Arizona School Risk Retention Trust, Inc.

Transcription

1 Arizona School Risk Retention Trust, Inc. Technical Information Bulletin No. 19 To: Re: Members, Arizona School Risk Retention Trust, Inc. Replacement Glass in Educational Buildings FOR USE BY: Business Managers, Purchasing Agents, Facility Directors and Maintenance Personnel. This Technical Information Bulleting was prepared for the Trust by Mr. Jay Norton, CSI, Associate AIA. Mr. Norton is a graduate of Arizona State University with a Master of Architecture Degree. As an Intern Architect and Specifications coordinator with BPLW Architects and Engineers, Inc. in Mesa, Arizona, he is involved on a daily basis in specifying a large variety of materials and methods to meet building codes as well as job requirements. In much of his work, he coordinates the use of products to meet not only the current code, but also the social and human rights requirements of the Americans with Disabilities Act. 1

2 Purpose School Districts are continuously replacing broken glass in their buildings because of accidents, vandalism, etc. It is extremely important that each piece of broken door or window glass receive a correct replacement. This not only insures the continued integrity of the building according to Construction and Fire Codes, but also the safety of those who attend, use or work at the school. In the case of older buildings, the codes may have changed since their construction. In these instances, the new replacement glass should be of higher quality to meet current safety standards. The safety of students, visitors and employees at our schools is of utmost importance. This Bulletin is designed to provide a School District with the most current information available regarding glass replacement CAVEAT This Bulletin applies only to the replacement of glazing in existing structures without modification to the opening or existing structure. Any new construction, remodeling or additions to existing buildings shall be done only after an appropriate review and approval by local building safety officials and shall be subject to the issuance of a building permit. If there is any question as to the exact type of replacement glazing required, local building officials should be consulted. Building Codes The model building code used throughout the State of Arizona is the Uniform Building Code (UBC). Changes are published yearly as supplements and the entire UBC is updated every threes (1988, 1991, 1994, etc.). Each County and City or Town adds its own particular amendments to the UBC to meet its local needs and desires. Some municipalities such as the City of Phoenix extensively modify the UBC. These amendments also are periodically updated and traditionally lag behind the UBC update by anywhere from one to several years. It is important to remember that while codes are the law, they provide only the minimum requirements for fire, life and structural safety. A companion to the UBC is the Uniform Fire code (UFC which also affects the use of glass in buildings. Buildings The UBC has various requirements for buildings based on: The Occupancy Group this includes not only the use of the building but also the number of people within. The Type of Construction the materials that form the basic structure are especially important in respect to its fire resistance and protection requirements. 2

3 Buildings are often comprised of various occupancy groups and types of construction. Sometimes various portions of a building are classified differently and other times the dominant occupancy group or construction type prevails. The final determination rests with the local building official. The occupancy group and construction types should be listed on the original construction drawings (usually called the As Builts or Record Drawings ). If the primary function of the building or area has not changed or the building or area has not been modified, this classification will not change. School buildings will fall into any of the five different construction types (Type I, II, III, IV or V and their various sub-types). The occupancy of school buildings normally falls under one of the following groups: Group A, division 1, 2, 2.1 or 3. Group E, division 1, 2 or 3. Depending on area use, other occupancy groups may also be used. If there is a question, consult your local building official. Separations between various occupancy groups and construction types are very important concerning the use of glazing materials, whether it be between buildings or within a given building. Due to the extend and intricacy of the glazing requirements of each Occupancy Group and Construction Type and the varying ages of buildings throughout our school districts, it is impossible to list all of the individual glazing requirements in this Bulletin. Presented below are general guidelines to assist schools in identifying existing glazing and required replacements. Upgrades shall be as determined by school officials or required by local building codes. Glazing Types of glass Definitions (ref UBC Standard 54-1). Float Glass is glass formed in a continuous ribbon by floating molten glass on a bath of molten tin in a controlled atmosphere; the glass is smooth with parallel surfaces and requires no further treatment. Virtually all glass is made by the float process Fully Tempered Glass is regular glass that has been heated and quenched in a controlled operation to provide a high level of surface compression; its strength is roughly four times that of regular glass for most types of loads; when fractured, it breaks into small relatively harmless particles; it is a safety glazing material. Heat-Strengthened Glass is regular glass that h been heated and quenched in a controlled operation to provide a degree of surface compression; its strength is roughly two time that of regular glass; when fracture, this glass breaks into large fragments, much like regular glass; it is not a safety glazing material. Insulating Glass is factory-fabricated double-glazing with the periphery of the air space sealed to minimize infiltration of water vapor. The panels comprising an insulated glass 3

