Fresh air heating Smeets remodeling possible?

I do not know whether Bien-Zenker Smeets installs, but I am aware that advertising is done, among other things, with an air-to-air heat pump.

Schwörerhaus also likes to do this in the standard version.

My parents bought one like that, and in cold winters the fortunately present wood stove runs daily because otherwise the place does not get warm enough.

Conversion is quite difficult. You are almost a bit bound to the air-to-air heat pump because for other heating types you would have to retrofit underfloor heating and all heating pipes.