When choosing to replace a window, customers come face to face with a variety of types and styles.
The two most popular types of windows for installation in the home are the casement and the sash window.
A casement window is one with hinges on the side or top that allows the window frame to open outwards or inwards.
A sash window is one that has two or more sliding panels, which can overlap each other to create an opening gap.
You can have one or more sliding panels, and they can slide horizontally or vertically, although the latter is by far the most common.
Sash windows have been around since the late 1700s. The design has not been much improved down the years except for the use of modern materials to make them more robust, long-lasting and easier to maintain.
The identity of the original inventor of the sash window is lost in time. Some historians suggest it was an English invention while others prefer to credit the Dutch.
What is known is that early-English sash windows date from the late 17th century but did not become commonplace for about 200 years.
By the Georgian period however they were becoming the window of choice for architects and builders, and in Victorian time it was unusual to use any other design.
It was only with the advent of modern materials for window manufacture that sash windows began to fall out of fashion. But they are still a popular choice in many homes thanks to their elegance and classic design.
Many period properties from the Georgian and Victorian eras were built with sash windows. Modern-day heritage homeowners prefer sash window replacement to ensure they are in keeping with the period style.
A sash window usually has two frames, one positioned above the other so that either panel can slide up or down to create a window opening. Although most sash windows slide vertically, some will open horizontally.
Sash windows often come with a counterbalance weight to help make opening and closing easier. It is usually concealed inside the frame with hidden pulleys. As the pulley system is shielded inside the frame, it rarely breaks down and can outlast the life of the window frame itself.
In a traditional sash window, both frames include several small panes of glass, often called lights, held in place by thin bars. In the early 19th century the technology to create large glass panels did not exist, so the only way to fill a large frame was with small glass panes.
By the time technology developed to allow the manufacture of large panes of glass, the small pane design had become iconic, and the use of small glass panels remained.
Nowadays, sash windows retain the traditional configuration of two frames with six small panels each, although many configurations are possible.
Window installation customers may come across the terms 'single-hung' and 'double-hung' when choosing a sash window.
Both types of sash window look precisely the same; the difference is whether one or both frames are moveable. With a 'single-hung' sash window one frame is permanently fixed in position while the other frame slides over it. With a double-hung' sash window, both panels are moveable.
Single-hung windows tend to be cheaper as there are fewer moving parts, and installation is slightly easier. They can be an advantage if you have many sash windows to replace in an old property.
Double-hung sash windows are a relatively recent innovation. As a result, they may not match original Georgian windows perfectly, but aesthetically there is virtually no difference.
Double-hung windows are more expensive but do have the advantage of being able to open top and bottom. They can also be easier to clean.
Flush sash windows describe windows where the inner and outer frames are flush with each other to give a flat overall surface.
As a style, both flush casement and sash windows have been around for a very long time. Most older properties (where the timber windows have survived) will have windows of this type.
It was in the 1950s that timber windows with a lipped design, where the window frame sits on top of a surround, became popular and the trend continued with the growth of double glazing.
The emergence of window manufacturing materials other than timber, such as PVCu and aluminium, triggered a resurgence in the traditional flush window design.
Flush sash windows have clean, uncluttered lines that look elegant and graceful with sashes fitting flush to the face of the window.
Modern flush sash windows often have inner and outer frames that appear the same width. They are said to have 'equal sightlines', and this can add further to the elegant appearance of a property.