Many different heating systems have been devised for heating buildings. Each has its own characteristics, advantages and disadvantages. They can be classified according to the method in which the heat is delivered, the nature of the heat, the fuel being used and the efficiency of the process. The fuel being used, can again be differentiated, and makes a significant contribution to the efficiency of the systems. Each fuel has its own advantages and disadvantages, such as availability cost, and the efficiency of the heating equipment which is dependent on system design and construction.
There are four mediums for transferring heat, that include air, water, steam and electricity, and heating methods may differ considerably in efficiency and desirability. Because of the various methods in practice, heating systems can vary, but most fall into different classes.
i) Warm-air heating systems: Air is used to transfer heat to various rooms. The main unit of the system is a furnace which can use any of the fuel sources. Cool air is heated and then distributed through the duct system, where the heat is transferred, recycled and re-distributed.
ii) Hydronic systems: Hot-water heating systems use water, which is heated in a boiler or water heater and circulated through the piping system or radiators or heating panel installed in the floors or ceilings. Hot water systems can be further classified according to the type of water circulation, the piping arrangement, and the temperature of the supply water.
iii) Steam heating systems: Steam is a very effective heating medium and was until recently, the most commonly used method for heating residential, commercial and industrial buildings. However, the use has diminished as less expensive methods have been developed. The steam produced when water is boiled is used to heat emitting units such as radiators and convectors located in rooms throughout the building.
iv) Electric heating: Electricity can be used both as a source and a fuel. For example, the boilers in the hot water system are heated with electricity, and electric furnaces can also be used to warm air in the forced-warmed heating systems. The electric systems may be cheaper but contain more components, variables and controls such as the electric furnace, the duct heaters, and heat pumps
There some advantages to using electric heating, that includes safety, and quiet operation, as fewer mechanical parts are involved. The heating units are very compact and there is no need for ducts or pipes.
In solar heating, the energy produced by the sun is used to heat water, which is used for domestic purposes. Solar hot water also has industrial applications, e.g. to generate electricity. Solar heating is being adopted in climates where the sun is and abundantly and readily available and as the technology improves, more widespread adoption and uses can be expanded.
The type of heating selected will depend on several factors, which should include the cost, efficiency, availability and suitability.