GLASS AND GLAZING AAMA CURTAIN WALL SERIES

STRUCTURAL PERTIES

TABLE OF CONTENTS

I. GLASS MANUFACTURING PROCESSES........................................................................................... 1 II. GLASS PRODUCTS............................................................................................................................. 1 III. GLAZING SECTION ............................................................................................................................ 3 IV. GLASS FRAMING CONSIDERATIONS ............................................................................................. 6 V. GUIDELINES for the GLAZING CONTRACTOR ................................................................................. 6 VI. SPECIAL GLASS WALL SYSTEMS ................................................................................................... 7 VII. GLASS and WIND LOADS................................................................................................................. 7 VIII. GLASS and HEAT TRANSFER......................................................................................................... 7 IX. GLASS and ACOUSTICS.................................................................................................................... 8 X. SAFETY GLAZING REQUIREMENTS................................................................................................. 9 XI. GLASS STANDARDS ......................................................................................................................... 9 XII. REFERENCE DOUCMENTS ............................................................................................................. 9 XIII. REFERENCE SOURCES................................................................................................................ 10 XIV. GLOSSARY..................................................................................................................................... 10

This publication was developed by representative members of AAMA as advisory information and published as a public service. AAMA disclaims all liability for the use, application or adaptation of materials published herein.

Copyright 1997 © American Architectural Manufactueres Association

1827 Walden Office Square, Schaumburg, IL 60173 Phone: 847/303-5664 . . . Fax: 847/303-5774

EMAIL: WEBMASTER@AAMANET.ORG

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This section is a guide to the use of glass in architectural applications and presents information regarding glass types and availability as well as the structural, acoustical and thermal performance of glass. This guide is intended to better acquaint those in the construction industry with glass manufacturing processes, glass types and strengths, wind load resistance, breakage behavior, and other mechanical and structural issues. I. GLASS MANUFACTURING PROCESSES Architectural flat glass may be produced via three different processes: Float, plate, and sheet. A. Float Glass — In this process, molten glass flows continuously from a furnace onto a large bed of molten tin (the bath). The molten glass floats on the tin, spreading in a controlled manner to a width from 90" to 160" (2286 mm to 4064 mm), depending on the size and glass thickness being produced. The glass is cooled sufficiently at the end of the bath so that it can be raised onto rollers without marring the surface or producing waves (distortion) in the glass. As it leaves the bath, the ribbon of glass is carried on rollers through an annealing lehr which provides controlled cooling. After several hundred feet of travel through the lehr, it emerges as a continuous ribbon of annealed glass which is fabricated (scored and snapped) to size and packaged for shipment. Float glass accounts for virtually all of architectural flat glass produced in the United States. B. Plate Glass — Plate glass manufacturing consists of grinding and polishing rough glass plates continuously formed by drawing semi-molten glass through textured, water-cooled, metal rollers. This is commonly referred to as polished plate glass. The plate glass manufacturing process is obsolete in the United States and has been replaced by the float glass process. C. Sheet Glass — Sheet glass is produced by continuously drawing molten glass from a tank through an annealing lehr. It may be drawn either vertically or horizontally over rollers. The sheet glass process was used prior to the float glass process and is virtually non-existent in the United States. II. GLASS PRODUCTS A wide variety of architectural glass products are available in the marketplace. Those products presented in this guide include annealed, heat-strengthened, tempered, insulating glass units, spandrel glass, laminated, coated, heat absorbing, safety, acoustical, fire rated, and patterned. In addition to these products, a number of specialty glass products are available to meet particular applications. Questions regarding specific products should be directed to the glass manufacturer. A. Annealed Glass — Float glass as received from a manufacturing process is annealed and can be fabricated to size. Annealed glass includes glasses which are tinted or pyrolytically coated before final annealing. Specifications for annealed glass are covered by ASTM C 1036, "Standard Specification for Flat Glass." B. Heat Treated Glass — When annealed glasses are heated to just below the softening point and then rapidly cooled by blowing air simultaneously on both surfaces, the cooling process locks the outer surfaces of the glass in a state of high compression and the central portion, or core, in tension. Varying the rate and amount of cooling will produce heat-strengthened or tempered glass. The rate of cooling is faster when producing tempered glass versus heat-strengthened glass.

Specifications for Heat treated glass are covered by ASTM C 1048, "Standard Specification for Heat Treated Flat Glass." Glass can not be fabricated to size after heat treating. 1. Heat-Strengthened Glass — The strength developed is at least twice that of annealed glass. Heat-strengthened glass does not meet the strength or breakage pattern criteria for safety glazing materials when glazed monolithically. Heat-strengthened glass breakage patterns are similar to those of annealed glass and is not susceptible to spontaneous breakage when thermally treated properly. It is often used in areas requiring increased strength due to thermal stress, wind load requirements, and/or glass retention in a frame. 2. Tempered Glass — The strength developed is at least four times stronger than annealed glass and thus more resistant to thermally induced stresses and cyclic wind loading. Tempered glass is susceptible to spontaneous breakage from small inclusions. If broken, fully tempered glass shatters into small particles that potentially cause less harm than shards of broken annealed glass. C. Insulating Glass Units — Insulating glass units consist of two or more lites of glass, any of which may be clear, tinted, coated, heat treated, and/or laminated, that enclose a sealed air space. It is industry practice to number the glass surfaces beginning with the outside surface as the first surface. The lites are separated by a spacer and sealed around the entire glass perimeter. The spacer should contain a moisture absorbent material called desiccant, which dries the air contained within the sealed airspace. Two (or more) different lites of glass also present four (or more) surfaces for coating applications. Coating location allows optimization of aesthetic and/or thermal performance characteristics for various geographic locations and exposure conditions. Other thermal performance enhancements may be gained by injection of various inert gasses, such as argon, into the space(s) between the lites of glass. Sealed insulating glass units are tested and rated according to ASTM E 773, "Test Method for Seal Durability of Sealed Insulating Glass Units," and E 774, "Specification for Sealed Insulating Glass Units." D. Spandrel Glass — Spandrel glass is utilized to cover the "between floors" and non-vision areas in buildings while aesthetically harmonizing with the vision area glass. It is normally coated with a ceramic frit, opacifier, or applied films with dark-colored solid backing permanently fused to one of the surfaces. Spandrel glass can be glazed monolithically or in insulating glass units, depending on desired aesthetics and thermal insulating properties required. Glass in spandrel areas is normally heat-strengthened to resist thermal stresses by high heat absorption of solar radiation due to the applied coatings. Heat-strengthened glass is normally preferred over tempered glass in spandrel applications. In the event of breakage, heat-strengthened glass is more likely to be retained in the opening since its breakage pattern is similar to annealed glass. Fiber reinforced tape or opacified films assist in retention of larger glass pieces if the spandrel glass breaks. Normal thickness of spandrel glass is 1/4" (6mm), other thicknesses may be available. Many aesthetic effects are available to match or harmonize with vision area glass including reflective coatings. Caution: When used in a dry glazed system, monolithic spandrel panel suppliers and sealant and/or gasket suppliers should all be consulted for material compatibilities.

