2 TERMINOLOGY
For the purpose of this Section, the following definitions shall apply, and for other terms those given in accepted standards [6-8(1)] shall apply.
2.1 Annealed Glass (see Glass) — Also known as ‘normal’ glass, which has not been subjected to toughening, lamination and heat strengthening. It is the product obtained from the process of slow and steady cooling of hot glass in order to relieve internal stresses or thermal induced stresses.
NOTE — This term is most commonly used for flat glass.
2.2 Annealed Fire Resistant Glass — Type of glass which is made out of annealed glass combination and is tested for the required duration and satisfies the intended criteria of fire resistance. These types of glasses may not possess the best of the impact resistance characteristics and may be used as vision panels.
2.3 As-Cut Finished Sizes — Finished panes of flat glass cut from stock/standard sizes. They may be subject to further processing, such as edge working drilling, face decoration, etc.
2.4 Aspect Ratio — The ratio of a longer side of glass pane to its shorter side.
2.5 Balustrade — A low barrier forming a parapet to a stair, ramp, balcony, raised level or a change in level.
2.6 Beads or Glazing Beads — A strip of wood, metal or other suitable material attached to the rebate to retain the glass in position in the frame.
2.7 Bite — The minimum distance by which the inner edge of a frame (or a stop) overlaps the edge of the glass panel.
2.7.1 Glazing Bite — The dimension by which the framing system overlaps the edge of the glazing infill.
2.8 Block (Setting Block) — A small piece of wood, plastic, rubber or other suitable material used between the edges of the glass (generally the bottom edge only) to centralize the glass in the frame (frequently called a setting block).
2.9 Chair Rail — A fixed rigid bar that provides protection from human impact.
2.10 Clear Glass — A transparent glass with neutral/near colourless appearance.
2.11 Coefficient of Linear Expansion — It is expressed as the strain (change in length per unit length) per unit variation of temperature of a material.
2.12 Combustible Material — The material which when burnt adds heat to a fire when tested for combustibility in accordance with accepted standard [6-8(2)].
2.13 Corridor — A common passage or circulation space including a common hall.
2.14 Coupled Glazing (also known as Secondary Glazing) — Two panes of glazing spaced apart in an opening, either in the frame or glazed separately, to form an unsealed cavity.
2.15 Curtain Wall — Non-load bearing structure/partition of glass attached to the building frame, usually on the exterior face. Curtain wall vertical framing members run past the face of floor slabs, and provision for anchorage is typically made at vertical framing members only.
NOTE — In contrast to combination assemblies and composite units, curtain wall systems often need to meet additional performance requirements for inter-story differential movement, seismic drift, dynamic water infiltration, etc. Operating vents and entrance doors are provided as separate inserts.
PART 6 STRUCTURAL DESIGN — SECTION 8 GLASS AND GLAZING
2.16 Distance Piece — A small piece of wood or other suitable material used to locate the glass between the bead and the back of the rebate to prevent lateral movement.
2.17 Door or Shutter Assembly Door-Set — A pedestrian door-set or industrial type door-set including any frame or guide, door leaf or leaves, rolling or folding curtain, etc, which is provided to give a fire resisting capability when used for the closing of permanent openings in fire resisting separating elements, which includes any side panel(s), vision panel(s), flush over panel(s) and/or transom panel(s) together with the building hardware and any seals (whether provided for the purpose of fire resistance or smoke control or for other purposes such as draught or acoustics) which form the assembly.
2.18 Double Glazed Fire Resistant Glass — A fire resistant glass that is used in a double glazed unit.
NOTE — These shall be tested as a complete Double Glazed Unit (DGU) or other multiple glazed units as the case may be. Double glazed fire resistant glass can be a combination of intumescent laminated fire rated or tempered fire resistant glass. Fire resistant glass cannot be combined with another glass and used as a DGU unless the combined double glazed or multiple glazed units are also tested.
2.19 Double Glazing — Glazing formed by an assembly of two glass panes separated by a spacer and the gap may be filled by vacuum, air or inert gases and hermetically sealed along the periphery to improve the thermal insulation.
