The Composite Revolution

Composite timber/aluminium products continue to be imported into the UK to meet the demand for ‘high insulation’ and ‘sustainable’ window solutions, but are imports really sustainable and the most economic solution for the UK’s construction requirements? Look to place an order today from a reputable European manufacturer and you can be quoted a 16 week plus lead time, and whilst this is just acceptable for new commercial projects it can be a non-starter for the refurbishment sector.

The transportation of readymade frames takes up much more space than window material in component form, so a readymade product starts to embody more energy and consequently more carbon prior to arrival in the UK. There are a few UK manufacturers of composite windows, all of which are experiencing good order books and with improved lead times to UK contractors over their European counterparts, their future seems to be set.

More recently systems companies in the UK have begun to develop products which can be easily manufactured alongside aluminium. These systems are in rapid growth at the moment look set to take an increasing share of the continental imports, offering contractors improved lead times from locally produced frames.

With ongoing campaigns by the timber producers, specifiers are now seeing the benefits of using high performance engineered timber profiles which can be coated to withstand up to 10 years weathering without the need for re-coating. Add a powder coated or anodised aluminium profile to the outside of the product, and, when designed correctly, the same timber window will last in excess of 30 years. As timber is a good insulator and sourced from sustainable forests, the timber/aluminium combination is attracting many specifiers in the public sector wishing to specify a sustainable product which is easy to deconstruct and offer 100% recyclability at some point in the future.

Some consultants have even stated that timber/aluminium composites are the lowest cost option when a 40 year life cycle analysis is undertaken against other materials and combinations.

Technically speaking there are basically two forms of timber/aluminium composites, a timber window with an external cladding of aluminium and an aluminium window internally clad with timber. The latter uses normal aluminium machinery to manufacture and can be non-insulated or is often insulated with polyamide. The internal surface of the product is then clad with timber which is fixed into place with ‘toggle’ type fixings to allow for the differential expansion between the two materials. This method of construction design offers a product which is more expensive than a typical high performance aluminium window, but does offer very slim sight lines. The high cost usually excludes fabricators on competitive tenders.

The former method, a timber structured window with extruded aluminium profiles added externally, fixed on ‘toggle’ fixings, vital to ensure long life expectancy to allow for the differential expansion, is the more competitive option. The downside is that until now the fabricator would need to purchase a large woodworking machine, often well into a six figure sum, plus dedicated machining cutters and a proprietary timber finishing system. So whilst a more competitive product can be made, it requires heavy investment and high throughput and the steep learning curve of adopting timber as a main structural framing material.

So whilst the aluminium framed composite is uncompetitive and the timber framed composite requires a heavy investment and steep learning curve, a barrier to entry exists for the fabricator which has ensured, until now. With the mergence into the market of systems companies this is set to change rapidly.The commercial sector specifying composite windows in ever increasing numbers, used in schools, hospitals, offices, hotels, apartments, in fact in all commercial applications. In home improvement, whilst PVC is now reaching maturity and with up to 40% over capacity in the UK market and with such low margins, will locally produced composite windows and doors be a lifeline to the ‘double glazing’ home improvement industry. Many specialists believe so and if public opinion is to be considered, timber composites have a much higher perceived value than PVC.

Can we sell a much higher value product against PVC? If we go back to the early 1980’s PVC was much more expensive than the then popular aluminium casement in a hardwood surround - so where there is an opportunity and a market demand...

Enter the Senior Hybrid System, simple ideas are often the best and it surprising until recently that this type of system has not been available. Simply provide finished timber profiles in ‘bar’ length, mitre and make up frames using a proprietary jointing method. With a minimal investment in a timber mitre saw and a simple router, frames can easily be made up in an aluminium fabrication shop and then re-enter the normal production process to have the aluminium external profiles added and then be bench glazed if required.The benefits are obvious to all fabricators and installers who manufacture from bar length. By offering shorter lead times from stock profile, utilising existing investment in machinery and workforce experience, can in turn result in better margins being obtained compared to a similar ‘bought-in’ composite product. Importantly, using this method of construction, windows can now be made from the results of a site measure, something not possible before due to extended lead times.

In the commercial market composite specification continues to grow and it is currently estimated that it enjoys a £500 million per annum installed value compared to aluminium’s £2.7 billion. Whist the external look of composites reflect aluminium’s good looks, composite systems will continue to take a growing share of all popular materials used for window construction in the UK not just aluminium. Major suppliers predict the composite market to easily double in size within the next 5 to 10 years.

In practice it is now feasible to install an all composite system on most projects to replace other, more traditional materials. But importantly this is now an aesthetic and environmental choice the specifier can make knowing he can obtain the relevant performance characteristics to suit the project.

So, the ‘revolution’ in composites in the UK can now be passed to the UK’s fabricators and installers who can begin to compete with competitive market costs and short lead times. Whilst the ‘Hybrid’ system from SAS is the first of it’s type in the UK, no doubt it will continue to have its followers in the coming years.

The ‘Hybrid’ system, designed and supplied by Senior Architectural Systems  offers open out and open in systems complete with a high performance curtain wall system. Further information is available on the companies website at or by phoning their head office in Doncaster on 01709 772600.

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