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E. Laminated Glass — This type of glass (similar to automobile windshield glass) is made by sandwiching an interlayer of clear or tinted material, typically polyvinyl butyral (PVB), between two or more lites of annealed, reflective, heat-strengthened, or fully tempered glass. The interlayer ranges in thickness from 0.15" to .090" (4mm to 2mm) or more, dependent upon desired usage. When laminated glass fractures, the particles of glass tend to adhere to the interlayer and maintain the building envelope. Generally, laminated glass is considered to be approximately 75% to 90% as strong as annealed glass of the same overall thickness. Its strength is dependent on aspect ratio and temperature. The ASTM E 1300 task group is developing design standards for laminated glass strength. Specialty laminated glass products such as burglar and bullet resistant glass are also available. F. Heat-Absorbing Glass — Tinted glass, usually referred to as heat-absorbing, is formulated to absorb much more solar radiation than clear float glass. This glass significantly reduces heat gain, glare, and light transmittance according to color and thickness. Tinted glass is available in various colors (bronze, gray, green, blue, etc.) and in thicknesses ranging from 3/32" to 1/2" (2 mm to 12 mm). With emerging technology new products are being developed that can provide improved spectral and/or thermal performance. G. Coated Glass — Glass spectral performance, thermal performance and/or aesthetics can be improved or changed through the use of metal or metallic oxide coatings applied to the glass. There are two methods used to manufacture coated glass: Pyrolytic and Magnetic Sputtered Vacuum Deposition (MSVD). Pyrolytic coatings are applied on a float glass production line either by the chemical vapor deposition (CVD) process in the float bath or the chemical spray process near the hot end of the annealing lehr. The pyrolytic process forms a coating which fuses into the glass surface. Annealed glass with a pyrolytic coating can be heat treated and/or bent without affecting the coating, as long as the deposition temperature is not surpassed. Additionally, pyrolytic coated glasses may be provided with the coating on first or second surface when used monolithically, and on any surface when used in insulating glass units. This flexibility is a result of excellent coating durability. Magnetic Sputtered Vacuum Deposition (MSVD), or sputtering, deposits a metal or metallic oxide coating on the surface of glass in a vacuum chamber. The sputtering process is accomplished by ionizing gas molecules with an electrical charge. These ions strike a metallic target, removing atoms of metal which deposit onto the glass surface. Most MSVD coatings are not post temperable; i.e., the coated glass cannot be heat treated or bent, but the coating can be applied to a heat treated or bent substrate. Daylight (visible light) reflectance can range from 6% to 48%, and visible light transmittance ranges from 7% to 78%; reflectance and transmittance depends on coating and glass substrate types. Environmental performance characteristics require that MSVD coatings not be installed with the coating on the first surface. The pyrolytic process is often referred to as hard-coat, while MSVD is referred to as sputtering, or soft-coat. Hard coatings are more durable because the oxide coating is fused onto the glass surface as the glass is cooled in the annealing lehr. Reflective coatings control solar radiation by reflecting heat. Low- emissivity coatings reflect solar heat and ultraviolet rays, and reduce the amount of radiant energy that can escape a building or home.

1. Reflective Glass — These are clear or tinted glass substrates with an extremely thin layer of metal or metallic oxide. The coatings are thin by design; otherwise they could not transmit visible light. Reflective coatings reflect radiant solar energy. These coatings reduce heat gain but allow visible light transmission to the interior. The major benefits of reflective glass include: 1) aesthetic appeal (many colors are available; contact glass manufacturer for details) which provide the architect more flexibility in exterior design, 2) energy savings by reflecting and absorbing radiant solar heat (reflective glass reduces interior solar heat gain), and 3) occupant comfort is improved when heat gain/loss differentials between sunny and shaded elevations are substantially reduced. 2. Low-Emissivity Glass (Low-E) — A clear metallic oxide coating is deposited on the glass either through the pyrolytic process or the MSVD process. This transparent coating reflects long-wave infrared energy, reduces ultraviolet transmittance, reduces summer heat gain, winter heat loss and condensation. Typically, these coatings allow greater visible light transmittance than reflective coatings. H. Safety Glass — Safety glazing materials are designed to reduce the possibility of bodily injury from glass shards upon breakage. They meet the requirements of ANSI Z97.1, Glazing Materials Used in Buildings, Safety Performance Specifications and Test Methods," (current edition) and/or the Consumer Product Safety Commission's safety standard, CPSC 16 CFR 1201, Safety Standard for Architectural Glazing Material." Safety glasses are identified by a permanent identification mark at the factory. Two glass types are classified as safety glazing materials: Fully tempered glass and laminated glass. Some acrylic materials may also classify as safety glazing materials, but are not addressed in this publication. I. Acoustical Glass — The reduction of sound by any barrier is related to density, area, limpness and air-infiltration. As later explained under the heading 'Glass and Acoustics,' Section IX, various types of glass and air space combinations have excellent sound transmission reduction properties. J. Fire Rated Glass — Several glazing products now have fire ratings: Wire glass, special processed float glass, optical quality clear ceramic, distorted quality clear ceramic, and multi-lite clear tempered glass with a polymer gel between the two lites of glass. These products are tested and certified as components of a complete system including the framing members and gaskets/sealants. The use of fire rated glass does not in itself qualify the entire assembly or installation as fire rated. There are size limitations for given fire ratings, types of glass, and framing systems. Fire ratings vary from 20 minutes through 3 hours. Size limitations may apply from building code restrictions as well as maximum size. Consult local codes, National Fire Protection Association publications, and manufacturer's data to determine fire ratings and maximum width and height dimensions for specific types of glass. K. Patterned Glass — This glass has a textured or patterned surface, and is often referred to as obscure or decorative glass. The surface can be formed by the continuous pour process, the use of a metal roller with protruding patterns, or other surface altering processes available. Patterned glasses are normally available in nominal thicknesses ranging from 1/8" (3 mm) through 7/32" (5 mm), with other thickness available at the option of the manufacturer. The pattern diffuses detail of objects viewed through the glass. These glasses are normally used

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in applications where obscure, light transmitting panels are required, and are not normally used in exterior applications. The glass manufacturer should be consulted for recommendations regarding the use of glazing materials to determine availability and proper type to meet requirements as specified. The FGMA Glazing Manual is a good source of information on general glazing guidelines. SWEET's publications are a good reference for specific manufacturers' products. III. GLAZING SECTION Proper glazing is a compromise between idealized criteria for proper support of the glass and the practical considerations of economics, tolerances and the provision of a good weather seal. To minimize potential glass breakage, the glass surround should not impose any bending or high concentrated compressive loads on the glass. The glazing system chosen should thermally isolate the glass from other parts of the wall. Glass should essentially 'float' within the glazing cavity. Ideally, the glass surround should be designed to permit trouble-free installation, minimizing the likelihood of glass damage. Glazing systems fall into two broad categories: Conventional and Structural Sealant. Buildings can utilize entirely one or the other type of system, although buildings utilizing both are quite common. Both categories of glazing systems occur in a wide variety of designs. The key feature that discriminates between Structural and Conventional systems is the method by which the glass is physically retained to the wall. In Conventional systems, the glass is retained by mechanical engagement along the perimeter. In Structural systems, the perimeter engagement is eliminated on one or more edges of the glass and is replaced with a carefully designed bead of Structural Silicone Sealant that secures that edge of the glass to an interior framing member. A third, but very specialized category, Structural Gasket Glazing, uses specially designed rubber gaskets to secure the glass to the surround. These seldom used systems require close design cooperation between the surround and gasket designer. As previously mentioned , the design of a glazing system takes into account the performance requirements, tolerances and economics on any project. It is critically important to recognize at the outset, that water management within the window system (i.e., weeps, etc.,) and proper sealing of the required internal metal joinery are paramount to the success of any glazed condition. These topics will not be covered in this document but should receive utmost consideration on every project. A. Conventional Glazing Conventional Glazing Systems may be designed to glaze from either the exterior or the interior, or both. It is also not uncommon for spandrel areas to be initially inside-glazed, and yet have provisions for re-glazing from the exterior. Because conventional glazing requires provisions to mechanically retain the glass in both directions on all four sides, provisions must be made to have a removable section, called a "bead" or "stop," on one or more sides which then facilitates the glazing/re-glazing process. These glazing stops may be either mechanically attached to the framing system with bolts or screws, or they may utilize a "snap-in" or "hook-in" feature which is held in place because of its geometrical interface with the framing system. If only one of the four sides has a removable stop, two opposing fixed glazing pockets result, and the opening must be "flush-" or "pocket-"

