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Helpful Resources | Terminology



Scientific study of sound


Australian Fenestration Rating Council

Air Gap

Air space between the panes of glass in an insulating glass unit (IGU).  Also known as a cavity, airspace or spacer width, even when another gas (eg argon) is used in the cavity instead of air.

Air Infiltration (air-leakage)

The amount of air leaking in and out of a building through cracks in walls, windows and doors.

Argon Gas

An inert, non-toxic gas used in insulating glass units to reduce heat transfer


Manufacturing of float glass and obscure glass, where the process of controlled cooling down to help prevent residual stresses in the glass.


Australian Standard

Aspect Ratio

The ratio of the longer side of a glass panel to the shorter side of glass panel


The reduction of sound intensity (or signal strength) with distance. Attenuation is the opposite of amplification, and is measured in decibels


Australian Windows Assocation


A vertical member supporting a handrail and forming part of a balustrade


A framed or unframed barrier between handrail and floor level

Bel (B)

Bel was originally called a transmission unit or TU, but was renamed in 1923 or 1924 in honor of the Bell System's founder and telecommunications pioneer Alexander Graham Bell.


The manufacturing process used for bent glass

Bent Glass

The process where glass is produced by heating annealed glass to a pint where it softens and then it can be pressed or sagbent over formers. Bends can be made in one or two planes. Bending can be incorporated in the toughening process. Bent glass can be toughened or laminated.


A sloping edge on a glass sheen, mostly used in glass for mirrors


The process of grinding and polishing a sloped angle on the face of the end of flat glass which results in a decorative edge appearance to the glass


The deposit of water vapour from the air on any cold surface whose temperature is below the dew point, such as cold window glass or frame that is exposed to humid indoor air.  (Liquid forming on the glass)


Heat transfer through a solid material by contact of one molecule to the next.  Heat flows from a higher-temperature area to a lower-temperature one.


A heat transfer process involving motion in a fluid (such as air) caused by the difference in density of the fluid and the action of gravity.  Convection affects heat transfer from the glass surface to room air, and between two panes of glass.


Cut to size term used for glass


Tool used for cutting glass and can also refer to the person who cuts glass




A unit of measure for decibels. The A-weighted scale indicates the human ear's sensitivity to various frequencies..

Decibel (dB)

Common measurement of sound level. A decibel (abbreviated dB) is defined as one tenth of a bel.

Decorative Glass

Clear or patterned glass for a decorative effect, used for stained glass, leadlights, sand blasted, acid-etched, embossed and printed glass. Some examples federation style windows and doors or leadlight pictures in churchs


Extremely porous crystalline substance used to absorb moisture from within the sealed air space of an insulating glass unit

Dew Point

The temperature at which condensation of moisture begins when air is cooled

Double Bevel

The surface edge of the glass on the face that is bevelled, the bevel consisting of two intersecting planes

Double Glazed Unit (DGU) also known as IGU



Integrated Glazing Unit - IGU's consists of two or more panels of glass separated by an air space and some type of spacer around the edges. The spacer contains a desiccant (drying agent) which eliminates moisture vapour in the cavity. The combination of the two panels of glass and the trapped air is what makes IGU's a superior energy efficient method of glazing. The IGU can perform a thermal and noise insulating function. The narrowest air gap used is 6mm, but wider gaps (10-20mm) will improve performance. For greater performance one of the glass panels should have a low-e coating and argon gas between the panes.

