The cutting edge of performance glass

by Tania Wannenburg
The cutting edge of performance glass

Glass and aluminium are the materials of choice for modern building projects.


The Sandton skyline is changing rapidly with modern high-rise glass, steel and aluminium buildings dominating the scene. Due to the way they are being procured these developments came with a surge in demand for large buildings to be built very quickly. Many blue-chip tenants are looking to move into brand new buildings with contemporary designs that fit their signature and brand, and which are compliant with the new regulations in terms of energy requirements.

With many novel state-of-the-art ideas coming from architects who follow international trends, everyone involved is challenged to raise the bar.

Changing the contract process

Neil Macleod, owner of Pure Consulting, who has been working in the façade industry since 1983. He says that in the last few years, with the growing demand for engineered façade systems, it became evident that it was necessary to change the way in which the industry approached procuring façades in order to evoke innovation and be more cost-effective.

“We realised that the traditional process limited the opportunity for innovation, because the detailed design work was not being done in the professional team, but by the contracting tenderer, who had very little time to unscramble what the architect wanted and come up with alternative systems where necessary to be cost-effective,” he explains.

“When working as part of a professional team, however, you have several months to discuss ideas and amend plans in a friendly environment; where you are free to take risks and there can be a collaborate effort in order to make the design work. In the past that didn’t happen because the projects were structured with the detail design work happening post-tender.”

When the company was appointed to the professional team on the Standard Bank project as structural, civil and Façade design engineers, they decided to try a new approach and did system definition drawings and detailed scope drawings that explored every single unit of what the Façade contractor needed to deliver on, pre-tender.

“Apart from the resulting savings, it was definitely a more efficient way to work,” says Macleod. “In fact, from the tender drawings to construction, we didn’t change anything except for adding one floor. Normally, we might experience issues such as slab edges and brickwork that are in the wrong places, and deal with other surprises on site, but on the Standard Bank project everything just seemed to fall into place. No doubt, because it was all explored in the drawings and therefore possible to coordinate everything much better.”

Standard Bank – triple-glazed innovation

The Standard Bank building boasts an incredibly innovative triple-glazed Façade with its unique Afrocentric design. It is made out of crystal clear, low-iron glass, argon-filled double glazing and automatic, motorised blinds that measure daylight and adjust accordingly.

In Europe, it is cutting edge to ventilate the cavity that contains the blinds to the outside, so that the energy, when the blinds heat up because of the sun, is released via air movement through the cavity. However, in Johannesburg, dust would have certainly created an unsightly problem and with the blinds situated in-between two glass skins, cleaning all the extra surfaces would be a big irritation and major maintenance cost.

In order to solve this problem, it was decided to close the cavity and ventilate it with an air-conditioning system to the inside of the building so that the Façade cavity receives cool, clean air, which is bled out by an independent system.

Success sparks succession

Following the success of the alternative contract process on the Standard Bank project, the industry started requesting the full documentation pre-tender service on several other large, innovative and expensive projects, which all, coincidently, involves glass and aluminium façades.

These include:
• Merriman Square in Stellenbosch.
• 90 Rivonia Road in Sandton, Johannesburg.
• New Sasol corporate offices in Katherine Street in Sandton, Johannesburg.
• New Discovery building in Sandton, Johannesburg.
• New Centre for Economic Management Sciences building at Unisa, Pretoria.

Merriman Square – reversing the glazing sequence

In the case of Merriman Square, a project that involved the recladding of two existing buildings of roughly 17 000m² for the developer Redefine, Pure Consulting developed a ground-breaking system to reverse the construction sequence which saved 30% on the budget.

Instead of cladding bottom to top and then working from the inside to remove the existing windows, the engineers found a way to start from the top down. This way the occupants will get to experience the benefit much quicker.

“Taking this risk was possible because it was explored in the professional team before going out on tender,” Macleod explains. “Should the challenge only have been addressed post-tender, it most likely would have been impossible to figure out a way in time.”

Subsequently, further innovation was also possible and came by way of the façade contractor, World of Windows Cape Town, who offered a different façade modulation since they were willing to handle bigger pieces of glass and therefore fewer units, resulting in more savings.

The push for performance glass

According to Sean Couzyn, partner at Pure Consulting, buildings across the world are getting more glassy and transparent.

The speed of construction is definitely a big motivator for the higher demand for glass and aluminium buildings, but so is the increased performance of glass as a material and the big drive towards energy-efficiency. “And the occupants of the building get the visual benefit of looking out a big pane of glass rather than sitting behind a brick wall,” he says.

