The options for heating a large space such as a warehouse or factory essentially come down to two types of heating – warm air or radiant. Each of these has particular characteristics so it’s very important to understand the nature of the space being heated and the type of heating required in order to make the right decision.
Warm air space heating systems use a fan to draw air across a heat exchanger, thereby heating the air and distributing it evenly throughout the space. As such, these are ideal for areas where a constant temperature is required throughout the space. The heat source for warm air heating can be a gas or oil fired burner, hot water circulated through the heat exchanger (the hot water being generated by centrally located heating plant) or an electric element. The heaters themselves can be suspended above the space being heated, mounted on walls or they can stand on the floor. Floor standing models may either use nozzles to direct the warm air locally or they can be connected to a ductwork system to distribute the warm air across a wider area. The most appropriate choice will depend on factors such as the layout of the space and the floor area available. For example, where floor space is at a premium a suspended or wall mounted solution will generally be the preferred choice.
With a warm air heating system some of the heated air will inevitably rise to the top of the building, potentially resulting in wasted energy. The solution is to combine warm air heating with destratification fans to return the warm air from the roof space back to the occupied space (see our separate paper on Destratification fans).
Free-standing air rotation heaters are a recent development in warm air heating. They use high-efficiency axial fans to move large volumes of air through the space at relatively low temperatures. They are especially suitable for warehousing/logistics facilities where dense racking may be in use and occupancy is occasional. The air rotation also eliminates the need for destratification.
Radiant heating in large spaces is typically provide by radiant tubes suspended from the roof, though in some cases radiant plaque heaters may be used. In both cases the heat energy is emitted in the form of infrared radiation from the hot surfaces of the heaters. This infrared radiation heats people and other objects that are exposed to it, without directly warming the air. As a result, the air temperature in a radiant heated space is typically lower than in a warm air heated space. However, body comfort is maintained as long as people are in ‘direct line of sight’ of the heat source. Where people may be shielded from the radiant heating by equipment or building structures, their body comfort is likely to be compromised. This imposes certain limitations on the layout of the working space and any future re-configuration of that space. Consequently, radiant heating is most suitable for areas with high air change rates, such as loading bays.