Frequently Asked Questions, State Law and Terminology

Frequently Asked Questions, State Law and Terminology

How often does the window film have to be replaced?
Contrary to what most people think, the window films we offer do not need to be replaced every 5-10 years like automobile tint.  In fact, some of our customers have been enjoying the tint on their windows for over twenty years.  Though the actual longevity of the film will vary in different circumstances, the products we offer will last as long as you are around.

Can the film be removed later if we decide we don't want it anymore?

Unlike factory tinted glass, the window film we offer holds to the glass by a strong adhesive, yet, that allows the film to be removed without damaging the glass at any time.


Nevada Highway Patrol Commonly Asked Questions
Vehicles that are 1993 or older may have windows tinted no darker than 28 percent (35 percent, with a 7 percent tolerance).  If the windows were tinted before July 1, 1993, anything is acceptable except the colors red and amber.  Vehicles from 1994 and newer must have factory tinting.

Here is a fantastic link that helps identify what you may be looking for AND answers any and all questions you may ever have about window film:


Window Film Dictionary

abrasion-resistant coating
a coating which resists abrasion; it may be hard or, alternatively, slippery. A device for testing abrasion resistance is typically the Taber-Abraser.

the ratio of the amount of radiative energy absorbed in a coating or film to the incident energy. All energy that is absorbed is converted to heat, raising the temperature of the coating or glazing medium. (The solar absorptance of a solar control film is a key factor affecting the suitability of a given window film for application to specific window system. It is one factor that is built into Solutia Performance Films' film-to-glass-recommendation chart.)

the chemical layer that serves to bind a window film to glass or other smooth surface. CPFilms offers a variety of such adhesives to serves different product needs. CDF (clear, distortion free), HPR (a pressure-sensitive adhesive called "high performance resin," generally for automotive films and a few architectural products), PS ("pressure sensitive," high impact, high peel-strength, generally for safety/security films), and RPS (a PS adhesive intended for easier removability than standard PS).
Association of Industry Metallizers Coaters and Laminators, a nonprofit international organization serving converters, suppliers, and users of metallized, coated, and laminated products since 1970.

to coat a surface by vacuum evaporation of aluminum. Also called "metallization."

ambient temperature
the outdoor air temperature (in the shade).

anchored installation
any mechanical or wet attachment system used to form an 'anchored' bond between safety film, glass and framing system on one or more sides.

angstrom (Å)
unit of length used chiefly in measuring wavelengths of light, equal to 10-10 meter. It is named for the 19th-century Swedish physicist Anders Jonas Ångström. The symbol is Å. The angstrom and multiples of it, the micron and the millimicron, are also used to measure such quantities as molecular diameters and the thickness of films on liquids [or other substrates]. (From Britannica.) Ten angstrom units = 1 nanometer. The average human hair is about 100,000 angstrom units.

annealed Glass
Thermal treatment of glass to alleviate or even totally eliminate internal stresses. The material is heated at a relatively high temperature at which material diffusion occurs. The material is held at that temperature for a certain time, and then is cooled very slowly, to avoid material stresses being reintroduced. Annealed glass (sometimes referred to as "ordinary" glass) is weaker than both heat-strengthened and tempered glass and is therefore more likely to suffer thermal shock failure (breakage) than these latter two types. See .

the process that provides a hard, durable oxide film on the surface of aluminum, by electrolytic action.  

American National Standards Institute - "The Institute's mission is to enhance both the global competitiveness of U.S. business and the U.S. quality of life by promoting and facilitating voluntary consensus standards and conformity assessment systems, and safeguarding their integrity." Quoted from ANSI web site.

anti-glare coating 
a coating which reduces the reflectance of a surface by increasing the diffuse reflectance from that surface.

anti-reflective coating 
a coating which reduces the reflectance of a surface by better optical coupling to the surface and therefore increasing the overall transmittance of the film.

application solution
slip solution specifically used for film positioning during the installation of films with pressure sensitive adhesive or in the case of dry chemical adhesive systems, for positioning and adhesive activation.
An inert chemical element that is a colorless gas. It has a high atomic weight and is sometimes used instead of air in sealed spaces between panes of glass in IG (insulating glass) units to reduce the conduction of heat. Heavier, slower moving gas molecules transfer their energy less efficiently from pane to pane. Krypton, a similar but heavier inert gas, is also used in this manner to reduce the rate of heat transfer by conduction.

American Society of Civil Engineers which sets standards for materials, e.g., ASCE 7-93 (formerly ANSI A58.1) "Minimum Design Loads for Buildings and Other Structures."  
American Society of Heating, Air-conditioning and Refrigeration Engineers.

American Society of Interior Designers. "The American Society of Interior Designers (ASID) is the oldest and largest professional organization for interior designers with the largest residential and commercial membership. With more than 30,000 members, ASID establishes a common identity for professionals and businesses in the field of interior design.... ASID's Industry Partners include more than 3,500 member firms and individual representatives, uniting the professional designer with manufacturers of design-related products and services. ... Professional members of ASID must pass rigorous acceptance standards: they must have a combination of accredited design education and/or full-time work experience and pass a two-day accreditation examination (National Council for Interior Design Qualification - NCIDQ). ...ASID promotes professionalism in interior design services and products for the workplace and home. To keep up with the unique needs of its members, ASID has created the Design Specialty Network (DSN) program. Eight defined areas of interior design are featured on Network ASID, an on-line program featuring specialized information, news bulletins, membership information, reports, publications, product options/availability and more. " (Quoted from ASID web site.)

American Society For Testing and Materials. Read their Mission statement.   
"What is ASTM? Organized in 1898, ASTM (the American Society for Testing and Materials) is one of the largest voluntary standards development organizations in the world.

"ASTM is a not-for-profit organization that provides a forum for the development and publication of voluntary consensus standards for materials, products, systems and services. More than 32,000 members representing producers, users, ultimate consumers, and representatives of government and academia from over 100 countries develop documents that serve as a basis for manufacturing, procurement, and regulatory activities.

"ASTM develops standard test methods, specifications, practices, guides, classifications, and terminology in 130 areas covering subjects such as metals, paints, plastics, textiles, petroleum, construction, energy, the environment, consumer products, medical services and devices, computerized systems, electronics, and many others. ASTM Headquarters has no technical research or testing facilities; such work is done voluntarily by the ASTM members located throughout the world.
"More than 10,000 ASTM standards are published each year in the 73 volumes of the Annual Book of ASTM Standards. These standards and related technical information are sold throughout the world." (Quoted from ASTM's FAQ page.)

ASTM F1233-98: Standard Test Method for Security Glazing Materials And Systems
The document specifying this testing standard can be purchased by visiting this web page  This test method specifies procedures for evaluating the resistance of security glazing materials and systems against the following threats such as Ballistic Impact, Blunt Tool Impacts, Sharp Tool Impacts, Thermal Stress, and Chemical Deterioration.

The center member of a double door, which is attached to the fixed or inactive door panel.

attachment system
a means to mechanically attach a safety window film to the window frame after installation to assist in keeping the pane in place should the glass be broken as a result of explosion, earthquake, forced entry attempts, etc. Increasingly, more such designs are coming on the market. 

a unit of pressure equal to the air pressure at sea level, approximately 14.7 lbs. per square inch (or 101,325 pascals).

A type of window with a top-hinged sash that swings out at the bottom -- lets in fresh air while keeping rain out.

bay window
A bay window is made up of three or more windows. The side or flanker units project out from the building in 30, 45, or 90 degree angles. The center is parallel with building wall and is made up of one or more windows. All the units can be stationary, operating, or any combination thereof.Click here for picture.

a glazing term referring to the dimension of the glazing leg which overlaps the edge of the glass (the extent to which the glass extends into the window frame).

the sticking together of layers of film on a roll often caused by a coating which has been deposited on the film.

Founded in 1915, Building Officials and Code Administrators International, Inc., is a nonprofit membership association, comprised of more than 16,000 members who span the building community, from code enforcement officials to materials manufacturers. They are dedicated to preserving the public health, safety and welfare in the built environment through the effective, efficient use and enforcement of Model Codes. BOCA's members are professionals who are directly or indirectly engaged in the construction and regulatory process.

Building Owners and Managers Association (BOMA). See

bow window
A series of four or more adjoining window units, commonly five in number, installed on a radius from the wall of the building. Click here for picture.

break strength
The ability of window film a given type and thickness to resist being pulled apart. The measurement is given in terms of force per unit width, such as pounds per inch, grams per centimeter, etc. Unlike tensile strength, break strength varies greatly with film thickness and substrate type and is used to gauge the absolute strength of a strip of the material of a given width. (See, however, FAQ #91 regarding laminated window films.)

BTU-British Thermal Unit 
The amount of heat energy required to raise the temperature of one pound of water one degree Fahrenheit. 1 BTU = 252 Calories (CAL). The metric equivalent is 1054.35 Joule.

BTU Meter
This device is essentially a wide-spectrum photocell used to measures the radiant solar energy intensity that is directly transmitted through a window. It sensitive to both visible and near infrared radiation. The device is calibrated in both BTUs per square foot per hour and in watts per square meter. Generally, it best used on a cloudless day. It should be pointed directly at the sun and a reading taken. A second reading should be taken behind the glass being tested (pointed again directly at the sun). Additional readings with different film samples can then be taken. (SeeHeat Box Demonstrator document to learn of an effective use for this tool.)

a blistering (or tenting affect) of window film at the glass surface generally resulting from residual moisture from installation, air or any number of potential contaminants.

the base unit of luminous intensity in the International System of Units that is equal to the luminous intensity in a given direction of a source which emits monochromatic radiation of frequency 540 x 1012 hertz and has a radiant intensity in that direction of 1/683 watt per unit solid angle -- called also candle; abbreviation cd(Merriam-Webster)

casement window
A window unit in which the single sash cranks outward, to the right or left, the projecting window hinged at the sides and usually opening outward like a door. A type of window with a side-hinged sash that opens like a door -- the best window for catching breezes and providing cross-ventilation. Usually the lites making up this window are less than 18 inches (less than half a meter) square and are installed with glazier's putty, making a window film installation very challenging to maintain cleanliness.

catch bar
a metal bar attached to the framing or wall area as a glass retention device where aesthetics are not a concern.

catch net
net attached to window framing or an adjacent wall area as a glass retention device where aesthetics are not a concern.

catch strap
strapping attached to window framing or an adjacent wall area as a glass retention device where aesthetics are not a concern.

catch system
used in combination with daylight installed window film as a net, strap, or "catch" system for broken glass hazard mitigation purposes.
the negatively charged electrode in a glow discharge system. In sputtering, the cathode is often called the target. It is attacked by positively charged ions and is composed of the material to be deposited.

