ROYAL CANADIAN MOUNTED POLICE TECHNICAL SECURITY BRANCH TECHNICAL OPERATIONS DIRECTORATE OTTAWA, ONTARIO K1A 0R2

SECURITY GUIDE TSB/SG-11 GLAZING JANUARY 1982 REVISED FEBRUARY 1988, APRIL 2000

Any suggested revisions and comments as well as requests for clarification regarding this Security Guide should be directed to the O i/c Technical Security Branch, attention: Physical Security Consulting Section, Royal Canadian Mounted Police, Ottawa, Ontario K1A 0R2. This is a third level reference document which becomes part of a series of reference documents listed in Chapter 2.1, Appendix B of the Physical Security Operational Standards (Security Volume of the Treasury Board Manual on Information and Administrative Management). This copy of the document originates from the Security Equipment Selection Instrument (SESI) which incorporates the other technical documents as well. Contact the Physical Security Consulting Section of the RCMP should you require a copy of any technical documents and you do not have access to SESI.

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TABLE OF CONTENTS PAGE 1.

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.

MANUFACTURING PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3.

OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.

APPEARANCE AND THERMAL PERFORMANCE . . . . . . . . . . . . . . . . . . . . . 2

5.

GLASS TYPES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Tempered Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Heat-Strengthened Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Laminated Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Wired Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Ceramic Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Transparent Mirrored Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Glass Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 Plastic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 Glass Clad Plastic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10 Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 2 3 3 3 4 4 4 4 5 5

6.

SECURITY GLAZING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Resistance to Burglary and Forced Entry . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Bullet-Resistant Glazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Bomb Blast Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Glazing Designed to Deter Electronic Eavesdropping . . . . . . . . . . . . . . 6.5 One-Way Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 6 7 7 8 8

7.

GLAZING FOR PROTECTION AND DETECTION AT PERIMETER . . . . . . . . 9 7.1 Bars and Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.2 Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

8.

CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

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1.

INTRODUCTION Glass is perhaps the most important material used when creating a pleasant indoor environment. Areas without glass can feel claustrophobic while glazed areas can feel expansive. Glass has the unique feature of offering a physical barrier while still allowing light to pass through it. From a security point of view, however, glass provides significant design challenges. In addition to allowing light in, glass can also expose the interior to viewing from outside. Glazed areas are often the point of unwanted entry. Broken glass can be a safety as well as a security concern. To address these and other challenges, it is essential that security consultants understand the characteristics of different types of glass and glass substitutes.

2.

MANUFACTURING PROCESS Glass is composed of three substances - sand, soda and lime - that are heated together to form a clear liquid. When this liquid is cooled under controlled conditions, glass is formed in a process known as “annealing”.

3.

OVERVIEW A variety of methods have been used to shape glass into a flat form. These methods have given names to some of the different types of glass, including sheet glass, plate glass and float glass. Float glass is currently the most common method of manufacturing. However, all three types are cooled under similar conditions, and are referred to as one type of glass, namely, annealed glass. Annealed glass is the most common and inexpensive form of glass. It is also the most vulnerable to attack as it is very easily broken. Annealed glass can be broken in large pieces having sharp edges, and can pose a safety hazard. A number of other glazing types, collectively referred to as safety glass, can be used to address these safety risks. Safety glass is required by building codes for doors and windows which would pose a risk to the public upon breakage. Tempered, wired and laminated glass are examples of safety glass. Insulating between warm and cold environments is the focus of a number of glass configurations and treatments. These include: insulating glass (two or more panes of glass separated by an air space), various coatings (reflective,

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low e) and glass with argon gas in the air space. Plastic is often considered as an alternative to glass. Plexiglass and Lexan are examples of plastic manufacturers’trade names. Plastic has properties that differ significantly from glass. 4.

