Steam heating is not as efficient as hot water heating, but it is far more efficient than other heating systems. Often, new parts can improve performance significantly.
Fireplaces lose most of the heat they generate through their chimneys, and furnaces waste a significant amount of energy heating and transferring air. Steam boilers are able to transfer a much higher percentage of generated heat to the structure. While their higher operating temperature makes them inherently less efficient when compared to hot water boiler systems, they do not need pumps to circulate water and are relatively simple to operate. Instead of purchasing a new boiler, homeowners see better gains by installing better insulation and patching air leaks in the building.
Central steam heating systems were popular in buildings up to the mid-20th century, but insulation technology and pipes have improved significantly since then. As a result, replacing worn pipes and upgrading components of the system can lead to better efficiency.