Glossary E-L

the great circle cut in the celestial sphere by an extension of the plane of the sun's apparent orbit around the earth. The great circle drawn on a terrestrial globe makes an angle of about 23.27° with the equator
effective temperature
the temperature of a black enclosure at 50% relative humidity (sea level), in which a solid body or occupant would exchange the same heat by radiation, convection, and evaporation as in the existing nonuniform environment
electromagnetic radiation
(1) emission or transfer of energy in the form of electromagnetic waves or photons. (2) these electromagnetic waves or these photons
hauteur angulaire (FR)
Höhenwinkel (DE)
altura angular (ES)
altezza angolare (IT)
elevasjonsvinkel (NO)
γ elevation angle
Unit: degree
Altitude angle above horizon of a point in the sky hemisphere. Also called altitude angle.
the ratio of the radiant energy emitted from a surface at a given temperature to the energy emitted by a black body at the same temperature
the ratio of the radiant energy emitted (in the absence of incident radiation) from a given plane surface at a given temperature to the radiant energy that would be emitted by a perfect black body at that same temperature
energy demand
Amount of energy required (e.g. for indoor climate control)
energy use
The amount of energy used (e.g. for indoor climate control), including losses of the installation
Total energy in a fluid (usually air) including both sensible energy (dry heat) and the latent energy associated with the water vapour in the air
environmental controls
means by which the physical environment can be controlled: these may be active, e.g. heating or cooling systems, fans etc which use energy, or passive, such as openable windows, blinds, etc.
environmental variables
Thermal characteristics of the environment; generally the air temperature (Ta), the radiant temperature (Tr), the water vapour pressure (Pa) (or humidity) and the air velocity (Va)
the exterior surface of a building including all external additions e.g. chimneys, bay windows, etc.
équation du temps (FR)
Zeitgleichung (DE)
équación del tiempo (ES)
equazione del tempo (IT)
tidsjevning (NO)
ET equation of time
Unit: minute
The equation of time describes the difference between clock time and true solar time due to the eccentricity in the earth's orbit and the tilt of the earth's axis with respect to the ecliptic plane. It is computed according to the recommendations of the Illuminating Engineering Society of North America, IES Journal N°13(4), 1984: Where J is the day of the year also called the Julian day (from 1 to 365, or 366 if the year is bissextile).
change of state from liquid to vapour
evaporative cooling
involves adiabatic heat exchange between air and water spray or wetted surface. The water is cooled by evaporation and assumes the wet-bulb temperature of the air
evaporative equilibrium
the condition attained when the wetted wick has reached a stable and constant temperature. When the instrument is exposed to air at velocities over 4.6m/s, this temperature may be considered to approach the true wetbulb temperature
the uncontrolled leakage of air out of a building e.g. through cracks
extinction coefficient
a property of glazing material that characterizes the solar absorption in the material, namely, the fraction of radiation that is absorbed per unit of path length through the material
éclairement énergétique normal extraterrestre (FR)
extraterrestrische direkte normale Einstrahlung (DE)
irradiancia normal extraterrestre (ES)
illuminamento energetico normale extraterrestre (IT)
ekstraterrestrisk vinkelrett irradians (NO)
Eesno extraterrestrial normal irradiance
Unit: W/m²
Irradiance produced by the sun, on a surface perpendicular to its rays, on the outer limit of the Earth's atmosphere. The product of the solar constant by the sun-earth distance correction factor.
rayonnement solaire extraterrestre (FR)
extraterrestrische Solarstrahlung (DE)
radiación solar extraterrestre (ES)
radiazione solare extraterrestre (IT)
buitenaardse zonnestraling (NL)
ekstraterrestrisk solstråling (NO)
extraterrester solstralning (SE)
  extraterrestrial solar radiation
CIE. Solar radiation incident on the outer limit of the Earth's atmosphere.
flat plate collector
a solar collector, a flat assembly containing a panel of metal or other suitable material, usually a mat black colour on its sunny side, that absorbs sunlight and converts it into heat. This panel is usually in an insulated box, covered with glass or plastic to take advantage of the greenhouse effect. In the collector, this heat transfers to a circulating fluid, such as air, water or oil
floor heating
Heated floor, which gives off heat to the room
focussing collector
a collector that has a reflector which focuses sunlight onto a smaller area for collection. A reflector of this type can obtain relatively high temperatures. The system is most effective for solar radiation not diffused by clouds
forced convection
convection heat transfer between a surface and an adjacent fluid (air in the present context)resulting from forced circulation of a liquid or a gas, as by a fan, jet or pump
free convection
See Convective heat transfer
free-running building
A building which is neither being mechanically heated nor cooled
gaseous state
one of three states of matter charactemed by the greatest freedom of molecules and lack of any inherent fixed shape or volume
système d'information géographique (FR)
Geografisches Informationssystem (DE)
  geographic information system
A Geographic Information System (GIS) is an organized collection of software and geographic data designed to manipulate, analyze, and display all forms of geographically referenced information.
