What Are UPVC Sash Windows?


Materials Used

Sash windows have been around for more than 400 years. Traditionally they were made out of timber, but recently different materials have been used.

Originally they were made from hardwood. In England oak was traditionally used in all areas of construction, and sash windows are no exception, although ash was another popular choice. These timbers are strong and – properly maintained – can be very long lasting. However, in modern times hardwoods are expensive and their use is the major cause of deforestation across the globe. Although modern timbers are supposed to be sourced responsibly, it has been estimated that over 60% of the UK’s tropical timber imports come from illegal logging.

Modern Softwood Sash

Because of this, modern timber sash windows are usually made from faster growing softwoods, such as redwood and douglas fir. Softwoods are much cheaper than hardwood, and are more likely to be responsibly sourced. However, softwood doesn’t last as long as hardwood, especially if it isn’t regularly treated and well maintained.

In the past 30 years other materials have been used to make the windows. First, aluminium was introduced, and has been used to make a wide range of sashes. At one end of the scale are very basic and simple, low cost unbalanced vertical sliders, often used in public buildings such as schools and offices. At the other end of the scale are sophisticated, fully featured and technologically advanced modern aluminium sashes, which come with a price tag to match.

In the mid 1980s the first uPVC sash windows were  Double Glazing Sash Windows Kent developed. From this outset these were designed to replicate traditional timber sashes as closely as possible. The first commercial uPVC sashes were developed by Rehau in association with the Peabody Trust in London – one of the capital’s largest housing associations, with thousands of period properties in the portfolio.

Sash Window Styles

Unlike casement windows, sash windows are, basically, all much the same; taller than they are wide and two sashes, on above the other. However there are variations on the theme. Double and triple window combinations are quite common, particularly in period properties. Arches and curves are another common feature – shallow curves above every window were particularly popular in Victorian properties. Less common are windows with unequal sash heights – typically the top sash is one third of the overall window height, while the bottom sash is two thirds. These tend to be found on smaller windows from the Georgian period.