Spectrally selective coatings

The industry is presently seeing an increase in spectrally selective glass coatings that are transparent to the light frequencies visible to the human eye, while blocking infrared (heating) and ultraviolet (fading) rays. In addition, Interpon has released a new range of powder coatings that is also reflective to infrared, so that the aluminium frame stays much cooler.

“The benefit here is that you can create a lot of daylight inside buildings, but keep out the infrared light that is adding heat load to the building and the ultraviolet rays that are fading your curtains and furniture,” Couzyn explains.


The specification secret

When it comes to the specification of products such as powder coatings for window frames, façades or flush glazing the secret to success lies in the details.

Chris le Roux, national specification manager of AkzoNobel Powder Coatings South Africa, points out that architects often only write a colour’s name in their specification, while quality and application are also important factors to consider. Is the powder coating meant for interior or exterior frames, how long should the colour and gloss last, and what guarantees are available?

Another way of ensuring the quality of the specification is by insisting that the powder coating should be done by one of the powder manufacturer’s approved applicators, which are all SABS approved by being SANS 1796:2013 compliant. 

“By including all the details in the specification, the architects can be sure that the specification won’t be changed down the value chain and what ends up on the building, is what was specified,” Le Roux says.

Example of a detailed powder coating specification:
Interpon D2525 Matt New Silver QQX 202, 25 years guarantee, applied by Interpon approved applicator.


Creating green glass buildings

Georgina Smit, a sustainability consultant at Arup, points out that a building’s façade plays a vital role in creating a sustainable building. If the architectural vision of the façade design incorporates significant amounts of glazing, it improves natural daylight and access to external views, but the challenge is to ensure that solar heat gains are controlled to minimise energy consumption and create a comfortable indoor environment.

Working on the fully glazed No. 1 Silo in the V&A Waterfront, the professional team’s interdisciplinary design addressed these challenges by making use of a double-skin façade fitted with automated blinds.

“The double-skin façade with an intermediate ventilated cavity is a trend mostly driven by increased desire for transparency and access to daylight, but also the need for a better indoor environment, improved acoustic insulation and the reduction of energy use during occupation,” Smit states.

On the V&A project, the double-skin concept has been extended to include automated blinds within the cavity, which intercepts the solar load before it can enter the building. Additionally, the blinds assist with glare control, particularly important for this building as it is located next to the harbour.

“With the combination of a high-performance, double-glazed inner skin and blinds that are protected by a single pane of glass on the outer skin, efficient shading is provided and heat is allowed to escape from the cavity, thus reducing cooling loads and improving thermal comfort during summer,” Smit adds. “During winter it is also able to capture the heat within the cavity without ventilating it to the outside.”

Overcoming challenges

Because of the major boom in the Façade industry, Clinton Peters, partner at Façade Solutions, says that from a contractor’s point of view, the biggest looming challenge is the limited pool of resources to tap into.

“At the moment, we have the competence and people, but we are fast approaching the time when projects that are being green-lighted will require mega resourcing and capacity and that is why we are constantly but carefully gearing our business to competently and responsibly meet these opportunities. We also see the urgent need for rapid succession plans in terms of training and development.”

Another challenge in the industry is the foreign exchange. Volatile markets affect most major materials and key components, which are popular at the moment, and even the aluminium systems that are generally designed and manufactured locally is directly linked to the London Metal Exchange. The most expensive and predominant material is the glass and all types of performance glass is specifically imported since the technology is not available in South Africa.

Building designs are also continuously becoming more technically challenging because of the many new designs breaking new ground.

“Architects follow world trends and technology, and we have to find ways to make it work in Africa. They are raising the bar with every project, so we have to do it as well – it’s a chain reaction,” Peters explains. “Where there are geometrically complicated designs, it challenges the parameters of the materials as well as our skills. We are equipped with the capital intelligence and sometimes may need to extend our material searches and procurement on a world wide scale but trust that our local suppliers position themselves suitably as well. All of this impacts project programmes and final delivery.

“We are going to see many more exhilarating developments over the next decade. This is a remarkable time for the Façade industry and Façade Solutions is extremely excited to be a part of the phenomena,” Peters concludes.

Full thanks and acknowledgement are given to Pure Consulting, Façade Solutions, Arup and AkzoNobel Powder Coatings South Africa for the information given to write this article.

Industry update:
Popular trends:
• Performance glass.
• Double glazing.
• Automated motorised blinds.
• Spectrally selective coatings.
• Non-ventilated triple glazing

• Limited skills resources.
• Foreign exchange for imports.
• Intricate designs that technically challenge materials and contractors.
• Demands for buildings to be built quickly.

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