Heating

 

A central heating system provides warmth to the whole interior of a building (or portion of a building) from one point to multiple rooms. When combined with other systems in order to control the building climate, the whole system may be a HVAC (heating, ventilation and air conditioning) system.

 

Central heating differs from local heating in that the heat generation occurs in one place, such as a furnace room in a house or a mechanical room in a large building (though not necessarily at the "central" geometric point). The most common method of heat generation involves the combustion of fossil fuel in a furnace. The resultant heat then gets distributed: typically by forced-air through ductwork.

 

Cities in ancient Greece used central heating systems, conducting air heated by furnaces through empty spaces under the floors and out of pipes in the walls - a system known as a hypocaust. A similar system of central heating was used in ancient Korea, where it is known as ondol. It is thought that the ondol system dates back to the Koguryo or Three Kingdoms (37 BC-AD 668) period when excess heat from stoves were used to warm homes.