Light Factors

Light Factors - essential to ensure the visual comfort of buildings - depend on Light Transmission (TL) and Exterior Light Reflection (RLE) and Interior Light Reflection (RLi), i.e. the percentage of light transmitted to the exterior or interior. 

Luminous Transmittance is the percentage of visible light that is transmitted directly through the glass.  The higher the light transmission, the more natural light is visible in the room, making it brighter. 

Light Transmission

Exterior Light Reflection (RLE)

Interior Light Reflection (RLI)

Nowadays, natural light is privileged over artificial light for allowing greater visual comfort and greater energy savings.

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Solar Factors

Solar Factors are composed of the Solar Factor (g) and the Shading Coefficient (SC).

The Solar Factor (g) is the percentage of solar energy transmitted directly or indirectly through the glass to the interior and measures the ability of the glass to reduce heat input. The Solar Factor of a glazed wall is the percentage of energy entering a location relative to the incident solar energy. Thus, the lower the g-factor, the lower the heat input. 

The Shading Coefficient (SC) is a measure of the heat gain through glass from solar radiation. The lower the CS, the lower the solar heat gain. 

The lower the solar factor and the CS, the better the solar control and as a result, the lower the expenditure required for air conditioning in buildings.

Solar Factor

Selectivity

Selectivity is the relationship between light transmission and the solar factor. The higher the selectivity, the greater the comfort in buildings. If selectivity > 2, the glass allows the passage of twice as much light as heat.

Selectivity

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Energy Factors

The energy factors are also essential to choose the ideal glass for each situation. These factors allow us to evaluate the thermal insulation between environments with different temperatures. 

When sunlight falls on glass, some of the energy is reflected, some is absorbed by the glass, and the rest is transmitted into the building. Therefore, to analyze the thermal insulation of a glass it is necessary to pay attention to the following points: Energy Transmission (U), the Energy Reflection (Re) and the Absorption.

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Thermal Transmittance

The thermal transmission allows you to evaluate the thermal insulation of the glass between environments of different temperatures. 

The Thermal Transmittance Coefficient (U) is defined as "the amount of energy transmitted per hour through a glass with an area of 1 m2, when the temperature difference between the outside and inside air is 1°C" (Saint Gobain, 2019).

The smaller the U, the lower the energy loss and the greater the thermal insulation of the glass. 

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