4 ensemble can be composed of a variety of glass types. They may be tempered, laminated, wired, etc. or combinations thereof. Laminated Glass is a sandwich of two or more glass plies bonded together with a resilient plastic interlayer, normally polyvinyl butyral; when this glass breaks, the fragments are held together by the plastic interlayer; it is a safety glazing material. Patterned Glass is a rolled glass with a pattern or texture impressed on one or both surfaces; some glasses with shallow patterns can be tempered or heat strengthened. Regular (Annealed) Glass is sheet (window) glass and plate glass with smooth surfaces that have not been modified after manufacture; it breaks into large pieces; although the terms sheet and plate glass are commonly used, they are misnomers since virtually all galls is made by the float process; this glass may be clear or tinted. Safety Glass is glass designed to minimize cutting and piercing injuries when impacted by people; fully tempered glass, laminated glass and wired glass are recognized safety glazing materials. Tempered Glass see Fully Tempered Glass Wired Glass is a single sheet of glass which has had a wire mesh embedded in roughly the thickness center during production; this glass, coupled with a suitable framing system, is fire rated; for low levels of impact, the wire in the glass will retain the broken fragments; it is a safety glazing material. There are also other highly specialized types of glass, normally found in unique situations and may not be prevalent in educational buildings. Although not specifically required, it is highly recommended that all replacement glazing in educational buildings should be safety glass. Regular Glass may be used where authorized but is only recommended in high locations where breakage possibilities are minimal or where, if broken, there is a minimal chance of the broken glass falling on someone. The three safety glasses are: Fully Tempered Glass: This glass should be the minimum acceptable glass used as replacement. It is much harder to break than regular (annealed) glass typically found in windows and its main safety feature is that it breaks into small particles. This becomes most important when glass shards fall from a broken window or a person falls into the glass and it shatters. Laminated Glass: This glass is best used as a replacement in areas where glass is subjected to repeated vandalism or the security of the room is of paramount interest. There are many levels of laminated glass. Certain laminated glasses are even considered bullet resistant and are used by bank drive-in locations and at ticket counters where robberies can occur. This glass is quite expensive compared to tempered or wire glass, but its safety qualifications are unparalleled. 4

5 Wire Glass: Though physically weaker than both tempered and laminated glass, wired glass is always used at fire rated locations where containment of a potential fire is required. When broken by impact or fire, the wire holds the glass together and prevents it from shattering. Wire glass will be found in frames rated at ¾ hr., 1 hr., and 1½ hr. The pattern of the wire (usually square or diamond) is purely aesthetic. The glass is always marred or matched to a rated door or window frame. This frame will carry an officially approved label that is affixed at the factory. Rated doors have a similar label on the door as well as the frame. The label on the door is usually found concealed on the top of the door. Always, repeat always; replace broken wired glass with wired glass of equal thickness, unless a clear fire-rated glass has been approved by local building safety officials. A fire-rated clear glass is on the market and it is very expensive compared with wire glass. Some building officials have been reluctant to allow its use, although the glass meets all the fire rated requirements. Other Glazing a) Sloped Glazing: In addition to traditional vertical glazing glass is found in various sloped installations, usually in skylights. If the skylight is glass, the UBC requires it to be either laminated, fully tempered or heatstrengthened glass. Laminated may be installed by itself, but tempered or heat-strengthened glass must have a screen installed within four inches of the glass that is capable of supporting the weight of the glass. The screen has other requirements (see UBC Chapter 34 and consult your local building safety official). b) Glass Block: If glass block must be replaced, there are now thick-walled units of different patterns available. These thick-walled units are naturally more impervious to breakage. c) Light Transmitting Plastics: some schools place clear or translucent plastic in areas where glass gets repeatedly broken. Though plastics (Lexan or similar brands) are harder to break than tempered glass, they scratch much easier than glass. Plastic cannot be used in doors or windows that require a fire-restive rating. Before using plastic as a substitute for glass, you must obtain local building safety approval. d) Fire Door Viewports: Certain fire doors have a small viewport in them. This viewport shall not be larger that 1-inch in diameter and required ¼ thick glass and a metal holder that will not melt out when subjected to temperatures of 1700 F. If such a viewport is broken, always replace with exactly the same rating glass. 5