glazed. Such a glazing technique requires at least one of those opposing fixed glazing pockets to be more than twice as deep as would otherwise be required for designed glass coverage. This is to allow the glass to be inserted far enough into the deeper pocket so as to clear the fixed glass stop of the opposite side of the framing system. The actual glass pocket depth required in the deeper pocket must account for glass size, glass bites, glass tolerances, framing tolerances, setting blocks and installation clearance. The surfaces of the glazing stops which face the glass should preferably be in the same plane, i.e., the face clearance should be equal on all edges. In some window and wall designs, the face clearance at the head and sill may be different than at the jambs, resulting in an off-set at each corner. Unless proper precautions are taken, such off-sets may produce significant localized bending stresses near the glass corners. As a minimum precautionary step, face-spacers or roll-in gasket thicknesses should compensate for the differences in face clearance. For major installations, it is always advisable to determine the steps to be taken, in cooperation with the glass and curtain wall producers, before the design is finalized. Conventional Glazing Systems can be characterized by three distinct types of glazing systems; Wet, Dry, and Wet/Dry. The use and position of gunnable sealant and mastic tapes (Wet components) and/or rubber gaskets and foam tapes (Dry components) determine which type of system is being designed. The components located in the primary seal position determine the system type. 1. WET Glazing In WET Glazing, a gunnable sealant or mastic tape is positioned as the primary seal at both the interior and exterior lite. In Detail 1, a mastic tape is positioned at the exterior and a recessed spacer shim with a gunnable sealant cap bead is positioned at the interior. Gunnable sealant cap beads are considered to be one of the most effective means to prevent water and air infiltration. However, they are typically the most labor intensive component and are susceptible to workmanship error. Additionally, a cap bead detailed at the exterior will likely require glazing from the exterior. Tapes generally require the use of a gunnable sealant to ensure a continuous seal at the corners.

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2. DRY Glazing Dry Glazing, sometimes called gasket glazing or compression glazing, is a term used to describe various means of sealing monolithic and insulating glass in the supporting framing system with synthetic rubber and other elastomeric gasket materials. The width of the glazing channel and the glass thickness are fixed dimensions with known tolerances. Various gasket profiles and durometers are utilized to provide a compression force of 4 to 10 lb./ln. (pounds per linear inch) (4.6 to 11.5 kg/cm) to resist penetration of air and water between the channel/gasket and gasket/glass interfaces. There are two basic design variations when dry glazing. Pressure bar systems have a continuous bar, usually separated from the mullions and rails by a thermal isolator, which is fastened with screws; Details (2) a, b. A torque wrench is used with some systems to compensate for standard material tolerances and to provide uniform gasket pressure. Snap covers conceal the attachment screws and weep holes in the pressure bar. Different colors and finishes may be specified for exterior and interior surfaces. Other dry glazing systems have combinations of fixed glazing channels and applied glazing stops; Details (3) a, b. A low durometer closed cell foam or medium durometer profile gasket is installed first, followed by glass, the stop, and then a dense wedge (roll in) gasket that provides the compression. The gaskets must be designed to compensate for dimensional tolerances of materials so as to provide the desired glazing pressure. Thermal isolation and finish options are also available with these systems. Compression gaskets should meet ASTM C 509, "Standard Specification, for Cellular Elastomeric Pre-formed Gaskets and Sealing Material," and ASTM C 864, "Standard Specification for Dense Elastomeric Compression Seal Gaskets, Setting Blocks, and Spacers." These specifications contain performance options to be considered. Gaskets supplied on reels must be cut accurately by the installer with a small additional length specified by the manufacturer added to the required length to prevent subsequent gaps at corners caused by gasket shrinkage. Pre-cut gaskets or gasket frames with pre-molded corners are available. Their use may reduce job-site installation labor and workmanship errors. Gasket and curtain wall manufacturers should be consulted on custom designs that differ from existing tested products. Gasket installation instructions should be requested from the manufacturer. CAUTION: When used in a dry glazed system, monolithic spandrel panel suppliers and sealant and/or gasket suppliers should all be consulted for material compatibilities. 3. WET/DRY Glazing WET/DRY Glazing systems combine the components of Wet and Dry systems in an attempt to take advantage of the best features of both the watertight integrity of Wet glazing and ease of installation of Dry glazing. A wet sealant (gunnable or tape type) is installed on one side of the lite (usually the exterior) and a rubber extrusion is installed on the other side of the lite. In the example shown in Detail 4, a mastic tape is installed on the exterior leg of the pocket. Serrations in the face of the exterior leg engage and maintain the position of the spacer shim in the tape. Tape corners are treated with a gunnable sealant. Setting blocks, glass and interior stop are installed, followed by a wedge gasket to the interior to

Snap CoverPressure Bar

Closed Cell or Profiled Gasket

Dense Gasket

VERTICAL MULLION – Figure 2A

Pressure Bar

Snap Cover

Weep

Profiled Gasket

Closed Cell or

Dense Gasket

HORIZONTAL RAIL – Figure 2B

Closed Cell Gasket Snap Cover

Dense Wedge

Applied Stop

VERTICAL MULLION – Figure 3A

Dense WedgeApplied Stop

Weep

Closed Cell Gasket

HORIZONTAL RAIL – Figure 3B

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Wedge GasketShimmed Type

WET/DRY GLAZING

Detail 4

*Weep holes and gunnable sealant applications pertinent in design performance are omitted for clarity.

