Insulating between floors?
Balancing your heating system would be the first step be it duct or radiant. You should have some mode of control as in dampers or balancing valves respectively. If it's forced air start by shutting down completely the second floor closing off the first floor and leaving the main ground floor open. The case with radiant should be relatively simple assuming valves are installed simply close the valves where there is too much heat. Keep in mind that the heating system knows nothing of the layout of your house it only knows what the thermostat can tell it so everything when it comes to balancing has to be centered around the thermostat.