CDF (Clear Distortion-Free)
A type of adhesive system used to bond window film to glass. It is to be distinguish from PS adhesives in that it is water-activated and non-reactivateable once cured. It is non-tacky to the touch but provides a very hard and extremely durable chemical bond to the glass with no optical distortion which can sometimes occur with thicker PS adhesives. Used primarily in flat glass/architectural applications for maximum durability and optical clarity. Normal curing time is 7-10 days, but can vary according to film type, temperature, and humidity. For full details on the differences between CDF and PS adhesives, see TB-37.

center of glass
All glass area of a window except that within 2.5" (10cm) from the edge of the glass -- used in measuring and calculating glazing performance such as R-values and U-values.
ceramic cutter
a hand-held device used in combination with a square-edge table or other flat surfaces to precisely trim safety film patterns to fit prior to installation. Photo.

cubic feet per minute - a unit of measure used in air infiltration testing, e.g., "maximum .10 cfm per foot of sash perimeter."

chill drum
the central drum in a vacuum roll coating machine, which maintains the film at a constant temperature while it is being coated.

(1) Aluminum or vinyl material attached to the outside of a window which creates a more durable, long-lasting window. Cladding is factory-applied in many colors and does not require painting.Click here for picture. (2) The term is also used in the window film industry to refer a protective deposition of material used to cover or encapsulate another more reactive metal or material within a film structure to reduce the likelihood of oxidation.

clerestory window
1. A window placed vertically in a wall above one's line of vision to provide natural light -- often at the intersection of two offset roof planes. 2. A venting or fixed window above other windows or doors on an upper outside wall of a room.

closed finger
see "finger."

the thin layer of material which is deposited onto the polymer film substrate.

coating weight
see pounds per ream

color temperature
the temperature of a black body, which emits light with the same spectral characteristics as the surface under consideration. Of an electromagnetic source, especially in the optical regime, the hue or wavelength (spectral content) expressed or specified as the hypothetical wavelength(s) emitted by an ideal blackbody having an absolute temperature of n kelvins (n K). Note 1: Higher numbers indicate hues in or toward the blue; lower numbers indicate hues in or toward the red.Note 2: Examples of color temperature are approximately 5000 K to 5500 K (daylight), approximately 4100 K (fluorescent lighting), and approximately 2800 K (incandescent). Note 3:Color temperature is commonly used to characterize ambient lighting or lighting employed for photographic purposes.

The change of a gas to a liquid state. Because warm air can hold more water vapor than cold air, as warm air cools its ability to hold water vapor is reduced. Excess moisture condenses on the warm side of glass. e.g., condensation on the outside of a glass of ice-water. Condensation can occur in the inner surface of a dual pane IG unit if the seals have failed and the temperature drops below the dew point.

a mode of heat transfer by which energy is transmitted through material objects, or from one object to another, by physical contact. Energy is transferred in this way because of a temperature difference between the materials. (See section 3.0.8 of the education guide.)

dirt, hair, fibers, fingerprints, insects, etc., trapped beneath installed window film.
a mode of heat transfer between two substances (one solid and the other a liquid or gas) of differing temperatures that are brought into contact with the subsequent movement of the liquid or gas, usually caused by gravity and the decreasing density of the liquid or gas. This process is illustrated by air coming into contact with a warmer glass surface, the air being heated by the glass and rising up away from the window like smoke rising up a chimney or steam up from a hot griddle.

a cardboard, resin impregnated cardboard, or plastic tube around which a roll of film is wound.

core plug
a plastic plug which is fitted into the ends of a core to retain an end plate and packaging material.

The Consumer Product Safety Commission. An independent federal regulatory agency that is commissioned to protect the public against unreasonable risks of injuries and deaths associated with consumer products via the formulation of various safety standards. One such standard that relates to the safety properties of glazing systems is CPSC 16 CFR 1201. (Click here to go to chart for complying films.)
very fine cracking of the surfaces of some plastics and ceramics than can occur as a result of bending, expansion, or contraction.
"The Construction Specifications Institute (CSI) is an individual membership technical society whose core purpose is to improve the process of creating and sustaining the built environment. The Institute provides technical information and products, continuing education, professional conferences, and product shows to enhance communication among all disciplines of nonresidential building design and construction and meet the industry’s need for a common system of organizing and presenting construction information. CSI’s more than 18,000 members include architects, engineers, constructors, specifiers of construction products, suppliers of construction products, building owners, and facilities managers. Founded in 1948, CSI is headquartered outside Washington in Alexandria, VA, and has 143 local chapters nationwide." (Quoted from the CSI website).

curing (drying) time
the duration of time that must pass for all application solution used during installation to evaporate from beneath the film and for the film's adhesive system to reach maximum bond strength.

Dade County protocol
represents a series of tests that must be met for an entire window unit (all components) to be considered "Dade County approved" for windstorm mitigation.

damage-weight transmission
measure of total solar transmittance which is damaging to surface finishes, fabrics, etc, including ultraviolet and visible-light effects, for wavelengths between 280 and 500nm. Weighted according to the Krochmann Damage Function but subject to review under NFRC procedures in North America.

daylight installation
An installation practice whereby film is installed to framed glass surfaces with a slight trim or gap remaining between the window framing system and the film product's edge.
daylight transmittance
The percentage of visible light that glazing transmits through a window -- a standard clear dual pane has a daylight transmittance of 82-88%. (Source)

decibel (dB)
a unit of power loss or attenuation used in EMI/RFI shielding: 1 decibel = 10 log (Power in/Power out). A 3dB loss is a fifty percent power reduction.

the process of cutting away the metal on the bottom of an aluminum thermal break cavity once the two-part polyurethane has reached full strength, thus creating a thermally broken extrusion.

Demand Analyzer
Demand Analyzer (see was developed by ITEM Systems as a front end to the DOE-2.1E program.  Using the built-in 17 building prototypes with 3 vintages of each prototype, Demand Analyzer allows a user to very quickly describe a building in the detail required by DOE-2, then simulate the building with DOE-2, and analyze the results of the simulations using a variety of publication-quality graphs and reports. (See also Demand Analyzer section on this web site.)

design load
the project wind load to be determined by the architect and expressed in psf, e.g., "the project design load shall be 38.7 psf, both positive and negative."

a porous crystalline substance used to absorb moisture and/or sealant solvents from within the sealed air space of an insulating glass unit.

detackified pressure sensitive (DPS) adhesive
See PSA (pressure sensitive adhesive) systems

dew point
The temperature at which water vapor will condense as warm, moist air is cooled. The dew point varies directly with relative humidity.

DGP (double glazing panel)
A removable interior glass panel which creates an air space between the exterior glazing and itself. It provides improved insulation and condensation control and allows for between-glass shading options such as muntins, blinds, and pleated shades.

light which is either transmitted through or reflected from surface but scattered in all directions.

an indentation in film caused by improper film manufacturing or a dirt particle.

direct gain
A direct gain passive solar system utilizes south-facing windows to open a house to the sun. A large window area accepts direct sunlight while thermal mass serves as storage.
CPFilms trademarked and recommended  solution for glass surface preparation and cleaning glass. Part of the "Two-Bottle System" CPFilms advocates. This liquid (Tool Catalog part #GT733) contains a solution that is extraordinarily effective at breaking down and stripping away oily residues saturating the surface and sub-surface pores of window glass. Cleaner glass will substantially increase the effectiveness (slipperiness) of the application solution. Experienced installers will recognize Dirt-Off as "X-100," a product also used for the installation of most (though not all) window films with the CDF mounting adhesive. This solution is mildly acidic and is mixed in a one-ounce-to-one-quart (30 ml-to-one-liter) ratio from its concentrate form. With one exception discussed in TBA-01, it should ONLY be used for prepping/cleaning interior surfaces of glass, and caution should be used to avoid excessive overspray on a vehicle’s interior upholstered surfaces and waxed car finishes. (It readily strips away wax and oily protectants used on vinyl and plastic surfaces, and therefore may cause streaking. Keep a bottle of a common vinyl protectant and a fine auto finish compound (wax or polish) handy in your shop to restore luster, as needed, to such surfaces.) See discussion in TBA-01. See also Film-On entry below.

Department of Defense

DOE-2 (see is a whole-building analysis computer program that calculates energy use and operating cost.  DOE-2 is widely used by consulting engineers for the design of energy-efficient buildings; by researchers for impact analysis of new heating, cooling, and lighting technologies; and by state and federal agencies for developing energy-efficiency standards.  DOE-2 is internationally recognized for the accuracy of its hourly analysis algorithms as well as its ability to model a wide variety of buildings, HVAC systems and energy conservation measures.  DOE-2 was developed by the Simulation Research group at Lawrence Berkeley National Laboratory for the U.S. Department of Energy.

Doggy door
attachment or anchoring method utilizing the upper horizontal portion of a framing system. Used to retain glass panels within the frame during seismic activity.

A space which protrudes from the roof of a house, usually including one or more windows.

double glazing
Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits (such as sound transmission reduction).

double-hung window
A window unit that has two operable sashes which move vertically in the frame. Two vertically sliding sash which by-pass each other in a single frame. Sashes typically fit within vinyl balances and tilt out and remove for safe, easy cleaning.

double-strength glass
Double-strength glass is 1/8 inch (3mm) thick glass, according to the GANA Glazing Manual, 1997 edition, page 14, which references ASTM C-1036. See entry for single-strength glass below and the related FAQ.

dry glazing
a method of securing glass in a window frame with a dry, preformed, resilient gasket, without the use of a glazing compound.

dual durometer
A material that has two or more levels of flexibility. An example is the weather stripping used between the frame and sash of a Pella casement window.

dual durometer bead
a vinyl glazing bead with a softer flap against glass and a harder section inserted into sash member.

dual glazed
two single lites glazed into a split sash with an airspace, not hermetically sealed, between the two single lites.

dual reflectance
The characteristic of a window film whose inside and outside surfaces have different visible light reflectance values. For a variety of reasons, some films are designed so that, for example, they are more reflective (shiny) to the exterior (to improve solar heat rejection) and less reflective to the interior (to reduce interior reflection of artificial lighting at night.)

The resistance of flexible material to indentation under conditions which do not puncture the surface. The most frequently used device to measure this value is the spring-loaded Shore Durometer. The scale runs from zero hardness for a liquid, to 100 for a hard plane surface such as glass. In the film industry, the durometer measurements are useful to quantify the relative hardness/flexibility of various kinds of rubbers or urethanes such as those used in squeegees for window film installation. 

