Windows Glossary

Bay windows are a specific window style that protrudes from the wall of a property, with the brick wall below the window being the same shape as the window so, therefore, supporting the weight of the window itself.
Typically, bay windows feature 3 windows; a picture window with two other windows on either side, that are fitted at angles of 90, 130, and 150 degrees.

Windows that are made-to-order for a particular customer. Bespoke windows are generally not the conventional rectangular window shape.

The window opens from the bottom of the frame, e.g. a sliding sash window or a bathroom window.

The horizontal bar across the bottom of the window frame, which sits above the cill.

Bow windows are recognised by their curved shape and the way they extend outwards from a building. Typically, bow windows feature 4-5 windows that are fitted at an angle of around 10 degrees.

A window sash that generally opens outwards from the side of the frame, available in uPVC, timber, and aluminium.

The window sash revolves on the central hinge. Typically fully reversible, centre hinged windows allow for a wider opening and easy cleaning.

The lowest horizontal ledge or bar that forms the bottom of the window frame.

Designed to reduce heat loss, noise, and UV rays, double glazing consists of two panes of glass with a gas-filled space in-between.

A double hung window has two moveable sashes, allowing both parts of the window to open and shut, e.g. a sliding sash window.

A fixed light is a window that cannot be opened, generally used to enhance far-reaching views and increase light and warmth.

Flush sash windows fit sleekly into the window frame, instead of slightly overlapping the window frame.

Glazing bars divide and hold individual panes of glass securely in place. Often designed into a grid pattern, they are typically used to create a heritage look.

The first horizontal bar that forms the top of the window frame.

Heritage windows are suited to period and historic properties and are either made from natural timber or high-performance uPVC that replicates the authentic appearance of timber windows. Heritage windows are designed to meet conservation guidelines.

Leaded glazing bars are the thin strips of wood or metal that were originally used to separate and hold panes of glass in place. Today they provide a heritage-inspired, decorative effect – the most popular designs being diamond and square bars.

Fitting inside the window frame, the sash is the section that moves and holds the glass panes safely in place.

A single pane of glass fitted over existing single glazed windows, ideal for windows that cannot be altered due to planning restrictions, e.g. listed buildings and conservation areas.

The window opens out from the side of the frame, e.g. a casement window.

A single hung window has one moveable sash, keeping the top sash in place and the bottom sash in full operation, e.g. a sliding sash window.

A window that consists of one or two movable panels, that vertically slide open and closed via a traditional counterweight system or a modern spring balance arrangement. Often divided into sections of 4 or 6, these windows are commonly associated with Georgian and Victorian architecture and are available in timber or uPVC profiles.

The vertical edges of the window.

Stormproof windows, also known as 'lipped casements', slightly overlap the window frame to stand slightly apart from the window.

A window that can either be tilted via a top or bottom hinge, offering a small gap at the top for safe ventilation or opened inwards from the side of the frame (like a traditional casement window) for easy cleaning. These types of windows are particularly popular in high-rise buildings or homes where exterior access is difficult.

The window swings open from the top of the frame, e.g. a fire escape window or a roof window.

The horizontal bar across the top of the window frame, which sits underneath the Head Jamb.

A trickle vent is a small slot or opening on a window that allows a room to remain ventilated when the window is closed.

Designed to reduce heat loss, noise and UV rays even further, triple glazing consists of 3 panes of glass with two gas-filled spaces in-between.

U-values measure how easily heat can pass through a material; the lower the U-value, the more efficient the material. By law, window manufacturers in England and Wales must demonstrate that their windows comply with the latest energy efficiency requirements, which is usually done by declaring the windows' U-value. U-values for windows and doors must meet minimum criteria, as stated by the latest building regulations.

The vertical bars that form the sides of the window.

Based on a scale of G to A+ (A+ being the most efficient), the Window Energy Rating (WER) indicates how energy efficient your windows are.