In examining the use of glass today, aspects of its appearance, function and performance are important. So too is its environmental impact in terms of embodied energy, its energy performance over a typical design life in buildings and its recyclability.
Aesthetics and structure
Glass has been the number one material in the past 30 or more years for design and architectural expression. There have been some notable examples of sheer architectural delight and some passing fads.
In most cases glass is being used as a 'cladding' material mechanically retained or bonded (structural silicone glazing) to a frame. The advent of 'structural' (or bolted frame-less) glazing in the early 1980s opened up new horizons for architecture.
Toughened glass is a good engineering material and has revolutionised architecture. Exploiting the potential of toughened - and more importantly - toughened laminated glass is just beginning to happen as architects and engineers begin to appreciate its possibilities.
Toughened laminated glass has also made possible some examples of what I loosely term 'glass nerds' - the use of glass in an inefficient way which usually results in flawed aesthetic, high cost, difficult maintenance and replacement procedures and poor durability.
Among the most elegant uses of glass around is the hand-painted glass tent at the British Diplomatic Club in Riyadh, Saudi Arabia. Other examples include the gable wall facades of the Kempensky Hotel at Munich Airport and the facades of the Western Morning News in Plymouth. The simplicity and sheer clarity of the gable wall facades at Thames Valley University in Slough and the Glass Bell Tower facades at Basildon are hard to ignore as classically beautiful architecture.
The new range of glass bending and laminating equipment is making possible new products previously thought of as novel, expensive or of poor quality. Single curvature glass ovens that bend and toughen the glass at the same time are capable of producing high-optical-clarity material with consistency and little distortion. Even double curvature is viable, though more expensive.
Laminating glass with various materials in the laminate sandwich is also becoming more common. The Money Zone at the Millennium Dome has £1 million in legal tender £50 notes laminated into the glass that makes up the facades and walls of the zone. Other laminates have incorporated dried tree leaves and stainless steel meshes. Glass has been successfully laminated with exceptionally thin natural stone such as marble to create translucent cladding.
Thermal and solar
The race is on among the glass producers and processors to convince architects that their product is the best and is better than their competitors. The demand in Europe and North America is for glass with high-visible- light transmittance and non-tinted glass with low-energy transmittance. The search for the perfect 'wonder product' remains elusive, despite the serious advances in vapour-deposition coatings using exotic metals such as silver, titanium and gold.
The trouble with these new soft coatings is that they are all still largely experimental and remain susceptible to oxidisation and suffer poor consistency in appearance. They are inappropriate for any unusual processes such as curving.
The modern all-glass building actually makes little sense from an environmental control and sustainability angle. The question - 'Why glaze?' - needs to be asked more frequently, with products such as inert gas-filled double- glazed units, the glass producers are trying to make a stronger case for glass everywhere. However, two years later, when all the gas has dispersed through the edge seal, the thermal insulation is back to three times the value of the minimum recommended under part L of the Building Regulations. The concept being, if form follows function, then one has to question the need to glaze.
Sustainability of glass
Glass in buildings more than 1000 years-old is still in use, which proves that glass as a simple monolithic material has almost infinite life. However, modern double glazing units will last anything from 10 to 30 years, with 20 the average. This is largely due to the break-down of the edge seals in double-glazing units. Conventional double glazing appears to make little sense from the sustainability angle, especially when embodied energy is considered. The poor recyclability of plate glass makes the situation worse.
Glass has very high embodied energy and its production uses natural resources that may not be readily renewable. The sealed air-conditioned box building with conventional double glazing is unlikely to survive if stiff regulation comes into effect, enforcing sustainable construction.
To that end, low-energy design is likely to focus on the possibilities of 'layered' systems incorporating monolithic glass for longer life with a carefully designed cavity for better thermal insulation, solar control and better fire and acoustic performance.
Design and education
Ted Happold once said that 'in a world so full of information, one needs the human experience to bring some sense into the design process'. This is very true in the field of glass and facades, which was one of the driving motives for Ted in setting up the Centre for Window and Cladding Technology (cwct) at Bath University.
Glass and facade design is not rocket science and is something that is becoming more readily recognised and appreciated. The cwct now runs a good postgraduate course for the sole purpose of training facade designers and engineers. This initiative has to be extended and followed up with undergraduate courses. Then perhaps universities will be providing industry with useful skilled graduates.