Dry Glazing

A method of securing glass in a frame by use of a dry, preformed resillient gasket without the use of a compound


Grinding the edge of flat glass to a desired shape or finish


The ability of material to emit radiant energy (heat). Emittance is the ratio of the total radiant energy emitted by a given surface to that emitted by an ideal black body at the same temperature. To emit is to give out, to discharge - in regards to glass, essentially to re-radiate absorbed energy (heat)

Exterior Glazed

Glass set from the exterior of the building

External Glazing

Glazing either side - the exposed side of the outside of a building


Any type of glass that is used on a building, that is a glass panel, window, glass door, glass curtain wall, skylight etc

Finished Size

The glass after processing and cutting is completed

Flat Glass

General term for float glass

Float Glass

A flat transparent glass that gives a clear clear vision and reflection


Cycles per second of sound.  This is expressed in Hertz (Hz)


Raw materials mixed together and melted to form glass



Gas Fill

The use of gases other than air (such as argon, krypton, xenon etc) in a sealed insulating glazing unit, for the purpose of reducing conductive/convective heat transfer


Glass panels that are placed into prepared openings, eg windows, door panels, curtain walls etc

Glazing Bead

Strip or trim surrounding the edge of the glass in a window or door that holds the glass in place.

Heat Absorbing Glass

Glass containing chemails (with gray, bronze or blue green tint) which absorb light and heat radiation and reduce glare and brightness (that is, Tinted Glass)

Heat Gain/Heat Loss

Heat Gain - The transfer of heat from outside to inside by means of conduction, convection and radiation through all surfaces of a building

Heat Loss - The transfer of heat from inside to outside by means of conduction, convention and radiation through all surfaces of a building

Heat Relecting Glass

Surface treated glass that reduces solar heat gain through reflection

Heat Resisting Glass

Glass with low co-efficient of expansion, which is therefore less liable to thermal shock.

Heat Strengthened Glass

Glass that has been heat treated to a state less than that of fully tempered glass (this is not considered a safety glass)

Heat Transfer

Heat transfer can be through one of three process conduction, radiation and convention

Heat Treated

Glass which is heat treated or heat strengthened or fully toughened (known as fully tempered glass)


Frequency cycles per second of sound

IGU - Integrated Glazing Unit

See Double Glazed Unit


Plastic material used between two or more glass panels in the manufacturer of laminated safety glass to bond the glass together



Laminated Glass

A composite unit of glass and interlayer material. Note that laminated glass will crack and break under sufficient impact but the glass will adhere to the plastiic interlayer instead of falling apart

Laminated glass is constructed by combining two panes of glass fused together with a middle layer of Polyvinyl Butylenes Film (PVB). PVB acts like a bonding agent to hold broken glass together. This feature creates an effective barrier against entry and reduces the chances of flying shards of glass.


Specific width of furnance which designates the sizes available from the glass float line


Refers to the ability of a material to emit radiant energy. To emit means to give out, to discharge. In the case of glass, essentially, to reradiate absorbed energy (heat).


In other words, low-e coating is equivalent to adding another pane of glass to the multipane unit.

Low Emittance (Low-E) Coating

A thin (<100mm thick) metal, metal oxide or multilayer coating deposited on a glazing surface to reduce its thermal infrared emittance and thereby reduce radiative heat transfer. A low e coating increases a window's ability to insulate (low u value). In other words, it has a microscopic coating applied during glass manufacturer and is durable hard coat bonded to the glass. It is measured from 0 to 1, the lower the number the better insulating properties the low-e glass has.

However, while a low-e coating on simple single glazing reduces that part of the heat transfer, it does nothing to reduce conductive and convective heat flow. A much better solution is to reduce all three forms of heat transfer. To do this, you need an insulating glass unit (IGU or double-glazing).




Specific marking on the glass so it helps minimise the potential for human impact or injury, that is motifs on glass - see AS1288-2006 Glazing Code

Maximum Thckness

The maximum thickness tolerance for a panel of glass

Minimum Thickness

The minimum thickness tolerance for a panel of glass


Smallest particle of substance that retains chemical and physical properties of the substance and is composed of two or more atoms, a group of like or different atoms held together by chemical factors

Monolithic Glass

A single light or piece of glass the opposite of laminated glass or a double glazed unit .

Monolithic glass is the most basic of glass forms. It is simply a single piece of glass constructed using one glass thickness. Monolithic glass is produced using either the annealed, heat-treated or tempered glass float method.


