Window Film Technical Terms

Window Film Technical Terms

Transmittance

Measures the percentage of solar energy and visible light (daylight) that passes through a glazing system. All solar control films reduce visible light transmission in order to provide solar heat control. Lighter films tend to transmit higher levels of solar energy and visible light while darker and more reflective films have lower transmittance levels.

Absorption

Measures the percentage of solar energy and visible light that are absorbed by the window film. As absorption levels of a particular film increase, so will the temperature of the glass. Always refer to a manufacturer’s film-to-glass installation recommendations.

Reflectance

Measures the percentage of solar energy and visible light that are being reflected by the window film. Highly reflective films offer high heat rejection capability. Newer technology films need not be dark nor highly reflective to provide impressive solar energy performance.

Emissivity

Measures the surface’s ability to absorb or reflect far-infrared radiation. The lower the emissivity the higher the far-infrared reflection.

U-Value

A measurement of heat transfer due to outdoor/indoor temperature differences; describing the dealt loss through a material. The lower the U-Value, the less heat transfers.

Solar Heat Gain Coefficient (SHGC)

The fraction of solar radiation transmitted through a window or skylight, expressed as a percentage. The lower a window’s SHGC, the less solar heat it transmits and the greater its shading ability. SHGC can be expressed in terms of the glass alone or can refer to the entire window assembly. Generally, a lower SHGC is desirable in warm climates, and a higher SHGC is desirable cold ones. SHGC has replaced shading coefficient (SC) as the standard indicator of a window’s shading ability.
Shading Coefficient (SC)
The ratio of solar heat gain passing through a glazing system to the solar heat gain that occurs under the same conditions if the window were made of clear, un-shaded double strength window glass. The lower the number, the better the solar shading qualities of the glazing system.

Total Solar Energy Rejected

Measures the window film’s ability to reject solar heat in the form of visible light and invisible infrared radiation.

Infra-Red Rejected (IR Rejection) IR Comparison

The percent of Infra-Red that is reflected by a glazing system

Sun Protection Factor (SPF)

A scale for rating the level of sunburn protection in sunscreen products. The higher the sun protection factor, the more sunburn protection it gives. Sunscreens with a value of 2 through 11 give minimal protection against sunburns. Sunscreens with a value of 12 through 29 give moderate protection. Sun protection factors of 30 or higher give high protection against sunburn. Also called SPF.