Emissivity in buildings - Revision history

Editor at 18:25, 1 December 2021

2021-12-01T18:25:49Z

← Older revision		Revision as of 18:25, 1 December 2021
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	There is also increasing interest in the urban heat island effect, a term given to localised higher temperatures that are experienced in urban environments compared with the temperatures of surrounding green spaces. This is predominantly a factor of solar absorption, but can be reduced by high emissivity.		There is also increasing interest in the urban heat island effect, a term given to localised higher temperatures that are experienced in urban environments compared with the temperatures of surrounding green spaces. This is predominantly a factor of solar absorption, but can be reduced by high emissivity.

−	= Related articles on Designing Buildings ~~Wiki~~ =	+	= Related articles on Designing Buildings =

	* Accredited construction details ACDs.		* Accredited construction details ACDs.
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	* Computational fluid dynamics (CFD).		* Computational fluid dynamics (CFD).
	* Cool roofs.		* Cool roofs.
		+	* Electromagnetic spectrum.
	* g-value.		* g-value.
	* Heat loss.		* Heat loss.

Editor at 17:05, 7 April 2021

2021-04-07T17:05:23Z

← Older revision		Revision as of 17:05, 7 April 2021
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	* Accredited construction details ACDs.		* Accredited construction details ACDs.
	* Albedo.		* Albedo.
		+	* Angular selective shading systems.
	* Birds and building collisions.		* Birds and building collisions.
	* Computational fluid dynamics (CFD).		* Computational fluid dynamics (CFD).

Designing Buildings at 06:28, 9 October 2020

2020-10-09T06:28:29Z

← Older revision		Revision as of 06:28, 9 October 2020
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	* Visible light.		* Visible light.

−	[[Category:~~Standards_/_measurements~~]] [[Category:~~DCN_Standard~~]]	+	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:Standards_/_measurements]]

Editor at 14:33, 17 June 2020

2020-06-17T14:33:26Z

← Older revision		Revision as of 14:33, 17 June 2020
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−	[[File:~~Tower glazing 2256490 640~~.jpg]]	+	[[File:Tower_glazing_2256490_640.jpg\|link=File:Tower_glazing_2256490_640.jpg]]

	The amount of long wave infra-red radiation which a surface of known temperature (such as the façade of a building) will emit to its surroundings is determined by its emissivity. According to Kirchoff's law, the emissivity of a surface is equal to its radiant absorptivity at a given temperature and wavelength.		The amount of long wave infra-red radiation which a surface of known temperature (such as the façade of a building) will emit to its surroundings is determined by its emissivity. According to Kirchoff's law, the emissivity of a surface is equal to its radiant absorptivity at a given temperature and wavelength.
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	* Accredited construction details ACDs.		* Accredited construction details ACDs.
	* Albedo.		* Albedo.
		+	* Birds and building collisions.
	* Computational fluid dynamics (CFD).		* Computational fluid dynamics (CFD).
	* Cool roofs.		* Cool roofs.
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	* Visible light.		* Visible light.

−	[[Category:Standards_/_measurements]]	+	[[Category:Standards_/_measurements]] [[Category:DCN_Standard]]

Designing Buildings at 11:57, 13 April 2020

2020-04-13T11:57:49Z

← Older revision		Revision as of 11:57, 13 April 2020
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		+	[[File:Tower glazing 2256490 640.jpg]]
		+
	The amount of long wave infra-red radiation which a surface of known temperature (such as the façade of a building) will emit to its surroundings is determined by its emissivity. According to Kirchoff's law, the emissivity of a surface is equal to its radiant absorptivity at a given temperature and wavelength.		The amount of long wave infra-red radiation which a surface of known temperature (such as the façade of a building) will emit to its surroundings is determined by its emissivity. According to Kirchoff's law, the emissivity of a surface is equal to its radiant absorptivity at a given temperature and wavelength.

Designing Buildings at 11:52, 13 April 2020

2020-04-13T11:52:12Z

← Older revision		Revision as of 11:52, 13 April 2020
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−	The amount of long wave infra-red radiation which a surface of known temperature (such as the façade of a building) will emit to its surroundings is determined by its emissivity. According to Kirchoff's law the emissivity of a surface is equal to its radiant absorptivity at a given temperature and wavelength.	+	The amount of long wave infra-red radiation which a surface of known temperature (such as the façade of a building) will emit to its surroundings is determined by its emissivity. According to Kirchoff's law, the emissivity of a surface is equal to its radiant absorptivity at a given temperature and wavelength.

