I currently live in a two family house built in 1923. Each unit is served by an individual steam boiler. Other than simply buying a newer steam boiler (which I am told will still only be about 80% efficient) what options are available to me to reduce my heating costs. Can I simply convert the existing system to a hot water or geothermal system. Running ductwork for a forced air system would be difficult. Please advise, thank you.