Simply put, a furnace heats air and a boiler heats water. Both systems ultimately are designed to provide space heating to a home or building. Boilers are less common to see in newer homes due to their higher cost of installation, but provide excellent heating. A typical residential boiler heating system works by distributing hot water to baseboard units, or throughout a radiant floor heating system. Forced air furnaces are the most common heating system in new construction and rely on blowing heated air through ductwork. The same ductwork for a forced air furnace can also be used in the cooling months to distribute the air conditioning. Most HVAC companies can service furnaces, whereas specialized boiler technicians are a bit harder to come by due to the fact that boilers involve plumbing as well as heating components.