	All bodies which are hotter than 0°K emit thermal radiation and absorb thermal radiation. The difference in the total amount of radiation emitted and absorbed by a body at any given moment may result in a net heat transfer which will produce a change in the temperature of that body.		All bodies which are hotter than 0°K emit thermal radiation and absorb thermal radiation. The difference in the total amount of radiation emitted and absorbed by a body at any given moment may result in a net heat transfer which will produce a change in the temperature of that body.
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	Thermal radiation includes all those wavelengths of the electromagnetic spectrum which will heat a body when absorbed by it, ranging from about 100 nm to 100,000 nm. In general, the higher the temperature of a body, the lower the average wavelength of the radiation it emits. The range of terrestrial temperatures experienced within the built environment is comparatively small, and relative to the temperature of the sun this range is ‘cold’ and hence radiating at a much longer wavelength. This anomaly allows us to categorise thermal radiation as solar radiation and terrestrial or long wave infra-red radiation.		Thermal radiation includes all those wavelengths of the electromagnetic spectrum which will heat a body when absorbed by it, ranging from about 100 nm to 100,000 nm. In general, the higher the temperature of a body, the lower the average wavelength of the radiation it emits. The range of terrestrial temperatures experienced within the built environment is comparatively small, and relative to the temperature of the sun this range is ‘cold’ and hence radiating at a much longer wavelength. This anomaly allows us to categorise thermal radiation as solar radiation and terrestrial or long wave infra-red radiation.

−	The wavelength of terrestrial radiation varies with temperature, however at room temperature approximately 97% of the radiation emanating from perfect emitter will be within the range 3,000 nm to 50,000 nm. Terrestrial surfaces emit long wave infra-red radiation in all directions within a hemisphere about their azimuth.	+	The wavelength of terrestrial radiation varies with temperature, however at room temperature approximately 97% of the radiation emanating from a perfect emitter will be within the range 3,000 nm to 50,000 nm. Terrestrial surfaces emit long wave infra-red radiation in all directions within a hemisphere about their azimuth.

−	This hemisphere can include a wide variety of thermal bodies, ranging from the clear night sky to relatively warmer solid bodies all of which will be emitting different intensities and wavelengths of thermal radiation themselves. In order to simplify this complex situation terrestrial radiation is generally treated as an average heat transfer based on hemispherical emissivities and average hemispherical surface temperatures.	+	This hemisphere can include a wide variety of thermal bodies, ranging from the clear night sky to relatively warmer solid bodies, all of which will be emitting different intensities and wavelengths of thermal radiation themselves. In order to simplify this complex situation terrestrial radiation is generally treated as an average heat transfer based on hemispherical emissivities and average hemispherical surface temperatures.

	Emissivity can be an important factor in selecting building materials. For example, glass, can be given a low-e coating to reduce heat loss to the outside. In effect, this coating increases the reflectance of long wave infra-red radiation back into the interior by reducing the emissivity of the glass (its long wave infra-red absorption). Conversely, ‘cool roofs’ benefit from high emissivity, re-radiating absorbed solar radiation to the sky to reduce overheating in the summer.		Emissivity can be an important factor in selecting building materials. For example, glass, can be given a low-e coating to reduce heat loss to the outside. In effect, this coating increases the reflectance of long wave infra-red radiation back into the interior by reducing the emissivity of the glass (its long wave infra-red absorption). Conversely, ‘cool roofs’ benefit from high emissivity, re-radiating absorbed solar radiation to the sky to reduce overheating in the summer.

Editor at 15:09, 21 November 2018

2018-11-21T15:09:28Z

← Older revision		Revision as of 15:09, 21 November 2018
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	There is also increasing interest in the urban heat island effect, a term given to localised higher temperatures that are experienced in urban environments compared with the temperatures of surrounding green spaces. This is predominantly a factor of solar absorption, but can be reduced by high emissivity.		There is also increasing interest in the urban heat island effect, a term given to localised higher temperatures that are experienced in urban environments compared with the temperatures of surrounding green spaces. This is predominantly a factor of solar absorption, but can be reduced by high emissivity.

−	~~= Find out more =~~	+	= Related articles on Designing Buildings Wiki =
−		+
−	=== Related articles on Designing Buildings Wiki ===	+

	* Accredited construction details ACDs.		* Accredited construction details ACDs.
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	* Cool roofs.		* Cool roofs.
	* g-value.		* g-value.
		+	* Heat loss.
	* Heat transfer.		* Heat transfer.
	* Low-e glass.		* Low-e glass.

Editor at 10:44, 16 July 2018

2018-07-16T10:44:06Z

← Older revision		Revision as of 10:44, 16 July 2018
Line 29:		Line 29:
	* Solar reflectance index.		* Solar reflectance index.
	* Solar transmittance (gtot).		* Solar transmittance (gtot).
		+	* The effects of electromagnetic fields in the workplace.
	* Thermal bridge.		* Thermal bridge.
	* Thermal optical properties.		* Thermal optical properties.

