I need advice. I currently have a house with 4 functional heating options. First the original part of the house (c 1958) has both a natural gas furnace and a fireplace. The addition (c 1994) which is as big as the original house, has a wood stove and a ventless propane wall furnace that I installed when I purchased it 7 years ago. The natural gas furnace is 53 years old. The whole house is built on a concrete slab with the plumbing set into the slab and no duct work to the furnace. Currently we are looking at updating a few thing and making more space in the lay out of the house. The furnace and hot water tank reside in a "closet" in our kitchen. We would like to go to a tankless water heater, as there is only one bathrrom, no dishwasher and only the kitchen and bathroom sinks to contend with. We are unsure of what to do as far as an enegry effieicent and cost efficient way to get the whole house on one heating system. Does anyone have any ideas?