6 Glazing Requirements All glazing must meet the testing standards of UBC Standard No for flat glass thickness, strength and imperfections. Safety glazing must also meet the testing standards of UBC Standard When replacing glass with safety glazing, make sure the unit is appropriately labeled. Wire glass is easy to identify and laminated/tempered glass will be etched designating the type and thickness of the glass. One very important requirement is to never use a replacement glass that is thinner than the glass being replaced. In replacing glass in older windows that have been broken, it is extremely difficult to determine how the UBC and UFC codes may have made the requirements more stringent since the original glass was installed. The following general guidelines are provided. Wired glass: Once again, wired glass is always required in fire-rated assemblies. An assembly includes the frame as well as the glass. Wired glass is most often seen in the interiors of buildings and can be found for one example between a classroom or office and a primary exit corridor. Seeing the wired glass is an indicator that the entire wall is a fire-rated assembly. Wire glass is found on the exterior of buildings when: a) Two adjacent buildings are in close proximity to each other. This varies depending upon size, Occupancy Group and Construction Type. b) The building is in close proximity to the property line (either the actual property line or an imaginary property line that is assigned by Fire Code precisely for fire separation purposes). Once again, this depends on the size, Occupancy Group and Construction Type of the building. c) Wire Glass in Doors Fire rated wood, plastic faced composite or hollow metal doors can have a glass area no greater than 1,296 square inches and attain 20 minute or ¾ hr. rating. Doors rated 1 hr. or 1½ hr. can only have a maximum area of 100 square inches and a minimum dimension of 4 inches in any direction. Minimum glass thickness is ¼. d) Wired Glass in Windows Fire rated windows (¾ hr. can have a maximum area not greater than 84 square feet and neither width can be longer than twelve feet. Safety Glazing: Safety glazing is mandatory in hazardous locations. The 1991 UBC considers any glazing in the following locations hazardous: a) Ingress and egress doors except jalousies. (Ref Drawing 1 Exhibit A) 6

7 b) Fixed and sliding panels of sliding doors assemblies and panels in swinging doors other than wardrobe doors. c) Storm doors. d) All unframed swinging doors. e) Doors for hot tubs, whirlpools, saunas, steam rooms, bath rubs and showers. This includes glazing in any portion of a building wall enclosing these compartments where the bottom exposed edge of the glazing is less than 60 inches above a standing surface and drain inlet. f) In fixed or operable panels adjacent to a door where the nearest exposed edge of the glazing is within 24 inches of the vertical edges of the door when it is closed and where the bottom exposed edge of the glazing is less than 60 inches above the walk surface. (Ref Drawing 2 Exhibit A) NOTE: This is a location most often found in office or classroom situations. Windows (often called lites ) are usually on one or both sides of an interior door. Newer lites beside doors or other openings will have an intermediate bar at approximately 3 feet AFF as extra protection but older buildings may not have windows with this extra protection. g) In a fixed or operable panel other than those locations described in Item (e) and (f) above, that meets all of the flowing conditions (Ref Drawing 3 Exhibit A) - Exposed area of an individual pane greater than 9 square feet. - Exposed bottom edge less than 18 inches above the floor. - Exposed top edge greater than 36 inches above the floor. - One or more walking surfaces within 36 inches horizontally of the plane of the glazing. h) In railings regardless of height above a walking surface. Included are structural baluster panels and nonstructural in-fill panels (Ref Drawing 4 Exhibit A). The Code lists exceptions to the above-listed locations (a. through h.). They are as follows: a. Item f When there is an intervening wall or other permanent barrier between the door and the glazing (Ref Drawing 5 Exhibit A). b. Item g When a protective bar is installed on the accessible sides of the glazing 34 to 38 inches above the floor. The bar shall be capable of withstanding a horizontal load of 50 pounds per linear foot without contacting the glass and be a minimum of 1½ inches in height (Ref Drawing 6 Exhibit A). c. Item g The outboard pane in insulating glass units and in other multiple glazed panels when the bottom exposed edge of the glass is 25 feet or more above any grade, roof, walking surface or other horizontal or sloped (within 45 degrees of horizontal) surface adjacent to the glass exterior (Ref Drawing 7 Exhibit A). 7