The harder (and sharper) the squeegee blade, the more application solution can be extracted (see detailed discussion of this issue in TBA-01), though a squeegee that is too hard can either scratch film or not flex well enough to follow the contour of curved auto glass. (An exception to this "sharpness" rule occurs when installing very heavy gauge safety films where high durometer but flattened [blunt] squeegee blades are often used with greater effectiveness, given the rigidity of the film structure. The sharpness of the blade ceases to be relevant here because the applied pressure is diffused over a very wide area of the glass under films greater thicker than 7 mils.) For most thins films, an ideal of maximum hardness (higher durometer) and blade sharpness is sought for film installation, consistent with no damage done to film. Lower durometer squeegees are required for glass preparation & cleaning. Click here for photo of Shore durometer measuring device.

dyed film
film, typically PET polyester, which has been colored by impregnation of a dyestuff into the film.

edge-to-edge installation
An installation practice whereby film is completely installed from edge to edge (or 100% of the surface) on unframed or framed glass surfaces with minimal trim factor.

electromagnetic spectrum
The possible range of frequencies of electromagnetic radiation. These waves can actually vary in length from 100,000,000 meters (108m, about ¼ the distance from the Earth to the moon) to the exceedingly short subatomic distances of .000000000001 meters (10-12m). Frequencies that correspond to these wavelengths range from about 3 cycles per second to 1024 cycles per second. The solar spectrum that reaches Earth represents a very tiny splice of this range: a mere 300-2500 nm. See section in Flat Glass Technical Manual.

electron beam (e-beam) evaporation
a vacuum evaporation process which uses a high power electron beam to melt the evaporant. This process is presently only used in large scale for aluminum and magnetic alloys.

electrostatic charge
an electrical charge, which builds up on a film due to its high dielectric strength, which is caused by rubbing of film against itself or against another non-metallic surface. This charge, which can be negative or positive, will cause large amounts of dust to be attracted to the film if it is not neutralized.

elongation at break
the percent increase in length of a sample at the point of separation when tested for Break Strength. Elongation measures the film's ability to stretch without separating (breaking apart). Reported in percent. A 100% Elongation at Break indicates the film doubles in length before separating/breaking.

EMI/RFI (Electromagnetic Interference/Radio Frequency Interference)
is interference to a signal caused by an external source, which is reduced by appropriate shielding.

emissivity (emittance)
Short definition: "the measure of a surface's ability of reflect or emit heat in the form of radiation(wavelengths from 2500-60,000 nm)."  (see also "thermal radiation")
Long definition/discussion:
 Emissivity is a measure of a surface's ability to emit radiation. When heated, a low-E surface will radiate less electromagnetic energy than a high-E surface at the same temperature. The "E" (Emissivity) value is actually the ratio of the amount of radiation emitted from a given surface to the amount of radiation emitted by an ideal "black body" at the same temperature. Thus, emissivity values must be between 0 and 1. (Emissivity simply answers the question: How good does this object radiate heat as compared to a black body?) In the process of emission (re-radiation), the surface is shedding radiant energy to the environment, thus cooling itself. A low-E surface cools itself more slowly than a highly emissive surface. Therefore, installers and sales reps should be aware that sun-exposed Low-E glass with film, all other factors being equal, will tend to remain at a higher temperature than a regular filmed glass. This fact is taken into consideration in the film-to-glass recommendations calculations.

Low-E surfaces also tend to reflect longer wave far-infrared radiation, the kind of radiation emitted by objects at room temperature, indeed by all objects cooler than about 1300°F (705°C). Many low-E coatings on window glass may be excellent reflectors of far-infrared (thus reducing winter heat loss through a home's windows) but very poor reflectors/absorbers of UV, visible, and near infrared wavelengths found in solar radiation, and thus may not be sufficient for solar control purposes without additional coatings (such as high-performance window films). There is some advantage in low-e coatings in summer since such glazing can reduce the transmission of far-infrared energy emitted by objects warmed by the sun outside a home (sidewalks, rocks, pavement, outside adjacent walls, etc.). See Low-E Facts and Myths.
Emissivity is a measure of how much heat is emitted from an object by radiation. Heat is transferred to and from objects through three processes: conduction, convection, and radiation. For instance, on a hot night, heat will be conducted through a window from the outside, causing the inside pane to become warm. Convection, or natural circulation, of the air in the room past the window will transfer some of that heat into the room. But the window will also radiate heat as infrared waves, which will warm objects throughout the room. This radiative heating is why you can feel the heat of a red-hot piece of metal (for instance, a heating element on an electric stove) from several feet away.

Low-emissivity, or low-e, coatings are put on window panes to reduce the amount of heat they give off through radiation. In hot climates, where the outside of the window will typically be hotter than the inside, low-e coatings work best on the interior of the outside window pane. In cold climates, where the inside of the window is typically hotter than the outside, the low-e coatings work best on the inside window pane, on the side that faces toward the outside. To learn more about window coatings, see "Advances in Glazing Materials for Windows,"prepared by the U.S. Department of Energy's Energy Efficiency and Renewable Energy Clearinghouse." Quoted from the following Department of Energy web site: ) 

end plate
an oversize, square cardboard or wooden plate which suspends a roll of film and keeps it from touching the ground. It is held in place by a core plug.

energy absorbing system
fragment retention system used in combination with a daylight film installation attached to the glazing system and other building structures such as a wall.

Ethylene Propylene Diene Monomer - a weather resistant synthetic rubber from which many flexible gaskets for windows are made.

ER Rating
Energy Rating number developed by CSA (Canadian Standards Association) to compare the thermal performance of windows. Measured in watts per square meter (W/m2).

a process of controlled selective chemical or laser removal of a coating to produce a pattern. Usually a mask, such as photoresist, is deposited on the coating, the exposed areas are then etched away, and then the mask is removed to expose the pattern.

far-infrared radiation
The wavelengths of electromagnetic radiation generated (emitted) by objects cooler than 1300°F (705°C), covering the sweep in bandwidth in the electromagnetic spectrum from 2500 - ~60,000 nm (some charts extend the complete far-infrared range to 200,000 nm).

Federal Emergency Management Agency

the arrangement, proportioning, and design of windows and doors in a building. From the Latin word, "fenestra," meaning "window."

a device used for precise, straight-edge film pattern cutting directly from the roll. Photo.

CPFilms trademarked and recommended application solution for pressure sensitive adhesive films and those films sensitive to acid-based application solutions (such as sputtered bronze films and those films with elemental silver). Film-On is one component of CPFilms' "Two-Bottle System." See discussion in TBA-01. This liquid (in concentrate form, Tool Catalog part #GT735) contains the surfactant/wetting agent used in baby shampoo—without the host of "contaminating" chemical extras, such as glycerin and various perfumes and coloring agents. It causes water to become slippery and is therefore excellent for the film mobility and squeegee lubrication needed for installation. It is neutral in pH (neither acidic nor basic) and therefore will not affect the chemical composition of the mounting adhesive nor the long-term stability of the metallic depositions in various films. Recommended mixed ratio: 3-6 ml (milliliters) per liter of purified water. Not recommended for cleaning windows; instead, Dirt-Off or X-100 should be used for window preparation. See discussion of Dirt-Off (in TBA-01) or the entry for Dirt-Off above.

"Finger" is the common industry term for a dart along the edges of a piece of film resting on a compound-curved (bowl-shaped) piece of glass (most commonly, automotive glass). Film is flat and therefore does not naturally adopt the curvature of a spherical surface, and so forms what appear to be elevated "fingers" along the periphery, darts that point to the center of curvature of the glass on which it is resting. The object of heat forming is to shrink these film fingers so that the film will naturally conform to the spherical glass surface without creasing during the installation process. The purpose of the heat gun, HotWing™, and other such tools is to do this as precisely and as quickly as possible. The general rule is that fingers can only shrunk down along a film edge that runs in the machine direction. Fingers can also be reduced in size by cutting the film into smaller strips separately installed (horizontally, in general). Installation tip: If one is using the multiple strip technique on a rear window of a vehicle, the point at which a finger terminates is the point at which a splice line should be made horizontally across the pane (at right angles to the "finger"). See also see TBA-05 on the techniques of heat forming and also the HotWing™ user guide. Click here for a photo of fingering on an automotive side window, or click here for a photo of fingers on a rear window.
     There are, in fact, two basic kinds of fingers. The first and most common occur on outwardly contoured  (spherical) glass, shown in the preceding linked photos, and are sometimes called "open" fingers. The second type are called "closed" fingers, a type that occur completely within the center areas of saddle-shaped windows. See photo by clicking here.

fire testing
testing conducted to determine whether a product is appropriate for its intended end use in accordance with building fire codes.

flat-foot blade
Squeegee blade, specially cut at 45 degrees, that provides a wider blade footing during squeegeeing of thick gauge films. Blade is typically cut to 6- and 8-inch widths. Photo.

float glass
A type of glass produced by drawing molten glass across a bath of molten tin upon which it "floats," giving it its flat, smooth surface.

flush mounting
The liquid-mounting of window film with a handle-mounted, sharp, semi-rigid, hard-edged tool for maximum extraction of the application solution with a single pass.

foam spacer
Foam material placed in the airspace of the insulating glass windows to enhance the appearance and improve the performance of the window.

forced entry (UL 972) test
test that measures and determines the burglary resistance of a glazing system. See UL 972.

four-sided attachment system
reinforcing system (for a film/glass combination) attached at the two vertical and two horizontal sides of a glass framing system.
The term "gauge" is used in the film industry as a unit of film thickness, and represents 1/100,000 of an inch. Typically, though, a 1-mil raw polyester film is "92 gauge" (rather than 100/100,000 inch); and a ½-mil film is "48 gauge." 

gauge band
a variation in the thickness of a roll of film in the transverse direction, observed as a dark band in the roll.

a rubber or plastic pliable material used to separate glass and aluminum or vinyl.

Glass and Glazing Federation. "The Glass and Glazing Federation (GGF) is the recognised leading authority for employers and companies within the flat glass, glazing, window, home improvement, automotive, plastics and film industries in the UK. With members in over 1,500 business locations – there is a GGF member in almost every UK town." (Quoted from the GGF web site.)

glare reduction
The percent by which visible light transmission is reduced by the addition of a filtering material. For example, if a clear glass pane has a VLT of 90%, and the addition of a window film yields a new VLT of 50%, then the GLARE REDUCTION is from 90 to 50. We compare the difference in light transmission to the original transmission to get the percentage of glare reduction.  The calculation runs as follows: (.90 - .50)/.90 = 44.4%.

glass surface numbers
a numbering system to identify glass surfaces. They always start from the exterior. For example, a regular insulating glass unit (IGU) has four surfaces: #1 = the outside surface of the exterior lite; #2 = the inside surface of the exterior lite; #3 = the outside surface of the interior lite; and #4 = the inside surface of the interior lite.  

