Comprehensive definitions of glass industry terms for replacement double & triple glazed units
Abbreviation of decibel, the unit of measurement of sound.
Approved Document L of the Building Regulations for England and Wales relates to the conservation of fuel and power.
Two panes of glass separated by a cavity and hermetically sealed in a factory, to provide thermal and/or acoustic insulation.
The reorientation of daylight by means of systems incorporating reflective and adjustable surfaces or grilles. Day lighting systems re-direct natural light, distributing diffused light in a room space and prevent strong areas of glare.
Symbols which, combined with a period of time, define the classifications for fire resistance. E: ability of a glazed material to prevent the spreading of flames or hot gases (integrity). EI: ability of a glazed material to limit heat transfer to the unexposed surface (integrity and insulation).
The distance between the edge of the glass and rebate.
The distance of the edge of the glass and sight line.
One face of the glass is enamelled, by applying a ceramic frit that is then fired into the surface of the glass at high temperature. Depending on the cooling regime employed, this then results in either a heat-strengthened or thermally toughened glass.
The difference between the amount of heat gain and heat loss through glazing. Also known as the "Effective U-value".
Conventional double glazing provides thermal insulation. Double glazing comprising a low-emissivity glass provides enhanced thermal insulation.
Emissivity is a surface characteristic of a material. It is the relative ability of a surface to absorb and emit energy in the form of radiation. Low-emissivity (Low E) coatings reduce the surface emissivity of the glass.
The front or face of a building.
The term used to describe the surfaces of the glass in numerical order from the exterior to the interior. The exterior surface is always referred to as face 1. For a double-glazed unit, the surface of the outer pane facing into the cavity is face 2, the surface of the inner pane facing into the cavity is face 3 and the internal surface of the inner pane is face 4.
The ability of a building material to provide an effective barrier against the passage of flames, smoke and toxic gases and/or to reduce the transmittance of radiated heat.
High quality, transparent flat glass manufactured by means of the float tank procedure that is floating molten glass on a "tin-bath" at extremely high temperature.
Abbreviation or symbol for Solar factor according to EN 410, formerly abbreviated to SF or TT.
Pre-formed glazing materials used for bedding or securing glass and to separate the glass from the frame or fixings.
The securing of glass into prepared openings. It also refers to the collective elements of a building comprising glass, frame and fixings.
The prevention of people falling wherever there is a change in floor level by means of a permanent barrier.
Glass which has been heat-treated in order to increase its mechanical strength and resistance to thermal breakage. It has fracture characteristics similar to that of ordinary annealed glass and is not classed as a safety glass to BS 6206.
Flat glass is described as high-performance when it features a low-emissivity coating that achieves an emissivity level of 3% or less.
An additional form of heat-treatment, which is carried out after the thermal toughening process in order to reduce the risk of spontaneous breakage of toughened glass in service due to "nickel sulphide inclusions".
When related to safety glazing this is the classification of safety glass when tested to BS 6206.
Glazing that is inclined at an angle between horizontal and 75° from horizontal.
See Double-glazed Unit.
The term applied to the material used in laminated glass to bond the glass leaves together. It can be either PVB, cast-in-place resin or intumescent.
Two or more sheets of annealed or heat treated glass are separated by one or more plastic inter layers (normally PVB) and subjected to heat and pressure, in order to ensure perfect adhesion between constituent elements.
The proportion of the visible spectrum that is transmitted through the glass.
Referring to extra clear glass, which has a reduced iron oxide content in order to lessen the green tinge inherent to ordinary clear float glass.
See Emissivity
A butyl-based sealant, for example polyisobutylene, applied to the edges of the spacer bar during assembly into double-glazed units, to ensure a watertight and airtight seal around the perimeter of the unit.
The plastic interlayer incorporated into laminated glass in order to ensure good adhesion and the mechanical and safety breakage characteristics of the glass.
A specialist metallic coating is applied to the glass "on-line" during the float glass manufacturing process. The high temperatures involved result in the metallic oxides fusing into the surface of the glass through pyrolysis and effectively forming part of the glass.
Glass which must have passed an impact test (BS 6206:1981) and either must not break or must break safely.
Glass with a photocatalytic and hydrophilic coating. The coating harnesses the dual-action of UV light and rain (or water) to break down organic dirt and reduce the adherence of mineral material. The glass stays cleaner for longer and is easier to clean.
The percentage of total solar radiant heat energy transmitted through glazing (the sum of energy transmitted directly and energy absorbed and re-emitted to the interior).
Generally an aluminium bar along all edges of a double-glazed unit, filled with desiccant, which separates the two panes of glass and creates a cavity.
An advanced metallic coating is applied to the glass "off-line" or after the float glass manufacturing process, by a technique called magnetically enhanced cathodic sputtering under vacuum conditions.
A type of metal frame that incorporates an isolating material of low thermal conductivity located between the inner and outer parts of the frame in order to reduce the rate of heat loss through the frame.
The term used to describe the internal stresses created when glass is subjected to variations in temperature across its area. If the temperature differentials in the glass are excessive, the glass may crack. This is referred to as thermal breakage or fracture.
Glass that has been subjected to a controlled heating and cooling process, in order to significantly increase its resistance to mechanical and thermal stress. Through the thermal toughening process, the glass attains its safe-breakage characteristics.
Three panes of glass separated by cavities and hermetically sealed in a factory, to provide maximum thermal insulation performance.
A measure of the rate of heat transferred (heat lost or gained) through glass by the combined effects of conduction, convection, and radiation when there is a temperature difference between the inside and outside of a building.
The percentage of solar energy in the form of ultra-violet radiation transmitted by glazing.
Glazing which is either true vertical, or within 15° either side of true vertical.