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THE FRAGMENTED nature of the window manufacturing sector in the UK can mean that innovation takes time to filter through the market, but I think that bonded window technology, widely used in continental Europe, is set for a major expansion in the UK. This potentially has a huge impact on the volume manufacturers, but the smaller fabricator and installer businesses can capitalise on the advantages of the process quickly with readily available solutions.

With this method of manufacture, the insulated glazing panel is securely bonded into the sash with ultra-strong adhesive – a change that immediately improves the performance of the window. The majority of post-installation problems arise due to the failure or inaccurate placing of glazing blocks and these problems are removed immediately.

For the fabricator, application of the bonding adhesive is done using an applicator gun: it’ s a quick and simple process and the adhesive can be used with most frame materials, so it’ s a relatively easy switch to make, with training readily available from manufacturers such as ourselves.

For the volume window manufacturers, there is more investment required as switching to a bonded process will involve a change to the entire manufacturing process. However, the advantages, in terms of improved efficiency with a fully automated process and

a reduction in waste, will show a return in the long term.

More important, perhaps is the impact of the technology on the aesthetic design of windows. In the UK, as in much of Europe, PVC dominates the window sector. Marketed as a low-maintenance alternative to wood, the material grew rapidly in popularity when introduced some forty years ago and now accounts for around 60 % of the windows installed into homes.

However, it has some disadvantages in terms of both performance and appearance. Its lack of inherent strength means that the PVC frames generally need reinforcement – often achieved through the use of metal reinforcement bars. This results in the bulky profiles that characterise PVC windows as well as opening the door to issues with thermal bridging.

Bonded windows, on the other hand, do not rely on the strength of the sash to support the glazing – in fact the situation is reversed: the glazing supports the sash which ends up functioning as little more than edge detailing. In the same way that bonded windscreens contribute to the structural integrity of a car, bonded windows will function as a structural element within a building.

The consequence is much greater freedom for designers to increase

the glass to frame ratio, maximising the availability of natural light and allowing for lighter, less obtrusive windows. With the trend towards fully glazed walls in houses and expansive picture windows in contemporary apartments, a technology that allows for greater freedom in the design of these elements is immediately attractive. I think it is the appeal of this design freedom that has led to the rapid rise in uptake of bonded window technology in Europe. Since the first bonded windows were introduced in the 1990s, we have seen the system adopted widely particularly in the Northern European regions of Scandinavia and Germany. The latest available figures suggest that some 28 million bonded windows are installed in Europe each year.

It could be argued that the UK market is sometimes slow to adopt innovation and in this aspect, we are certainly behind the rest of the continent. However, I

do see a distinct change in focus from the systems houses and window designers selling in to this market. It is clear that the emphasis is on reduced profile size and towards lighter, less obtrusive windows and doors that allow for greater flexibility for the building designer.

For this reason, I think that the market is now ready for bonded windows and the rewards could be huge for the first companies to take up the technology. Experts from our European operations are on hand to advise new entrants with the benefit of twenty years’ experience of bonded window technology behind them.

For independent fabrication and installation companies, the Sikasil AS66 adhesive is supplied in a battery-operated gun that can be used both in production and on site. For the volume window manufacturer Sikasil WT 480 is the adhesive designed for use in fully-automated window manufacturer with the promise of cost reduction and improved window performance.