1. the process of installing glass or panels into the sash or frame of the window; 2. the window panel material itself (glass, acrylic, polycarbonate, etc.).

gloss level
a measure of the amount of non-specularly or diffusely reflected light from a surface. A highly diffuse surface has a low gloss level.

glow discharge
a process of electrical conduction through a gas caused by the ionization of the gas molecules and accompanied by the emission of light. Film is commonly treated to improve adhesion by subjecting it to a glow discharge. Sputtering is a form of glow discharge.

Identical to the solar heat gain coefficient, the g-value is given as the percentage of total solarenergy transmittance through a glazing system. (Solar energy reaching the surface of the earth extends in wavelength from 300 nm to 2500 nm). Solar energy transmitted includes the solar radiation directly transmitted as well as that which is absorbed and re-radiated and conducted/convected to the interior. The lower the g-value, the lower the solar gain.

graffiti application
a removable application of safety film to any non-porous surface (e.g. glass, stainless steel) to protect the surface from vandalism.

greenhouse effect
The property of glass that permits the transmission of short-wave solar radiation, but is opaque to long-wave thermal radiation. The interior of a car heating up in direct sun illustrates the greenhouse effect.

A term referring to windowpane dividers or muntins, usually a type of assembly which may be detached for cleaning

grilles-between-the glass
Aluminum bars in varying thicknesses and profiles sealed between insulating glass panels to simulate muntin bars.

ground plane
a conductive coating on film which is at earth (ground) potential.

GSA Conditions
A classification scheme adapted by the USA General Services Administration to specify the  hazard level associated with window glass fragmentation. Hazard levels range from 1 to 5, with 1 being the lowest level of risk to human safety and 5 being the highest. View the one-page explanatory document, or go to a series of charts.

a concealed, strong, right-angled shape used to reinforce mitered corners in tubular aluminum extrusions.

hard coat
a coating deposited on a surface, which is hard and resists abrasion. It may also be an anti-glare coating.

the amount of light, which is non-specularly transmitted through or reflected from a film.

heat loss reduction
The percentage by which heat energy loss (via conduction, convection, and radiation) through a given glazing system is reduced by the addition of an insulating material. For example, if a clear glass pane has heat loss value of .9 BTUs per square foot per hour per degree F, and the addition of an insulating window film reduces the heat loss to .5 BTUs per square foot per hour per degree F, then the HEAT LOSS REDUCTION is from .9 to .5. We compare the difference in heat loss to the original heat loss to get the percentage of heat loss reduction.  The calculation runs as follows: (.9 - .5) / .9 = 0.44, or 44%.

heat mirror film
a class of window films that transmit most visible light but reflect most (or proportionately more) of the infrared energy of the solar spectrum. See also "spectral selectivity."

heat stabilized
the effect of heating film to a temperature above its temperature of use so that its thermal shrinkage properties are minimized.

heat-strengthened glass
Stronger than annealed glass but weaker than fully tempered glass. Heat-treated glasses are classified as either fully tempered or heat strengthened. Heat-strengthened glass must have a surface compression between 3,500 and 10,000 psi, or an edge compression between 5,500 and 9,700 psi. The fracture characteristics of heat-strengthened glass vary widely from very much like annealed glass near the 3,500 psi level to similar to fully tempered glass at the 10,000 psi level. Source: .

hermetically sealed unit
an insulating glass unit (IGU) that is sealed against moisture. The unit is made up of two lites of glass, separated by a roll-formed metal spacer tube (at the full perimeter) which contains a desiccant (moisture and/or solvent absorbing material). The unit is then completely sealed, creating a moisture free air space.  

HVAC Companies
Heating, Ventilation, Air Conditioning companies. The following links are important ones for the entire HVAC industry: ; .

IG Unit
"insulated glass" unit, comprised of at least two sheets of glass separated by an air space and joined along the perimeter by an edge spacer filled with a desiccant, and rendered air and moisture-tight with a primary sealant (and usually a secondary sealant as well.)

IGCC (Insulating Glass Certification Council) is a non-profit organization which sponsors and directs a program of periodic accelerated laboratory testing and unannounced plant inspections to insure continuing product performance through specified standards. (Click here for more details.)

Insulated glass unit.

incident solar radiation
Solar radiation that directly strikes a surface, such as a window pane, table top, or measuring device (e.g., BTU meter). Such radiation is distinguished (for a variety of purposes) from radiation that may be reflected, scattered, or re-radiated from such a surface.

See nickel sulfide inclusion.

infrared radiation
That portion of the electromagnetic spectrum embracing both the near-infrared and far-infraredbands extending from 780-200,000 nanometers. Invisible to the human eye, this form of radiation is felt only as heat, and is is easily absorbed by most objects causing their temperatures to climb. 53% of the sun's energy reaching Earth is in the form of infrared (780-2500 nm, the near-infrared band).

indium-tin oxide (ITO)
a semi-conducting coating which is transparent to visible light and yet can be made to be electrically conductive. It can be readily patterned by means of etching.

insulating glass unit (IGU)
two pieces of glass spaced apart and hermetically sealed to form a unit with an air space between. Heat transmission through this type of glass may be as low as half that without such an air space.  

ITEM Systems
ITEM Systems® is a consulting and software development company specializing in energy and economic analysis of buildings and utility markets, with over 25 years of experience working with clients and customers throughout the world; producer of the Demand Analyzer program. 

See indium-tin oxide.

International Window Film Association

jalousie window
A series of small horizontal overlapping glass slats, sections, jalousies or louvers held together by a metal end frame attached to the faces of the window frame side jambs or door stiles and rails. Click here for picture1Click here for picture 2.

Krochmann Factor
 (or Krochmann Damage Function)
Named for the German scientist, KROCHMANN, who has done work on damage to fabrics, paintings, etc., by solar energy. The Krochmann Factor is the transmission value of radiation in the typical UV range from 300 to 380 nanometers plus the visible transmission from 380 to 550, where damage may also occur. WINDOW 5 (software from LBNL) runs a report on this "damage weighted transmittance" under Tdw.  In short, the Krochmann Damage Function represents a weighted transmission of the glass in the 300-550 (though some references assert the range extends to 600) nanometer portion of the solar spectrum. This value includes both ultraviolet and the portion of the visible light spectrum that can cause fabric fading. See Andersen's web site define the TDW as follows: "Transmission Damage Function (TDW)": The transmission of UV and visible light energy in the 300-600 nanometer portion of the solar spectrum. The value includes both the UV and visible light energy that can cause fabric fading. This rating has also been referred to as the Krochmann Damage Function. This rating better predicts fading potential than UV transmission alone. The lower the Damage Function rating, the less transmission of short wave energy through the glass that can potentially cause fabric fading. Fabric type is also a key component of fading potential." See for charts showing various performance values for commercial windows referencing the "Krochmann Damage Function." 
     You will see the Tdw value given in percentage form. The lower the value, the better the performance in terms of reducing fading. In the case of window films and glazing systems, in almost all cases, the Tdw value will be higher than the percentage of UV transmission alone because far more visible light is being transmitted than UV.

A very heavy, inert, colorless gas used instead of air in sealed spaces between panes of glass in insulating glass units to increase insulation (slower moving atoms transfer heat by conduction at a much slower rate). Provides greater insulation than Argon.

A measure of the insulation value of a glazing system. The K-value is the metric equivalent of theU-value and is a measure of the heat transfer that occurs through the glazing system between its outer and inner surfaces. The units are watts per square meter per degree centigrade.

laminated glass
Laminated glass consists of a tough plastic interlayer made of polyvinylbutyral (PVB) bonded together between two panes of glass under heat and pressure. Once sealed together, the glass "sandwich" behaves as a single unit and looks like normal glass. Annealed, heat strengthened or tempered glass can be used to produce laminated glass. Similar to the glass in car windshields, laminated glass may crack upon impact, but the glass fragments tend to adhere to the plastic interlayer rather than falling free and potentially causing injury. (Quoted from

a process of bonding together two films or a film and a solid surface with or without a separate adhesive layer.

light-to-solar-heat-gain ratio (LSG)
the ratio of the amount of visible light to the amount of solar heat that is allowed to pass through a glazing system. If this ratio is greater than 1.00, it means that the glazing system (a window system with film installed on it, for example) blocks more heat than light, which requires the selective blocking of more infrared radiation than visible light. This term is replacing "LE" (luminous efficacy) because of the gradual extinction of the term "shading coefficient." The higher the LSG ratio, the better the glazing is at reducing unwanted solar heat gain and maximizing desirable natural light transmittance. This term is replacing "luminous efficacy" in the industry.VLT / SHGC = LSG.

A single pane of glass. Often used to distinguish to a single pane which may be part of a multi-pane window unit. For measurement, installation, and other sales bid purposes, most installation companies measure individual lites rather than window units. (Sometimes spelled "light.")
The common expression referring to "low-Emissivity." See Emissivity.

Low-E2 is a term referring to glass products that have both low-E and solar control coatings. Usually in such products the #2 surface is coated with microscopically-thin, optically transparent layers of silver sandwiched between layers of anti-reflective metal oxide coatings. See also TBF-41.

low-e films
Films with improved far-infrared heat reflection, with the ability to reduce winter heat loss through windows. The reflection of far-infrared heat also reduces the need for summer cooling by reducing the transmission of far-infrared heat from outdoor objects through windows into the interior of a home or building. See Emissivity. See also PPG's comments on low-e surfaces.

a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity. (Britannica) . Museum conservators, for example, generally strive to keep light intensity levels at or below 5-10 lumens/ft2 (5-10 foot-candles, 50-100 lux) where watercolor paintings are involved, since they especially vulnerable to light. (from Britannica)See luminous intensity.
LSG Ratio
See "Light-to-Solar-Heat-Gain Ratio."
luminous efficacy
A measure of how effective a glazing product is at reducing unwanted solar heat gain without significantly altering visible light transmission. LUMINOUS EFFICACY = Visible Light Transmission (in decimal form) divided by the Shading Coefficient. This ratio of light transmission to shading coefficient is referred to as "Coolness Index" or "Lighting and Cooling Selectivity (LCS) Index" by some glass and window manufacturers. A number great than 1.0 indicate the film or glazing unit is "spectrally selective," blocking more of the near infrared than the visible light components of the solar spectrum. See the Technical Bulletin (TB-35) on the subject. 
Relevance to customer:
 Luminous efficacy helps a customer decide which product is more efficient at blocking heat rather than light. 

