Heating films are a method of electric resistance heating, providing relatively low temperatures (compared to many conventional heating systems) over large areas. Heating films can be directly installed to provide underfloor heating, wall radiant heating and ceiling radiant heating. The films can also be used in heating panels to produce wall or ceiling panel heaters. Although heating films do not usually run at very high temperatures (typically 30 °C (86 °F) on floors and up to 40 °C (104 °F) on walls), due to the large surface area they cover, they can provide significant energy output. Also due to the low temperature, undesirable heat losses can be lower, when compared to higher temperature wet heating systems with losses from long pipe runs from the central heating source.
Description Electric resistance heating films consist of a substrate film, most commonly made from plastic, printed or coated with a resistance material and electric contact busbars. This is laminated or coated with another layer of insulating film, usually similar to the substrate. Electrical contacts can be made using various types of crimp contacts, which make contact through the covering films to the internal busbars. If the operating voltage is high enough, the contacts must be additionally insulated and additional safety insulation or safety earth covering must be provided over the film to protect users from shock, in case of damage to the installed film. Heating films can be used as a replacement for conventional heating systems, as a primary heat source or used to augment existing systems. Due to the simplicity of installation and ease of hiding the installation, it can be popular with DIY installers. The films can be placed or removed when needed, when installed under carpets of other easily removable floor covering. Heating controllers can allow the residents to select which surface will be heated. Films are available with different power outputs per m2. The required power output will depend on the area covered, building insulation, required energy input to the room and maximum desired surface temperature. Many countries have regulations for the maximum floor or wall temperature. Thermostats with surface temperature sensors may be required in these jurisdictions. This heating system is mainly used in Asian countries like Korea, where it is considered as a modern version of ondol heating. Some heating films are semi-permanent, meaning that they need to be changed after a certain period of use, and are not widely available everywhere. However, many modern heating films can be considered permanent, lasting at least 20 years with no degradation in performance. Heating films are becoming increasingly popular globally
Ondol radiant floor heating
An ondol, also called gudeul (Korean: 구들), in Korean traditional architecture, is underfloor heating which uses direct heat transfer from wood smoke to the underside of a thick masonry floor. Many modern Korean houses use a radiant underfloor heating system that's called ondol, referring to the traditional ondol heating system. In fact, Korean people refer to any domestic heating system as ondol. Technically, the modern day ondol is based on the same concept as the underfloor radiant heating invented by the American architect Frank Lloyd Wright, who was interested in Japanese architecture. Wright came with the idea while visiting a Japanese nobleman's house, where he found a tea room that was different from the rest of the house, using a Korean ondol as a heating system. He then took the same idea to create a heating system that fits American houses. Wright invented modern radiant floor heating, using hot water running through pipes instead of hot air through flues. A heating film, itself, is a variation of the modern ondol, but it doesn't require hot water and pipes as it is fully electric. There are also many variations of this underfloor heating system, as many underfloor heaters are based on PTC heating element, far-infrared rays, carbon film, or cables, etc.
Operating voltage Heating films for domestic heating are available to be powered directly from the mains electricity supply in different countries, e.g. 120 volts AC, 220 volts AC, etc. or low voltage, e.g. 24 volts.
Mains voltage In general, due to safety issues, heating films supplied directly from the mains are only installed underfloor or in ceilings. Due to potentially hazardous voltages from mains electricity, protection from electric shock is usually required, either due to damage (e.g. nails) or water ingress. Most commonly, additional insulation layers are added over the heating film and sealed with waterproof tapes, although this does not provide protection from shock due to damage like nails. Metalised bags or sheets, connected to earth can also be used, relying on earth leakage (RCD) protection devices on the mains supply to provide protection from shock due to damage. Due to the additional protection layers, the heating efficiency of mains films can be reduced, however the lack of power supply makes these types of heating film attractive.
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