Glass adds sophistication and class to any building, and numerous advances in the functionality and versatility of glass over the last few years have expanded architects’ design freedom. Apart from more design options in building interiors, glass offers many benefits in construction and often replaces more conventional materials such as metal or stone in facades to create greater views and allow in more natural light.
The only downside though, especially when used on building exteriors, is that glass often comes with a compromise in terms of thermal comfort and glare that have to be counterbalanced by air-conditioning and shading, which in turn means more energy consumption and emissions.
This fact, however, has led to many innovations aimed at making glass windows and facade elements more multifunctional. At the international Glasstec Trade Fair, it was clear that the glass industry understands the need to combine these functions in glass products and is focused on the development of integrated solutions.
While many facade elements already include control functions and sun protection, the future will see even more functions such as lighting elements, heat exchangers for the production of solar heat and mechanical ventilation and aeration elements being added.
Switchable glass that automatically adjusts to lighting conditions is already a reality, and companies are experimenting with different mixtures of liquid crystals to develop panes that can respond to the intensity of daylight even faster, within seconds, and which also come in a wider variety of colours.
Although electrochromic glass is still more expensive than conventional insulation glass and electricity is required for the switching function, the investment does pay off. This is thanks to the substantial improvement in energy efficiency, without the requirement for external shading devices.
Taking facades that adjust to lighting and siphon off hot air a step further, future solutions are set to integrate solar technology to produce heat and electricity that can be stored on site in batteries and heat-storing units – a big step in getting buildings closer to being self-sufficient.
Project focus: A glimpse of the future
The 8 500m² glass facade of the 67m tall Festo Automation Centre in Germany functions as an exhaust air facade where the air is continually siphoned off between the inner anti-glare shield, the aluminium components of the unitised facade and the glazing. This means that heat cannot penetrate to the inside of the building.
Further light and heat protection is created with the help of electrochromic glass which can be dimmed as required, blocking off sunlight. These “sandwich” panels are covered with an extremely thin layer of tungsten oxide nanoparticles that turn blue whenever voltage is applied.
According to German manufacturer, Econtro-Glas, it takes between 20 and 25 minutes for the system to switch from brightest to darkest and when fully dimmed, only 12% of sunlight is allowed through while the rest is reflected. The glass can be dimmed manually or automatically in response to signals from sensors.
The glass facade of the new Festo Automation Centre has been designed as an exhaust air facade. Using electrochromic window panes, it adjusts itself automatically to the prevailing lighting conditions. Courtesy of Messe Düsseldorf/ctillmann and Festo
Structural glass engineering
Glass has its own load-bearing qualities, which means that flat glass can serve as a primary building material and can be used as a structural support element. And since it can be reinforced, the normal load-bearing capacity of glass, as well as its residual load-bearing capacity after potential breakage, can be enhanced.
If an appropriate and structurally efficient film is used, manufacturers today can produce a laminated glass that will carry the weight of a person after breakage, despite a nearly 30% reduction in thickness. It is expected that in the future, the shear modulus of structural film will play an even bigger role in the structural analysis of construction components. This coefficient provides information about linear elasticity, for example when exposed to a shearing force.
The type of mounting option that is applied to material on the support structure has a big influence on the final outcome and appearance of the facade.
Linear mounting is one of the most common practices, where the main components are horizontal and vertical exterior mullion-and-transom designs with interior pressure bars and elastic supports such as silicon. The result is a sleek silhouette.
In turn, a spot-fitted bracket has stainless-steel retaining bolts which hold the glass pane in place and eliminate the need for sections. However, the glass needs to be drilled through, creating highly concentrated tension at the drill hole, which is why conventional spot fittings only permit the use of pre-stressed glass.
An alternative, a so-called undercut anchor, fulfils the same function as a drilled-through, spot-fitted bolt, but the drill hole is conical in shape, and does not go all the way through. This results in a completely smooth surface on the outside.
Apart from drilling through the panes, a rear-ventilated facade also allows the use of clamping mounts on edges and joints, holding the pane in place.
Traditionally glass panes are firmly bonded into the facade’s support structure using a durable, weather-resistant silicone adhesive. But while structural glazing can have a support structure, composite glazing only requires glass-fibre reinforced plastic. Likewise, thanks to developments in bonded panes, these in itself now have the relevant load-bearing properties.
Balustrades with load-bearing properties are also becoming more in demand for spaces where it is important to have an unobstructed view, but which need to be safe.
