Solar Energy Technicial Definitions

Solar Radiation Transmittance
The solar radiation transmittance is the percentage of solar energy in the solar spectrum directly transmitted through the glass. The lower the number, the less solar radiation transmitted. The spectrum of solar radiation is from 280nm to 2500nm (nanometers).

Solar Radiation Absorption

The solar radiation absorption is the percentage of solar energy that is absorbed through the glass. The lower the number, the less solar radiation absorbed.

Solar Radiation Reflectance

The solar radiation reflectance is the percent of solar radiation this is directly reflected by the glass to the outside of the building. The lower the number, the less solar radiation reflected.

Visible Light Transmittance (VLT)

The visible light transmittance (VLT) is the percentage of total visible light that is transmitted through the glass. The lower the number, the less visible light transmitted. The spectrum for visible light is from 380nm to 780nm.

Visible Light Reflectance

The visible light reflectance is the percentage of total visible light that is reflected by the glass to the outside of a building. The lower the number, the less visible light reflected.

Emissivity

The emissivity is the measure of a surface’s ability to absorb or reflect far-infrared radiation. The lower the emissivity rating, the better the insulating qualities of the window system.

U-Value

The U-Value is a measure of how well heat flows through an object (thermal conductivity). It is the rate of heat gain or loss through glazing due to environmental differences between outdoor and indoor air. It is dependent upon the local climate or environment where the window is located. It affects the level of heat transfer and the rate. The lower the U-Value, the better the insulation value of the glass.

Shading Coefficient

The shading coefficient is the ratio of solar heat passing through the window as compared to the solar heat gain that occurs through 1/8” (3mm) clear glass. The lower the number, the better the solar shading qualities of the window system.

Solar Heat Gain Coefficient

Solar heat gain coefficient (SHGC) measures how well a product blocks heat caused by sunlight. The lower the coefficient number for a particular window system, the better it is able to reduce heat. The SHGC is the fraction of incident solar radiation admitted through a window, directly transmitted and absorbed, then subsequently released inward. SHGC is expressed as a number between 0 and 1.

Ultra Violet Light

Ultra violet light is the percent rejection of invisible, high energy wavelengths emitted by the sun which is the primary cause of fading and discolouration of furnishings and materials, as well as causing skin to burn.

Glare Reduction

Glare Reduction is the reduction of visible light by a window system as compared to a window without KristalBond.

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