A wall hung Munchkin boiler was put into this house. We also replaced the conventional water heater with a indirect waterheater and were able to tuck it under the steps to save floor space. This house was a gravity hot water system and had a two story addition added to the rear back in the 1930's. The addition never heated. Not on the first floor or the second floor. The installer tapped into the gravity system and somehow expected flow to go in a direction opposite what the original plumber designed. We zoned the rear on its own circulator, and now both halves of the house heat very well. The Munchkin is so efficient that we nearly doubled the amount of space being actually heated now, yet the gas bills didn't go up any.