satellite géostationnaire (FR)
Geostationärer Satellit (DE)
  geostationary satellite
An artificial satellite that travels above the equator and at the same speed as the earth rotates, so that the satellite constantly overlooks the same part of the earth.
condition of vision in which there is discomfort or a reduction in the ability to see details or objects, caused by an unsuitable distribution or range of luminance, or to extreme contrast
glare, disability
glare that impairs the vision of objects without necessarily causing discomfort
glare, discomfort
glare that causes discomfort without necessarily impairing the vision of objects
glass used in a window
éclairement énergétique global horizontal (FR)
globale horizontale Einstrahlung (DE)
irradiancia horizontal global (ES)
illuminamento energetico orizontale globale (IT)
global horisontal stråling (NO)
Eeg global horizontal irradiance
Unit: W/m²
Irradiance produced by solar radiation on a horizontal surface on the earth.
rayonnement solaire global (FR)
Globalstrahlung (DE)
radiación solar global (ES)
radiazione solare globale (IT)
totale zonnestraling (NL)
globalstråling (NO)
promieniowanie sloneczne calkowite (PL)
globalstralning (SE)
  global solar radiation
CIE. Sum of direct solar radiation and diffuse solar (sky) radiation.
Greenwich (FR)
Greenwich (DE)
Greenwich (ES)
Greenwich (IT)
Greenwich (NL)
Greenwich (NO)
Greenwich (PL)
Greenwich (SE)
Borough of East Greater London in England, located at a latitude of 51.47°N and a longitude of exactly 0°.
albédo du sol (FR)
Bodenreflektivität (DE)
albedo del suelo (ES)
albèdine del suolo (IT)
bakkealbedo (NO)
ρg ground albedo
Unit: 1
Ratio of the radiant flux reflected by the ground to the incident flux.
form of energy that is transferred by virtue of a temperature difference. see latent heat, radiant heat, sensible heat
heat accumulation
Heat Heat stored in the thermal mass (of a building). See Thermal mass
heat balance model (of thermal comfort)
A model of human thermal response based on the assumption that a necessary condition for thermal comfort is a balance between the metabolic heat production and the heat loss from the body (generally an analytical model)
heat capacity
the amount of heat necessary to raise the temperature of a body by one degree. Numerically, the mass multiplied by the specific heat
heat demand
The amount of energy needed to keep the temperature of a room or building at a given value
heat exchanger
a device, usually consisting of an arrangement of metal tubing used to transfer heat from one fluid to another, often used to conserve energy by heating incoming air using the heat from outgoing air
heat gain
Sum of internal heat gains (like heat gains from persons, lighting and apparatus) and solar heat gains
heat load
The heat flux which has to be removed from a room to maintain (or prevent to exceed) a required air temperature or humidity
heat loss (from the body)
the loss of heat from the surface of the human body by conduction, convection, radiation and evaporation
heat loss (from a building)
heat flow through building envelope components (walls, windows, roof)
heat pump
Apparatus that transfers heat from a low (unusable) temperature level to a (usable) higher temperature level
heat recovery
the process of extracting heat, (usually from a fluid, gas or air) that would otherwise be wasted. For example heat recovery using a heat exchanger between incoming and exhaust air
heat transmission
Heat transfer through a construction, due to conduction, convection and radiation
heat transmission coefficient
heat transmission per unit temperature difference per area unit (usually used for total constructions)
The process of active heat supply for the benefit of climate control
heating degree-days
see degree days
heating season
the period of the year during which heating the building is required to maintain comfort conditions
humidifying/dehumidifying effect
latent heat of water vaporization at the average evaporating temperature times the number of pounds of water evaporated or condensed in watts
the "dampness" of the air expressed either as a subjective sensation or as a physical measure of the water vapour in the air (see relative humidity, water vapour pressure)
heating, ventilating and air conditioning: A term generally applied to the hardware or the industry concerned with the supply of environmental control in buildings
hybrid solar heating system
solar heating system that combines active and passive techniques
éclairement lumineux (FR)
Beleuchtungsstärke (DE)
iluminancia (ES)
illuminamento (IT)
verlichtingssterkte (NL)
belysningsstyrke; illuminans (NO)
natezenie oswietlenia (PL)
illuminans; belysningsstyrka (SE)
Ev illuminance (at a point of a surface)
Unit : lx
CIE. Quotient of the luminous flux dΦv incident on an element of the surface containing the point, by the area dA of that element. Equivalent definition. Integral, taken over the hemisphere visible from the given point, of the expression Lv cos(θ) dΩ where Lv is the luminance at the given point in the various directions of the incident elementary beams of solid angle dΩ and is θ angle between any of these beams and the normal to the surface at the given point.