Note: Because the term "shading coefficient" is becoming less often used in the glass industry, the concept of luminous efficacy has been redefined is the "Light-to-solar-heat-gain ratio" (or "LSG")

luminous intensity
"The quantity of visible light that is emitted in unit time per unit solid angle. The unit for the quantity of light flowing from a source in any one second (the luminous power, or luminous flux) is called the lumen. The lumen is evaluated with reference to visual sensation. The sensitivity of the human eye is greatest for light having a wavelength of 555 manometers (10-9 meter); at this wavelength there are 685 lumens per watt of radiant power, or radiant flux (the luminous efficiency), whereas at other wavelengths the luminous efficiency is less. The unit of luminous intensity is one lumen per steradian, which is the unit of solid angle--there are 4 pi steradians about a point enclosed by a spherical surface. This unit of luminous intensity is also called the standard candle, or candela, one lumen per steradian." (from Britannica).

the illumination intensity that exists on a surface at a uniform distance of one meter from a point light source emitting one international candle (now called a candela). One lux is equal to 0.0929 foot-candle. (Britannica). See TBF-40 describing a device to measure this value.

machine direction (MD)
The direction in which window film runs through the production equipment and is wound onto rolls. This direction is important to know since this is the direction in which film shrinks when heat is applied to get it conform to compound curvatures of glass. Orthogonal (at a right angle) to this direction is the Transverse Direction (TD).

magnetron sputtering
glow-discharge film deposition process related to sputtering where a shaped magnetic field is used to confine electrons in the discharge and greatly increase its efficiency and the deposition rate.

mechanical anchoring system
structural attachment system used to unify and reinforce the structural integrity of safety film, glass, and a framing combination, usually composed of metal extrusions mounted to existing framing systems.

median U-value
See U-value.

to coat a surface by vacuum evaporation, usually with aluminum.
The phenomenon of an object (such as window film) appearing to shift in color under different lighting conditions, such as in the move from artificial light (incandescent or fluorescent) to natural sunlight. This is an especially serious concern in color matching film samples in the film industry since two samples can appear to be a perfect match in one set of lighting conditions, but appear quite different under different conditions of illumination. For more detailed information on this and a variety of other issues, see "Frequently asked questions about Colour Physics" by Dr. Stephen Westland at Colourware, by visiting the following web site: " Dr. Westland's definition: "Metamerism refers to the situation where two colour samples appear to match under one condition but not under another; the match is said to be conditional. Metamerism is usually discussed in terms of two illuminants (illuminant metamerism) whereby two samples may match under one illuminant but not under another. Other types of metamerism include geometrical metamerism and observer metamerism. Two samples that conditionally match are said to be a metameric pair. If two samples have identical reflectance spectra then they cannot be metameric - they are an unconditional match."

Unit of length in the metric system, equal to one millionth of a meter. Also equal to 1000 nanometers. In inches, 1 micron (micrometer) = .00003936996 inches (3.936996 x 10-5)

a unit of thickness equal to one thousandth of an inch (not to be confused with a "millimeter"). A film 1 mil in thickness = 25.4 microns. A 7-mil safety film is 178 microns thick. A wavelength of visible light at 550 nanometers is .55 microns across, about 50 times narrower than than the thickness of a 1-mil film.

mounting adhesive
adhesive designed to bond film to a glass surface.

1. Wood or metal part used to structurally join two window or door units. an extrusion that joins windows; 2. A wood or metal part used to structurally join two window or door units; 3. The vertical or horizontal divisions or joints between individual windows in a multiple window unit; 4. Applies to any short or light bar, either vertical or horizontal, used to separate glass in a sash into multiple lights. Also called a windowpane divider or a grille. See muntin.

mullion cover
an extrusion that joins panning perimeter legs that extend over existing mullions.

1. Applies to any short or light bar, either vertical or horizontal, used to separate glass in a sashinto multiple lites. Also called a windowpane divider or a grille. Sometimes these bars or strips are adhesively attached to the surface of a large pane of glass to simulate the appearance of many small panes (they can be removed and adhesively remounted with foam tape and/or silicone after a film installation). Often this lattice work or grille (simulating the appearance of French panes) is a single molded plastic unit that can be removed via perimeter screws so that the entire pane can be filmed at once, with the grille being replaced afterward. (Use extreme caution if removing the grille in the event that these screws also hold the window unit in place). 2. extrusions in the sash which are exterior (outside of the glass exterior face), internal (in the insulating glass airspace), or true (dividing the glass) which appear to or actually divide the glass into smaller lites
One billionth of a meter. The standard unit of measure for wavelengths in the solar spectrum. There are 1000 nanometers in one micron (one millionth of a meter).

Electromagnetic radiation with wavelengths in the range of 780-2500 nanometers. Objects warmer than about 1300°F (705°C) begin to glow (radiate) in this band, and as their temperatures rise, emitted wavelengths shorten. Wavelengths shorter than 780 nm become visible as red light.Click here to see spectrum of wavelengths emitted by the sun (the "solar spectrum") that reach earth's surface. 
"National Fenestration Rating Council (NFRC) is a non-profit, public/private organization created by the window, door and skylight industry. It is comprised of manufacturers, suppliers, builders, architects and designers, specifiers, code officials, utilities and government agencies. NFRC provides consistent ratings on window, door and skylight products. ...NFRC's primary goal is to provide accurate information to measure and compare the energy performance of window, door, or skylight products." Quoted from the NFRC website.

nickel sulfide inclusion
A small crystal ("stone") of nickel sulfide that has become trapped as a contaminant within a glass lite during its manufacture in the molten state. If one such crystal should be trapped near the surface of the lite, and the pane is then tempered, there is a possibility of a future "spontaneous" breakage, usually within 4-5 years of its manufacture. This crystal may continue to grow very slowly, eventually overcoming the compressive forces in the glass surface introduced by the tempering process, resulting in sudden, catastrophic failure of the glass, accounting for many instances of what has come to be called "spontaneous glass failure." (See article titled "Temper Temper: Managing the Problems Inherent in Tempered Glass" by Regina R. Johnson, in the April 1998 issue of  US Glass magazine. Archived file: click here.) In the photo shown here, the pane stayed intact and the inclusion could be identified as the culprit. Note the larger glass pellets in the middle, in the form of a figure-8 pattern. The NiS stone would be located between them, a round and very tiny yellow-black particle (see photo at right). See also a Viracon publication on this subject and how glass manufacturers try to avoid or minimize this kind of breakage.

a synthetic rubber having physical properties closely resembling those of natural rubber. It has extremely good weather and temperature resistance, both heat and cold, with ultraviolet stability.

neutral films
The term "neutral," as applied to certain metallized films, refers to those films that have a very uniform (flat) transmission throughout the visible portion of the solar spectrum, resulting in an excellent transmitted color balance, no region of the color spectrum being preferentially transmitted over the others. Most neutral sputtered films also have a relatively flat transmission curves into the near infrared band as well. Contrasted with "spectrally selective" films

the unit of force in the metric system equal to the force required to accelerate a mass of one kilogram at the rate of one meter per second per second.

obscure glass
mainly used for decoration, diffusion, or privacy. The pattern is rolled into the hot glass during glass manufacturing.

Ohms/square ("ohms per square")
the measure of electrical resistance of a coating. 

property of a glazing system (or any material of any coloration) that does not permit sufficient light transmission to see any images through it. (Term is to be distinguished from "translucent" and "transparent.")

open frame testing
blast test consisting of two identical stand alone (not in a building structure) panels of glass in frames, one with safety film installed and the other without.

open air arena testing
true to life performance testing of glass retention systems or methods using large explosive devices and glazing systems installed in simulated enclosed structures.

optical density
a logarithmic measure of the transmission of a coating; Optical Density, OD = - log 10(T), where T is the transmittance.

oriel window
a window with unequal sash.

The compass direction that a structure faces. To maximize heat-gain in the northern hemisphere, the major facade of a building should face South (a variation as much as 30 degrees east or west of south will not seriously affect performance).

Palladian window
A large, arch-top window flanked by smaller windows on each side. Named after Andrea Palladio (1508-1580), an Italian architect.

a set of extrusions which are fastened to a new window to cover the exterior perimeter of an existing opening in a retrofit application.  

a unit of pressure in the metric system equal to one newton per square meter. Named after Blaise Pascal (1623-1662), a French philosopher and mathematician.
peel strength
In the field of window films, this value is given in terms of pounds per inch, grams per centimeter, grams per inch, etc., and measures the ability of an adhesive system to resist a force that is pulling the film away from the glass surface either at right angles or 180° to the glass surface (depending of the testing criterion).

PET polyester
polyethylene terephthalate polyester film, which has excellent optical clarity, smoothness, and process ability.

an instrument for measuring the transmittance, optical density, or reflectance of a coating.

planar magnetron
a type of magnetron sputtering source in which deposition occurs from a planar surface, usually a metal plate. 

a highly ionized gas caused by electrical breakdown of the gas between the electrodes of a glow discharge or sputtering system.

plasma deposition
a glow discharge, thin film deposition process in which gases introduced into the glow discharge react chemically to produce a coating.

a film (or plastic) with high light transmission, clarity and toughness, but low chemical resistance. Abrasion-resistant protective coatings are available to improve its chemical resistance.

a film with high heat tolerance and a distinctive amber color. Used primarily in the flex-circuit industry.

the accumulation of large amounts of residual moisture from the installation and forming pools or bubbled areas beneath window film.

pounds/ream of coating
a measure of the amount of dry coating or adhesive applied to a surface. One ream equals 3,000 square feet.
PSA (Pressure Sensitive Adhesive)
Pressure sensitive adhesive is the generic term referring to a type of adhesive system used to secure window film to glass, and is to be distinguished from CDF (Clear Distortion Free) adhesive. PS adhesives are tacky to the touch and remain so during their effective life. Films with PS adhesives are generally easier to install, providing rapid tack to glass and easier removability. They are used most commonly for automotive film installation. While automotive films provide the most common applications of PSA, safety/security films also require such adhesive systems (often of a heavier, tackier nature) owing to their heavier gauge thicknesses and the special requirements of impact absorptance. DPS (detackified pressure sensitive) adhesives are simply PS adhesives coated with a water soluble layer of polyvinyl alcohol, intended to prevent the film from sticking to itself as the liner is stripped away. The coating must be washed away before laying up the film on glass. Normal full cure for PS films averages three days, though this time is a function of temperature, humidity, and film type and may require up to 30 days in some situations. For full details on the differences between CDF and PS adhesives, see TB-37

pounds per square foot (often referred to in discussions of design wind load conditions on glazing systems or other structures).

puncture strength
The ability of a material (such as window film) to resist penetration or "puncture" with a blunt probe of specified size and shape. Measurement is in terms of force, such as pounds.