complete the system. Additional information on this topic may be found in AAMA 850, "Fenestration Sealants Guide Manual". In window applications with interior stops and without adequate water head, the use of gunnable sealants as heel beads, toe beads, and air seals may be required to improve resistance to water and air infiltration. Compatibility of these sealants with insulating glass, laminated glass, other sealants, and all other materials with which they may come into contact is essential. B. Structural Sealant Glazing Structural Sealant glazing systems have become very popular due to the aesthetic results of being able to glaze without metal extrusions creating a break between adjacent lites of glass. Structural Sealant glazing requires very specific design considerations for the structural sealant bead. The dimensions of the bead are primarily governed by the size of the lites and the design loads for the wall. A system design used successfully on one project may not be appropriate for the next project due to an increase in lite size, or design load. All suppliers on a Structural Sealant glazing project need to be aware of the intended end use of their products. Each manufacturer will take special steps, whether in design or testing, to provide for the specific requirements for their products. Project specifications, along with codes at all levels, need to be researched to ensure that all requirements for Structural Sealant glazing are met. Information on the design of Structural Sealant glazing system is available in AAMA Curtain Wall #13, "Structural Sealant Glazing Systems," and ASTM C 1249, "Guide for Secondary Seal for Sealed Insulating Glass Units for Structural Sealant Glazing Applications." One important consideration used in designing a glazing system is whether the system will be glazed from the interior or the exterior of the structure. Many glazing systems can be installed either way, but the specific selection and positioning of components may change given the specific requirements of each project. Structural Sealant glazing systems rely solely on Structural Silicone Sealant beads to structurally secure a lite of glass to the framing along one or more sides. Systems are designed with all or any combination of edges being structurally adhered. The most common systems have two

opposite edges (head and sill) conventionally glazed and the remaining opposite edges (jambs) structurally glazed. Typical Structural Sealant glazing systems include a "tensile" or "structural" bead positioned between the metal framing and the interior surface of the glass and a "weather seal" or "weather-bead" positioned between the glass edge and metal framing or glass edge to adjacent glass edge. The dimensions of the "structural" bead are critical and are dependent on the glass dimensions and design wind loads for each project. Design of a successful structural sealant glazing system requires close collaboration between glass, metal, and sealant suppliers. Local and national codes may require specific restrictions regarding the allowance and/or installation of Structural Sealant glazing systems. Detail 5a depicts a common Structural Sealant glazing system in which the "structural" bead is installed from the interior side of the glass, while in Detail 5b the "structural" bead is installed from the exterior side of the glass. It is important to note that "structural" beads installed as shown in Detail 5b are very difficult to install properly. (Bedding of the glass into the structural silicone sealant is not recommended.) Special care is required to ensure that complete filling of the allotted sealant space and full contact of the sealant on the surfaces by tooling is accomplished. Additional information on this topic may be found in Curtain Wall #13.

AluminumFrame

STRUCTURAL SEALANT GLAZING

A A

BB

StructuralJoint

Backer orSpacer Structural

Joint

Weatherseal JointA>B

Detail 5a

AluminumFrame

Structural andWeatherseal Joint

A>B

B B

A A

Backer orSpacer

Backer orSpacer

Detail 5b

C. Structural Gasket Glazing Systems Structural Gasket glazing systems, known as "Lockstrip or "Zipper"

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Lockstrip

STRUCTURAL GASKET Glazing

Detail 6a Detail 6b

gasket glazing, may be considered a special type of dry glazing. It is unique, however, in that it relies solely on the gasket to secure the lite to the framing system. In Detail 6a, the glass is set into the gasket before the rubber locking strip is installed. Once the locking strip is installed (Detail 6b) the glass is secured in place. D. Factory Glazing System Factory Glazing systems allow fabricators the advantages of installing glass and glazing in their own shops under controlled conditions. Factory glazing of some systems, i.e., structural sealant system, may be required by code. Factory Glazing may be accomplished while the frame is in the horizontal or vertical position. When the glass is structurally glazed, the units should not be moved until the sealants have sufficiently cured. When the units are glazed in the horizontal position, the glass should be set firmly against the setting blocks to minimize shifting of the lite when the frame is rotated to the vertical position. After the sealant is cured, the frame may be rotated to its final vertical position, and should remain vertical until installed on the building. Most curtain wall frames are not completely rigid prior to being fastened to their building anchors. When they are factory glazed, rigid supplementary frame stiffeners are sometimes utilized to prevent glass and sealant damage during normal handling. These can be made removable once the glazed unit is in place on the building. Some factory glazed designs require that the glazing be blocked on all four sides to hold the glazing in place while sealants cure and to provide greater stiffness and resistance to shifting and racking during transportation and erection. IV. GLASS FRAMING CONSIDERATIONS While typical building construction documents often illustrate openings to receive glass framing systems as true, plumb and square, the realities of construction tolerances must be considered during manufacturing and assembly. Tolerances must be built into the design of the products and the installation techniques must compensate for openings that are not true plumb and square. Glass manufacturers often recommend minimum and maximum allowable glass edge bite and glazing pressures. For various types of glass, notably multi-lite insulating glass units, thick laminated glass, such as bullet resistant, as well as some of the new higher performing

thermal units, the dimensional tolerances may be greater than that for other, more standard types of glass. The framing manufacturers and the installers of glazing systems must allow for these glass tolerances to ensure that there is adequate bite and edge pressure on the glass to maintain a seal against air and water infiltration. Excessive bite on the glass may produce significant thermal stresses at the edges of heat absorbing and heat reflecting glasses. Excessive glazing pressures may cause seal failures or increase glass stress levels. Another concern for the framing manufacturer and installer is that enough edge clearance for the glass be allowed for proper installation of the glazing, as well as providing a means for restricting the movement of the glass after installation. Unprotected or restricted edge clearances may result in glass damage from glass to metal contact caused by normal building movements. In systems using lock strip (structural) gaskets, close framing tolerances are needed to ensure that the glass and frame are properly gripped and to maximize the roll out resistance of the gasket, i.e., the ability of the gasket to retain the glass in the opening under wind loads. With the popularity of structural sealant glazing, and the fact that the glass may be structurally adhered to the framing system with the use of silicone on one, two, or more of its edges, the tolerances built into a system play a critical role in the performance of the system. Since silicone manufacturers specify minimum widths and depths of a structural silicone joint, it is extremely important that the framing systems allow for the glass to be installed in such a way that these minimums are maintained on all aspects of the installation. Individual framing members must be inspected to be sure that they are not excessively racked, twisted or bowed. It is also important that the framing joinery not allow for excessive offsets of the glazing pockets at framing intersections, corners, miters, etc. Framing member deflection should be limited to ensure a maximum deflection of L/175 of the unsupported (clear) span length. This limitation should protect the glass edges from contact with the framing member. Irregularities such as these may cause glass breakage during glazing or may contribute to subsequent breakage when their effect is combined with edge thermal stresses, wind buffeting or building movement. V. GUIDELINES for the GLAZING CONTRACTOR General glazing procedures and guidelines may become part of an architectural specification. The following guidelines would apply for most glazing systems. Since some glazing system designs require more specific recommendations, the glass, gasket, and sealant manufacturers should be consulted in these cases. Compatibility of all glazing components should be established with the respective suppliers prior to installation. A. All glass systems dead-loaded at the sill should be set on two identical setting blocks located at the quarter points. Setting blocks meeting ASTM C 864 with an 85 + 5, "Shore A" durometer are recommended. The length of each setting block should be 0.1" (3 mm) for each square foot of glass area, but never less than 4" (100 mm) in length. Setting blocks should normally be located at quarter points equidistant from the center of the glass. As a means of reducing deflection of the glass supporting member, most glass manufacturers will allow the blocks to be located at eighth points. Setting blocks should never be positioned such that the jamb edge of the block is less than 6"

