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As we discuss controlling interior heat and light from the sun, it is important to understand a few energy terms so you can better decide which product is best to meet your needs. The focus in general will be 1) on how (solar) window film relates to these terms. 2) Some of these terms also apply to various blinds and shades. 3) Other window related terms are listed at the bottom of the page.
Film Related Terms
The surrounding or encompassing atmosphere.
A measurement of the percentage of solar heat and visible daylight that are absorbed into window film. As absorption levels increase, so will the temperature of the glass.
The difference between the inside and outside temperatures.
This can only occur if there is air on the glass (broken seals, etc.)
A solar film's ability to stretch. It is relative to the 'peel'.
A measurement of a surface's ability (glass) to absorb or reflect far-infrared radiation or heat. The lower the emissivity, the less room heat is absorbed and the more heat is reflected back into the room. The amount of heat from an object that will re-radiate causing ambient air temperature to increase or decrease. The goal is to reduce the heat loss in the winter and cool loss in the summer. The lower the emissivity, the higher the insulation qualities of the window film. Example: tin foil in an oven does not absorb much heat, which is why you can remove food on it with your bare hands).
A measure of UV spectrum through glass. UV 0-300 - does not transmit through the glass, UV 300-380 - film treats it, but does not harm plants or photosynthesis (water them less, but check for rare plants), and UV over 380 - no damage is caused through the glass.
Press to pull solar film off the glass when the glass would break.
A window product that releases or reflects heat or energy.
R-Value (Absorption Value):
The amount of cold that passes through the glass. To get an R-value for the glass: divide the U-value by '1'. Ex. 1 / 1.12 (U-value) = .89 R-value.
A measurement of the percentage of solar heat and visible light that are reflected by solar film. Highly reflective films provide high heat rejection capabilities. Newer film technologies now provide impressive solar energy properties for lighter films as well as darker or more reflective films.
Shading Coefficient (SC):
A ratio of: solar heat gain passing through a piece of solar film to the solar heat gain that occurs under the same conditions with no film and made of clear non-shaded double strength window glass. The ability of film to reduce heat on the glass from the visible light spectrum or to shade off damaging heat. The closer to '0' the better (reciprocal of '1'). The greater the number the more light spectrum, but transparency is reduced.
Solar Heat Gain Coefficient (SHGC):
A ratio of: total solar heat transmitting through a window product to the solar heat incident on the projected window surface at normal solar incidence. The lower the SHGC the higher the heat reduction.
Protect the glass from breaking (solar film being greater than the glass).
A measurement of the percentage of solar heat and visible daylight that pass through a piece of glass.
Total Solar Energy Rejection:
A measurement of a window film's ability to reject solar heat in form visible light and visible infrared radiation. The higher the number the more heat rejected.
U-Value (Reflect Value):
The ability for heat to transfer through 1 square foot of window film for each 1 degree F variance in temperature. Factors include the local climate and area where the window is located in determining the level of heat transfer and the rate. Summer heat transfers from outdoor air to indoor air. Winter heat from indoor air to outdoor air. It is the ability of film to reflect heat and not absorb it. The lower the u-value (closest to '1') the less heat transferred and better the solar film.
Three or more windows set as angles to each other within a recessed area.
A treatment constructed of wood or a molded material designed to cover a blind or shade headrail. These are very decorative and are available in various sizes and intricate detail. They can be richly stained or embellished with fabric.
A crank operated window that can open inward or outward.
The top portion of a window treatment often pleated or tabbed.
A top fabric treatment that cascades from the top of brackets, pole or other that loops downward and then back up one or more times.
A piece of fabric cut in various styles designed to hold drapery panels in place.