APPEARANCE AND THERMAL PERFORMANCE Manufacturers have developed several methods for controlling the movement of heat through glass. Insulated glass (also called double pane, triple pane or thermal pane) is typically used on exterior walls in Canada. It was developed initially to prevent frosting of windows in colder climates. A typical pane of insulated glass for commercial applications consists of 6 mm glass, 13 mm air space and 6 mm glass. The air space is usually filled with ordinary dry air, however, for increased thermal performance it may be filled with argon gas. Other treatments that improve thermal performance include tinting and reflectivity, which can significantly alter the appearance of the glass as well as reduce solar heat gain. The properties of a glazing system should be understood when substituting security glazing for regular glazing. For example, a standard section of tinted, insulated glass might be replaced by a bullet-resistant 25 mm solid laminated piece of glass. The laminated glass would have significantly poorer thermal qualities (possibly frosting on the inside in winter) and might have a different appearance.

5.

GLASS TYPES

5.1

Tempered Glass Tempered glass is produced by heating a piece of annealed glass until it reaches its softening point, and then chilling it rapidly. This changes the stresses in the glass, leaving the surface in compression while the centre remains in tension. The result is that tempered glass is much more difficult to break, having approximately three to five times the strength of annealed glass. When broken, the entire sheet of tempered glass disintegrates into small cube-like pieces which are less harmful than the dagger-like shards that annealed glass

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produces.

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5.2

Heat-Strengthened Glass Approximately twice as strong as annealed glass, heat-strengthened glass is created by a process similar to tempered glass, except the cooling process is not as rapid. Although not categorized as safety glass, heat-strengthened glass provides increased impact resistance where the added strength is required because of high thermal and wind loads. Heat-strengthened glass is not at risk of spontaneous breakage (a risk inherent in tempered glass). If heatstrengthened glass should break, the pieces will be larger and less likely to fall out of a window frame.

5.3

Laminated Glass Laminated glass is made by sandwiching a thin layer (often as thin as 0.015 of an inch) of plastic (polyvinyl butyral resin or similar bonding agent) between two or more layers of glass. The glass and plastic are bonded together using heat and pressure. The resistance of laminated glass is essentially similar to that of non-laminated glass. However, when the laminated glass is broken, the plastic sheet holds the broken pieces of glass in place. The glass used in manufacturing laminated glass may be either annealed or tempered, and may also be tinted or treated with other coatings. Laminated glass may be used in combination with other glass types in insulating units. A characteristic of laminated glass is that it cannot be cut from one side only.

5.4

Wired Glass Wired glass is annealed glass which contains a wire mesh embedded inside the glass. It is intended to be used to satisfy building code requirements for fire protection. The impact resistance and breakage pattern of wired glass is similar to annealed glass. The difference is that when the glass is broken, the embedded wire mesh helps to hold broken glass pieces together and keep them in the window frame. Wired glass is intended to remain in place during a fire even after it has been exposed to the heat of the fire and then subjected to a stream of water from a fire hose (thermal shock).

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Wired glass does offer some increased resistance to forced entry over annealed or tempered glass. When broken by force, however, the wire in wired glass has a limited ability of holding the glass together. Broken bits of glass and sharp edges could create a hazardous condition. 5.5

Ceramic Glass Ceramic glass is a relatively new product which has been introduced as an alternative to wired glass where fire protection is required. Its clear and wireless appearance may make it more desirable in some locations. The properties of ceramics include minimal thermal expansion and the ability to withstand extreme heat. These properties allow it to pass the fire and hose stream tests required for the appropriate fire rating. Similarly to annealed glass, ceramic glass forms large shards when broken. Its impact strength is lower than that of annealed glass, however, laminated versions of ceramic glass are available for areas requiring a safety rating.

5.6

Transparent Mirrored Glass Mirrored glass is produced by applying a special chrome alloy to the surface of glass. This glass, also known as one-way glass, will permit viewing in one direction only, under appropriate lighting conditions.

5.7

Glass Blocks Glass blocks are available in a variety of shapes and sizes and can be either solid or hollow. Light passing through a glass block is scattered, reducing the ability to recognize images though it, depending on the style of block chosen. Hollow blocks, the most common type, have greater insulating value for heat and sound. Solid glass blocks offer greater resistance to ballistics and forced entry. Most glass blocks carry a higher fire rating than annealed glass and can be used in fire separations over a larger area.