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(150 mm) from the glass edge. Setting blocks should not restrict water flow to weep holes, or in any way interfere with operation of the weep system. In these instances, the glass manufacturer should be consulted to ensure the acceptability of the proposed design. Further information can be obtained from the FGMA Glazing Manual. B. Generally, glass should be centered in the opening both vertically and horizontally, and should maintain consistent edge bites. Special considerations may be necessary due to splice joint locations requiring increased edge bites to accommodate movement. C. To prevent lateral 'walking' of large glass lites, edge blocking may be appropriate. Edge blocks (anti-walk blocks) should be a minimum of 3" (75 mm) in length and located near the bottom and top of the vertical glazing channels. (NOTE: In seismic zones, it may be necessary to consider alternate locations for edge blocking.) When edge blocks are not self retained or bonded adhesively in place to prevent dislocation, other means should be used to prevent glass walking and breakage. Edge blocks should be of a "Shore A" durometer specified by the glass manufacturer. A nominal clearance of 1/8" (3 mm) should be maintained between the block and the edge of the glass. D. Insulating glass units and heat treated glass (tempered and heat-strengthened) cannot be cut after fabrication. Glass thicker than 3/8" (10 mm), both clear and tinted, require greater expertise when cutting, and therefore, it may be appropriate to order these pre-cut to the proper size. No further modification should be made to these glass types after fabrication. E. A moisture barrier seal should be provided between the face of the glass and the glazing stops. The glass should be allowed to 'float' in the opening by maintaining the recommended edge and face clearances of the glass supplier. Consult the suppliers' literature for the appropriate clearances. If a toe bead or heel bead is required to provide a proper weather seal, the sealant should be one specifically recommended by the sealant supplier and glass manufacturer for the specific application. In any case, the heel or toe bead should not interfere with the operation of the weep system. For lockstrip glazing systems, recommendations can be obtained from the gasket manufacturer. F. For laminated glass, insulating glass units, and other specialty glass types, use a compatible sealant, tape, or gasket. As is the case with any sealant, tape, or gasket, the compatibility of these products should be verified by the material supplier and glass manufacturer. VI. SPECIAL GLASS WALL SYSTEMS Because of the desire of some architects to "open-up" the glass areas and eliminate conventional metal mullions, 'all-glass' systems have been devised. These might be categorized into four groups: A. Suspended Glazing In this system, the glass is suspended by hangers which clamp the top glass edges. To provide the lateral support normally offered by metal mullions, similar suspended glass stiffeners, projecting as fins perpendicular to the vision glass surface, are adhered to the glass near the glass joints. The dead weight of the glass is totally supported by the hangers, with the sill (conventionally glazed without setting blocks)

providing resistance only against inward/outward glass movement. B. Butt Joint Glazing In this system the glass is conventionally glazed at the head and sill but with no support for the abutting vertical edges. Joints are usually sealed with a silicone sealant. Thicker glass is required for a given opening size and wind load than would be required if it were supported on all four sides. Butt joint glazing is not recommended for insulating glass units, unless the installation is approved by the insulating glass unit manufacturer. C. Glass Mullion System In this system the glass is supported at the sill in the normal fashion, but fin-like glass stiffeners are used as mullions, in place of metal, much as in the suspended glazing system. Provisions for building frame movement must be made at the head. The fundamental difference is that in the glass mullion system there are no hangers used, and the dead weight of the glass and stiffeners is totally supported at the bottom edge. D. Structural Glazing In this system, glass and a structural sealant are used to provide a relatively flush outdoor wall surface. Silicone sealant is used to adhere the glass to the aluminum back-up mullions on the room-side. See Section III, D, in this document, for additional information. VII. GLASS and WIND LOADS The performance of glass under wind loads depends primarily upon 1) the glass thickness and dimension, 2) glass type, i.e., annealed, tempered, etc., and 3) the support system. The deflection of framing systems is limited to a maximum of L/175 at the design wind load and span for the framing support to be considered rigid. A. Glass Supported at Four Edges The resistance of glass to uniform loading changes with aspect ratio. Consult the glass manufacturer for allowable loading on glass or reference the current version of ASTM E 1300. B. Glass Supported at Two Opposite Edges (Butt-Joint Glazing) For this support condition, the span dimension between supports (usually the glass height), is the critical factor. The other dimension of the glass does not influence its resistance to uniform loading when support is at two opposite edges. VIII. GLASS and HEAT TRANSFER A structure's exposure to direct solar heat, and the vision glass area's capability to reduce solar energy transmittance must be clearly evaluated in minimizing cooling requirements and operating costs required to compensate for solar induced heat transfer through its facade. The most important factor to consider in evaluating a vision glass product's capability to reduce solar induced heat transfer into a building interior is its shading coefficient. The shading coefficient is the ratio of direct and diffused solar heat gain (to the interior) of any glass unit (or glass and shading combination) compared to that of monolithic 1/8" (3 mm) clear, unshaded glass. Solar heat gain is the

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summation of the transmitted solar energy component and the absorbed and re-radiated component of the sun's energy entering a building through glass. The portion of absorbed solar energy that is conducted and convected into the building is included in a vision glass product's shading coefficient. Monolithic 1/8" (3 mm) clear glass has a shading coefficient equal to 1.00. All monolithic tinted, heat absorbing, coated reflective, insulating glass products, and monolithic clear glass in thicknesses greater than 1/8" (3 mm) have shading coefficients less than 1.00. All of these products, or glass and shading combinations, have lower shading coefficients and transfer less solar energy to the interior of the building as compared to 1/8" (3 mm) clear monolithic, unshaded glass. NOTE: a) A clear vision glass area's shading coefficient may be improved significantly by utilizing interior or exterior shading devices. b) Tinted, heat absorbing products transfer less solar energy than clear glass. The overall relative effect of shading devices towards the shading coefficients are reduced. c) Reflective, coated glass products generally transmit substantially less solar energy than clear glass and significantly less solar energy than tinted glass. Utilizing shading devices with these products do not yield substantially lower shading coefficients. d) Some high light transmitting, reflective coatings applied to clear glass have higher initial shading coefficients, and interior shading devices may offer significantly lower shading coefficients. The performance and aesthetic values of vision glass products must be analyzed thoroughly to ensure the selection of the most appropriate material in achieving project goals. IX. GLASS and ACOUSTICS Reductions of sound transmission through a building's shell is measured in decibels and is referred to as Sound Transmission Loss (STL). The STL across a barrier is typically measured, in accordance with ASTM E 90, "Test Method for Laboratory Measurement of Airborne-Sound Transmission Loss of Building Partitions," at sixteen discrete frequency bands between 125 and 4,000 Hertz (Hz) inclusive. The effectiveness of a barrier type in reducing sound transmission is dependent upon the barrier's mass, stiffness, and damping characteristics and for a given barrier type, the effectiveness will be relative to the frequency being analyzed. For example, the STL of a one inch (25 mm) insulating unit composed of two 1/4" (6 mm) lites separated by a 1/2" (12 mm) air space surpasses that of 1/4" (6 mm) monolithic glass at high frequencies. At certain low frequencies, however, the 1/4" (6 mm) monolithic glass out-performs the insulating glass unit. The performance of the same insulating unit will exceed that of 1/2" (12 mm) monolithic glass at certain middle frequencies, but not at the low or high frequencies. In the early 1970's, ASTM first published E 413, "Classification for Rating Sound Insulation." This documentation provided a single number rating for sound attenuating barriers. Manipulation of STL data in accordance with the procedures of E 413 resulted in the Sound Transmission Class (STC) of the barrier. Although originally developed for interior wall partitions, this system was often adopted for rating products and materials used across a building envelope. Due to the frequencies and amplitudes that are addressed in the procedure, it is inappropriate for exterior applications.

