Introduction to Security Window Film
Like this article?
Visit our Security Tips page for more than 75 additional articles on a variety of topics related to physical security
Follow us on Twitter to be notified when new Security Tips are published
Security window film is used to enhance the security of regular window glass. When properly applied, security window can provide the following benefits:
Security window film can increase the strength of the window, which can delay or prevent entry by a burglar.
Security window film can reduce injuries caused by flying glass when the window is shattered. This could occur because of an accident, an act of vandalism, a bomb blast, or a natural disaster.
Certain types of security window film can provide benefits not directly related to security. These can include tinting of the window, reduction of the heat passing through the glass, and the reduction of damages caused by the sun's ultraviolet rays.
Types of Security Window Film
Security window film consists of one or more layers of polyester film, laminated together with special adhesives. Security window film typically ranges in thickness from 4 mils (100 micron) to 14 mils (350 micron) or more. Thicker films are usually constructed by laminating multiple layers of thinner film together. Different types of films and adhesives are used depending on the characteristics desired in the finished product. Security window film is packaged in rolls of varying widths, the most common being 36", 48", 60", and 72". The length of film on a roll usually varies between 50 and 100 feet.
In general, the thicker the film is, the stronger it is. As the thickness of the film increases, the degree of break strength, tear strength, and puncture strength also increases. Thicker film usually costs more due to the greater amount of materials needed and the additional manufacturing time required.
For most security applications, 8 mil to 14 mil thickness film is commonly used. Thinner films are often used in lower threat environments or when the primary reason for installing the film is for tinting or solar protection. Thicker films are often used in higher threat environments where additional security protection is needed.
Installation of Security Window Film
Security window film is most commonly installed on a retrofit basis on the inside of existing windows. The installation is done at the job site, and involves the cutting and applying of the film to the surface of the glass of each window. The film is attached using a special adhesive and must be carefully installed to eliminate creases and air bubbles. Correctly installing security window film requires a high degree of skill and is generally done by professional installers.
The most widely used method of installing window film on existing windows is known as the "daylight" method, where the film is applied leaving a slight gap between the edge of the film and the edge of the window frame. The daylight installation method provides a reasonable degree of protection against forced entry and flying glass and is considered adequate for most facilities.
However, many security experts feel that the daylight method does not provide an adequate amount of protection against the forces generated by a bomb blast or an attack by a particularly aggressive intruder.
When an increased degree of protection is required, a different type of installation method, known as the "anchored" method, should be used instead of the daylight method. There are two types of anchored installation methods, the "mechanical" method, and the "wet" method. The mechanical method involves the physical attachment of the window film to the window frame. Using this method, the window film is applied to the glass, but instead of being cut near the edge of the glass, it is overlapped over the window frame, and mechanically attached to the frame itself. The film can be attached to the frame using metal batten strips, or by using one of several devices designed specifically for the purpose. Depending on the degree of strength desired, the film can be attached on one, two, or all four sides of the window pane.
The wet method involves the attachment of the window film to the window frame with an adhesive sealant. Using this method, the window film is applied to the glass using the daylight method, but a little less gap is left between the film and the edge of the frame. A bead of special adhesive sealant is then applied around all four edges of the film, creating a tight bond between the film and the window frame. The use of adhesive sealant can have a negative impact on the appearance of the window, particularly if poorly installed. To solve this problem, there are products manufactured that can be installed along the edge of the glass to conceal the sealant and create a finished appearance.
Tempered glass windows shatter into tiny cubes when broken, making the use of the daylight installation method ineffective on these windows. Either a mechanical or wet anchored installation method should be used on tempered glass windows.
Anti-Graffiti Window Film
There is a special type of window film designed specifically to prevent damage caused by graffiti. This film is installed on the exterior of the glass (unlike security film, which is installed on the inside) and is designed to absorb damage caused by painting, etching, and other types of "tagging". This film is sometimes called "sacrificial film", because it is intended to be removed and replaced after a tagging attack. The cost of replacing film is much less than the cost of replacing the glass, making it economical for use in locations where graffiti on windows is an ongoing problem.
It is important to note that anti-graffiti film does not provide any significant protection against intrusion or bomb blast, so there may be cases where both types of film may be needed on the same window (anti-graffiti film on the outside, security film on the inside.)
Suggestions for Using Security Window Film
The decision to use or not use security window film should only be made after a comprehensive security assessment has been conducted. The security assessment should provide guidance as to where security window film should be used, and establish the type of security film and attachment methods to be used based upon the level of risk at the specific facility.
The use of security window film to mitigate the effects of bomb blast is a complicated matter. If your primary reason for installing window film is to reduce injuries caused by bomb blast, a detailed blast analysis should first be conducted by a qualified bomb blast consultant. This consultant can help to specify the type of window film that should be used and the recommended attachment method. This consultant may also specify supplementary "catchment" systems that catch the glass when it is blown out of the frame, greatly increasing the degree of blast protection.
Choose a reputable local installation contractor to install your security window film. Obtain and check references, and ask to visit other facilities in the local area where the same type of product as you are considering has already been installed. If possible, visit installations that are at least several years old so you can see how the film looks after it has aged.
Any type of anchored security window film installation is only as strong as the window frame itself. In some cases, reinforcement or replacement of the window frames may be required in order to provide the desired level of protection.
In some cases, windows may already have tinted or solar window films installed upon them. These films typically do not provide any significant protection against intrusion or bomb blast and may need to be removed from the windows prior to the installation of security window film.
Security window film is not bullet-resistant. If your facility requires protection against bullets, consider the use of bullet-resistant glass and other materials.
Many intrusion alarm (burglar alarm) systems make use of glass breakage sensors to detect when a window has been broken. These can include sensors that mount on the glass itself, as well as acoustical sensors that are mounted to the walls or ceilings and listen for the sounds of breaking glass. The use of security window film may reduce the effectiveness of these sensors - be sure to notify your alarm company prior to installing window film and test all sensors for proper operation after the film has been installed.