not permitting gas or water pass through
incident angle
the angle between the beam of solar radiation and a line perpendicular (normal) to the irradiated surface
indirect cooling
a system in which a liquid, such as brine or water, cooled by the refrigerant, is circulated to the material or space refrigerated or is used to cool air so circulated
indirect gain
The indirect transfer of solar heat into the space to be heated from a collector that is coupled to the space by an uninsulated, conductive or convective medium (such as thermal storage wall or roof pond)
indirect lighting
lighting achieved by reflection, usually from wall and/or ceiling surface
induced draft flue system
a term referring to a type of gas heating system equipped with a fan downstream of the fumace. The fan pulls gases from the fumace and propels them to the outside, thereby eliminating the requirement for dilution air
the uncontrolled movement of outdoor air into the interior of a building through cracks around windows and doors or in walls, roofs and floors. This may work by cold air leaking in during the winter, or the reverse in the summer
infrared radiation (IR)
electromagnetic radiation with wavelengths longer than that for light (>700 nm). Infrared is often divided into the near infrared (wavelength 800-2000 nm) and the far infrared (>2000 nm). Almost all energy radiated by surfaces with a temperature beneath 6000 K is heat radiance. Glass, which is most transparent for visual light radiance (400 nm to 800 nm), is not always transparent to heat radiance. This is the preponderant form of radiation emitted by bodies with moderate temperatures such as the elements of a passive building
insulation material
A material with a low thermal conductivity (e.g. below 0.2 W/m²K) applied to reduce thermal losses through building envelope (e.g. walls, roofs, floors)
internal (heat) gains
the energy dissipated inside the heated space by people (body heat) and appliances (lighting, cooker, etc.). A proportion of this energy contributes to the space heating requirements (kWh)
internal sources
the sources of internal heat such as appliances, lights and people
intrinsic heat
heat from human bodies, electric light bulbs, cooking stoves, and other objects not intended specifically for space heating
See radiation
éclairement énergétique (FR)
Bestrahlungsstärke; Einstrahlung (DE)
irradiancia (ES)
illuminamento energetico (IT)
bestralingssterkte (NL)
irradians (NO)
natezenie napromienienia (PL)
irradians (SE)
Ee irradiance (at a point of a surface)
Unit: W/m²
CIE. Quotient of the radiant flux dΦe incident on an element of the surface containing the point, by the area dA of that element. Equivalent definition. Integral, taken over the hemisphere visible from the given point, of the expression Le cos(θ) dΩ where Le is the radiance at the given point in the various directions of the incident elementary beams of solid angle dΩ and θ is the angle between any of these beams and the normal to the surface at the given point.
an adjective describing a reversible adiabatic process a change taking place at constant entropy
The International Standards Organisation, based in Geneva
The Standard for calculating the effect of indoor environments using the PMV/PPD indices of Fanger, produced by ISO
(l) prefix meaning constant: as in isothermal (constant temperature); isentropic (constant entropy); isobaric (constant pressure); etc.; and (2) in chemicals, one having different characteristics but with the same number and kind of atoms
courbe isoéclairement lumineux (FR)
Isolux-Linie (DE)
curva iso-iluminancia (ES)
curva isoilluminamento (IT)
isolux lijn (NL)
isoluxkurve (NO)
izoluksa; krzjwa izoluksów (PL)
isoluxkurva (SE)
iso-illuminance curve; isolux curve or line
Locus of points on a surface where the illuminance has the same value.
an adjective used to indicate a change taking place at constant temperature
isolated gain
the transfer of heat into the space to be heated from a collector that is thermally isolated from the space to be heated by physical separation or insulation (such as an attached sunspace with an insulated common wall)
an adjective used to indicate a change taking place at constant temperature
isotrope (FR)
isotrop (DE)
isotrop (NO)
Having NO dependence on direction or angle.
Kata thermometer
A special thermometer whose purpose is to measure the cooling power of the environment. Often used as an anemometer
Time delay between, say, the peak outdoor temperature and the indoor temperature, also applied to the time required for the sensing element of a control system to reach equilibrium with the property being controlled
latent heat
the energy required to change the state of a unit mass of material from solid to liquid (fusion) or liquid to gas (evaporation), without a change in temperature. This energy is then released, again without change of temperature (provided super cooling does not occur), when the material reverts from gas to liquid or from liquid to solid. (Wh/kg, kJ/kg)
latitude (FR)
geografische Breite (DE)
latitud (ES)
latitudine (IT)
breddegrad (NO)
Φ latitude
Unit: degree
The angular distance north or south from the earth's equator measured through 90°. The latitude is taken positive in the northern hemisphere.
