Heat pump or efficient furnace for old Midwest house – GreenBuildingAdvisor

Hello GBA, I would appreciate input or direction to existing articles that would help us make a decision on a suitable gas furnace replacement. We have an 1890 masonry ‘ worker house’ in the upper Midwest and are planning multiple upgrades, including attic insulation, new windows and doors. Our first floor and basement uses a gas powered water boiler for heating. We installed a split system several years ago to provide cooling in the summer. The upstairs, approximately 800 SF but with lots of windows and skylights, has an existing gas furnace with short duct runs. It provides heat and cooling but is very loud and inefficient. For our forthcoming work we want to include an upgrade to this 2nd floor system. We would prefer to not upgrade all the mechanicals because we are already pushing our budget limit. I am concerned that replacing the furnace with ducted heat pumps will not provide enough heat. Our exterior walls remain uninsulated, and we have many windows and skylights. We would also still need gas service due to the boiler. Thoughts and recommendations would be greatly appreciated.