Not just a pretty facade

by Tania Wannenburg
cladding jnl8

The social and environmental importance of 21st century cladding systems- the good, the bad and the ‘very expensive’.  

A decade ago, social and environmental responsibility in building practices were still a controversial topic. It was a practice carried out by a few dedicated architects and construction companies who had little resources to help them create green buildings that were built to last. Clarissa van der Merwe balances cost, sustainability and aesthetics by investigating the latest cladding tendencies.

By definition, cladding refers to a metal coating bonded onto another surface in a high pressure and temperature process. However, it now generally refers to a wide range of general products and solutions that can be applied to save energy and improve a building’s overall structural capacity.

Cladding selection is usually based predominantly on aesthetics and cost, although more and more developers and architects understand that durability is paramount, and therefore, so is correct specification and application of cladding materials. More recently the industry, like many others, has become a lot more focussed on using sustainable materials for cladding.

By way of example: Byron Ninham from Archiway, when asked about the current trends in architectural cladding, noted: “Environment, climate and location play a significant role in the type of materials that could be used. We recently completed a truck dealership, which has sheet-metal side cladding and roof, and we used a white finish that reflects a lot of the heat and assists with climate control.”

In South Africa, where we deal with very high and quite low temperatures and big temperature variations daily (i.e. in Pretoria in winter the temperature will start as low as -2⁰C and climb as high as 21⁰C on the same day), as well as highly corrosive industrial and coastal regions, using a hard-wearing product will give the project longevity. Physical interactions also need to be taken into account: Is it a high traffic area, indoor, outdoor or a feature wall behind reception in a corporate office?

New ideas
The Fraunhofer Centre for Surface and Laser Processing in Plymouth, Michigan (USA), recently developed a new cladding process, which utilises  a 3 KW direct diode laser and a coaxial powder-feeding nozzle.

The process reduces the operational cost of conventional CO2 systems and lowers investment costs by utilising smaller laser systems.

The process originated in the oil industry, where it is usually applied to down-hole drilling equipment. The Fraunhofer Centre developed new superior wear coatings, which were tested and applied on a number of oilfield tools. The Centre aims to apply the technology in the repair of tools and to increase cladding efficiency even further with special plasma and induction-based hybrid technologies.

Diode laser deposits porosity-free and crack-free nickel-based coatings with a high content of globular tungsten carbide onto metal surfaces. The process reduces the operational cost of conventional CO2 laser systems by at least a factor of three and lowers investment costs by utilising smaller laser systems.

The Centre also developed hybrid technologies that combine laser cladding with induction preheating or plasma welding technologies to increase the process speed and quality. This process reduces auxiliary time even further by removing the preheating with a torch and providing better process stability, especially on large parts, which cool down after long process times. The combination of plasma welding and laser cladding is used on large surfaces that need to be coated, and requires precise deposition in certain functional areas. This guarantees efficiency without sacrificing quality.

These cladding technologies can be used to effectively apply wear- and corrosion-resistant layers on surfaces, remanufacturing tools and dies and for rapid prototyping.

Ventilated facades:
A building’s “skin” is one of the most important steps in design and construction.

A ventilated facade system architecturally embraces the building and allows it to breathe, so that the movement of air keeps the building warm in the winter and cooler in the summer.

The outside of a ventilated facade is made up of a layer of cladding, attached to the building by an anchorage structure, normally made of aluminium, and a layer of insulation anchored to the grid that supports the cladding. The gap formed between the structure and the building thus becomes a space that utilises the circulation of air to decrease temperature excursions, which improves the building’s performance.

Ventilated facades work by the stack effect (hot air moving upwards), which helps the building to maintain a consistent temperature.

This system also maintains a degree of independence from the architectural design of the building, as the principle behind it lies in the static independence of each individual tile, eliminating the mortar used to hold tiles in place. This allows the use of any cladding material on the facade, which leaves a variety of options open regarding the final appearance of the building.

The benefits of ventilated facade systems include easy installation, allowing maintenance and work on individual panels, reduction of the risk of cracking and detachment, protection against atmospheric agents, and the elimination of thermal bridges and surface condensation. These 100% recyclable systems also substantially improve the building’s energy-efficiency, while providing protection against atmospheric agents and a reduction of noise pollution inside buildings.

The ventilated facade systems also allow the use of new-generation, technologically advanced materials that can be used to create an aesthetically perfect final product that is kind to the environment and lasts a lifetime.