Developments in bonded window systems have seen those with suitable panes in different thicknesses being about 20% lighter than conventionally wedged solutions. They need less maintenance, wind can’t enter through the casements and their U-values have been improved through better isothermal patterns. What’s more, bonded insulation glass scores higher in terms of rigidity, load transfer and durability.
Project focus: Apple’s glass cube
The Apple Cube on Fifth Avenue, New York, comprises of pure glass, yet it has all the necessary load-bearing functions without any frames, mullions or transoms.
Each side of the cube has three slabs of laminated safety glass, in five layers, with shear-resistant ionoplast interlayers, 3,3m x 10,3m in size, combined with a rigid, self-supporting roof structure. The connecting titanium fittings, which bond the panes to two continuous glass fins in the area of the two vertical joints, were laminated into the laminated safety glass and are almost imperceptible.
Sedak, the glass-finishing company, also applied some bending to the panes during the lamination process, to ensure that rainwater can run off more easily.
In the residential market, there is a growing demand for slim sections in bonded windows with home owners looking to enlarge window areas with panes down to floor level, with fewer load-bearing elements and more seamless transparency.
As seen at Glasstec, the market has responded with some remarkable products. Large windows and sliding doors can be divided with the help of a classic mullion-and-transom design at a visible frame width of 50mm, and as lean as only 15mm, while still reaching a heat coefficient of 0,90W/m²K.
Glass in interiors
Inside homes, hotels, offices, shopping centres and restaurants, glass lends elegance and vibrancy to a space. Whether choosing transparent, coloured, translucent or opaque glass to be used on stairs, banisters, wall panels, partitions or even furniture, the options are endless.
Popular as a design material, interior applications often see lacquered glass applied as kitchen back walls, wall panels or furniture fronts. With screen and digital printing, flat glass can be used for tailor-made designs or for applying decorative motifs, while sandblasted glass offers further decorative images or patterns. Coloured foil integrated in laminated safety glass coupled with strategically placed lighting can create a specific ambiance.
In addition, UV bonding can create a variety of three-dimensional glass structures for the furniture industry as well as store and exhibition construction.
New in decorative glazing
Thanks to new developments in processing methods and modern designs, the range of glass products in the market is growing. Some of the newest products see design glass featuring embossed sections, design patterns that create material depth, more colour options, and combinations of glossy and matt surfaces in matching hues.
Digitally printed and powder-coated float glass is specially designed with excellent high abrasive strength and high resistance to condensation, UV and scratches so that it can be used as table tops or work surfaces, partition walls or wall panelling, and even shop fitting and exhibition construction.
Intelligent architectural glass now also employs technology that permits products to fulfil different technical requirements for interior applications. One example is adding a light-conducting layer in laminated glass to turn a window or partition into a source of light. Certain systems can be controlled and programmed with an app, or can self-regulate and adjust to different lighting conditions.
And by using electrochromic glass for windows or facades, these can also be used to set the interior mood whenever required, apart from managing thermal heat and glare.
Configurations for inside and out
With the glass industry continuously coming up with new designs and technological advances, glass is growing in stature as a design element, not only to add light, brilliance and transparency to buildings, but also to play a bigger role as structural element and functional building material.
Full thanks and acknowledgment are given to Messe Düsseldorf and the Glasstec International Trade Fair for Glass Production, Processing and Products for the information given to write this article.
New developments in glass:
• Multifunctional glass with lighting elements, heat exchangers for the production of solar heat, and mechanical ventilation and aeration elements.
• Electrochromic glass – faster switching times.
• Solar technology with storage options.
• Reinforcing the normal load-bearing capacity of glass.
• Composite glazing.
• Advanced bonded window systems – requiring less maintenance, better U-values and more.
• Larger sizes with slimmer bonding sections.
• For interiors: 3D glass, embossed sections and powder-coated float glass with advanced benefits.
• Intelligent architectural glass that conducts light.
Caption (main picture): The discreet yet smart design of the facade of the Kilden Theatre and Concert Hall, Kristiansand, Norway, consists of segments which are each about 3m wide and 2m high. Courtesy of Messe Düsseldorf, © Jansen AG
Caption: The glass facade for the stair tower consists of spot-fitted sun protection insulation glass with screen printing and mounts, each made from hot-stored toughened safety glass and from tempered and partially toughened glass for the roof. The spot-fitted insulation glasses, up to about 2m x 4m in size, are joined to a supporting steel structure via so-called spiders.
Courtesy of Messe Düsseldorf, © ISOLAR® Group