Allder Group - Glass and Locks

Allder Group - Glass & Locks

Types of Windows

Double-hung sash window

This sash window is the traditional style of window in the UK with two parts (sashes) that overlap slightly and slide up and down inside the frame. The two parts are not necessarily the same size. Nowadays, most new double-hung sash windows use spring balances to support the sashes, but traditionally, counterweights held in boxes on either side of the window were used.

Single-hung sash window

One sash is movable (usually the bottom one) and the other fixed.

Horizontal sliding sash window

Has two or more sashes that overlap slightly but slide horizontally within the frame

Casement window

A window with a hinged sash that swings in or out like a door comprising either a side-hung, top The casement window is the main type of window now found in the UK

Louvered window

Also known as a louvered window consists of parallel slats of glass or acrylic that open and close like a Venetian blind.

Church window

A window set in a roof structure or high in a wall.


A flat or slope window built into a roof structure that is out of reach.

Roof lantern

A roof lantern is a multi-paned glass structure, resembling a small building, built on a roof for day or moon light.

Bay window

A multi-panel window, with at least three panels set at different angles to create a protrusion from the wall.

Oriel window

A window with many panels. It is most often seen in Tudor-style houses and monasteries. An oriel window projects from the wall and does not extend to the ground. Oriel windows started as a form of porch.

Fixed window

A window that cannot be opened, whose function is limited to allowing light to enter (Unlike an unfixed window, which can open and close). Clerestory windows are often fixed. Transom windows may be fixed or operable.

Picture window

A very large fixed window in a wall, typically without glazing bars, or glazed with only perfunctory glazing bars near the edge of the window. Picture windows are intended to provide an unimpeded view, as if framing a picture.

Emergency exit/egress window

A window wide enough due to special hinges and low enough so that occupants can escape through the opening in an emergency, such as a fire.

French window

A French window, also known as a French door is really a type of door but one which has one or more panes of glass set into the whole length of the door, meaning it also functions as a window. They are very common, usually overlooking a garden or patio.

Insulated Glazing or Double Glazing

Double Glazed Units (DGUs) are manufactured with glass in range of thickness from 4 mm to 10 mm or more in special applications. Laminated or toughened glass may also be used as part of the construction. Most units are manufactured with the same thickness of glass used on both panes but special applications such as improved acoustic requirements or security may require wide ranges of thicknesses to be incorporated in the same unit.

For ease of description the surfaces of a double glazed unit are named according to the following convention: Surface 1 (facing outside), Surface 2 (inside of outside pane), Surface 3 (outside of inside pane) and Surface 4 (inside surface of inside pane).

The glass panes are separated by a "spacer". A spacer is the component, or piece, used in window manufacturing that separates the two panes of glass in a double glazed unit, and seals the air space between them. Originally spacers were made of aluminum,. However, metal spacers act as a heat conductor, reducing the ability of the DGU. This may result in water or ice forming at the bottom of the sealed unit because of the heating/cooling loss through the window. To reduce heat transfer through the spacer and increase overall thermal performance, the spacer may be constructed of a less-conductive material such as structural foam. New technology has emerged to combat the heat loss from traditional spacer bars. These are called “warm Edge” spacer bars

Typically, spacers are filled with or contain desiccant to remove moisture trapped in the air space during manufacturing, thereby lowering the dew point of the air in that space, and preventing condensation from forming on surface 2 when the outside glass pane temperature falls.

DGU’s are manufactured on a made to order basis on factory production lines. The width and height dimensions, the thickness of the glass panes and the type of glass for each pane as well as the overall thickness of the unit must be supplied to the manufacturer. On the assembly line, spacers of specific thicknesses are cut and assembled into the required overall width and height dimensions and filled with desiccant. On a parallel line, glass panes are cut to size and washed to be optically clear. An adhesive sealant (polyisobutylene or PIB for short)is applied to the face of the spacer on each side and the panes pressed against the spacer. If the unit is gas filled (Argon or Kryptonite), two holes are drilled into the spacer of the assembled unit, lines are attached to draw out the air out of the space and replacing it with the desired gas. The lines are then removed and holes sealed to contain the gas. The more modern technique is to use an online gas filler, which eliminates the need to drill holes in the spacer. The units are then sealed on the edge side using either polysulphide or silicone sealant or similar material to prevent humid outside air from entering the unit. The desiccant will remove traces of humidity from the air space so that no water appears on the inside faces of the glass panes facing the air space during cold weather. Some manufacturers have developed specific processes that combine the spacer and desiccant into a single step application system.[2]

The life of an DGU varies depending on the quality of materials used, size of gap between inner and outer pane, temperature differences, workmanship and location of installation both in terms of facing direction and geographic location. DG units typically last from 10 to 25 years, with windows facing south (Northern Hemisphere) or the north (Southern Hemisphere) often lasting less than 12 years. DGUs typically carry a warranty for 5 years depending upon the manufacturer. If DGUs are altered (such as installation of a solar control film) the warranty may be voided by the manufacturer. Also failing to keep up with the general maintenance of paint work on timber frames will null and void warranty. Timber frame installations are guaranteed up to two years. PVCu and aluminium up to five years

For a standard construction DG unit, condensation collects between the layers of glass when the perimeter seal has failed and when the desiccant has become saturated, and can only be eliminated by replacing the DGU..

Large temperatures differences between the inner and outer panes stresses the spacer adhesives which can eventually lead to it failing. Units with a small gap between the panes are more prone to failure because of the increased stress. A very badly failed unit can eventually fill with water

Acoustic Glazing

In some situations the insulation is for sound control. In these circumstances a large air space improves the noise insulation quality or sound transfer. Asymmetric double glazing, using different thicknesses of glass rather than the conventional symmetrical systems (equal glass thicknesses used for both panes) will improve the acoustic performance of the DGU. More recently, acoustic laminated glass types have been produced, in varying thickness’s, which can be used in a single glazing applications as well as in double glazed to increase the acoustic performance considerably. We carried out a large installation of acoustic laminated single glazing on “Millionaires Row” as it became know, on Kensington High Street, London, where the original Georgian appearance of the properties had to be maintained, making it impossible to use double glazed units. The resulting internal db rating reduction was quite incredible.

Leaded Lights & Stained Glass

Leaded Lights or lead lights are made up from small panes of glass joined together with lead H section. This is known as came. They individual pieces of lead are then soldered together. Sometimes, especially on larger lead lights, short lengths of copper wire are soldered into The whole panel is then cemented together with a type of putty being pushed into the joints with a scrubbing brush. This is then covered with a white powder (hardener) that removes the moisture contained within the cement. It is then left to cure or set and neatly knifed off. The leaded light is finally cleaned up, polished and blacked up with Zebo™ grate polish.