2.20 Edge Deterioration — The discolouration of the reflective coating at the edge of the silvered glass.
2.21 Edge Faults — The faults that affect the as-cut edge of the glass. They may include entrant/emergent faults, shelling, corners on/off and vents.
2.22 Edge Polished — It is usually applied to flat glass, the edges of which have been polished after cutting.
2.23 Edging — Grinding the edge of flat glass, to a desired shape or size.
2.24 Exposed Edge — A glass panes' edge that is not covered.
2.25 Facade — It is the front or face of the building which is part of framed or frameless system.
2.26 Faceted Glazing — It is a type of glazing in which flat panes of glass are installed vertically at an angle to each other to form a faceted surface.
2.27 Fenestration — All area (including frame) in the building envelope that let in light, including window, plastic panels, clerestories, skylight, fanlight and glass doors that are generally more than one-half the floor height, and glass block walls.
2.28 Fin — A piece of glass positioned and fastened to provide lateral support.
2.29 Fire Separation — The distance, in metre, measured from the external wall of the building concerned to the external wall of any other building on the site, or from other site, or from the opposite side of street or other public space for the purpose of preventing the spread of fire.
2.30 Float Glass — Flat, transparent, clear or tinted soda-lime silicate glass having parallel and polished surfaces obtained by continuous casting and floatation on a metal bath.
NOTE — Flat glass is a general term covering sheet glass, float glass and various forms of rolled and plate glass in which shape of the glass is flat and commonly used for windows, glass doors, transparent walls and other architectural applications.
2.31 Flush Over Panel — A panel which is incorporated within a door-set or openable window and fitted above the leaf or leaves within the frame head and the jambs and with no transom.
2.32 Frame — An element made of timber/metal/aluminium or other durable material/combinations of materials, such as glass fins and structural sealant, supporting the full length of a glazed panel edge.
2.33 Frameless Glazing — An unframed glazing which maintains the integrity through pointed support structures.
2.34 Front Putty — The compound forming a triangular fillet between the surface of the glass and the front edge of the rebate.
2.35 Fully Framed Glazing — The glazing whose panels have all its four edges framed.
2.36 Gap — A clearance between two adjacent surfaces and/or edges, for example between the edge of the leaf and the reveal of the frame or between the face of the leaf and the frame stop.
2.37 Glass — An inorganic product of fusion which has cooled to a rigid condition without crystallizing. It is typically hard and brittle, and has a conchoidal fracture. It may be colourless or tinted and transparent to opaque. The term glass refers to monolithic glass unless specified otherwise.
2.38 Glass Appearance Faults — Faults such as spot and/or linear and/or enlarged area faults which alter the visual quality of glass.
2.39 Glazing — Act of securing of glass or other glazing material into a building in prepared openings in windows, door panels, partitions, etc.
2.40 Guard Rail — A permanent physical barricade used to prevent human impact on glass/glazing.
2.41 Hairline Scratch — Very fine scratch that can hardly be seen with naked eye and is associated with glass cleaning techniques.
2.42 Halo — It is the distortion zone around a spot fault.
2.43 Heat Soaking — It is done on toughened/tempered glass by reheating to a temperature of 290∘ C and keeping it at this temperature for 8 h and cooling it gradually. The glass can break spontaneously and without provocation due to possible impurity of nickel sulphide in basic glass used for toughening/tempering. This risk of spontaneous breakage can be minimised by heat soaking process by forcing such glasses to break during the test itself.
2.44 Heat Strengthened Glass — Glass within which a permanent surface compressive stress has been induced by a controlled heating and cooling process in order to give it increased resistance to mechanical and thermal stress and prescribed fracture characteristics.
2.45 Hermetic Seal — A complete seal (especially against the escape or entry of air which is impervious to outside interference or influence) done on insulating glass units.
2.46 High Activity Area — An area where multiple and major human activity takes place.
2.47 High Risk Area — An area prone to human injury and causality.
2.48 Infill Balustrades — The balustrades in which the supported glass resists an infill pressure and/or point load applied to the glass panel.