In 1990, ASTM developed E 1332, "Standard Classification for Determination of Outdoor-Indoor Transmission Class," for determining the Outdoor-Indoor Transmission (OITC) rating of a barrier. This procedure expands the measured frequency spectrum to 80-4,000 Hz inclusive and is designed to be representative of road, rail and airplane traffic. Due to its relative infancy, the OITC system is not yet the recognized standard for acoustically rating building envelope components. In most cases, STC remains the typical reference. AAMA has, however, attempted to break this erroneous trend with the recent development of a new standard. AAMA 1801, "Voluntary Specification for the Acoustical Rating of Residential, Commercial, Heavy Commercial and Architectural Windows, Door and Glazed Wall Sections" was adopted in 1995 for the acoustical rating of residential, commercial, heavy commercial and architectural windows, doors, and glazed wall sections. This procedure uses the STL data of ASTM E 90 and the OITC number of ASTM E 1332, for acoustically rating a product. If the frequency of a particular noise source is known, an evaluation of that frequency band and the associated STL of a product will generally be more useful than its STC or OITC rating. (e.g., if reduction of automobile, bus or truck noises is of primary concern, glass acoustical performance in frequencies up to 1,000 Hz (low frequency) would be most important and generally those from 1,000 to 4,000 Hz would be less significant. Acoustical performance of glass for the entire 80 to 4,000 Hz range should be considered for a building located in the flight path of jet planes. Acoustical performance of glass for buildings located off to the side of a runway near an airport should be evaluated primarily in the 500 to 2,000 Hz range.) STC rating specification for exterior glass do frequently appear in architectural specifications. Compared to windows single glazed with 1/4" (6 mm) float, a glass area's STL may be increased by: 1. Increasing the glass thickness. 2. Double glazed with varying glass thicknesses and air spaces. (Perimeters of air spaces may be specially insulated to improve the STL of a window.) 3. Glazed windows with laminated glass (monolithic, insulating, or double glazed with varying airspace thicknesses). The interior lite of insulating or double glazed units may be non-laminated, but using laminated in both lites will generally yield higher STL's, STC's, and OITC's. Laminates normally used range from .030 to .060 inches (0.8 to 2 mm) in thickness and are available in polyvinyl butyral or ultraviolet cured resin interlayers. Due to its limpness and damping effect, laminated architectural glass has the potential to increase STL's more than non-laminated glass at most sound frequencies. Some of the items to be considered in selecting appropriate materials to achieve a desired STL or OITC rating are the structures' intended use, interior masking of noises, the frequency of occurrence and intensity of intrusive noises and sound reduction provided by the building's walls. The window area is a component of the wall and must be evaluated in conjunction with other component materials to determine the STL of the total wall. Improved STL's of a good acoustical glass can be partially offset or negated if passage ways for sound transmission are not adequately sealed.

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The final choice of glass and glazing details should be made after consultation with a qualified acoustician. X. SAFETY GLAZING REQUIREMENTS On July 6, 1977, the Consumer Product Safety Commission's (CPSC) 16 CFR 1201 standard became effective. The standard prescribes the safety requirements for: 1) storm doors or combination doors, 2) ingress and egress doors, 3) bathtub doors and enclosures, 4) shower doors and enclosures, and 5) sliding glass doors (patio type). Storm windows, prime operating windows and fixed lites of glass as used in curtain wall construction, do not fall under the requirements of CPSC 16 CFR 1201, unless they are located within a specified distance from a door or walking surface. CPSC 16 CFR 1201 has preempted all state safety glazing laws and the glazing sections of all building codes except for those products which are exempt from the standard such as glazed panels, leaded glass, curved panels in revolving doors, and louvers in jalousie doors. Building codes may require that safety glazing meet the requirements of ANSI Z97.1 where the product and its use are not covered by CPSC 16 CFR 1201. XI. GLASS STANDARDS The following are the universally accepted current standards from the American Society of Testing and Materials (ASTM) applying to the various types of architectural glass: A. ASTM C 1036, "Standard Specification for Flat Glass," replaces the Federal Specification (FS)DD-G-451D, "Federal Specification Glass, Float or Plate, Sheet Figured." This specification covers quality requirements for cut sizes of all types of monolithic glass, including wire and heat-absorbing glasses. Always refer to current version. B. ASTM C 1048, "Standard Specification for Heat-Treated Flat Glasses-Kind HS, Kind FT Coated and Uncoated Glass," replaces Federal Specification (FS) DD-G-1403B, "Federal Specification Glass, Plate (Float), Sheet, Figured and Spandel." This specification covers requirements for heat-strengthened and fully tempered coated and uncoated flat glass products used in windows, doors, and spandrel applications. Included are dimensional tolerances for allowable bow (warp), durability of ceramic colored (spandrel) glasses and strength requirements. Always refer to current version. C. ASTM C 1172, "Specification for Laminated Architectural Flat Glass" covers requirements for laminated glass usage. Always refer to current version. D. ASTM E 1300, "Practice for Determining the Minimum Thickness and Type of Glass Required to Resist a Specified Load," covers requirements for glass thickness determination to resist a specified load for given applications. Always refer to current version. E. American National Standard Institute's (ANSI) Z97.1, covers the safety requirements for fully tempered, laminated and wired glass as well as rigid plastics. It is directed primarily toward assuring that safety glazing have fail-safe characteristics when broken by human impact, and has been referenced in virtually all codes, laws and ordinances requiring the use of safety glazing materials in buildings. However, as previously indicated, this standard has been superseded in most architectural applications by CPSC 16 CFR 1201. Always refer to current version.

XII. REFERENCE DOCUMENTS The following is a listing of related publications which are reference documents (consult organization for current revisions): AMERICAN ARCHITECTURAL MANUFACTURERS ASSOCIATION (AAMA) AAMA 850-91, Fenestration Sealants Guide Manual AAMA 1801-95, Voluntary Specification of the Acoustical Rating of Residential, Commercial, Heavy Commercial, and Architectural Windows and Doors and Glazed Wall Sections AAMA CW #13-1985, Structural Sealant Glazing Systems AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI) ANSI Z97.1-1984, Glazing Materials Used in Buildings, Safety Performance Specifications and Test Methods AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) ASTM C 509-94, Specification for Cellular Elastomeric Preformed Gasket and Sealing Material ASTM C 846-94, Practice for Application of Cellulosic Fiber Insulating Board for Wall Sheathing ASTM C 1036-91, Specification for Flat Glass ASTM C 1048-92, Specification for Heat Treated Flat Glass-Kind HS, Kind FT Coated Insulation ASTM C 1172-91, Specification for Laminated Architectural Flat Glass ASTM C 1249-93, Guide for Secondary Seal for Sealed Insulating Glass Units for Structural Sealant Glazing Applications ASTM E 90-90, Test Method for Laboratory Measurement of Airborne-Sound Transmission Loss of Building Partitions ASTM E 413-87 (1994), Classification for Rating Sound Insulation ASTM E 773-88, Test Method for Seal Durability of Sealed Insulating Glass Units ASTM E 774-92, Specification for Sealed Insulating Glass Units ASTM E 1300-94, Practice for Determining the Minimum Thickness and Type of Glass Required to Resist a Specified Load ASTM E 1332-90, Classification for Determination of Outdoor-Indoor Transmission Class CONSUMER PRODUCTS SAFETY COMMISSION (CPSC) CPSC 16 CFR 1201, Safety Standard for Architectural Glazing Materials GLASS ASSOCIATION OF NORTH AMERICA (GANA) (Formerly Flat Glass Marketing Association (FGMA) FGMA GLAZING MANUAL

