Solar Energy Technical Definitions
Solar transmittance
The percent of incident solar radiation that is transmitted through the window film/glass system. The lower the number, the less solar radiation transmitted.
Solar absorptance
The percent of incident solar radiation that is absorbed by the window film/glass system. The lower the number, the less solar radiation absorbed.
Solar reflectance
The percent of incident solar radiation that is reflected by the window film/glass system. The lower the number, the less solar radiation reflected.
Visible light transmittance
The percent of total visible light that is transmitted through the window film/glass system. The lower the number, the less visible light transmitted.
Visible light reflectance
The percent of total visible light that is reflected by the window film/glass system. The lower the number, the less visible light reflected.
Emissivity
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 film/glass system.
Winter U-Factor (W/m²°C)
The amount of heat energy which transfers through an area of 1m2 with a temperature difference of 1°C. The lower the U-factor, the better insulating qualities of the window film/glass system.
Shading coefficient
The ratio of solar heat passing through window film to the solar heat gain that occurs under the same conditions if the window were made of clear, unshaded double strength window glass. The lower the number, the better solar shading qualities of the window film/glass system.
Solar heat gain coefficient
The ratio of the total solar heat passing through a given window product relative to the solar heat incident on the projected window surface at normal solar incidence (i.e. perpendicular to the glazing surface). The lower the coefficient number for a particular window film/glass system, the better it is able to reduce heat.
Solar selectivity index – luminous efficacy
Ratio of visible light transmittance to the Shading Coefficient (VLT/SC). The higher this number is, the more efficient a film is at transmitting visible light without transmitting excessive heat. The more over 1.00, the greater a film’s spectral selectivity.
Light to solar heat gain factor
Ratio of visible light transmittance to Solar Heat Gain Coefficient (VLT/SHGC). The higher this number is, the more efficient a film is at transmitting visible light without transmitting excessive heat. The more over 1.25, the greater a film’s spectral selectivity.
ltraviolet light blocked
The percent rejection of invisible, high energy wavelengths emitted by the sun which is the primary cause of fading and discoloration of furnishings and materials.
Total solar energy rejected
The percent of total solar energy (heat) rejected by the window film/glass system. The higher the number, the more total solar energy (heat) is rejected.
Summer solar heat gain reduction
The percent reduction in transmitted solar heat gain by the addition of window film compared to that of the same window without film.
Glare reduction
The percent reduction of visible light by the addition of window film compared to that of the same window without film.