Electromahgnetic radiation within the visible spectrum (wavelengths between approx 400-800 nm)
lightwell absorption fraction
the fraction of solar radiation that directly heats the air after it is transmitted through the glazing and after each reflection from interior surfaces. It is intended to simulate the presence of lightweight objects that absorb solar radiation and rapidly convect heat to the air
liquid state
one of three states of matter characterized by limited freedom of molecules and by substantial incompressibility
load collector ratio
longitude (FR)
geografische Länge (DE)
longitud (ES)
longitudine (IT)
lengdegrad (NO)
λ longitude
Unit: degree
The arc or portion of the earth's equator intersected between the meridian of a given place and a reference meridian (usually the one from Greenwich, England). The longitude is taken positive east of the Greenwich meridian and negative west of the Greenwich meridian.
longitudial sampling
A method of sampling a population in which a large number of comfort votes is sought from each of relatively few subjects (cf Transverse sampling)
long-wave radiation
radiation emitted between roughly 5000 and 30000 nm wavelength, as in thermal radiation from the surfaces of a room, or from the outside surface of the roof
louvre system
an assembly of sloping vanes intended to permit air to pass through and to inhibit transfer of water droplets. Also used as an solar control, either external to the building or internally (e.g. venetian blinds)
low-e glass
Glazing with a low thermal transmittance (U-value), due to a heat reflecting coating(s) applied in the gap of double glazing. The applied coatings are visually transparant
low energy building
A very good insulated and passive solar building, with a very low remaining heating and cooling demand
lumen (FR)
Lumen (DE)
lumen (ES)
lumen (IT)
lumen (NL)
lumen (NO)
lumen (PL)
lumen (SE)
lm lumen
CIE. SI unit of luminous flux. Luminous flux emitted in unit solid angle (steradian) by a uniform point source having a luminous intensity of 1 cd. (9th General Conference of Weights and Measures, 1948). Equivalent definition. Luminous flux of a beam of monochromatic radiation whose frequency is 540 1012 Hz and whose radiant flux is 1/683 W.
luminance lumineuse (FR)
Leuchtdichte (DE)
luminancia (ES)
luminanza (IT)
luminantie (NL)
luminans (NO)
luminancja swietlna (PL)
luminans (SE)
Lv luminance (in a given direction, at a given point of a real or imaginary surface)
Unit: cd/m²
CIE. Quantity defined by the formula: Where dΦv is the luminous flux transmitted by an elementary beam passing through the given point and propagating in the solid angle dΩ containing the given direction: dA is the area of a section of that beam containing the given point: θ is the angle between the normal to that section and the direction of the beam.
efficacité lumineuse d'un rayonnement (FR)
photometrisches Strahlungsäquivalent; Lichtausbente (DE)
eficacia luminosa de una radiacion (ES)
coefficiente di visibilità di una radiazione (IT)
fotometrisch stralingsequivalent (NL)
lysekvivalent for stråling (NO)
skutecznosc swietlna promieniowania (PL)
ljusekvivalent för stralning (SE)
K luminous efficacy of radiation
Unit: lm/W
CIE. Quotient of the luminous flux Φv, by the corresponding radiant flux Φe: When applied to monochromatic radiations, the maximum value of K(λ) for photopic vision is: Km=683 lm/W for λm=555nm
flux lumineux (FR)
Lichtstrom (DE)
flujo luminoso (ES)
flusso luminoso (IT)
lichtstroom (NL)
lysfluks (NO)
strumien swietlny (PL)
ljusflöde (SE)
Φv luminous flux
Unit: lm
CIE. Quantity derived from radiant flux Φe by evaluating the radiation according to its action upon the CIE standard photometric observer. For photopic vision: where dΦe(λ)/d(λ) is the spectral distribution of the radiant flux and v(λ) is the spectral luminous efficiency.
luminous intensity
quotient of the luminous flux dFv leaving the source and propagated in the element of solid angle containing the given direction, by the element of solid angle
lux (FR)
Lux (DE)
lux (ES)
lux (IT)
lux (NL)
lux (NO)
luks (PL)
lux (SE)
lx lux
Unit: lm/m²
CIE. SI unit of illuminance: llluminance produced on a surface of area 1 square meter by a luminous flux of 1 lumen uniformly distributed over that surface. A non-metric unit is the lumen per square foot lm/ft² also called the footcandle (fc) equal to 10.764 lx.