2.49 Insulating Glass Unit (IGU) — An assembly consisting of at least two panes of glass, separated by one or more spaces, hermetically sealed along the periphery, mechanically stable and durable.
2.50 Interlayer — Layer or material acting as an adhesive and separator between plies of glass and/or plastic glazing sheets.
NOTE — It can be designed to give additional performance to the finished product, for example impact resistance, fire resistance, solar control and acoustic insulation
2.51 Internal Partition — An interior dividing wall or such portion of an interior dividing wall that is not a door, side panel, shop front or atrium wall.
2.52 Laminated Safety Glass — It is a glass made of two or more pieces of glass which are held together by an interleaving layer or layers of plastic materials.
2.53 Light Transmission — It is the measure of light passing through a transparent or a translucent material.
2.54 Light Transmittance — It is the measure of percent of visible light transmitted through glass pane
which depends on type of body substrate and coating done on glass.
2.55 Linear Defects — They are the scratches and extended spot faults on the glass.
2.56 Manifestation — Any technique for enhancing a person's awareness of the presence of transparent glass.
2.57 Maximum Thickness — The thickness of a pane of glass at the maximum thickness tolerance.
2.58 Minimum Thickness — The thickness of a pane of glass at the minimum thickness tolerance.
2.59 Modulus of Elasticity (Young's Modulus) — This modulus expresses the tensile force that theoretically has to be applied to a glass specimen to stretch it by an amount equal to its original length. It is expressed as a force per unit area (for glass, E=0.7×105N/mm2=70GPa ).
2.60 Monolithic Glass — A single sheet of flat glass which could be either annealed, toughened or heat strengthened.
2.61 Mullion — Vertical framing member separating and supporting two adjacent panes of glass or panels.
2.62 Nominal Thickness — A numeric designation that indicates the approximate thickness of glass.
2.63 Non-Combustible Material — A material not liable to burn itself or to add heat to a fire when tested for combustibility in accordance with good practice [6-8(2)].
2.64 Organic Coated Glass — A sheet of glass coated on one or both sides with an applied organic coating or sheeting.
2.65 Pane — A single piece of glass or plastic glazing sheet material in a finished size ready for glazing.
2.66 Panel — An assembly containing one or more panes of glass.
2.67 Partition — It means an interior non-load bearing divider, one storey in height or part.
2.68 Partly Framed or Unframed Glazing — The panels that have one or more edges unframed.
2.69 Passive Solar Gain — The solar radiation in the form of energy and light which is transmitted through the glazing into the building and which can be utilized as a source of energy to reduce the need for artificial lighting.
2.70 Patterned Glass — A rolled glass having a distinct pattern on one or both surfaces.
2.71 Protective Coating(s) Faults —The faults where the metallic layer is exposed. They can be scratches or loss of adhesion of the protective coating(s).
PART 6 STRUCTURAL DESIGN — SECTION 8 GLASS AND GLAZING
2.72 Rebate — The part of a surround; the cross-section of which forms an angle into which the edge of the glass is received.
2.73 Reflective Coated Glass — It is a glass with reflective coating which uses the principle of increasing the direct reflection to maximize solar energy attenuation. In comparison with clear glass, its absorption of solar energy is also increased.
NOTE — In comparison with float glass surface, these reflecting coatings (due to their composition) exhibit lower level of emissivity which improves their U-value.
2.74 Reflective Silver Coating Faults — It is the fault on reflective silver layer which shall alter the appearance of the silvered glass. They consist of scratches, stains, colour spots and edge deteriorations.
2.75 Residual Protection — It is the protection provided to avoid the human impact on glass. It is provided on the side of glass where there are chances of human impact. It can be achieved by providing a sill structure or a grill inside.
2.76 Shading Coefficient — The ratio of the rate of solar heat gain through a specific unit assembly of glass to the solar heat gain through a single light of 3 mm clear glass in the same environment.
2.77 Sheet Glass — Glass made in large sheet directly from furnace or by making a cylinder and then flattening it.
NOTE — These transparent glass have a glossy, fire-finished, apparently plane and smooth surfaces, but having a characteristic waviness of surface.
