?

Main reasons: cost and installation complexity.

The Midea PortaSplit is very attractive price-wise and performs surprisingly well.

A permanent split system would likely have required:

• different outdoor unit placement
• longer refrigerant lines
• cable ducts through several rooms

If done properly this can quickly become much more expensive and invasive.

🪟 Why not just run the hose through the window?

I wanted a permanent summer setup.

Opening and closing the window every day to install/remove the hose would have been annoying.

Leaving the window permanently open was also not ideal because of:

• worse cooling performance
• outside noise
• security concerns

🧱 Why not use a plexiglass / Styrodur window insert?

Those solutions can absolutely work — especially in:

• quiet areas
• upper floors
• rental apartments

In my case the window faces the street, so I preferred a solution that:

• reduces outside noise
• keeps the window fully lockable
• doesn’t look like an open invitation

👍 Would you build it again?

Yes.

After about a year of use I’m still very happy with the solution.

The PortaSplit works great and the passthrough makes it feel almost like a semi-permanent AC installation during summer.

🧑🔧 License & Community Use

This model is free for private use and further development within the maker community.

Feel free to:

• print it
• modify it
• remix it
• adapt it to your own window setup

That’s exactly what the maker community is about.

🏭 Commercial Availability

Commercial production and distribution is handled by SureParts.

If you like the idea but don’t have access to a 3D printer, you may find ready-made versions online (for example on eBay).

I’m not running the shop myself — they simply took care of turning the concept into a commercially available product.

DIY builders are of course always welcome to print and improve their own version. 🔧