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Sunlight reaches the double glazing in the form of electro-magnetic waves of different lengths—basically ultraviolet, visible and infrared radiations. Of the total solar energy reaching the glass (lg), part is transmitted directly through the glass (T), another part is rejected by reflection (R) and the rest is absorbed by the mass of glass (A), and subsequently irradiated to the exterior (Ae) and the interior (Ai) of the enclosure.
Sunlight reaches the double glazing in the form of electro-magnetic waves of different lengths, between 0.3 and 2.2 µm.
Basically, it consists of ultraviolet, visible and infrared radiation. The glass is practically impermeable to ultraviolet radiation and reacts differently to infrared energy (heat) and light energy depending on its composition.
Of the total solar energy reaching the glass (lg), part is transmitted directly through the glass (T), another part is rejected by reflection (R) and the rest is absorbed by the mass of glass (A) , and subsequently irradiated to the exterior (Ae) and the interior (Ai) of the enclosure.
The fraction of energy transmitted plus the part absorbed and irradiated to the interior by the glass is what we call the Solar Factor (SF).The Solar factor is the ratio between the total energy entering the premises and the incidental solar energy. This value varies depending on the angle of solar impact and the external conditions of natural convection and the wind speed.
In the Northern Hemisphere, due to variations in the solar elevation, the solar factor drops in summer. This is important to bear in mind when calculating the annual energy balance of a glazing system.
The solar factors of the different glazes in the technical documents refer to an angle of solar elevation of 30º from the horizontal plane perpendicular to the facade.
For the visible part of the radiation, the treatment is identical to that of the heat energy, and we can define the Light Transmission (LT) Factor as the ratio between the light passing through and the light impacting on the glass.
CLIMALIT’s sun control parameters (SF and LT) vary depending on the glass used in their composition:
- Colourless, non-absorbent PLANILUX glass.
- Coloured, non-absorbent PARSOL glass.
- Coloured, non-absorbent PINK glass.
- Coloured, absorbent PARSOL glass.
- Solar control COOL-LITE, REFLECTASOL glass.
- Low emission Planitherm “S” glass.
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