The abbreviation for polyvinylbutryal, the tough, viscous interlayer used to bond sheets of glass together to make laminated glass; generally sold under the brand name of Saflex, manufactured by Solutia which is the parent company of CPFilms Inc.

pyrolytic deposition
A deposition onto glass where the coating (metal or any number of other oxides or compounds) is chemically-bonded to the glass at the molecular level while it is still in the semi-molten stage by chemical vapor deposition, resulting in an extremely durable and stable coating that is impregnated right into the surface of the glass, forming a "hard coat."

a mode of energy transfer in the form of electromagnetic waves across space.

Invented by William Crooke (c. 1875), this is a device used to show the energy intensity of light and radiant heat. It consists of a partially evacuated glass chamber (similar to a light bulb), sealed to a flat plate at the bottom so that it stands upright. In the center is a glass 'post' with a small metal needle. On top of the needle is balanced a glass sheath with four vertical metal 'flags,' like weather vanes, black on one side, white on the other. If the radiometer is placed in light (sunlight or a strong light bulb), it will spin as the radiant energy affects the little flags. The spin rate is essentially a function of the intensity of the light. Click here for Photo #1 or Photo #2of radiometers.

the ratio of the amount of energy reflected by a coating to the amount of incident energy. Note that for a semi-transparent film, Transmittance + Absorptance + Reflectance = 1.

release sheet
a sheet of film used to protect a surface, such as a coating or adhesive, which has a light tack to that surface and is removed prior to use.

rotatable magnetron
a type of magnetron sputtering source in which deposition occurs from a cylindrical source, usually a metal tube. Typically more efficient than planar magnetrons; however source materials are not as readily available.
Inverse of the U-value. See U-value below.

safety and security film
Safety and security films constitute a special category of window films (flexible organic coatings adhesively applied to glass) distinguished by their physical properties and intended uses. Safety films are intended to provide protection against human injury due to broken glass shards, protection superior to that of standard solar control films by virtue of their increased thickness and superior break, peel, and puncture strength. Security films are intended to provide physical protection beyond personal safety to include hazard mitigation from bomb blasts, wind storms, earthquakes, and spontaneous glass failures, as well as resistance to forced entry and graffiti vandalism. Selection of particular films for an intended use should always take into accountperformance as defined and demonstrated by relevant testing standards.

The inner frame which holds glass in operable and fixed window units. 2. the operating portion of a hung or horizontal sliding window. A single assembly of stiles and rails made into a frame for holding glass. The framework holding the glass in a window unit. It’s composed of two stiles (sides) and two rails (top and bottom).

sash balance
A coiled spring or spiral system integrated into the jamb liners to allow double hung or single hung sashes to open and close. They also allow the sashes to remain open in varied positions.

sash cord
In double-hung windows, the rope or chain which attaches the sash to the counter balance.

sash lift
A protruding handle screwed to the inside bottom rail of the lower sash on a double-hung window. Available on all Pella double-hung windows.

sash lock
Generally, a cam-action lock applied to the check rails of a double/single hung window, or sliding window to pull the check rails tightly together. They are also applied to the open edges of a projecting window to seal the sash tightly to the frame. Sash locks provide security and weatherability.

sash stop
cover in jamb track that reduces sash travel on hung windows.

sash weights
In older double-hung windows, the concealed cast-iron weights which are used to counterbalance the sash.

scratch resistant (S/R) coating
see Abrasion Resistant Coating.

secondary glazing system
a duplicate glazing system using glass and glass retention film applied or laminated glass designed solely for glass hazard mitigation purposes.

See Solar Heat Gain Coefficient.
Safety Glazing Certification Council - administers tempered glass testing and certification program. Quote from their site:

The Safety Glazing Certification Council (SGCC) is a non-profit corporation, established in 1971 by manufacturers of safety glazing products, building code officials, and others concerned with public safety. SGCC maintains a program which provides for the certification of safety glazing materials found to be in compliance with one or both of the following specifications:

American National Standard for Safety Glazing Materials used in buildings - Safety Performance Specifications and Methods of Test: ANSI Z97.1-1984

Consumer Product Safety Commission Safety Standard for Architectural Glazing Materials - codified at Title 16, Part 1201 of the Code of Federal Regulations: 16 CFR 1201.

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 relative to a standard window. 
Relevance to customer: The smaller the number, the greater the solar heat reduction. This term is a standard measure in the glass industry; used to rate the relative effectiveness of a glazing system compared to a "standard window." However, the glazing industry is moving away from use of the term since a "standard window" is no longer a single pane clear window with double strength glass. SHGC is a better term for quantifying glazing performance because if allows for easy comparison of of the solar performance of a given window to any other.

sheet resistance
for a rectangularly shaped section of coating, the resistance measured in a direction parallel to the coating surface is R = rL/S, where the surface through which the current flows is (S) = the coating thickness (t) x the breadth of the coating section (b), and L is the length of the coating section. The resistivity of the coating is r, with units of ohm-cm, etc. If L = b, then R = r/t, i.e., the resistance of a square of coating is independent of the size of the square and is called the "sheet resistance."

shock tube testing
use of an air blast from a tube to simulate a bomb blast's positive pressure-impulse against a glazing system.

silicone coating
a type of coating often used on a release sheet (film liner).

single-strength glass
Single-strength glass is 3/32 inch (2.5mm) thick glass (according to the GANA Glazing Manual, 1997 edition, page 14, which references ASTM C-1036.) See entry for double-strength glassabove and the related FAQ.

the process of cutting a large roll of film to several shorter or narrower rolls.
solar direct absorptance (ae, SEA, or A-sol)
The ratio of the amount of solar energy absorbed by a glazing system to the amount of solar energy falling on the glazing system. Solar absorptance is that portion of total solar energy neither transmitted nor reflected. Since solar transmittance and solar reflectance are measured directly, the following equation should be used in calculating solar absorptance. Solar absorptance =1.00 - (solar transmittance) - (solar reflectance). 
Relevance to the customer and specifier: This number is a critical determinant in the potential for thermal stress (how hot the glass gets). Too much absorptance can cause glass failure. SeeFilm-to-Glass Recommendation Chart.
solar direct reflectance (re, SER, or R-sol)
The ratio of solar energy which is reflected outwardly by the glazing system to the amount of total solar energy falling on the glazing system. Value is usually expressed as a percent.
Relevance to the customer and specifier: This number together with the T-sol determines thesolar absorptance value of the film. This latter value is most critical in determining what film is suitable for a given glass type & situation.
solar direct transmittance (te, SET, or T-sol)
The ratio of the amount of total solar energy in the full solar wavelength range (300-2,500 nanometers) that is allowed to pass directly through a glazing system (e.g., a film/glass combination) to the amount of total solar energy falling on that glazing system. Value is usually expressed as a percent.
Relevance to the customer and specifier: The smaller this number, the cooler objects will be when directly exposed to sunlight passing through the window, since they will be absorbing less incident solar energy.

solar heat gain coefficient
The SHGC (also know more simply as the g-value) is the fraction of incident solar radiation that actually passes through that window, including solar energy that is both directly transmitted and that which is absorbed and subsequently released inwardly by re-radiation and conduction. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits. This number is the mathematical complement of the TSER value:

The sum of the TSER (Total Solar Energy Rejection, in decimal form) of a glazing system and its SHGC value is 1; therefore,

Thus, if the TSER of a specified film/glass combination is 58%, then 1 - .58 = .42, which is the SHGC of the window.

Note: This term is being increasingly used in the window film industry because it is a central term in the window glazing industry which does not use the term TSER.
solar heat reduction
The percent by which incoming solar heat energy is reduced by the addition of a filtering material. For example, if a clear glass pane has solar heat gain of 86% (a solar heat gain coefficient of .86), and the addition of a window film yields a new solar heat gain of only 40%, then the HEAT REDUCTION is from .86 to .40.  We compare the difference in heat gain to the original heat gain to get the percentage of heat gain reduction. The calculation runs as follows: (.86 - .40)/.86 =  0.535, or 53.5%.

solar spectrum
the range of electromagnetic energy emitted from the sun and reaching Earth, ranging in wavelength from about 300 to 2400 nanometers. To be distinguished from the far broaderelectromagnetic spectrum.

Sound Transmission Class (STC)
A rating measure for the ability of glazing to block out sound from outside sources. The higher the STC rating the better the sound blockage (and the quieter the home).

spandrel glass
glass mounted between floors of a building. It is usually made opaque to hide building components.

specialty window
A type of window with distinct shapes, such as octagons, round-tops, ellipticals, rakeheads -- virtually any shape can be custom manufactured.

spectral selectivity
The term is used differently in different contexts in the glazing and window film industry. Very generally, any film product or glazing system is "spectrally selective" if it singles out specific regions of the solar spectrum (certainly ranges of wavelengths of electromagnetic radiation) to be preferentially blocked or transmitted.  (Nearly all high quality films "selectively" block nearly all the UV portion of the solar spectrum while blocking differing amounts of visible light and near infrared radiation.)  Recently, the term has been given restricted application to those window films that selectivity block all or most of the near-infrared region while allowing the transmission of most of the visible light, that is, those that have a light-to-solar-heat-gain ratio (LSG) is greater than 1.0.For general solar control purposes, spectral selectivity (in this more restricted sense) is desired because it means that far more of the (invisible) infrared part of the spectrum is being blocked than the visible portion, thus maintaining higher levels of light transmission while substantially reducing solar heat gain. Non-spectrally selective (neutral) films more evenly block both the visible and infrared regions of the spectrum.

an instrument for measuring the transmittance and reflectance of a coating as a function of wavelength.

term applied to radiation which is incident or reflected from one direction only, i.e., in a mirror-like fashion.

spontaneous glass failure
see nickel sulfide inclusion

spreader roller
a roller in film transport equipment which prevents thin film from wrinkling.

