Portable AC with no window to open: how to cool the room

A fixed or picture window has no opening, so there is nothing to run an exhaust hose through without altering the building. This is the hardest case, and most of the advice you will read for it is wishful. Here are the options that actually work, in the order most renters should consider them.

1. Vent through a different opening

Look around the room. An adjacent openable window, or, very commonly in EU flats, a balcony or French door, gives you somewhere to run the hose. This is almost always the right first answer. A one-box portable plus a door seal handles a balcony door cleanly.

2. Choose a mobile split

A mobile split keeps its compressor outside and joins the indoor unit with a flat 2.7 cm refrigerant line, not a 150 mm air hose. That line can pass through a much smaller gap: a cracked-open adjacent sash, a small wall penetration, or a door seal. For a room with only fixed glazing, it is the cleanest way to get real cooling without touching the glass.

3. Through-the-wall vent

A core-drilled wall vent (typically 125 to 162 mm) lets a one-box portable exhaust through the wall instead of a window. It is a permanent change. In rented housing it needs the landlord’s written consent, and for a portable it is rarely worth the work.

What not to do

Do not run the exhaust hose into a closed adjacent room, a chimney or a dropped ceiling. The heat and moisture have to leave the building, not move to the next space. And do not try to remove a modern sealed glazing unit to fit a vent panel; those panes are not designed to come out, and a DIY attempt risks the seal and the glass.

The practical takeaway

If the room has any other opening, vent through that. If it genuinely does not, a mobile split is the sensible buy, because it asks the least of the window. Run the finder and answer “fixed” for the window; it will steer you toward the units that suit.