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FEDERAL SPECIFICATIONS (FS) FS-DD-G-1403B-1973, "Federal Specification Glass, Plate (Float), Sheet, Figured and Spandrel" — Discontinued and replaced by ASTM C 1048. FS-DD-G-451D-1977, "Federal Specification Glass, Float orr Plate, Sheet Figured" — Discontinued and replaced by ASTM C 1036. XIII REFERENCE SOURCES American National Standards Institute (ANSI) 11 West 42nd Street New York, NY 10036 PH: 212/642-4900 . . . Fax: 212/398-0023 American Society for Testing and Materials (ASTM) 100 Barr Harbor Drive West Conshohocken, PA 19428 PH: 610/832-9500 . . . Fax: 610/832-9555 Glass Association of North America (GANA) 3310 S.W. Harrison Street Topeka, KS 66611 PH: 913/266-7013 . . . Fax: 913/266-0272 National Fire Protection Association (NFPA) #1 Batterymarch Park Quincy, MA 02269 PH: 617/770-3000 . . . Fax: 617/987-7057 McGraw Hill Company, Sweets Group 1221 Avenue of the Americas New York, NY 10020 PH: 800/442-2258 . . . Fax 212.512-2348 XIV GLOSSARY ACRYLIC — A group of thermoplastic resins formed by polymerizing the esters of acrylic acid. ACTIVATOR — A material which, when added to the base compound of a multicomponent system, will initiate or accelerate the curing mechanism. ADHESION — The property of a coating or sealant to bond to the surface to which it is applied. ADHESIVE FAILURE — Loss of bond of a coating or sealant from the surface to which it was applied. ADHESION-IN PEEL TEST — A quantitative measure of bond strength, whereby the material is pulled away from the mating surface at a 90 degree angle or a 180 degree angle to the plane to which it is adhered. Values are generally expressed in pounds per inch width and as to whether failure mode was adhesive or cohesive. AIR POCKETS — Bubbles of air entrapped within a sealant, or between two adjacent beads of sealant applied successively in a joint. ANNEALING LEHR — An on-line, controlled heating/cooling apparatus located after the tin bath and before the cooling conveyor of a float glass production line. Its purpose is to relieve induced stress from the flat glass product to allow normal cold end processing.

ANTI-WALK BLOCKS — Elastomeric blocks that limit glass from moving lateral in the glazing rabbet which may result from thermal, seismic, wind load effects, building movement, and other forces that may apply. APPLICATION LIFE — The period of time during which a sealant, after being mixed with a catalyst or exposed to the atmosphere, remains suitable for application; also referred to as work life, or pot life. ASPECT RATIO — The quotient of the long side of a glazing lite over the short side of that lite. BACKER ROD — A polyethylene or polyurethane foam material installed under compression and used to control sealant joint depth, provide a surface for sealant tooling, serve as a bond breaker to prevent three-sided adhesion, and provide an hour-glass contour of the finished bead. BED or BEDDING — The bead of compound applied between two materials, normally the glass or panel and the stop or frame. BITE — The dimension by which the framing system overlaps the edge of the glazing infill. BLEEDING — A migration of a liquid to the surface of a component or into/onto an adjacent material. BOND BREAKER — A material used to prevent adhesion of the sealant to a surface to which adhesion is not desired. BUBBLING — Open or closed pockets in a sealant caused by release, production, or expansion of gasses. BUILDING ENVELOPE — Term used to describe the outer skin of a building that provides resistance to water and air infiltration. BUTTERING — Application of compound or sealant to the surface of a member before placing it into position. BUTYL — A non-hardening compound formed by the copolymerization of isobutylene with isoprene. CAP BEAD — A beveled seal applied to the top of the glazing rabbet to shed water away from the glazed infill. CATALYST — A material which speeds the cure of a compound. CAULK — The application of a sealant to a joint, crack, or crevice. CAVITY WALL — A type of building wall construction consisting of an outer wall secured to an inner wall separated by an air space. CHEMICALLY CURING SEALANT — A base sealant that relies upon added chemicals to initiate the curing process. COHESIVE FAILURE — Internal splitting of a compound resulting from over-stressing of the compound. COMPATIBILITY — The ability of two or more materials to exist in close and permanent association for an indefinite period with no adverse effect of one on the other. COMPOUND — A chemical formulation of ingredients, used to produce a caulking, elastomeric joint sealant, etc.

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COMPRESSION GASKET — A gasket designed to function under compression. COMPRESSION SET — The permanent deformation of a material after removal of the compressive stress. CONSISTENCY — Degree of softness or firmness of a compound as supplied in the container, varying accordingly to the method of application such as gun, knife, tool, etc. CURING AGENT — Generally a part of a two-part system which, when added to the base material, cures by a chemical reaction. DRY GLAZING — Also called "Compression Glazing," is a term used to describe various means of sealing monolithic and insulating glass in the supporting framing system with synthetic rubber and other elastomeric gasket materials. DUROMETER — Measurement of hardness of a material. EDGE BLOCK — See anti-walk block. ELASTOMERIC — An elastic rubber like substance. EPDM — A synthetic rubber; Ethylene Propylene Diene Monomer. EXPANSION JOINT — A separation between building elements that allows independent movement without damage to the assembly. EXTERIOR GLAZED — Glazing infills set from the exterior of the building. FACE GLAZING — A system having a triangular bead of compound applied with a glazing knife, after bedding, setting and clipping the glazing infill in place on a rabbetted sash. FILLET BEAD — Caulking or sealant placed in such a manner that it forms an angle between the materials being caulked. GASKET — Pre-formed shapes, such as strips, grommets, etc., of rubber and rubber-like composition, used to fill and seal a joint or opening either alone or in conjunction with a supplemental application of a sealant. GLAZING (n) — A generic term used to describe an infill material such as glass, panels, etc. GLAZING (v) — The process of installing an infill material into a prepared opening in windows, door panels, partitions, etc. GLAZING BEAD — A molding or stop used to hold glazing infills in position. GUN GRAY CONSISTENCY — Compound formulated to a degree of viscosity suitable for application through the nozzle of a caulking gun. HEEL BEAD — Sealant applied at the base of a glazing channel, installed after setting the glass and prior to installation of the removable stop. Its primary purpose is to prevent leakage of air and/or water past the stop. When applying a heel bead, sealant should be lapped onto the lite a minimum of 3/16" (5 mm) and have positive contact with the sash. Heel beads are used primarily in unwept sash.