National Average Climate (Australian)


National Fenestration Rating Council (International)


The word "Noise" is derived from the Latin word "nausea", meaning seasickness.  Noise can be defined as electrical or acoustic activity that can disturb communication, or anything that prevents a clear signal or message being transmitted.

Noise Reduction Co-efficient

The measure of the ability of material to absorb sound. NRC is generally a number between 0 and 1. A material with an NRC rating of 1 absorbs 100% of incoming sound, ie no sound is relected back fromt he material.

Noise Reduction

The quantitative measure of sound isolation between spaces is called Noise Reduction(NR)

Noise Level Reduction

NLR is used to describe the reduction of environmental noise souces, eg aircraft.

Obscure Glass

Any textured glass(frosted, etched, fluted, ground etc) used for privacy, light diffusion or decorative effects


The interval between two points where the frequency at the second point is twice the frequency of the first.



Single sheet of glass

Patterned Glass

Glass that has a patterned on one or both sides, normally used for diffusing light, privacy, bathrooms and decorataive glazing - often referred to as obscure glass

Polyisobutylene (also known as Butyl rubber)

Synthetic rubber or elastomer.  Is impermeable to air and used in many applications requiring an airtight rubber. Polyisobutylene is used in making adhesives, agricultural chemicals, fiber optic compounds, caulks and sealants, cling film, electrical fluids, lubricants (2 cycle engine oil), paper and pulp, personal care products, pigment concentrates, for rubber and polymer modification, as a gasoline diesel fuel additive, and even in chewing gum. The first major application of butyl rubber was tire inner tubes This remains an important segment of its market even today.


A sulphide having more than one atom of sulphur in the molecule

Processed Glass

Glass where the surface has been altered by etching, sandblasting, chipping, grinding, etc and is used to change its light diffusion or for decorative effects and it can then be further treated for edge work, tempered, stained glass etc after forming

Pyrolytic Coating

Coating applied during the manufacture of glass to make it an extremely hard and durable surface


The transfer of heat in the form of electromagnetic waves from one separate surface to another. Energy from the sun reaches the earth by radiation, and a person's body can lose heat to a cold window or skylight surface in a similar way.


Re-radiation of heat stored in the glass contributes to the total heat gain through the window.


The higher the R-value the termal resistance of the glazing system, meaing the less heat transferences allowed. It is the reciprocal of the u-Value



Weighted sound reduction index that uses airborne sound and is viewed as being more appropriate for rating the attenuation of external low frequency noise, eg traffic



Sound Transmission Class - measuring internal sound transmission

Safety Glass

Glass that has been manufactured or treated into a form that reduces the likelihood of personal injury through cutting or piercing if the glass should be broken by human or other type of impact. Safety A Grade glass is either toughened or laminated glass

Solor Energy Transmittance

Percentage of ultra-violet light, visible and infra-red energy within the solar spectrum that is transmitted through the glass

Shading Co-efficient (SC)

The ratio of Solar Heat Gain Co-efficient (SHGC) or a glazing system, for a particular angle of incidence, to that of reference, clear single 3mm glass, under the same conditions. The latter has a Solar Heat Gain Co-efficient of 0.87, so that the relationship between SC and SHGC for tinted, single glass is SC = SHGC/0.87


The Solar Heat Gain Coefficient (SHGC) measures how well a window blocks heat from sunlight. The SHGC is the fraction of the heat from the sun that enters through a window. SHGC is expressed as a number between 0 and 1. The lower a window's SHGC, the less solar heat it transmits, and the greater its shading ability

Tempered Glass

Treated glass that is strengthened by reheating it to just below themelting point and then suddenly cooling. When shattered it breaks into tiny pieces, it is five times stronger than annealed glass and is mainly used in glass doors



U-value is the measure of heat loss or gain due to the differences between inside and outside air temperature. The lower the U value the better the insulating performance.




The distance between two similar points on a curve


Windows Energy Rating Scheme

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