Glass is a common material for curtain wall infills. But not any old glass will do. Learn more in our article.
When the first glass-blowers made jars and vases out of glass, they would never have believed that one day entire buildings would be made out of the stuff.
Yet here we are in the 21st century with financial districts that have more glass than a tumbler factory. Skyscrapers, bridges, elevators, staircases – name an architectural feature and there's probably a glass version somewhere in the world.
In most examples of structural glazing, the capacity to bear a load is paramount. This could be a human load (people walking over a glass walkway) or a structural load (the roof sitting on top of a glass wall). In either case, load-bearing is governed by strict regulations to maximise safety.
Curtains walls, by contrast, carry no structural load. They are, in fact, non-structural. Their job isn't to prop up any other part of the building. Instead, they cover the building, protecting it from the elements.
This means it can be made from lightweight materials. But there's lightweight and then there's
lightweight. The job of a curtain wall is to shield a building from wind, rain, debris and even hurricanes. Rice paper isn't going to cut it.
Glass, on the other hand, will. Glass is just one choice of material for "infills", as they're known. But for many architects, it's a no-brainer.
Curtain wall glass has to be the right type and thickness – and there are considerations to be made that don't apply to all structural glazing. In this article, we talk you through them.
What is a curtain wall system?
Curtain walls and curtain wall systems are the same in all but name. A system will consist of a frame, typically made of aluminium, and infills. These can be made of glass, stone veneer, metal panels or louvres.
Curtain wall systems cover multiple floors. This distinguishes them from storefront systems, which typically cover just one floor. They're identified with the modernist movement in architecture.
Why choose glass for curtain wall infills?
Infills can be made out of a variety of materials. But for our money, glass is best for three key reasons.
First, it's an affordable material. Working with glass can reduce the overall cost of the project – something that will be welcomed by all, especially as the reduction in price doesn't lead to any reduction in quality or safety.
Secondly, it's widely considered aesthetically pleasing. Glass curtain walls are a familiar sight in many cities for a reason. Architects rate them for their sleek, minimalistic, uncluttered appearance.
Taste is subjective, of course. But whatever your personal opinion, it's undeniable that
architectural glass looks grand, imposing and modern, whether you're at the airport or walking through the financial district.
Last but not least, glass infills let natural light flood into the building. This is good for a business's carbon footprint, dramatically reducing the need for artificial lighting.
It's also said to improve the morale of employees. Light alone won't make you happy – but the difference between a spacious office filled with sunlight and a cramped windowless cell is obvious.
For all these reasons, glass is widely used as the material of choice for curtain wall infills. But not any old glass will do.
Types of glass for curtain walls
The most common material for curtain walls is float glass. This type of glass was pioneered by Pilkington in the 1950s and has been a staple material ever since.
One reason for float glass's celebrity is its versatility. Customers and architects can choose from a wide range of colours and opacities. It can also be cut to size down to the millimetre.
Curtain wall glass tends to be transparent, but translucent glass is occasionally used for added privacy or specific aesthetic effects. Opaque glass is also sometimes used to hide features behind the curtain wall.
Depending on local building regulations and specific project requirements, the glass may also be toughened or laminated.
Many curtain walls have knock-out panels in case of fire. A float glass panel would break into dangerous shards that could fall and injure a passerby. Toughened glass, by contrast, breaks into lots of small, harmless pieces.
Meanwhile, laminated glass is used to make curtain walls blast-resistant. This has been a priority for curtain wall manufacturers, installers and designers since the bombing of the Alfred P Murrah Federal Building in Oklahoma City, Oklahoma, in 1995.
This deadly truck bombing made clear that curtain walls are vulnerable to explosions. Laminated glass gets around this problem by breaking but not shattering.
Similarly, laminated glass is used for curtain wall systems in areas prone to hurricanes. This limits the damage done if wind-borne debris hits the curtain wall.
How thick should curtain walls be?
In the glass industry, thickness is a vital consideration. It's not something that can be estimated or overlooked. It's no exaggeration to say that in structural glazing, a millimetre can be the difference between life and death.
In both commercial and domestic curtain wall systems, there are two glass thicknesses to consider. The first is for monolithic glass, typically used for spandrels. The second is for insulating glass, which makes up the rest of the building's infills.
In commercial projects, the monolithic glass is typically ¼ inch or 6.4 millimetres. The insulating glass is usually one inch or 25 millimetres. In residential projects, the monolithic glass is typically ⅛ inch or 3.2 millimetres and the insulating glass is ⅝ inch or 16 millimetres.
The glass can be thicker, however, in buildings that need extra soundproofing or thermal control – acoustic glass in recording studios, for instance, or protective glass in laboratories. In some cases, curtain wall glass can be triple or even quadruple-glazed.
Looking for high-quality
glass for architecture? Look no further. Founded in 1993, ToughGlaze has become one of the UK's most trusted glass processing firms.
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