2.78 Skylight — A fenestration surface having a slope of less than 60∘ from the horizontal plane. Other fenestration, even if mounted on roof of a building is considered as either a vertical glazing or sloped glazing depending upon the angle of the glazing.
2.79 Sloped Overhead Glazing — A glazing that is inclined at less than 75∘ to the horizontal and located, wholly or partially, directly above an area that may be used by people.
2.80 Solar Energy Absorption — The percentage of the solar spectrum energy (ultraviolet, visible, and near-infrared) from 300 nm to 2 500 nm that is absorbed by a glass product.
2.81 Solar Energy Transmittance (Direct) — The percentage of energy in the solar spectrum, ultraviolet, visible, and near-infrared energy, 300 nm to 2 500 nm, that is directly transmitted through the glass.
2.82 Solar Heat Gain Coefficient (SHGC) — The SHGC is the fraction of incident solar radiation admitted through a fenestration, both directly transmitted, and absorbed and subsequently released
inward through conduction, convection and radiation.
2.83 Spandrel — A non-vision portion of the exterior wall of a building.
2.84 Spot Faults — The nuclei (solid or gaseous inclusions), deposits, crush marks, etc, in the glass. In certain instances spot faults are accompanied by a distortion zone called ‘halo’. The nucleus of the spot fault is measurable.
2.85 Stain — An alteration of the reflective coating characterized by a more or less brownish, yellowish or greyish colouration of zones which can sometimes cover the whole reflective surface.
2.86 Stock/Standard Sizes — The panes of flat glass such as coated, mirror, enamelled glass, etc, supplied with as-cut edges which are intended for further processing. These are generally corresponded with manufacturer's production size.
2.87 Tempered or Toughened Glass — Flat glass within which a permanent surface compressive stress has been induced by a controlled heating and cooling (quenching) process in order to give it greatly increased resistance to mechanical and thermal stress and prescribed fragmentation characteristics.
2.88 Tempered Fire Resistant Glass — A single piece of specially thermally-treated or chemically treated glass, tested for fire resistance for the required duration and having such a stress pattern that the piece when fractured, it reduces to numerous granular fragments, with no large jagged edges.
2.89 Thermal Transmittance (U) — Thermal transmission through unit area of the given building unit divided by the temperature difference between the air or other fluid on either side of the building unit in steady state conditions. It is also called as U-value. Its unit is W/m²K.
NOTES
1 Thermal transmittance differs from thermal conductance insofar as temperatures are measured on the two surfaces of a building unit in the latter case and in the surrounding air (or other fluid) of the material on the two sides, in the former case. Thermal conductance is a characteristic of the building unit whereas thermal transmittance depends on conductance and surface coefficients of the building unit under the conditions of use.
2 In the case of glazing, thermal transmission is taken through the central part of the glazing, that is, without edge effects.
2.90 Through Component/Connection — The internal spacer or fixing that either penetrates through the door-set or openable window from one face to another or directly connects the faces of one to the other.
2.91 Tinted Glass — A normal flat glass to which colourants (normally metal oxides) are added during
manufacturing process to achieve tinting and solar radiation absorption properties. It is also referred to as body tinted glass.
2.92 Toughened Safety (Tempered) Glass — A single piece of specially heat-treated glass, with a stress pattern such that the piece when fractured reduces to numerous granular fragments, with no large jagged edges.
2.93 Transom — A horizontal cross bar connecting two vertical members in a glazing frame.
2.94 Unframed Glazing — A glazing with one or more edges unframed.
2.95 UV Transmittance — The percentage of energy in the ultraviolet (UV) spectrum from 300 nm to 380 nm that is directly transmitted through the glass.
2.96 Vertical Fenestration — All fenestration other than skylights. Trombe wall assemblies, where glazing is installed within 300 mm of a mass wall are considered walls and not fenestration.
2.97 Wired Glass — It is a type of glass into which a wire mesh is embedded during production. Wired glass has an impact resistance similar to that of normal glass, but in case of breakage, the mesh retains the pieces of glass.