I've never seen an instant shower here. Typical water heating in old flats is a 10l natural gas boiler, or if upgraded to central heating a combo heating/hot water gas boiler. There is central heating with heat from power plants (maybe) but sure from waste burning. I think these lines run on steam. Many public buildings are supplied with this type of heating. The standard electrical suplly for flats, more or less regardless of the size, was for a long time 1x 20A, only people with an electric range had 3x20.
Windows: the standard window here was for a long time the double-sash casement. It simply has an inner and outer sash, most continental europeans will probably know them. They were pretty good, but are now being replaced (at least for new construction, but many maniacs also rip out their old windows) with plastic or wooden thermal casements. So double glazing has a long tradition here. Sngle hung guillotine windows were only used here for bays or screened porches where casements would be in the way when open.
