Radiant heating
Encyclopedia
Radiant heating is a technology for heating indoor and outdoor areas. Heating by radiant energy
is observed everyday, the warmth of the sunshine being probably the most commonly observed example. Radiant heating as a technology is typically more narrowly defined. It is the method of intentionally using mostly the principles of radiant heat to transfer radiant energy
from an emitting heat source to an object. Designs with radiant heating is seen as replacement for conventional convection heating
. But also as a way of supplying confined outdoor heating.
(mostly convection heating
). The technology has existed since the Roman
use of hypocaust
heating. Underfloor radiant heating has long been widespread in China
and Korea
. Another example is the Austrian/German Kachelofen or masonry heater
. The heat energy is emitted from a warm element, such as a floor, wall or overhead panel, and warms people and other objects in rooms rather than directly heating the air. The internal air temperature
for radiant heated buildings may be lower than for a conventionally heated building to achieve the same level of body comfort, when adjusted so the perceived temperature is actually the same.
The radiant heating systems can be divided into:
Underfloor and wall heating systems often are called low-temperature systems. Since their heating surface is much larger than with other systems, a much lower temperature is required to achieve the same level of heat transfer
. The maximum temperature of the heating surface can vary from 29–35 °C (84.2–95 F) depending on the room type. Radiant overhead panels are mostly used in production and warehousing facilities or sports centers; they hang a few meters above the floor and their surface temperature is much higher.
The systems can be divided as:
And example of the overhead radiant heaters are the patio heaters
often used with outdoor serving. The top metal disc reflects the radiant heat onto a small area.
Radiant heating can also be used for snow melting
and for roof and gutter de-icing
applications. Snow and ice melting can be achieved on concrete, asphalt, pavers and other surfaces by placing heating units (electric heating elements or hydronic tubing) under the substrate, embedded into the substrate, or retrofit by saw-cut into the substrate of the surface to be free of snow and ice buildup. For roof de-icing, heating elements can be placed on the surface of the roofing material and some technologies can be placed underneath the roofing materials. Heating elements are used in gutters and downspouts to prevent ice buildup that can cause ice dams and icicles. Radiant heating is also used on roofs to eliminate heavy snow loads that can cause structural damage.
Radiant energy
Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be calculated by integrating radiant flux with respect to time and, like all forms of energy, its SI unit is the joule. The term is used particularly when radiation is emitted by a source into the...
is observed everyday, the warmth of the sunshine being probably the most commonly observed example. Radiant heating as a technology is typically more narrowly defined. It is the method of intentionally using mostly the principles of radiant heat to transfer radiant energy
Radiant energy
Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be calculated by integrating radiant flux with respect to time and, like all forms of energy, its SI unit is the joule. The term is used particularly when radiation is emitted by a source into the...
from an emitting heat source to an object. Designs with radiant heating is seen as replacement for conventional convection heating
Convector heater
A convection heater is a heater which operates by air convection currents circulating through the body of the appliance, and across its heating element. This heats up the air, causing it to increase in volume and so become buoyant and rise...
. But also as a way of supplying confined outdoor heating.
Indoors
Radiant heating heats a building through radiant heat, rather than other conventional methods such as radiatorsRadiator (heating)
Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating. The heating radiator was invented by Franz San Galli, a Prussian-born Russian businessman living in St. Petersburg, between 1855–1857.- Radiation vs...
(mostly convection heating
Convector heater
A convection heater is a heater which operates by air convection currents circulating through the body of the appliance, and across its heating element. This heats up the air, causing it to increase in volume and so become buoyant and rise...
). The technology has existed since the Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
use of hypocaust
Hypocaust
A hypocaust was an ancient Roman system of underfloor heating, used to heat houses with hot air. The word derives from the Ancient Greek hypo meaning "under" and caust-, meaning "burnt"...
heating. Underfloor radiant heating has long been widespread in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
. Another example is the Austrian/German Kachelofen or masonry heater
Masonry heater
A masonry heater is a device for warming a home that captures the heat from periodic burning of fuels , and then radiates that heat over a long period at a fairly constant temperature. The technology exists in many forms from the Roman hypocaust to the Austrian/German kachelofen...
. The heat energy is emitted from a warm element, such as a floor, wall or overhead panel, and warms people and other objects in rooms rather than directly heating the air. The internal air temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
for radiant heated buildings may be lower than for a conventionally heated building to achieve the same level of body comfort, when adjusted so the perceived temperature is actually the same.
The radiant heating systems can be divided into:
- Underfloor heatingUnderfloor heatingUnderfloor heating and cooling is a form of central heating and cooling which achieves indoor climate control for thermal comfort using conduction, radiation and convection...
systems—electric or hydronic - Wall heating systems
- Radiant ceiling panels
Underfloor and wall heating systems often are called low-temperature systems. Since their heating surface is much larger than with other systems, a much lower temperature is required to achieve the same level of heat transfer
Heat transfer
Heat transfer is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase-change transfer...
. The maximum temperature of the heating surface can vary from 29–35 °C (84.2–95 F) depending on the room type. Radiant overhead panels are mostly used in production and warehousing facilities or sports centers; they hang a few meters above the floor and their surface temperature is much higher.
Outdoors
In the case of heating outdoor areas, the surrounding air is constantly moving. Relying on convection heating is then in most cases impractical. The reason being, that once you heat the outside air, it will blow away with air movement. Even in a no wind condition the buoyance effects will carry away the hot air. Outdoor radiant heaters allow specific spaces within an outdoor area to be targeted, warming only the people and objects in their path.The systems can be divided as:
- Trace heatingTrace heatingElectric trace heating, also known as electric heat tracing, heat tape or surface heating, is a system used to maintain or raise the temperature of pipes and vessels. Trace heating takes the form of an electrical heating element run in physical contact along the length of a pipe. The pipe must...
- Gutter and Roof De-icing - Snowmelt systemSnowmelt systemA snowmelt system is used to remove snow and ice via embedded electric cables or hydronic tubing. Common areas for snowmelt systems are: driveways, walkways, parking areas, stairways, loading docks, and around car washes. A snowmelt system is usually installed during the original construction in...
- Electric or Hydronic - Overhead natural gasNatural gasNatural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
-fired radiant heaters
Patio heater
A patio heater is an appliance for generating radiant heat for outdoor use.A burner on top of a post, burns LPG or propane, and directs the flames against a perforated metal screen. Heat is radiated from the surface of the screen in a circular pattern around the appliance...
often used with outdoor serving. The top metal disc reflects the radiant heat onto a small area.
Radiant heating can also be used for snow melting
Snowmelt system
A snowmelt system is used to remove snow and ice via embedded electric cables or hydronic tubing. Common areas for snowmelt systems are: driveways, walkways, parking areas, stairways, loading docks, and around car washes. A snowmelt system is usually installed during the original construction in...
and for roof and gutter de-icing
Trace heating
Electric trace heating, also known as electric heat tracing, heat tape or surface heating, is a system used to maintain or raise the temperature of pipes and vessels. Trace heating takes the form of an electrical heating element run in physical contact along the length of a pipe. The pipe must...
applications. Snow and ice melting can be achieved on concrete, asphalt, pavers and other surfaces by placing heating units (electric heating elements or hydronic tubing) under the substrate, embedded into the substrate, or retrofit by saw-cut into the substrate of the surface to be free of snow and ice buildup. For roof de-icing, heating elements can be placed on the surface of the roofing material and some technologies can be placed underneath the roofing materials. Heating elements are used in gutters and downspouts to prevent ice buildup that can cause ice dams and icicles. Radiant heating is also used on roofs to eliminate heavy snow loads that can cause structural damage.