Don't the "Old Town" buildings have their own heating? Maybe have a look at how that is coded?

Selfheated houses have nothing to do with heating pipe input...

Thanks its not Self heating. I live in a house that had a heating input from the 50's that was heated like in game was trying to add the pipe from the heat plant to the house and I think i have worked it out by adding a heat input and power input to the house.