How to Vent a Portable AC Through Swiss Windows Without Drilling

Every portable air conditioner has to push its heat outside, and that is exactly where Swiss apartments fight back. Our windows tilt and turn instead of sliding, and most of us rent, so drilling through the frame or the facade is off the table. The good news: you can vent properly without a single hole. Here is every method that works with Swiss windows, from a simple fabric seal to the flat-line trick that lets you close the window almost completely.

Why are Swiss windows a problem for portable ACs?

Almost every Swiss apartment has tilt-and-turn windows. A tilted window opens a large wedge at the top, and a turned one swings the whole casement into the room. Neither gives you the small, defined opening a round 15 cm exhaust hose needs. Warm outside air streams back in around the hose, and a chunk of your cooling is gone before you feel it.

The slider panels bundled with most portable ACs assume American windows that slide up or sideways. Nothing in a Swiss apartment slides. That is why expat forums are full of improvisation: one member of the Swiss English forum describes building a contraption out of cardboard and shutters just to sort out "the hole for the hot air outlet", which he calls the tricky part of the whole project (swissforum.co.uk). It does not have to be that way.

Which no-drill venting options work in Switzerland?

Three approaches work with tilt-and-turn windows: a fabric seal kit that zips around the tilted window, a rigid panel cut to fit the opening, or a portable split whose thin refrigerant line passes through a window that is closed to a slit. All three are reversible and renter-safe. They differ a lot in cost, effort and how much heat they let back in.

Option 1: fabric window seal kit

A seal kit is a textile membrane that attaches around the window frame and the sash with self-adhesive velcro, plus a zip where the hose exits. Tilt the window, zip the fabric shut around the hose, done. It fits tilt windows and balcony doors, goes on in about 15 minutes and peels off without residue when you move out.

The honest downside: the fabric is thin and the window behind it is wide open, so on a 34 °C afternoon heat still conducts through the membrane. For a monoblock it is the sensible minimum, not a perfect seal. You will find ours under window seal kit, along with foam strips and extensions in the accessories section.

Option 2: rigid panel insert

A sheet of acrylic or coated board, cut to the tilt opening with a round cut-out for the hose, insulates clearly better than fabric. Clamp it or use a compression fit; no screws need to touch the frame. This is the grown-up version of the forum cardboard hack. The downsides: you have to measure and cut it for your exact window, it looks like DIY, and the 15 cm hose problem is still there.

Option 3: the flat line of a portable split

A portable split does not blow air outside at all. The indoor and outdoor units are connected by a thin refrigerant line, about 2.7 cm flat, as Stiftung Warentest noted in its portable AC coverage. The window closes onto the line to within a finger's width, and a foam strip seals the rest. This is the only method where the "opening" essentially disappears.

Why does a flat line beat a 15 cm hose?

Two reasons: opening size and air pressure. A hose needs a palm-sized opening plus a metre of hot plastic radiating heat back into the room. Worse, a single-hose monoblock creates negative pressure: it blows room air outside, so the same volume of warm air must leak back in through every gap in the apartment. A split moves heat in a closed refrigerant loop. No air leaves the room, so nothing gets pulled back in.

Stiftung Warentest's verdict on mobile monoblocks fits in one line: flexible, but not very efficient (test.de). The portable split concept sidesteps both weaknesses, which is why devices like the Midea PortaSplit and our SplitClima S12 cool a room with a fraction of the leakage losses.

How do you seal a tilt window for a monoblock, step by step?

You need a seal kit sized for your window, rubbing alcohol and 15 to 20 minutes. Clean the frame, stick the velcro, attach the fabric, tilt the window and zip the hose in. Nothing is drilled and everything comes off later.

1. Wipe the window frame and the sash with alcohol so the adhesive velcro bonds properly.
2. Stick one velcro strip around the fixed frame and one around the tilting sash.
3. Press the fabric onto both strips, working corner by corner without tension.
4. Tilt the window and close the zip.
5. Open the zip a hand's width, insert the hose end and pull the fabric snug around it.
6. Check the hinge side for gaps and press the fabric down where it lifts.

Point the hose end slightly downward so rain cannot run in, and take the fabric off before storms: a tilted window with fabric acts like a sail.

How do you route a portable split line without drilling?

Place the indoor unit within reach of the window or balcony door, hang or stand the outdoor unit outside, lay the flat line over the sill, close the window onto it and seal the last slit with foam. No tools beyond a screwdriver for the bracket, no holes in the building.

1. Pick the window or balcony door closest to where the unit will stand. The PortaSplit's line is 2 m long, so measure before you commit.
2. Get a second person. Owners on Reddit report the indoor unit weighs around 45 kg, "really hard to move into position" alone (redditrecs.com).
3. Hang the outdoor unit on the balcony parapet with its bracket, or stand it on the balcony floor.
4. Lay the flat line over the window sill or through the lower corner of the balcony door.
5. Close the window gently onto the line. The line is built to be clamped this way.
6. Seal the remaining gap with the foam strip from the kit.

At move-out, everything lifts off without a trace. The S12 ships with the complete window kit in the box.

What about roller shutters and balcony doors?

Balcony doors are often the easier route: the opening is lower, larger seal kits fit them, and a split line passes under-used corners cleanly. Two rules for roller shutters: never lower a shutter onto a hose or line, and do not route anything through the shutter box itself. During the day, keep the shutter halfway down over the sealed window; it shades the fabric and cuts the heat load.

Will this damage the window or cost you your deposit?

No. Velcro peels off, foam strips pull out, clamped panels lift away. Nothing described here alters the building, and that is the line that matters for tenants: fixed installations need the landlord's approval and often a cantonal permit, while a mobile unit vented through an existing window opening generally does not (homegate.ch).

Two honest caveats: cantons treat air conditioning differently, and Geneva is stricter than most, so check before you buy anything fixed. And noise rules apply to every device, everywhere, especially at night. You will find the details in our guides hub and the FAQ.

If you want the smallest possible opening, a portable split is the clean answer: the Midea PortaSplit (CHF 1'190.–) and our SplitClima S12 (CHF 799.–, window kit included) both vent through a window closed to a slit, and the window seal kit covers any monoblock you already own. All units are currently sold out; join the waitlist on the product pages for 48-hour early access when the spring 2027 batch lands.