Dislocation of surface atoms of a metal from bombardment by high-energy positive ions from an argon gas plasma and the deposition of these freed atoms onto a substrate. Sputtering offers a lower-temperature process than thermal evaporation and produces deposits that more closely replicate the initial composition of the metal, allowing thin depositions of a great variety of materials that have a much higher melting point than aluminum. Atoms freed in the sputtering process unite easily with gases such as oxygen to produce reactive deposits to achieve metallic oxide coatings with transparent and/or insulating properties. "Sputtering" is the general term used to refer to this method of depositing metals and oxides to film substrates.

a portion of a framing system that stops or regulates glass movement.

structural glazing
(1) Typically, a system for mounting glass in curtain wall configurations in which the predominate framing material is extruded aluminum. A special sealant is usage to bind the glass to the framework, and to achieve this, the extruded aluminum is finished with either powder coatings or anodizing which are applied under strict factory conditions which makes aluminum the preferred structural material for Structural Glazing Systems. Since the sealant is the only structural link which holds the glass in place, the adhesion and chemical compatibility of all elements must be thoroughly tested, analyzed and verified in accordance with ASTM C 1087-87. (2) Sometimes, however, the term is applied to another form of glazing in which stainless steel attachments actually mount through holes in the (fully tempered) glass to yield a curtain wall suspended from a top beam or directly to an inner adjacent lattice work of steel members. This permits a smooth, outer glazed surface without the traditional frame supports along the panes' perimeters. (Click here and here for drawings or visit for a description of this kind of glazing.)  

the face of the cathode in a sputtering apparatus. It is the material which is converted to the coating (deposited onto the film substrate).
The "damage weighted transmittance" of a glazing system that includes the effects of damage from both the ultraviolet and visible portions of the solar spectrum. See also the Krochmann factor.

a distortion of a roll of film where the individual layers slide over each other laterally and can cause scratches in the film.

tempered glass
Glass manufactured to withstand greater than normal forces on its surface. Stronger than both annealed and heat-strengthened glass. When it breaks, it shatters into small pieces to reduce hazard. Tempered glass is made by taking annealed (ordinary) glass and heating it to its softening point of approximately 700°C. Its surface is then rapidly cooled while the inner core is allowed to cool gradually. This results in layers of high compression on the surface counter balanced by high tension at the center resulting in a glass that is four to five times as strong as annealed glass. Should accidental breakage occur, the resulting fragments are small and granular and present minimal possibility of injury. Such breakage is also called "pelletizing" or "dicing." According to Federal Specification ASTM-C1048-85, fully tempered glass must have a surface compression of 10,000 psi or more, or an edge compression of 9,700 psi or more.
"Through the tempering process, a system of residual stresses is introduced to convert normal flat glass to safety glass when the stress level is high enough. Glass is tempered by heating sized, edged glass in a tempering furnace to approximately 1,200 degrees F, then rapidly cooling, or quenching, the glass to approximately 400 to 600 degrees F. In quenching, air jets quickly cool and set the surfaces, leaving the inner portion of the glass thickness relatively hot and cooling at a slower rate. The surfaces become rigid, but the center is still pliable and contracting as it cools, thus compressing the surface. Compressive residual stresses imposed on the glass surface, which close up any cracks, are balanced by residual tensile stress in the center of the glass.
     "These stresses make tempered glass approximately four times stronger than annealed glass, making it ideal for applications where maximum resistance to thermal and cyclic wind loading pressures is required. In addition, if broken, fully tempered glass breaks into relatively safe, small pieces, rather than shards." (Quoted from "Temper Temper: Managing the Problems Inherent in Tempered Glass" by Regina R. Johnson, in the April 1998 issue of US Glass magazine.  Archived file: click here.)

Fully tempered glass is a safety glazing material when manufactured to meet the requirements of the ANSI Z97 and Federal Standard CPSC 16 CFR 1201, as well as state and local codes, which require safety glazing material where the glazing might reasonably be exposed to human impact. This includes doors, tub and shower enclosures, side lights, and certain windows. Applicable building codes should be checked for specific information and requirements. (

tensile strength
The strength of a material to resist being pulled apart (under tension). Measurement of tensile strength is always measured in terms of force per unit of cross-sectional area (such as pounds per square inch or "psi"). Tensile strength of various materials can vary with the direction of the forces applied, owing the possible "grain" characteristics of the material. Wood, for example, has greater tensile strength in the direction of its grain, as one might expect. The tensile strength of a material does not change with its thickness, though its "break strength" does. (See, however,FAQ #91 regarding laminated window films.)

thermal break
1. An air space or insulating material which prevents the direct coupling of a cold surface to a heated surface; 2. an element of low conductivity (polyurethane) placed between elements of higher conductivity (aluminum) to reduce the flow of heat and cold; 3. The addition of a thermal insulating material between two thermally conductive materials

thermal bridge
The direct coupling of a cold surface to a heated surface, allowing heat transfer via conduction.

thermal mass
the amount of heat storage capacity available in a given material or assembly. Thermal mass in a home (tile floors, stone fireplace, etc.) will absorb excess heat generated during the day and store it until ambient temperature drops.

thermal radiation
Electromagnetic radiation emitted by any warm body—such as the sun, a light bulb, a campfire, a rock, a person, indeed any physical body whose temperature exceeds absolute zero.

thermal shock
Glass breakage as a result of uneven glass heating. Rapid expansion of certain sun-exposed areas of a window pane while the other regions of the glass (shaded areas or borders shielded by the frame in the "edge-bite" area under the gaskets) remain cool can cause tensile forces beyond what the elasticity of the glass can tolerate. Window film with very high absorptance values can cause thermal shock; hence the importance of following the film-to-glass recommendation chart or using soon-to-available (mid-2001) bid proposal generation software that automatically incorporates factory-specified film-to-glass formulae. Thermal shock is to be distinguished from other kinds of glass breakage such as physical impact, torsion, sheer, bending, compression, or nickel sulfide inclusion. See technical bulletin on thermal shock and glass breakage.

Air conditioning system type Approximate kW required per Ton
Large (over 100 tons) water cooled chiller system 1.00
Small (less than 100 tons) air cooled chiller system 1.40
Rooftop units (air cooled, direct expansion units) 1.4-1.6
Heat pump units 1.6
Window air conditioning units 1.8
Through-the-wall units common in motels


TON (of air-conditioning)
One ton of air conditioning = 12,000 BTU/Hour. Tonnage refers to an AC system's capacity to remove BTUs (units of heat energy) from a building. The most efficient air conditioning systems require 1 kilowatt (1000 watts) of electricity to remove 12,000 BTUs in one hour. An efficient 5-ton system, for example, can remove 60,000 BTUs in one hour, requiring 5000 watts of electricity during that period (5 kW-hrs); at $.08/kW-hr, the cost would be $0.40. See table at right for kW required per ton for different kinds of air conditioning systems.

A unit of atmospheric pressure equal to 1/760 of an atmosphere, or about 133.3 pascals.
total solar energy rejection (TSER)
The percent of incident solar energy rejected by a glazing system. This value equals solar reflectance plus the part of solar absorptance that is both re-radiated and conducted/convected outwardly.
Relevance to customer: Like "shading coefficient" in the glass industry, this term has been a standard one in the film industry. The number is a good way to compare relative performance of various products. (Remember that this number is measured for a film on clear, 3mm glass, unless otherwise stated.)

the ratio of the amount of directly transmitted energy to the amount of incident energy.

a property of a glazing system that transmits light, but does so by scattering it so that a hazy, "frosted" appearance is rendered and no clear image can be seen except when the object to be viewed is within inches of the pane. Term "translucent" is to be distinguished from "transparent" and "opaque."

A small window that fits over the top of a door or window, primarily for additional light and aesthetic value. In older homes and office buildings the transom window could be swung open (hinged on either the upper or lower edge) for ventilation.

a property of a glazing system that transmits light, and does so without scattering it so that clear images can be seen through it. Transparent media may reduce light transmission (via tinting) and still be properly referred to as "transparent." When light transmission is reduced to the point where distinct images can no longer be seen (very close to 0% VLT), the medium is said to be "opaque."

transparent conductor
a coating which is at least semi-transparent and which has a finite electrical conductivity. These coatings are generally of two types; (1) metal oxides which are highly transparent but which have a low conductivity and; (2) thin metal coatings which have lower transmittance but a high conductivity.

transverse direction
the direction the cuts across the machine direction, at right angles to the direction in which film runs through the production equipment. Abbreviated "TD."

trim factor
the width of the gap left between the film product's edge and frame or glass edges.

two-side attachment system
reinforcing system (for a film/glass combination) attached at the two vertical or two horizontal sides of a glass framing system.

true divided light
term that refers to windows in which multiple individual panes of glass or lights are assembled in the sash using muntins. This traditional method of window construction does not have the strength or durability of the Integral Light Technology™ used in Pella Architect Series® windows
UL Standard for Safety for Bullet-Resisting Equipment. The Scope is characterized a  follows (quoted from ):

These requirements cover materials, devices, and fixtures used to form bullet-resisting barriers which protect against robbery or holdup.

As used in these requirements, the term "bullet-resisting" signifies that protection is provided against complete penetration, passage of fragments of projectiles, or spalling (fragmentation) of the protective material to the degree that injury would be caused to a person standing directly behind the bullet-resisting barrier.

These requirements also cover electrically-operated equipment, such as teller's fixtures using electrically-driven deal trays or package passers, and intercommunication or other electrical equipment that is an integral part of the bullet-resisting product.

The term "product" as used in this standard refers to all bullet-resisting equipment or any part thereof covered by this standard unless specifically noted otherwise.

A product that contains features, characteristics, components, materials, or systems new or different from those covered by the requirements in this Standard, and that involves a risk of fire, electric shock, or injury to persons shall be evaluated using the appropriate additional component and end-product requirements to determine that the level of safety as originally anticipated by the intent of this Standard is maintained. A product whose features, characteristics, components, materials, or systems conflict with specific requirements or provisions of this Standard shall not be judged to comply with this Standard. Where appropriate, revision of requirements shall be proposed and adopted in conformance with the methods employed for development, revision, and implementation of this Standard.