5.8

Plastic Plastic glazing material is manufactured using either acrylics or polycarbonate. Both materials have a number of advantages and disadvantages. The clarity of vision is superior with acrylic than polycarbonate. Acrylic’s impact strength is

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approximately 17 times greater than glass, while polycarbonate is about 300 times stronger than glass. Both acrylic and polycarbonate are about 50% lighter than glass of equal thickness. Although both materials have excellent impact strength qualities, they share several disadvantages. Both materials will scratch easily and will deform under heat. Although mar-resistant coatings are available, the glazing will still mar easily if scratched with a penknife or stone. Both can be cut in lesser thicknesses and drilled with comparative ease. Acrylic burns vigorously, while polycarbonate burns to a lesser degree. The use of plastic glazing is still possible In buildings requiring construction materials to be noncombustible, but its location and quantity are restricted. The restrictions vary depending on the flame spread rating of the material, which must be tested in accordance with CAN/ULC-S102M, “Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies”. Articles 3.1.5.4(2) and (3) of the National Building Code allow the use of combustible vertical glazing having a flame spread rating of 75 within the first two stories in a building required to be of noncombustible construction. Combustible glazing with a flame spread rating of 150 is allowed in limited locations. 5.9

Glass Clad Plastic Glass clad plastic is intended to offer some of the properties of both glass and plastic. This type is manufactured using multiple pieces of glass, plastic (usually polycarbonate) and interlayers of urethane that are bonded together under heat and pressure. The glass surface offers protection against marking and flammability, while the plastic provides impact strength. When impacted, the glass surfaces will break into a “spider web”pattern while the plastic core remains intact. The material has the potential of delaminating, thus affecting visibility through the glass.

5.10

Film Window film can serve a variety of applications. Some film is designed to reduce

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solar gain (or heat loss), while other film is intended for safety and security uses. The film makes the glass more shatter-resistant by holding the glass pieces together upon breakage. They are usually thicker than solar film, and have a more aggressive adhesive. A window with security film will perform similarly to laminated glass, with some inherent advantages and disadvantages. One advantage to film is that it can be used as a remedial solution on existing windows. In these cases, the film is applied in the field, extending over the daylight portion of the glass to the edge of the frame. With some manufacturers, the film may adhere to the frame to provide additional strength. The film is exposed to the interior, meaning they are also subjected to wearing and scratching. Although it is promoted as having a scratch-resistant surface, film can be easily scratched if a deliberate attempt is made. Many permanent type markers will mark the surface indelibly. Cleaning the windows on the film side requires reasonable care. Film has a maximum available width, which may result in a visible seam in large windows. The seam will reduce the security performance of the window. 6.

SECURITY GLAZING Security glazing refers to a variety of products designed to enhance security against specific threats. The materials used in security glazing may be any of the above-mentioned materials or a combination thereof. The material is then tested for its resistance to specific threats, including: a. burglary and forced entry, b. bomb blasts, c. ballistic attacks, and d. electronic eavesdropping.

6.1

Resistance to Burglary and Forced Entry Burglary and forced entry threats can involve the use of a variety of objects and tools - singly or in combination, e.g., rocks, drills, hammers and torches. The expectation is that the material will not prevent access indefinitely, but will resist

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penetration for some period of time, allowing other security measures to take effect. The ability of glass to withstand burglary and forced entry threats can be measured by standard testing procedures, including UL 972 (12) and ASTM F 1233 (11). UL 972 is intended to address smash and grab threats. In order to be listed, the glass must withstand multiple impacts from an 83 mm steel ball. Standard two-ply laminated glass and annealed glass with security film can pass this test. ASTM 1233 (11) is intended to address a greater variety of threats, including the use of blunt objects, sharp objects, thermal stresses and chemicals. The glazing must resist various sequences of these threats in order to pass classes of threats, from a Class I sequence (ten blows with a ball peen hammer) to a Class V Sequence (41 varying attacks, including using a sledge hammer, propane torch and chemicals). As one would expect, an increase in the thickness of a material increases its resistance to forced entry. Glass has a better resistance to chemical attack over most plastic. Plastic, however, offer a better impact resistance for a given thickness. Glass clad polycarbonate appears to take advantage of the properties of each material in resisting forced entry. 6.2

