Most products are based on systems that use well-known brand names, but there is a feeling that if you pay more for a bespoke solution you will be buying a better product. This isn't necessarily the case. Customised designs quite often don't perform satisfactorily, or even as well as a system-based product.
One thing to bear in mind about a good bespoke design, however, is that its functional heart will be based on tried-and-tested technology, which is an essential ingredient if the product is to give a guaranteed performance.
Fenestration products are available in aluminium, steel, timber and PVCu. PVCu systems dominate the mass domestic market, where cost tends to override any other criteria. PVCu products are rarely bought for their good looks, but because they give low-maintenance, reasonably durable performance – if the system is well designed, manufactured and installed.
It is not the material of choice for prestigious projects – and the sustainability lobby may not be comfortable with its green credentials.
Steel has produced the most elegant solutions in the last century, but is now virtually a niche market. Steel windows are basic, but they are elegant and have "honest", simple hardware. Typically, the sightlines are minimal due to the inherent strength of the steel. Traditionally, steel frames with putty-sealed glass provided abundant strength because of the composite action of glass and frame. This is a very desirable property that modern systems companies have overlooked with the introduction of glass sealed with gaskets rather than putty.
Timber is a niche product in the UK and is chosen for its look, not because it is likely to give minimal sightlines or a neat appearance.
The demand now is for a new design philosophy – not just tweaks of incremental development but a fundamental re-examination of the basic underlying principles
The timber fenestration elements that I have seen have been very basic and badly finished. Double-glazed timber units seem to last half the length of time they should, thanks largely to poor integrated drainage design.
This leaves aluminium, which in our end of the industry – commercial and large residential – is used most frequently. Aluminium fenestration owes its place to the aircraft engineers who adapted their skills to construction after the Second World War. In that era, people wanted quick and easy installations. Nobody seemed to care as much about thermal bridging or air tightness, let alone slim sightlines and elegance.
However, the innovations of the 1950s and 1960s are beginning to feel dated. Significant development has taken place in the last three decades, but the products evolving from this stream of thinking are reaching the end of their useful life. In the 21st century, with a society that has style high on its agenda and Building Regulations that are requiring ever-better performance, we don't have systems to meet both demands.
In recent years, I have come across many projects where the architect effectively wanted one piece of monolithic glass to clad an entire building. At the same time, the client wanted the huge glass facade to be thermally wonderful, behave acoustically like a 300 mm concrete wall and last forever without maintenance. Clearly, I am exaggerating, but my point is that the fenestration industry needs to innovate again and again to meet the constantly developing demands of the marketplace.
I believe the demand now is for a new design philosophy – not just tweaks of incremental development but a fundamental re-examination of the basic underlying principles. This means looking at everything from basic structural principles, through building physics and acoustics, to the dynamics of application and use. The industry needs to develop systems more in line with automotive or aircraft fenestration.
Stephen Tanno is group director of Buro Happold Facade Engineering.