8 d. Openings in a door through which a 3-inch diameter sphere will not pass. e. Assemblies of leaded, faceted or carved glass in Items a, b, f and g when used for decorative purposes. f. Curved panels in revolving door assemblies. g. Doors in commercial refrigerated cabinets. h. Glass block panels in exterior walls that have less than144 square feet of unsupported wall surface or 15 feet of length in any dimension. Glass block panels in interior walls that have less than 250 square feet of unsupported area of 25 feet of length in any dimension. As has previously been noted, the older a building is, the harder it will be to determine if certain glass should be replaced with an upgraded type of glass. The most difficult of all will be the question, Does this window or door require wire glass as a replacement? Remember that even if it is determined that a new pane should be wired glass, the frame and the surrounding wall will most likely not be of the required rating. The issue to consider here is the dividing line between maintenance and renovation. If a single pane of glass is broken and requires replacement, then this is maintenance. To lessen the chances of a pane being broken again, or if broken, injuring a person, the obvious choice is, replace the pane with fully tempered glass. If, however, an entire ensemble of a window and frame or frames are being replaced, then renovation becomes an issue and local building officials should be asked as to: Is this planned action considered renovation (or remodeling, etc.)? Is wire glass and a rated ensemble required? Once the ruling has been made, the appropriate action can be taken. To assist personnel in properly ordering glass and to insure the appropriate glass has been received/installed, Purchase Order information is provided (Exhibit B). The bottom line of any glass replacement should be the age-old adage It is better to be safe than sorry. The few extra dollars required to purchase a stronger, safer glass will most likely prove to be a very worthwhile investment. 2 Attachments: Exhibit A Exhibit B 8

9 Exhibit A 9

10 Exhibit B Glass Ordering information for Purchase Orders (Most Commonly Required Types) FLAT GLASS (Float Glass) SAFETY GLAZING (Tempered Glass, Laminated Glass, or Wire Glass) Shall meet the applicable provisions of ASTM C , Canadian Specifications CAN M76, and Uniform Building code Standard 54. Shall be suitable for use as a safety glass as defined by Consumer Products Safety Commission 16 CFR 1201, ANSI Standard Z97.1, 1984, and Canadian Standard CAN/CGSM-12.1-M90. Shall meet the requirements of: ASTM C ASTM C ANSI Standard Z97.1, 1984 UBC Standard 54-2 and those of the Safety Glazing Certification Council (SGCC) as well as Canadian Specification CAN/CGSB-12.1-M90. Shall bear the manufacturer s label designating the type and thickness of glass. (Some building officials will allow the label to be omitted if an affidavit is furnished by glazing contractor certifying that each light is glazed in accordance with approved plans and specifications. Check with local officials).. All safety glazing installed in a hazardous location shall be identified by a label which will specify the labeler, whether the manufacturer or installer, and state that safety glazing material has been utilized in such installation Each unit of tempered glass shall be permanently identified by the manufacturer. The identification shall be etched or ceramic fired on the glass and be visible when the unit is glazed. When ordering glass, thickness required and color (if any) should also be included. Insulated glazing traditionally comes as a unit, two panes. A wide variety of films and gas are available to fill the void between the panes. To match existing it is suggested the original manufacturer or installer be contacted (if known). 10