Why the choice is aluminium
Graham Lindsay, founder of Weru UK Network, discusses the role aluminium plays today.
In recent years, homeowners and commercial developers have chosen aluminium windows and doors over PVCU when building or renovating their properties.
I find it is really important to ensure that my customers have all the information to make an informed decision that ultimately suits their home and their long-term requirements.
In the UK market, aluminium was the go-to double glazing material of the 70s, and those early products are still present, albeit tired in many homes today. Profile design was very basic, and without suitable consideration for thermal bridging it was often a liability with high condensation risk. While aluminium has generally remained a staple within commercial projects it lost almost all its market share to PVCU in the crowded price-driven domestic market.
Aluminium is light and strong and, if well designed and fabricated, offers a long-term solution with the big benefits of choice in format and unlimited colours and textures. While PVCU was often the regular choice because of cost and ease of fabrication, it did not offer as many options, and was often perceived as bulky, cheap and cheerful. This was more noticeable with architects and specifiers, and aluminium was then perceived as being more of a premium product with a longer service life.
This perception and material preference I feel is often misunderstood. In reality both materials offer big benefits in their own rights; we are seeing high growth in the combi-type products where the slim sharp lines of aluminium as an outer framework is combined as a two-part window or cladded to timber, PVCU or modern GFP composites.
A favourite with UK architects is the timber/aluminium solution, mainly from the large Scandinavian, German and latterly Eastern European manufacturers. These are typically at the premium end with ultra-low U-values and triple glazed as standard. Generally, the combination of both materials gives a good technical solution with good stability and security.
As demand has risen so has the push to gain UK market share by cutting corners to drive prices down. We do see a lot of design compromises whereby any water ingress between two substrates is bad news and can cause problems that only create serious building issues in later years.
The other big challenge with modern build is to ensure all compliance criteria are met and, where possible, along with some future proofing. The demands on thermal performance will only increase, meaning aluminium systems should in my opinion cater for taking good triple glazing thus ensuring low U-values can be achieved. This will entail new and deeper profile sections where possible with slim face widths. These stronger profiles should ensure room for details such as a third gasket to meet the demands for very low air leakage. The larger section will also offer a stronger more secure window which is again an increasing requirement to Secured by Design.
In describing the above evolving design changes with the new demands for slim or concealed sight lines it has created an influx of continental profiles that give the exact aesthetics that many architects are now looking for. This is a growing sector, especially in the last 12-18 months.
However, the very slim Alu profiles may not have an adequate thermal break or structural integrity; in many cases these slim profiles cannot accept a proper triple glazed sealed unit.
The excuse that the UK climate does not need three-pane glazing will soon no longer be accepted as performance demands increase. There is much debate on this issue; my own view – having installed predominantly triple glazed windows for the last decade – is it will change but may take time. To offer <0.8W/m2k U-values along with superb summer cooling cannot be ignored in the longer term with energy costs and global warming.
In summary, I see the future is bright for aluminium, especially when combining the benefits of other materials within combi windows and using the latest composite materials, eg GFP.
There are already some new innovative system designs with totally concealed sashes offering a fully flush finish, which is currently very much in vogue in all materials. As a company we have experienced a strong swing in this direction with no signs of it abating.
