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Origin Doors

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Glossary of Windows Terminology


The U-value is a measure of how effective a material is as an insulator. The more effective the material, the lower the U-value will be, meaning more heat or cooling is kept inside. Building Regulations often specify that windows should not exceed a certain U-value, which can differ depending on whether the windows are being fitted into an addition/new build or replacing old windows.

Origin Windows exceed current Building Regulations, achieving a U-value of 0.24 for triple glazing and 0.26 for double glazing.


Aerogel is a solid and porous material derived from gel. The liquid component of the gel is replaced with gas, creating very low thermal conductivity. Aerogel is also sometimes known as ‘frozen smoke’ or ‘solid air’ because its translucent.

Aerogels can be made out of wide variety of substances, but they will all have the same kind of geometric structure. The type of aerogel used in Origin Windows offers the lowest thermal conductivity of any known solid material - it’s even used for space shuttles and space suits.

Casement window

Hinged by one or more hinges at the side of the frame, casement windows are typically installed as a single or a pair within one frame. Casement windows are held open using a casement stay.

Awning window

An awning window is almost identical to a casement window, except that it’s hinged from the top of the frame rather than the sides. This means an awning window will open outwardly, which is especially useful for ventilation.

Glazing Bead

The glazing bead is of a piece aluminum that firmly holds the glass panel in place, with the help of a wedge gasket. It typically sits in the corners of the window, out of sight.

Double and triple glazing

Double glazing consists of two panels of glass separated by a vacuum filled with gas in order to trap air and reduce the transfer of heat between the indoors and outdoors. Triple glazing is the same idea but using three panels of glass instead.

Also known as ‘insulating glass’, double and triple glazing units are commonly manufactured with a thickness range of 3-10mm.

French windows

Frequently used in modern properties, French windows have two large panels of glass that extend the full length of the window and open outwardly.

Egress windows

Egress windows are windows big enough to allow emergency exits in the case of fires. They must meet minimum requirements as specified in building regulations.

Gable window

A gable window is triangular in shape and designed to fit in the space where two sloping roofs of a building meet.


A mullion is a vertical part of the window frame that forms a division between the different sashes or fixed windows. It provides structural support.


The sash of a window is the operational part of casement and awning windows. The glass fits into the sash. Fixed frames do not have sashes unless non-operational sash material is added to look like an operational window.

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