Here’s a range of industry terms that might be used by your builders, architects or throughout the course of installing double glazing into your new home or when you are replacing your existing windows and doors.

Accoustic Instulation

Acoustic insulation, such as double glazing, is used to reduce the nuisance caused by outside noise. Acoustic insulation works by reducing a sound wave’s energy.


Australian Standard covering “Construction of buildings in bushfire-prone areas.“ Incorporates Bushfire Alert Level Ratings (BAL)

Bay Window

An angled combination of three windows that project out from the wall of the home. The windows are commonly joined at 30- or 45-degree angles.


The accumulation of water vapours or droplets is the result of warm, moist air coming in contact with a cold surface and cooling to its dew point temperature. Condensation may occur when a cold window glass or frame is exposed to humid indoor air. Low-conductivity, insulated glass and warm-edge spacers reduce condensation. Read more about condensation.

Double Hung Window

A window that has two operable sashes which slides vertically.

French Door

A particular design of swing door, all or a large part consisting of divided glass panes. More information on door opening styles is available here.

I.G. Unit (Insulating Glass Unit)

Two or more plates of glass separated by a spacer and hermetically sealed at the glass edges.


A horizontal framing member placed across the top of the rough opening of a window or door opening to prevent the weight of the wall or roof from resting on the window frame.


A vertical or horizontal connecting unit between two or more windows.

Patio Door

A glass door that slides open and closes on adjustable tandem rollers. Available in 2- or 3-lite configurations with the operable panel available in any position.


The horizontal, bottom section of the main frame.

Slider Window

A window in which the sash move horizontally. Sliders are available in a 2- or 3-lite configuration, with the 3-lite having operable end vents


Material placed between two or more pieces of glass in order to maintain a uniform width between the glass, and prevent sealant distortion.

Triple Glazing

Glazing that incorporates three panes of glass, enclosing two separate air spaces.



Vinyl Council of Australia. View the website

Air Space

The space in the cavity between two panes of glass in an insulated glass unit.


Australian Glass and Window Association. View the AGWA website here.

Casement Window
A window with a side-hinged sash that opens outward for ventilation. View window opening styles here.

A space which protrudes from the roof, usually including one or more windows.


An architectural term referring to the arrangement of windows in a wall.


A pliable, flexible continuous strip of material used to affect a watertight seal between a sash and frame much like the seal around a refrigerator door.



Vertical sections of the main frame.

Low E (Emissivity) Glass

Glass with a transparent metallic oxide coating applied onto or into a glass surface. The coating allows short-wave energy to pass through but reflects long-wave infrared energy which improves the U-value.

Obscure Glass

Glass that has been made translucent instead of transparent.

Safety Glass

A strengthened or reinforced glass that is less subject to breakage or splintering, such as glass for storm doors and some windows

Single Hung Window

A window in which one sash slides vertically and the other sash is fixed.

Sloped Sill

The sill of the window that has a downward slope to the outside. This sill has sufficient degree of slope to aid in water runoff.


Tempered Glass

Glass with a surface compression of not less than 10,000 psi, or an edge compression of not less than 9,700 psi. When broken, the glass breaks into pebbles instead of shards


UPVC Window Alliance. View the website.

Visible Light Transmittance

The percentage of light that is transmitted through glass in the visible light spectrum (380 to 720 nanometers). The higher the number the higher the percentage of visible light transmitted through the window.


Argon Gas

An odourless, colourless, tasteless, non-toxic gas that is six times denser than air. It is used to replace air between the glass panes to reduce temperature transfer.

Awning Window

A top-hinged window that swings outward for ventilation. View window opening styles here.


A window near the top of an outside wall.

Double Glazing

Glazing which incorporates two panels, separated with an air space, for the purpose of thermal and acoustic insulation.


That part of a window assembly surrounding the sashes or fixed glazing.



The process of sealing the glass to the sash

Laminated Glass

Specially designed glass where two panes of glass are bonded to a durable interlayer, providing increased safety, UV protection and noise reduction. If the window or door gets broken the glass will adhere to the plastic interlayer-preventing glass fallout in the home.


Main Frame

The head, sill and jambs sections of a window.


A sheet of glass for glazing a window.


The part of the window which contains the glass.


Single-strength Glass

Glass with a thickness of approximately 3/32

Solar Heat Gain Coefficient (SHGC)

The percentage of heat gained from both direct sunlight and absorbed heat. The smaller the number, the greater the ability to reduce solar heat gain.


Tilt and Turn Windows

Windows with fittings that make it possible to rotate the window through 180º so that the exterior pane is facing inwards. This is very practical when washing windows. More window opening styles available here.


Amount of heat transferred through a material. The lower the U-value, the slower the rate of heat flow and the better the insulating quality.

Weep/ Drainage Holes

Slots or holes in the sill (bottom) member of the sash frame that allows water to escape. Weep flaps add a drainage cap to keep insects out

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