If you live in a Dachgeschosswohnung, you already know it's the hottest flat in the building — sometimes brutally so. A Midea PortaSplit can rescue an attic room, but only if you account for why these spaces get so hot. Here's how to make it work.
Why attic flats get so hot
Top-floor flats sit directly under a roof that bakes in the sun all day, and that heat radiates downward into your living space long after the sun moves. Roof windows (the Velux-style kind) let in strong, direct sunlight, and there's little mass above you to buffer the temperature. The result is a room that keeps heating through the afternoon and stays warm into the night — the toughest cooling job in a typical German home.
Size the PortaSplit generously
Because an attic room has a high heat load, don't size the unit to floor area alone. The extra heat coming through the roof and roof windows means you need more cooling power than the same-sized room on a lower floor would require. Sizing generously lets the PortaSplit keep up instead of running flat out and never quite winning. See our BTU sizing guide and lean toward the higher end.
Shade aggressively — it's half the battle
In an attic, shading matters even more than usual. Shade roof and wall windows from outside wherever possible, because sunlight stopped before it enters never becomes indoor heat. External blinds or shades on roof windows make a dramatic difference. Without shading, the PortaSplit spends all its power fighting incoming sun; with it, the unit can actually get ahead.
Seal, pre-cool, and run smart
Treat the room as a sealed box:
- Close the door and any other windows so you're cooling one contained space.
- Pre-cool during the late afternoon before the evening heat peaks.
- Use sleep mode overnight so it runs quietly while maintaining the temperature.
- Ventilate hard at night when the outside air finally drops, to flush stored heat.
Combine with no-AC tactics
Even with a PortaSplit, the whole-flat basics help: shade everything, ventilate at night, and keep heat-generating appliances off during the day. The cooler you keep the rest of the attic, the less the unit has to fight. Our heatwave survival guide covers these in depth.
The takeaway
An attic flat is the PortaSplit's hardest assignment, but a winnable one: size it generously, shade the roof and windows aggressively, seal and pre-cool the room, and run it on sleep mode. Get those right and even the hottest Dachgeschoss room becomes a comfortable retreat. First, though, you need the unit — check the live PortaSplit map and reserve when it's in stock near you.