Our paramedic simply laid the two supply lines to the children's rooms, which run through the hallway, generously in two loops (at 4sqm) through the hallway. So not the direct route. If you now heat the children's rooms normally, the hallway is slightly heated as well. This also seemed to us as a pragmatic solution without much fuss, additional electricity, and big ruckus. I would probably see it differently with a larger play hallway or library hallway.