Visible Light Transmitted (VLT)

The percent of total visible light (380-780 nanometers) to be passed through a glazing system. Test method - ASTM E 903-96.

Visible Light Reflected (VLR)

The percent of total visible light to be reflected by a glazing system. Test method - ASTM E 903-96.

Total Solar Energy Reflected

The percent of total solar energy (300-2500 nanometers) to be reflected by a glazing system. Test method - ASTM E 903-96.

Total Solar Energy Transmitted

The percent of total solar energy (300-2500 nanometers) to be passed through a glazing system.

Total Solar Energy Absorbed

The percent of total solar energy (300-2500 nanometers) to be absorbed by a glazing system. Solar absorption is that portion of total solar energy neither transmitted nor reflected.
Since solar transmittance and reflectance are measured directly, the following equation is used for calculating solar absorption. Test method - ASTM E 903.
Total solar energy absorbed = 100% - (Total solar energy reflected) - (Total solar energy transmitted).

Ultra Violet Block

The percent of Ultra Violet radiation (300-380 nanometers) to be blocked by a glazing system. Ultra-violet is one portion of the total solar energy spectrum which greatly contributes to fading and deterioration of fabric and furnishings.

Emissivity

A measurement of a surface’s ability to absorb or reflect radiant energy. For windows with film, emissivity refers to the heat reflected back into the room. The lower the emissivity rating, the better the insulation characteristic of the glazing system in regard to heat loss.

Shading Coefficient (SC)

The ratio of the solar heat gain through a given glazing system to the solar heat gain under the same conditions for clear, unshaded double strength window glass (DSA).
Shading coefficient defines the sun control capability or efficiency of the glazing system.

Glare reduction

Glare usually defined as being the difficulty of seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Window film can provide glare reduction of up to 95%.

Solar Heat Gain Coefficient (SHGC, or G-value)

The percentage of solar energy directly transmitted into, or absorbed and re-radiated into a building.
The lower the SHGC, the better the solar control properties of the film.

Total Solar Energy Rejected (TSER)

Measures the window film’s ability to reject solar energy in the form of visible light, infrared radiation and ultraviolet light.
The higher the TSER number, the more solar energy is rejected away from the window.

Light to solar heat gain ratio

A measure of the ability of a glazing to provide light without excessive solar heat gain. It is the ratio between the visible transmittance of a glazing and its solar heat gain coefficient.

Luminous Efficacy Constant

Indicates a window’s relative performance in rejecting solar heat while transmitting daylight. It is the ratio of the visible transmittance to the shading coefficient.

U-value (U-factor)

The overall coefficient of heat transfer is a measure of the insulation level, mainly as applies to heat loss through glazing. Expressed in this book in both metric (SI) W/(°K x m2) and imperial (IP) BTU / (hr x °F x ft2) units, and given as center-of-glass value in winter conditions. The lower the U-value, the better the insulation qualities of the glazing system. U-value is the reciprocal of R value (thermal resistance).