Underwriters Laboratory Test UL 972 for Burglary-Resistant Materials. This test subjects the glazing sample to the assaults defined in set of tables available on the following Solutia (Saflex) web site. 
Test Requirements--Burglary-Resistant Glazing Material
UL 972 Tests1 Impacts
per Sample
Impact Energy Temperature
Multiple Impact 5 50 ft.-lbs. 70°F-80°F(21°C-27°C)
Outdoor Use2 5
40 ft.-lbs.
40 ft.-lbs.
14°F (-10°C)
120°F (49°C)
Indoor Use2 5
50 ft.-lbs.
50 ft.-lbs.
95°F (35°C)
55°F (13°C)
High-Energy Impact3 1 200 ft.-lbs. 70°F-80°F(21°C-27°C)
Tests consist of dropping 3-¼" 5 lb.(~2.25kg) steel ball through a designated vertical distance; sample size 24"x 24" (~61cm x ~61cm).
The steel ball shall not penetrate the laminate on any of five impacts on nine of the 10 samples tested.
3 the steel ball shall not penetrate the laminate on any of the three samples tested.

ultraviolet radiation
That portion of the electromagnetic spectrum which includes the UVA (380-320 nm), UVB (320-280 nm), and UVC (280-100 nm) bands extending from 100-380 nanometers. Invisible to the human eye, this form of radiation is the most immediately harmful to human health and damaging to organic materials. 3% of the suns energy reaching Earth is in the form of ultraviolet light. See ultraviolet transmittance.

ultraviolet (UV) transmittance
The ratio of the amount of total UV solar energy (from 300-380 nanometers) that is allowed to pass through a glazing system to the amount of total UV solar energy falling on the glazing system (little if any UV light from 100-300 penetrates glass). Ultraviolet is one portion of the total solar energy spectrum which greatly contributes to fading and deterioration of fabrics and furnishings. Sometimes UV performance numbers are given in term of how much is "rejected," that is, what percentage of incident UV is prevented from passing through the glazing system. UV is generally subdivided into 3 smaller bands, progressively smaller in wavelength (therefore higher in frequency): UVA (380-320nm); UVB (320-280); UVC (280-100). See Flat Glass Training Manual for more information. Clear glass blocks very little UVA but most UVB. High quality window films can block well over 99% of both UVA and UVB.
Relevance to customer: This parameter is a very important factor in the purchase of window films. Excessive UV is the most dangerous part of the solar spectrum for human health (it’s implicated in cataracts and skin cancer, and adversely affects people with Lupus, Xeroderma Pigmentosum, Porphyria, and other such diseases. See article on UV and Human Health.) UV is generally the biggest factor in damage to drapes, carpets, furniture, though shorter wavelengths of visible light (extending into the violet and blue bands) may play an important role as well (see the Krockmann Factor). UV blocking is also important for the longevity of the window film itself.

the lack of variation in the properties of a coating along and across a piece of film. 

UV-cured coating
 - a coating which is reacted or polymerized through the action of ultra-violet light rather than heat. Most SR coating are cured this way.

UV absorbers
chemicals used to protect window film's polyester and adhesives from the sun's damaging ultraviolet rays.

The band of ultraviolet radiation with the longest wavelengths, ranging from 320-380 nm. Seeultraviolet transmittance.

The band of ultraviolet radiation with intermediate wavelengths, ranging from 280-320 nm). Seeultraviolet transmittance.

The band of ultraviolet radiation with the shortest wavelengths, ranging from 100-280 nm. Seeultraviolet transmittance.

The U-value (sometimes called the "U-Factor") should be understood as the overall heat transfer coefficient of the glazing system. The U-value is a measure of the heat transfer that occurs through the glazing system between its outer and inner surfaces. This value is a function of temperature, and is expressed in BTUs per square foot per hour per degree Fahrenheit ( BTU/ ft2/hr/°F or w/m2). The lower the U-value, the better the insulation qualities of the glazing system. Alternative definition: The "coefficient of heat transfer;" a measure of the ability of a material to resist heat transfer. The number is actually the number of BTUs per square foot per hour per °F of temperature difference (or w/m2 per °C) across a barrier. The lower the U-value, the slower heat moves by conduction through the material.

Others in the insulation and construction industry use the measure of "R-Value," which denotes a material's ability to act as an insulator. The higher the R-Value, the slower the heat transfer rate; it is the reciprocal of the U-Value, expressed as R = 1/U. A window with a U-value of 0.25 has an R-value of 4.0 (1 divided by 0.25).

U-Value and R-Value measurements are similar—but reciprocal—in nature. They quantify the rate at which heat is transferred through a material due to temperature differences between its opposing surfaces. The window films industry uses two standards of measurement to determine U-values for glazing systems:

Winter U-value: With (a) the outside temperature set at -0.4°F (-18°C), (b) the inside temperature set at 69.8°F (21°C), (c) no sunlight illuminating the glass, and (d) the outside wind speed set at 12.3 mph (5.5 m/s). The "Winter U-value" can be measured in terms of the number of BTU’s per square foot per hour (w/m2) lost through the glass.

Summer U-value: With (a) the outside temperature set at 89.6°F (32°C), (b) the inside temperature set at 75.2°F (24°C), (c) sunlight illuminating the exterior of the glass at the intensity of 248.2 BTUs per square foot per hour (783 w/m2), and (d) the outside wind speed set at 6.2 mph (2.8 m/s), the "Summer U-value" can be measured in terms of the number of BTUs per square foot per hour (w/m2) gained through the glass by conduction and re-radiation.

Relevance to the consumer or specifier: U-values of glass are not much affected by most films, although newer classes of low-e films offer significant heat loss reduction in winter, and improved heat rejection in summer by reflecting re-radiated far-infrared energy.

Relevance to the customer: U-values of glass are not much affected by most films, but new low-e films (such as those in the EnerLogic Series) offer very significant heat loss reduction.

visible light transmittance (VLT)
The ratio of the amount of total visible solar energy (380-780 nanometers) that is allowed to pass through a glazing system to the amount of total visible solar energy falling on the glazing system. Value is usually expressed as a percent. Glare is influenced by visible light transmittance through a glazing system. Visible light accounts for about 44% of the sun's energy reaching Earth's surface. The VLT value is often weighted or measured in the area of the spectrum most easily sensed by the human eye, around 550nm. 
Relevance to the customer: The smaller this number, the greater the glare reduction. Of concern to many clients because while they want glare reduction, they often do not want a room "too dark."

visible light reflectance (VLR)
The percent of total visible light falling on a glazing system that is reflected by that system. Generally, VLR values are for exterior surfaces, those exposed to sunlight, unless otherwise specified. For dual-reflectance films, values are often given for each surface, the exterior(usually listed first in specification charts) and the interior (listed second).
Relevance to customer: A guide to how "shiny" a film looks from the exterior of a building relative to other films. Clear glass has a VLR of about 8%. And the lower the interior reflectance value, the less shiny the window will appear at night from the interior when it is very dark outside but brightly lit inside.

warm edge spacers
Insulating spacers used to seal panes of glass in the manufacture of insulated glass units. Edge conductivity is lessened for improved window energy performance and reduced condensation problems.

 a general term for a roll or expanse of film, or other thin extruded material.

weep slot
an opening cut into a window sill and/or sash rail to allow water to drain to the exterior.

wet-glaze anchoring system
structural sealant attachment system used to unify and reinforce the structural integrity of safety film, glass and a framing system combinations.

A wall opening in a building added for the purpose of letting in light and air, usually sealed from the elements in some way, using a frame and sash containing glass or another type of transparent material, and usually (but not always) able to be opened and shut. Windows containing glass began being heavily used in the late nineteenth century with advances in glass technology and frame construction. Windows gave building occupants options about views, ventilation, and exterior design.

Window 4.1
Window 4.1 (see is a fenestration analysis program that calculates the thermal and solar properties of glazing systems.  Window 4.1 was developed by the Windows & Daylighting Research group at Lawrence Berkeley National Laboratory for the U.S. Department of Energy.

Sometimes referred to as the "windscreen," the forward-most lite in a motor vehicle. Auto windshields in the US are made of safety glass, made up of two pieces of annealed glass with a thin layer of PVB (polyvinylbutyral) sandwiched between them. The three layers are laminated together by applying heat and pressure in a special oven called an autoclave. When a small object strikes a piece of safety glass, often only the first layer breaks. This is what makes windshield rock chip repair possible. In a more severe impact, the glass "shatters" but does not fly apart -- the broken pieces of glass adhere to the vinyl inner lining, preventing shards of glass from flying into the passenger area. Laminated safety glass makes object penetration from the outside very difficult and makes passenger ejection through the windshield very unlikely.

wire glass
1/4" clear or obscure glass having a layer of diamond or square pattern wire mesh embedded in the glass lite for increased safety. (From a thermal stress perspective, installation of solar control films [other than clear UV control or safety films] on sun-exposed wire  glass is not recommended since generally when this glass is cut to size it is impossible to obtain unflawed edges. Serious edge flaws increase the likelihood of heat-induced cracking.)
Winter U-value
See U-value.

water vapor transmission rate; the rate at which moisture moves through a porous or semi-porous (permeable) medium, such as a window film; term is used in comparing the differing rates at which window film will dry after a wet installation.

XP denotes the medical condition "Xeroderma Pigmentosum," a condition for which there is at present no cure. XP is the result of a genetic trait that causes people to be acutely sensitive to all forms of ultraviolet light, and in particular, sunlight. It has many far reaching associated health issues. For links related to this disease, click here:
Available from CPFilms Inc. in concentrate form, this liquid is used to both prepare the surface of glass and apply CDF adhesive-type films (with a few important exceptions). See the technical bulletin TBF-04 on the use of X-100 and the MSDS sheet. The solution should be diluted to one ounce (about 30ml) per quart (about 1 liter). It contains a surfactant and a mild concentration of phosphoric acid (used in Coca-Cola and other soft drinks) to far more effectively remove dirt and oily contaminants from glass, and also help activate the CDF adhesive during installation. Read label instructions and TBF-04 carefully before use. Similar in composition to Dirt-Off

NOTE: X-100 should not be used for the mounting of N-Series Bronze films or specific film products (such assilver-based low-e films such as VE/LE-35 and VE/LE-50, etc.) whose exclusions are clearly marked in their respective installation instructions.  Remember, too, that since X-100 is slightly acidic it can cause slight etching of marble surfaces and certain furniture finishes if allowed to soak for long periods of time. Always drape such surfaces (sills, furniture, floors) with absorbent drop-cloths or use Film-On or Johnson's Baby Shampoo if necessary instead of X-100 in such delicate circumstances where marbles surfaces, etc., may be at risk. For a complete list of LLumar film products that should NOT be installed with X-100, see Technical BulletinTB-38.

Young's Modulus
A term in physics named after Thomas Young, an 18th-century English physicist. Young's modulus, also known as the modulus of elasticity, is a constant in the mathematical equation representing the relationship between a force applied to, say, a rod or a strip of polyester film, and the degree of compression or stretch the rod or film undergoes (within the elastics limits of the material). If we know the tensile stress (applied force per unit of cross-sectional area) and divide this by how much a strip of film lengthens (under the same tensile force) relative to its original length [(Ln-Lo)/Lo, also known as "strain"], we have the Young Modulus. At low levels tensile stress, there is a linear or proportional relationship between stress and strain (known as Hooke's Law) and the slope of the straight line is the modulus of elasticity. 

Young's modulus = stress / strain  =  (F/A)   /    (Ln - Lo)/Lo

"Young's modulus is meaningful only in the elastic range in which the stress is proportional to the strain, and the material returns to its original dimensions when the external force is removed. As stresses increase, Young's modulus may no longer remain constant but decrease, or the material may either flow, undergoing permanent deformation, or finally break." (From Britannica)

Source materials for this dictionary include:

  1. British Fenestration Rating Council
  2. Encyclopedia Britannica
  3. Fenestration Glossary, compiled by A.M. Cohen
  4. Hawk Retrofit Inc. ( )