INTERIOR GLAZED — Glazing infills set from the interior of the building. JAMBS — The vertical frame members at the perimeter of the opening. JOINT — The space or opening between two or more adjoining surfaces. KICKER — See activator. KNIFE CONSISTENCY — Compound formulated to a degree of firmness suitable for application with a glazing knife such as used for face glazing and other sealant applications. LATEX — A colloidal dispersion of a rubber resin (synthetic or natural) in water, which coagulates on exposure to air. LITE (LIGHT) — A term for a single pane of glass used in either monolithic or insulating glass units. MASTIC — Descriptive of heavy-consistency compounds with adhesive characteristics. MIGRATION — Spreading or creeping of a constituent of a compound onto/into adjacent surfaces. See bleeding. MODULUS — Stress at a given strain, or tensile strength at given elongation. MULLION — A horizontal or vertical structural member that supports and holds such items as panels, glass, sash, or sections of curtain wall. MUNTIN — The horizontal and vertical bars that divide a large lite into smaller lites of glass. NEOPRENE — A synthetic rubber having physical properties closely resembling those of natural rubber. It is made by polymerizing chloroprenes, and the latter is produced from acetylene and hydrogen chloride. NON-DRYING (NON-CURING) — A sealant that does not set up or cure. NON-RESILIENT TAPE — A high solids content, mastic material furnished in varying thicknesses and widths, in a roll form; easily deformed and permanently soft and tacky. NON-SAG — A sealant formulation having a consistency that will permit application in vertical joints without appreciable sagging or slumping. A performance characteristic which allows the sealant to be installed in a sloped or vertical joint application without appreciable sagging or slumping (thixotropy). NON-SKINNING — Descriptive of a product that does not form a surface skin. NON-STAINING — Characteristic of a compound which will not stain a surface. NON-VOLATILE — Any substance which does not evaporate or volatize under normal conditions of temperature and pressure. NOZZLE — The tubular tip of a caulking gun through which the compound is extruded.

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OLEORESINOUS — A compound consisting of natural and synthetic resins mixed with drying oils. ORGANIC — Any compound which consist of carbon and hydrogen, with a restricted number of other elements, such as oxygen, nitrogen, sulphur, phosphorous, chlorine, etc. POCKET (CHANNEL) — A three-sided, U-shaped opening in a sash or frame to receive glazing infill. Contrasted to a rabbet, which is a two-sided, L-shaped section, as with face glazed window sash. POCKET (CHANNEL) DEPTH — The inside dimension from the bottom of the pocket to the top. Pocket depth equals the bite plus the edge clearance. POCKET (CHANNEL) WIDTH — The measurement between stationary stops (or stationary stop and removable stop) in a U-shaped channel. POLYBUTENE — Straight chain, non-drying, non-reactive, inert aliphatic hydrocarbon polymer. Used as a component in some sealing and caulking compounds. POLYESTER RESIN — Any of a group of thermosetting synthetic resins which are poly-condensation products of dicarboxylic acid and dihydroxy alcohol. POLYETHYLENE — A straight chain plastic polymer of ethylene. POLYISOBUTYLENE — See Polybutene - Frequently associated as having higher molecular weight. POLYMER — An organic product of polymerization composed of an indefinite number of monomers. POLYMERIZED — Treated by heating or cooking so that molecules of different substances unite into larger molecules of a different substance with individual characteristics. POLYSULFIDE SEALANT — Polysulfide liquid polymer sealant which are mercaptan terminated, long chain aliphatic polymers containing disulfide linkages. They can be converted to rubbers at room temperature without shrinkage upon addition of a curing agent. POLYURETHANE SEALANT — An organic compound formed by the reaction of a glycol with an isocyanate. POT LIFE — The time interval following the addition of an accelerator before a chemically curing material will become too viscous to apply satisfactorily. PRE-SHIMMED TAPE SEALANT — A sealant having a pre-formed shape containing solids or discrete particles that limit its deformation under compression. PRIMER — A coating specifically designed to enhance the adhesion of sealant systems to certain surfaces, or to form a barrier to prevent migration of components, or to seal a porous substrate. PVC — Polymer formed by polymerization of vinyl chloride monomer. Also known as polyvinyl chloride (vinyl). RABBET — A two-sided, L-shaped recess in sash or frame to receive glass lites or panels.

RACKING — A movement or distortion of sash or frames causing a change in angularity of corners. REACTION — A mutual action of chemical agents upon each other resulting in a chemical change. RESILIENT TAPE — A pre-shaped, rubbery sealing material furnished in varying thicknesses and widths, in roll form. May be plain or reinforced with scrim, twine, rubber or other materials. SASH — The window frame which receives the glazing infill. SEALANT — An elastomeric material with adhesive qualities applied between components of a similar or dissimilar nature to provide an effective barrier against the passage of the elements. SEALANT BEAD — A sealant or compound, such as caulking or glazing bead, etc., applied to a joint regardless of the method of application. Also, a molding or stop used to hold glass or panels in position. SELF-LEVELING SEALANT — A sealant formulation having a consistency that will permit it to achieve a smooth level surface when applied in a horizontal joint. SETTING BLOCK — Blocks placed under the bottom edge of glazing infill to position it and to prevent its contacting the frame. SHORE "A" HARDNESS — Measure of firmness of a compound by means of a Durometer Hardness Gauge (A hardness range of 20-25 is about the firmness of an art gum eraser. A hardness of 90 is about the firmness of a rubber heel). SIGHT LINE — The line along perimeter of glazing infills corresponding to the top edge of stationary and removable stops. The line to which sealants contacting the glazing infill are sometimes finished off. SILICONE SEALANT — A sealant having as its chemical composition a backbone consisting of alternating silicon-oxygen atoms. SOLIDS CONTENT — A determination of the non-volatile matter of a compound at a specified temperature and time interval. Usually expressed in percentage by weight and the difference between this figure and 100%, represents the volatile matter or loss by evaporation. SOLVENT RELEASE SEALANT — A sealant that cures primarily through solvent evaporation. STOP — Either the stationary lip or the removable molding of the rabbet, serving to hold the glazing infill in the sash or frame, with the help of spacers. SUBSTRATE — A base material to which other materials are applied. TAPE SEALANT — A sealant having a pre-formed shape, and intended to be used in a joint under compression. TOE BEAD — Sealant applied at the base of a glazing channel, prior to setting the lite. Its purpose being a secondary seal to prevent leakage past the exterior stop. When applying a toe bead, make certain it is large enough to contact both the sash and the glass.

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TOOLING — The operation of pressing in and striking a sealant in a joint, to press the sealant against the sides of a joint and secure good adhesion; the finishing off of the surface of a sealant in a joint so that it is flush with the surface. TWO-PART (MULTI-COMPONENT) SEALANT — A product comprised of a base and curing agent or accelerator, necessarily packaged in two separate containers which are uniformly mixed just prior to use. ULTRAVIOLET — The invisible rays of the light spectrum which are below the visible range consisting of radiation below 400 nanometers. UNITED INCHES — The sum of one length and one width of a glazing infill. URETHANE SEALANT — See polyurethane sealant. VENTING — Providing circulation of air or ventilation between two walls or partitions. VINYL — Derived from ethylene (hydrocarbon gas), the compounds of which are polymerized to form high molecular weight plastics and resins, such as vinyl acetate, vinyl chloride, styrene, etc. It is a base material for plastisols and organisols, and is also widely used in emulsion form as polyvinyl acetate (See PVC.) WEEPHOLE — An opening to drain moisture.

published by AAMA 1827 Walden Office Square, Schaumburg, Illinois 60173