I am living in a large house with radiators and two heating zones in New England. I have the thermostat set to the lowest possible setting in the zone of the house I don't use. Even at that, it is burning a lot of oil to maintain that minimum temperature. How can I shut off that zone and part of the house completely and avoid having the water in the pipes freeze? Would keeping the water circulating through the pipes and radiators be enough? There is no domestic plumbing in the part of the house I want to shut off.