This is a bit like diagnosing a disease AND prescribing treatment without seeing the patient.
- My gut reaction is converting from steam to hot water heat would be one great option.
- Some modern high-efficiency condensing gas boilers modulate based on outdoor temperatures, which means they save an incredible amount of energy while also dramatically increasing comfort and control.
You need to have an energy audit performed by a BPI-Accredited heating company that has experience converting from steam to hot water. The report from the energy auditor should show you a few different strategies and include cost/benefit analysis.
For more information:
Read Richard Parker's Q&A "Can you help me select a high efficiency furnace?"