Editor at 12:54, 8 February 2018

2018-02-08T12:54:20Z

← Older revision		Revision as of 12:54, 8 February 2018
Line 3:		Line 3:
	All bodies which are hotter than 0°K emit thermal radiation and absorb thermal radiation. The difference in the total amount of radiation emitted and absorbed by a body at any given moment may result in a net heat transfer which will produce a change in the temperature of that body.		All bodies which are hotter than 0°K emit thermal radiation and absorb thermal radiation. The difference in the total amount of radiation emitted and absorbed by a body at any given moment may result in a net heat transfer which will produce a change in the temperature of that body.

−	Thermal radiation includes all those wavelengths of the electromagnetic spectrum which will heat a body when absorbed by it, ranging from about ~~100nm~~ to 100,~~000nm~~. In general, the higher the temperature of a body, the lower the average wavelength of the radiation it emits. The range of terrestrial temperatures experienced within the built environment is comparatively small, and relative to the temperature of the sun this range is ‘cold’ and hence radiating at a much longer wavelength. This anomaly allows us to categorise thermal radiation as solar radiation and terrestrial or long wave infra-red radiation.	+	Thermal radiation includes all those wavelengths of the electromagnetic spectrum which will heat a body when absorbed by it, ranging from about 100 nm to 100,000 nm. In general, the higher the temperature of a body, the lower the average wavelength of the radiation it emits. The range of terrestrial temperatures experienced within the built environment is comparatively small, and relative to the temperature of the sun this range is ‘cold’ and hence radiating at a much longer wavelength. This anomaly allows us to categorise thermal radiation as solar radiation and terrestrial or long wave infra-red radiation.

−	The wavelength of terrestrial radiation varies with temperature, however at room temperature approximately 97% of the radiation emanating from perfect emitter will be within the range 3,~~000nm~~ to 50,~~000nm~~. Terrestrial surfaces emit long wave infra-red radiation in all directions within a hemisphere about their azimuth. This hemisphere can include a wide variety of thermal bodies, ranging from the clear night sky to relatively warmer solid bodies all of which will be emitting different intensities and wavelengths of thermal radiation themselves. In order to simplify this complex situation terrestrial radiation is generally treated as an average heat transfer based on hemispherical emissivities and average hemispherical surface temperatures.	+	The wavelength of terrestrial radiation varies with temperature, however at room temperature approximately 97% of the radiation emanating from perfect emitter will be within the range 3,000 nm to 50,000 nm. Terrestrial surfaces emit long wave infra-red radiation in all directions within a hemisphere about their azimuth.

−	Emissivity can be an important factor in selecting building materials. For example, glass, can be given a low-e coating to reduce heat loss to the outside. In effect, this coating increases the reflectance of long wave infra-red radiation back into the interior by reducing the emissivity of the glass (its long wave infra-red absorption). Conversely, ‘cool roofs’ benefit from high emissivity, re-radiating absorbed solar radiation to the sky to reduce overheating in the summer. There is also increasing interest in the urban heat island effect, a term given to localised higher temperatures that are experienced in urban environments compared with the temperatures of surrounding green spaces. This is predominantly a factor of solar absorption, but can be reduced by high emissivity.	+	This hemisphere can include a wide variety of thermal bodies, ranging from the clear night sky to relatively warmer solid bodies all of which will be emitting different intensities and wavelengths of thermal radiation themselves. In order to simplify this complex situation terrestrial radiation is generally treated as an average heat transfer based on hemispherical emissivities and average hemispherical surface temperatures.
		+
		+	Emissivity can be an important factor in selecting building materials. For example, glass, can be given a low-e coating to reduce heat loss to the outside. In effect, this coating increases the reflectance of long wave infra-red radiation back into the interior by reducing the emissivity of the glass (its long wave infra-red absorption). Conversely, ‘cool roofs’ benefit from high emissivity, re-radiating absorbed solar radiation to the sky to reduce overheating in the summer.
		+
		+	There is also increasing interest in the urban heat island effect, a term given to localised higher temperatures that are experienced in urban environments compared with the temperatures of surrounding green spaces. This is predominantly a factor of solar absorption, but can be reduced by high emissivity.

	= Find out more =		= Find out more =
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	* Solar heat gain coefficient.		* Solar heat gain coefficient.
	* Solar reflectance index.		* Solar reflectance index.
		+	* Solar transmittance (gtot).
	* Thermal bridge.		* Thermal bridge.
	* Thermal optical properties.		* Thermal optical properties.

Designing Buildings at 08:48, 10 September 2017

2017-09-10T08:48:02Z

← Older revision		Revision as of 08:48, 10 September 2017
Line 26:		Line 26:
	* Thermal bridge.		* Thermal bridge.
	* Thermal optical properties.		* Thermal optical properties.
		+	* Thermography for traditional buildings.
	* Urban heat island effect.		* Urban heat island effect.
	* U value.		* U value.