The heating system must cover all heat losses, both from transmission and ventilation. Three main types of heating systems can be outlined:
• Radiant heating • Air heating • Convective heating
Radiant heating transfers heat to surfaces and objects without warming the air on the way. Surfaces are heated and then in turn heat the air within the room. People experience the direct contribution of radiant heat as warmth. The room feels comfortably heated even if the air temperature is relatively low. Radiant heating also prevents overheated air gathering under the ceiling. The equalized distribution of temperature vertically as well as the somewhat lower air temperature contributes to large energy savings. Radiant heat effectively counteracts cold radiation and cold draughts from large windows, for example.
Heating with warm air covers transmission and ventilation losses by supplying heated air to the building. The warm air cools along the outer walls, due to transmission losses. Therefore, the supply air temperature must be higher than the desired room temperature. Because the heated air is lighter and rises in the room, large temperature differences between the ceiling and the floor can occur. At times, it may be necessary to equalize the differences with e.g. ceiling fans.
Convective heating transfers heat to the room by warming the air as it passes hot surfaces, radiators, or convectors. The air flow past the radiator or convector is maintained by thermal currents. The warmed air rises and is replaced by colder air. Rotation, or convection, of the air occurs.Cold draughts from e.g. windows are effectively counteracted by the rising stream of warm air if the heat source is placed under the window.