Dictionary

Absorptance
The part of the radiation which strikes a surface and is absorbed (gets caught in the material). Expressed as a percentage.

Air temperature
The temperature of the air.

Aluminum
A high gloss metal with unique reflective properties. One of the most common elements on Earth. 

Brightness
See Candela

Candela
SI unit of light intensity (light intensity is the flow of light in a specific direction). Abbreviated cd or lm/sr (lumens per steriadian).

Emissivity
A measure of how much heat a material radiates compared with an ideal blackbody

Energy
Measured in joules (J). 1 joule of energy = enough energy to produce 1 W continuously for 1 s.

g-total
Total solar energy transmission through a window and sun blind together.

g-value
The sum of primary and secondary transmittance. The G-value indicates the total solar energy transmission through the window or sunblind. Indicated by a value between 0 and 1 or as a percentage. The higher the value, the more energy passes through.

Heat radiation
Long-wave radiation. Wavelengths in the range 5000 - >25000 nm.

Insulating glass
A window structure using two or three panes of glass. There is often gas (for example argon) between the panes and a low emissive layer in order to prevent the absorption of heat radiation (which prevents heat loss).

kWh
1000 Wh = 3 600 000 Joules. See Watt-hour.

Lumen
SI unit of luminous flux (light energy per unit of time). Abbreviated lm.

Luminance
Light intensity (candela) per square meter. Measured in cd/m².

Luminous flux
See Lumen

Long-wave radiation
Wavelengths in the range 5000->25000 nm. Also known as heat radiation.

LT
See Tvis

Lux
SI unit of illuminance, lighting (luminous flux per lit area). Abbreviated lx or lm/m².

Openness factor
The proportion of open spaces in the product. A percentage to describe the amount of direct insolation allowed through.

Operative temperature
The perceived temperature. Approximately the average of air temperature and radiation temperature. 

Primary transmittance
See Tsol

Radiation temperature
All materials emit radiation in the form of heat (or cold). 

Reflectance
The part of the radiation which strikes a surface and is reflected back. Expressed as a percentage.

Secondary transmittance
The heat transfer supplied to the room due to absorbed solar radiation from e.g. windows and sunblinds.

SF - Solar factor
See g-value

Shading coefficient
Indicates the g-value for sun blinds. This figure is worked out by dividing gtot by gwindow = gsolar protection (this value can only be used in the case in question).

Short-wave radiation
Wavelengths in the range 320-2500 nm. See Solar radiation

Solar protection glass
Dark glass which screens out parts of the insolation. The aim is to screen out UV and IR, but this cannot be achieved without also screening out parts of the visible light.

Solar radiation
Short-wave electromagnetic radiation consisting of UV, visible light and IR. Wavelengths in the range 320-2500 nm.

ST - Solar energy transmission
See Tsol

Thermal comfort
Normally, a person experiences thermal comfort when the operative temperature is between 20 and 24 degrees.

Transmission
The part of the radiation which strikes a surface and is transmitted (passes through). Expressed as a percentage.

Tsol
Primary transmittance of solar radiation through a window or sunblind, for example; i.e. direct insolation. Indicated by a value between 0 and 1 or as a percentage of the total solar radiation. 

TST – Total solar energy transmission
See g-value

T-value
See Tsol 

Tvis
Percentage of Tsol that consists of visible light. 

U-value
Heat transfer coefficient, i.e. describes the insulating properties of the material, and is specified in W/m2 K. The lower the U-value, the better the insulation.

Watts
SI unit of output (energy per second). Abbreviated W.

Wh - Watt-hour
A unit of energy which is defined as the output of one Watt over 1 hour, and so 3600 watt-seconds = 3600 Joules. 

Visible light
Part of solar radiation with wavelengths in the range 380-780 nm. Also known as daylight.

Visual comfort
When a person does not experience disruptive glare or reflections caused by a light source such as the sun. 

 

Sign up for our newsletter