Cast in stone
Another popular cladding process is stone cladding. In this process, a thin layer of stone or simulated stone is applied to a building.

Stone cladding is sometimes applied to concrete and steel buildings and forms part of the architecture. It often refers to lightweight, simulated stone products with a concrete-type base. These products are then fitted to lightweight substrates to reduce the material cost of construction.

A typical installation on a lightweight substrate would use ply bracing as an alternative to fibre-cement sheet. Stone cladding can also be a natural stone that has been quarried and cut to reduce weight. Heavier stone cladding products often need mechanical fixing to adhere to substrates.

There are a few important factors that need to be kept in mind when establishing a stone-cladding anchoring system. These factors help to determine the size and thickness of the stone panels that will be used, as well as the back-up system to which the panels will be attached.

Tips for a successful stone-cladding anchoring system:
A number of factors should be established before successfully selecting a stone-cladding anchoring system. These include:

  • The physical characteristics of the stone.
  • Design loads and safety factors.
  • Wind and seismic loads on the building.
  • Anticipated dimensional changes in the building.

Trends and projects
When specifying projects, architects and building designers should consider materials and structural systems that allow flexibility and adaptability to meet future changes in building functions. These aspects will assist with economic impacts and the cautious use of resources throughout the building lifecycle.

Pre-finished steel is easily refurbished to extend a building’s functional lifetime and is itself ideally suited for refurbishment projects. These materials are also a proven favourite of architects, as it gives a modern, clean finish that lasts a lifetime. It is also weather-resistant, shock-resistant, vibration-absorbent and easy to install.  Charl-Pierre Cilliers, the director of Cube Architects, says: “Commercial retail, car dealerships and office developments make use of aluminium cladding, which gives the projects a clean-cut finish and the desired colour.”

Ninham also notes: “We have just finished a Toyota dealership and part of the specification is that we use aluminium cladding, which you see on all the Toyota dealerships as this gives a neat, clean line to the building. We are also busy with a project in Nigeria where we are using stainless steel cladding which is aesthetically pleasing, but very expensive.”   

Light steel is a definite favourite in terms of style and quality. Another perfect example of light-steel cladding is the House of Enslin at Hartebeespoort Dam.  

Cost is always an important factor. When it comes to sustainable building, this becomes more important than ever, as materials with environmentally-friendly long-lasting qualities tend to be more expensive than traditional alternatives.

According to Pretoria’s AIF Design Architects, location also plays a role in price. “The bigger the demand, the higher the price is. Climate and environment may mean that you might have to add additional materials to comply with the finished product, but it doesn’t influence the price of the materials itself. However, environmental materials are generally more expensive. Also, if you are building down at the coast, for example, environmental factors like rust, wind speed and humidity need to be taken into consideration when choosing materials.”

The Moses Mabhida Stadium in Port Elizabeth is one of South Africa’s landmark stadiums that were used during the 2010 Fifa Soccer World Cup, and truly one of the best examples of the enormous impact of cladding on a structure.
It features a base that is surrounded by aluminium flat cladding. A perforated facade-cladding system was developed for the project, as multi-functionality was an important factor in the design and construction of the stadium. The result was a structure that can withstand enormous wind loads, provide adequate cross-ventilation and allow sufficient light into the structure.

Specially developed fixing systems accommodate the raking and ensure that the sheets meet the life expectancy of the stadium. The stadium’s aluminium cladding adds aesthetic appeal, durability, cost-efficiency and environmental benefits.

Making the right choice
Although design features and the owner’s aesthetic and quality expectations generally have a major influence on the choice of cladding, there are other important factors that need to be kept in mind, which often differ from one project to the next.

Firstly, cladding systems need to be appropriate for the location in which it will be used. Additionally, environmental factors such as wind load, high wind areas, corrosion potential, rainfall and temperatures need to be kept in mind.

Other less obvious factors such as the way in which window and door joinery is integrated into the system also play a part in the final decision-making process. Allowances for thermal movement should be generous, especially when using metal cladding, and the modifications made to the cladding by other contractors such as electricians need to be well thought through.

Choosing a specific cladding product therefore depends not only on the cost-efficiency and aesthetic quality, but on the building or project’s unique specifications and considerations.

Full thanks and acknowledgement are given to AIF Design Architects (www.aifdesign.co.za), Byron Ninham from Archiway (www.archiway.co.za),
Charl-Pierre Cilliers from Cube Architects SA (www.cubearchitects.co.za),
www.ilt.fraunhofer.de and the CSIR for the information given to write this article.

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