‘Composites - A Natural Choice’

There is no doubt that the use of timber/aluminium composite windows is still on the increase after huge growth over the last few years. With the ever increasing insulation requirements to meet the UK building regulations and the need to use the most sustainable materials available timber/aluminium composites fit these requirements perfectly. Add to these requirements the many recent campaigns to use more of our renewable resource ‘wood’ and today’s improved machining techniques and methods of preserving timber and we have a winning and ‘natural choice’ for fenestration products.

There are few materials that can boast the renewable qualities of natural timber and the indefinite recycling properties of aluminium, but there is more to these two products when used in combination.

Composite windows are perceived as a modern 'top of the range' product and yet often recommended by consultants as the lowest cost option when a 40 year life cycle costing is undertaken.

Its also fair to say that composite frames are ahead of the pack when it comes to contemporary popularity and, with softwood timber being an extremely good thermal insulator an aluminium timber composite window offers leading thermal performance.
There are many designs available but these fall into basically two groups. An aluminium structured product which use timber profiles as the internal finish and insulating component. Secondly the timber structured product which uses external aluminium pressings or extrusions for improved performance. The latter product is more widespread and uses traditional techniques of timber window manufacture with aluminium externally offering exceptional weathering characteristics and colour options.

Cost implications of these two types favour the timber structured product which is generally know as an ‘aluminium clad - timber composite’. These are often the more competitively priced product as the method of constructing the timber frames is virtually fully automated.

So far we have just mentioned composites as windows but we should also remember that doors and curtain walling are also available which can offer a total solution for virtually any building project. Doors are not just limited to balcony door applications either. Depending on the traffic requirements high usage doors on automatic door equipment is available. Curtain walling is also not just limited to a window wall type application either, as in a composite curtain wall structure timber replaces aluminium or steel as the internal structural component which can be of any size. Externally high quality aluminium components with sophisticated gasketry offers high performance for low or high rise applications.

Specification freedom is also enhanced when is comes to composites limited only by costs. The traditional softwood internal profile can be finished in high quality, water based and breathable finishes which can give the timber many years of low maintenance use. These finishes can be solid, transparent, gloss, mat, again with very few restrictions. It’s also worth remembering that other timbers can also be used for their attractive looks and higher strength characteristics.

Aluminium externally is well known for its excellent weathering characteristics and is again virtually maintenance free apart from routing cleaning and there are no limits on colour availability. Whilst not used a great deal today the aluminium can also be natural anodised which offers an attractive silver finish or is available in a basic range of colours.

Timber and aluminium are dissimilar materials and. whilst they are happy in working together and do not effect each others properties there are expansion issues which must be considered. Timber tends to expand across the grain as moisture content increases and aluminium tends to expand when temperature increases. It is vital therefore that these characteristics are catered for in the product design so the choice of supplier must be carefully considered. Many products now use a nylon or polyamide strip or toggle to join the two materials which caters both for movement and also further improves thermal performance. Having a ‘gap’ between the materials also ensures that air can circulate around the timber thereby ensuring that moisture is not trapped against the wood.

Specifiers are continuing to recognise that the combination of materials in the ‘composite’ window offers a near perfect solution to meet today’s sustainability and environmental issues. Pressure continues to increase as these requirements are backed up by some of the words largest green lobbyist organisations and increasingly by Government bodies.

The areas of growth in composes has come from, Social Housing where best value product are required, waterside residential developments where the natural apperance internaly of timber adds value, hospitals in traditional applications and schools both new and refurbished.

Research shows that timber aluminium composites have created their own market niche and have taken market share from all the other materials currently avaialable to the specifier.

As manufacture of timber frames is a specialist sector requiring a six figure investment and a heavy research and design programme most systems are available on a fabricated basis made to either agreed sizes or site measure, but mostly the former. Very few systems are available for fabrication within traditional fabrication shop and these are generally based on the aluminium structured design.

Few of the major players in the market offer the Main Contractor or customer the 'full package'; that is to say that some of the largest companies only offer windows on a supply only basis.  Main Contractors generally prefer to place one contract for supply and fix. Not all companies offer a full product range which includes windows, doors and curtain wall in a 'matching' composite system.

Compared to the £2.7 billion installed value in 2007 for commercial aluminium framed products composite window use is much smaller at circa £500 million but this has grown rapidly over the last 10 years due to environmental forces and is set to continue its rapid growth. Estimates vary as to the potential market growth for the product but most of the major suppliers agree that the market size will easily double in the next 10 year period.

The sector is currently dominated by imported product with very few UK manufacturers of Composite systems. These imports can be divided into two groups, ‘Scandinavian’ and ‘German/Italian and others’.

The 'Scandinavian' imports represent by far the largest percentage with the main players and design usually of an open out configuration, this configuration is popular in the UK, but delivery lead in periods are usually extended well beyond what is regarded as acceptable within UK construction.

The Germanic or Italian window systems are based on tilt and turn open in principals and are often aluminium structured. Although some open in window systems are used in the UK it represents a small percentage of windows specified. Most of the windows in this second group are seen as being over engineered for the UK market. There are similar windows imported from Eastern Europe but again these are mainly of an open in design. Some PVC-U timber composite windows are even imported from America but these are generally marketed from a range of standard sized windows.

Labour and material costs in mainland Western Europe are similar to the UK therefore if a UK business wanted to fabricate a timber aluminium composite window it should be able to compete with the Scandinavian manufacturers.

Given the size of the European fabricators they appear to focus on very large orders leaving a potential opportunity for UK installers to undertake smaller projects but never the less quite substantial projects. Given an economical source of local supply with short lead times and recognised product quality more installers are adding timber composites to their product portfolio.

AM Profiles are members of TRADA and the CAB and are proud to be one of the only UK companies offering a broad range of products to the industry.