Bomb Blast Resistance Glazing, often the most vulnerable material in the vicinity of a bomb blast, must withstand two types of attacks in order to offer protection. The first type is the shock or blast wave which travels from the explosive charge in all directions as it detonates. The second assault is caused by objects propelled by the explosive. Ordinary glazing can contribute to the destructive potential of a blast. This is because the destructive power of a bomb blast is increased when it propels fragments such as glass. Glazing intended to offer increased safety in a blast situation should, therefore, be designed to be retained in the frame of the window. This suggests that the design of the window frame is significant in

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determining the effectiveness of the protection offered. Testing of glass resistance to bomb blasts is, therefore, best performed using the actual frame to be used with the glazing. The ASTM test protocol “Standard Test Method for Glazing and Glazing Systems Subject to Airblast Loadings”ASTM F 1642 (21) addresses this issue. 6.3

Bullet-Resistant Glazing Bullet-resistant glazing can be used to help protect people from both direct bullet injury and flying glass fragments. Glazing intended to provide such resistance can be tested and rated in accordance with UL 752. A summary of these ratings follows:

Rating Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 Level 7 Level 8 Suppl. shotgun

Ammunition 9 mm .357 Magnum .44 Magnum .30 caliber rifle (.30-06) 7.62 mm rifle (.308) 9mm 5.56 mm rifle (.223) 7.62 mm rifle (.308) 12-gauge lead slug 12-gauge lead buckshot

Weight

Velocity

No. of

(grain)

(m/s)

shots

124 158 240 180 150 124 55 150 437 650

358 381 411 774 838 427 939 838 483 366

3 3 3 1 1 5 5 5 3 3

Levels 1, 2 and 3 can be achieved with one- to two-inch thick laminated glass or polycarbonate. Higher levels of protection require greater thicknesses or more complex systems. In a ballistic attack, the system may be susceptible to spalling when glass is the layer of material closest to the secure side. Laminated glass will appear shattered when struck by a bullet even if it remains held together and resists penetration. Polycarbonate, however, will remain unaltered except for the area of penetration. It is noteworthy that glass having effective bullet resistance may not necessarily provide comparable protection against a significant force attack.

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Glazing Designed to Deter Electronic Eavesdropping The loss or theft of information is often more significant than the loss of physical property. Advances in technology have brought about new methods of electronic eavesdropping. Theft can be achieved through the monitoring of electromagnetic radiation produced by computers. Damage to information can occur through engines powering construction equipment and by solar flare activity. Electronic security glazing is intended to reduce the transmission of electromagnetic radiation through glass. The manufacturing process involves placing a layer of metallized fabric mesh within a piece of laminated glass. The mesh is similar to a window screen except that it is very fine, typically with 100 to 400 openings per inch. The mesh is practically invisible, adding only a slight but uniform hue to lighting. This glazing can be combined to other security features provided by laminated glass.

7.

GLAZING FOR PROTECTION AND DETECTION AT PERIMETER

7.1

Bars and Screens Bars and screens on windows have been used for centuries to deter unwanted entry or exit at the perimeter of buildings. The protection offered varies with the strength of the material used as well as the fastening method. Bars and screens are highly visible, and can give a building a more institutional appearance. They also interfere with the view. Screens are designed to address the unattractive appearance of bars and wire mesh. They are made of perforated metal, similar to insect screening except that the perforations are significantly larger. The screens can be mounted on the interior or exterior, and are operable from the interior to allow for emergency egress. They are recommended when the probability of vandalism is low and appearance is a factor.

7.2

Alarms As previously mentioned, the protective measures discussed in this guide will not prevent access indefinitely. The aim is to resist penetration for a sufficient

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amount of time to allow other security measures to take effect. Alarms can reduce response time by quickly detecting and annunciating an intrusion. In certain situations, alarms may provide a more cost-effective method of reducing response time. Some alarms are associated specifically with forced entry through glazing; these include window contacts; glass break detectors; foil on glass sensors and film in glass sensors. Motion detectors with coverage adjacent to windows will also detect intrusions. The type and quality of alarms used should be considered in conjunction with other protective measures.

8.

CONCLUSION Selecting the most appropriate glazing system is a complex process that requires an understanding of the type and level of protection desired as well as the properties of the various materials available. This must then be balanced with both initial and life cycle costs. Unfortunately, no one material is the best choice for all circumstances. The selection criteria must evaluate each particular situation and purpose.

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