Radiant heating (cost varies greatly; wall panel from £200)
Technically, the sun warms us by radiant heat, as does an open fire – which also warms us through convection (which is what radiators do ironically). ‘Radiant heating’ is more narrowly defined as a method of intentionally using the principles of radiant heat to transfer radiant energy from an emitting heat source to an object.
Utilising radiant heating has existed since the Roman use of hypocaust heating, and underfloor radiant heating has also long been widespread in China and Korea. Modern wet underfloor heating systems may be regarded as radiant heating, although again there is an element of convection (and conduction) employed.
Specifically, long-wave heat energy is emitted from a heat source, such as the floor, a wall, or overhead panel, which warms people (and surfaces) directly rather than heating the air. Internal air temperatures for radiant heated buildings are often lower than for conventionally heated buildings, since the same level of body thermal comfort is perceived.
Many modern outdoor heaters are radiant heaters.
Since their heating surface is much larger than other systems, underfloor and wall radiant heating are often called low-temperature systems, as a much lower temperature is required to achieve the same level of heat transfer. This also provides an improved room climate with healthier humidity levels and less likelihood of mould growth.
Radiant overhead panels are often used in large production and warehousing facilities, churches or sports centres - they hang a few meters above the floor pointing down so as to provide a more directional form of heating, rather than heating the whole space.
Radiant heating is generally electric, and even though less heat is required, electric heating is still an expensive option, both on your pocket and the environment – unless of course you’re generating your own.
A more modern development called thin film radiant heating converts 99.9% of the electricity to long wave infrared radiant energy, and 85% of the surface area is covered with heating element. By increasing the heated surface area, the efficiency of the thermal transfer is increased, and the radiant heating film warms up more area, more quickly and at lower temperatures using less energy, significantly increasing efficiency.