Composite Windows

Early in the second half of the twentieth century, extruded aluminium windows were introduced to the United Kingdom, some say from Canada, some from Scandinavia. Either way it was the start of a revolution in the design of composite windows for the UK which had predominantly only hardwood or softwood frames to choose from prior to this.

Initially the aluminium frames were fixed directly to the brickwork but it soon became apparent that aluminium windows and doors performed more efficiently if they were installed in a timber sub-frame prior to installation – and composite windows were born.

Aluminium composite windows and doors are still available for domestic properties but are more expensive than uPVC windows and doors due to the method of manufacture, longer installation time and lower manufacturing quantities. Advancements have been made however and modern aluminium windows and doors tend to have thermal breaks so that the inner surface is not as cold as the outer surface – hence reducing condensation on the inside of the frames. They also tend to be powder coated to various different colours, rather than having a plain aluminium appearance.

Specialist manufacturers have also come up with variations on this theme with some companies offering windows which include virtually maintenance-free aluminium on the outside and timber for its aesthetic qualities on the inside.

Ever since the first white uPVC window was manufactured and installed, companies have strived to make a uPVC window look like a timber one. To achieve this, woodgrain effect foils were produced which attempted to replicate the appearance of various types of timber.

These foils were bonded onto the surface of the uPVC extrusions prior to fabrication, either onto both sides of the frame or just on the outside. The early versions of woodgrain effect uPVC windows and doors attempted to provide the appearance of mahogany, though with little success as they were not UV stable and the frames tended to fade or discolour over time. Foils with UV filters were produced to prevent discolouration but the poor interpretation of real mahogany remained.

With advancements in technology, more realistic woodgrain foils were produced and now versions of rosewood, oak and other types of timber began to appear. They also had a definite grained feel to the surface, rather than having a flat, unrealistic appearance.

Nevertheless, although these new foils were more realistic interpretations of the various types of timber, manufacturing processes of uPVC windows ensured that they still didn’t have the look of genuine hardwood.  One reason for this is that when uPVC windows and doors are fabricated, the frames have diagonal welds in the corners and at the intersection of transoms and mullions.

These are a distinct giveaway for a uPVC window frame masquerading as a hardwood one. Although little could be done about the manufacturing processes of uPVC windows to improve the situation, companies also recognised that sometimes real hardwood windows were painted rather than stained. This led to foiled profiles for uPVC windows and doors in traditional colours such as cream, pale green, grey and black – all with a ‘grained feel’ to the frames.