Hi
We found a Reihenhaus to buy but the dorms are on the top floor. It has a Flachdach... how will sleep be during the hot summer months? any experience?

We rent at the moment a maisonette and in the attic is unbearable warm. (Regular Roof - Schrägdach)

if the roof has been insulated/renovated, what shall I look at?

a different apartment

Look at how the hot air will rise and whether that inevitably makes the bedrooms warm or not.

We have a full height sloping ceiling in the main part of the house which channels the rising heat into the bedrooms, but even so if we keep the doors closed and open windows at night it is bearable. Or we sleep in the basement for a night or two.

Almost all houses have the bedrooms at the top, so I don't think that specifically is a criteria for choosing.

ps. it's almost more of a problem in winter, when I want the lower living rooms warm but the bedrooms cooler.

Actually, lots of new ones don't. Our last one had bedrooms at the bottom, and north facing so wonderfully cool in the summer.

Friends of ours have recently bought a new build and the bedrooms are below the living accommodation.
I've seen others like this too - especially those with a view.