High-performance building design – a balancing act

by Tania Wannenburg
High Performance building design

High-performance buildings integrate carefully selected products that each contribute to reaching the optimal balance for maximum efficiency.

When designing a high-performance building – whether it is a six-star Green Star rated building or one with a specific critical function – it is all about achieving the perfect balance between the practical requirements and the aesthetic vision.

Ultimately, products are selected and specified with the goal to get a building to operate at its maximum efficiency potential.

Key considerations when designing hi-spec
According to Lloyd Rubidge, director at Van der Merwe Miszewski Architects (VDMMA), durability and guarantees on materials are fundamental when designing high-performance buildings. “We wouldn’t even consider products that don’t have a long life expectancy. We also look for materials that require minimal maintenance and come from a reputable source with a track record,” he states.

VDMMA was part of the architectural team that designed the multiple award-winning No. 1 Silo office development in the V&A Waterfront in Cape Town. It was the first development to receive six green stars for both its design and the completed building respectively, and is thus far the only project awarded the six-star Green Star SA “As Built” rating.

Rubidge notes that the site, the client’s brief, and the technical, spatial and aesthetic development of the design determine the functional needs of the building and lead to specific performance requirements. Then one has to look at the performance of each material from a number of angles. “For example, glass facades: While looking to maximise outside views and minimise reflectance from a visual point of view, one has to balance insulation and thermal values, light transmittance, solar shading and aesthetics to achieve optimum comfort and energy efficiency,” he explains.

“Generally price, function and aesthetics weigh most when selecting products. Obviously cost is always an issue, because even on hi-spec projects there are definite budget constraints. In terms of functionality we look at things such as performance, durability, abrasion resistance and test results. The aesthetics leave a bit more freedom for personal judgement, but we look at various criteria such as, in the case of glass, clarity; visual light transmittance and colour.”

For Lood Welgemoed from Boogertman + Partners Architects, the main consideration is upkeep, selecting long-life materials that require minimal servicing. This is closely followed by sustainability– whether the material is recycled, recyclable and locally available. “The aim is to minimise the building’s carbon footprint and to determine each product’s yield to the overall energy efficiency of the building in keeping long-term running costs as low as possible,” he says.

“To this end, we focus on getting the basics, such as orientation, right from the start and work with mechanical engineers and sometimes sustainability consultants to do energy modelling,” he adds.

Boogertman + Partners designed the headquarters for the Department of Environmental Affairs (DEA), the first government building to have achieved a six-star Green Star SA Office V1 Design rating.

According to Welgemoed, the mechanical and electrical features are also a vital part of high-performance buildings. “The aspirations in terms of ventilation, air quality and acoustics have to be matched by the electrical equipment, so these must adhere to an equally high standard of specification as the building materials,” he emphasises.

“Finally, coordination is of key importance. We always try to ensure that all the consultants working on a project use the same drawing software to have all the models in the same format. This is to avoid clashes and wastage on site, which in turn leads to a greener building that is completed quicker, within budget,” Welgemoed says.

Intelligent buildings
Once the building is operating, building automation systems are valuable in avoiding unnecessary energy loss by automating things like blinds or lighting, according to Rubidge. “One of the important rules of sustainable design is that one has to measure the performance of the building, which can be done through sensors measuring water and electricity usage and supply,” he points out.

Local vs import
Just because a building is high performance by design, doesn’t automatically imply imported solutions. Both Rubidge and Welgemoed recognise the importance of first considering local products if they are available.

“Many high-end international products are supplied locally or while the material might be imported, the finishing is done here, for example glass coatings,” says Rubidge. “But there are limitations.”

Welgemoed agrees, saying that high-performance glass is something that is usually sourced from overseas since the market for it is still quite small in South Africa. He warns though that one of the challenges is stock availability and management, because some types of glass have a shelf life and can’t be ordered in bulk. “We experienced this during the DEA project, where the glass had to be glazed within six months from the manufacturing date because of the coating on them. When considering the period at sea and at customs, time runs out quickly,” he explains.

Another material often imported specifically for hi-spec projects is tiles, such as full-body ceramics and hi-tech printed tiles. Local volumes are too small for the industry to grow significantly in South Africa to equal the international standard.

However, Welgemoed points out that imported products are becoming more accessible, even cost wise, and that sometimes the sustainable benefits and long-term maintenance characteristics of a product outweigh the cost to import it.

Future outlook
Since the focus of high-performance buildings is on achieving the highest level of performance with the least amount of input, Llewellyn van Wyk, principal researcher in the Built Environment Unit at the CSIR, predicts that high-performance standards could soon apply to every single new building, instead of being the exception.

“The National Development Plan says that by 2030, buildings in South Africa should be net zero in terms of energy,” he notes. “And while it hasn’t been articulated yet, I think the same will apply in terms of water due to fast emerging water challenges. The question is: How will we get there?

“Meeting this challenge will require a whole lot of new innovations, and we will progressively see building technologies being developed in response to these performance requirements,” he says.

Pushing the (building) envelope
According to Van Wyk, the glazing industry is responding with advances in performance glass, the roofing industry is experimenting with cool pigment paints and innovative lightweight building systems are becoming available as alternative to traditional brick walls.
“Internationally there is massive investment in driving down the energy demand associated with making cement, either by increasing its strength so that less is required or by finding alternatives,” says Van Wyk.

The CSIR’s built environment division is currently researching geo-polymers and natural fibre composites, and will be testing these in a project in Mongolia later this year.

Functional glazing
“With glass being one of the weak points in buildings in terms of energy efficiency, there is also an enormous amount of development happening around high-performance glazing,” Van Wyk points out.

Some of the advances in glazing showcased at Glasstec 2014:
–    High-performance thermal and solar control glass – double-pane insulating glass filled with argon gas and used with warm-edge spacer systems currently achieves a thermal transmittance value of about 1,0W/m²K. Even lower values are possible with triple-pane configurations.
–    Glass with performance characteristics such as light control and energy production via its surface.
–    Printable, wafer-thin photovoltaic semi-conductors that enable solar films to be produced, which transforms windows or facades into electric power generators.
–    Switchable glazing – liquid crystal or polymer dispersed liquid crystal glass that turns opaque at the push of a button. This function is based on a film laminated between two glass sheets and connected to a power source. While no voltage is applied, the glass remains dense, but electricity causes the liquid crystals to align in such a way that the sheet turns transparent.
–    Thermochromic glass which changes its light transmission characteristics in reaction to temperature changes.
–    Luminescent glass that, through the combination of glass and light-emitting diodes, produces impressive light effects in single or multi-coloured motifs.

In Hamburg, a bio-reactor facade was created as renewable energy source for a five-storey apartment building called the House with Bio-intelligent Quotient. Micro-algae are cultivated in-between the glass panels to generate energy for heating purposes, as well as biomass, which is used to produce biogas.

Phase-changing boards
The roofing system, and in particular insulation, is also making way in addressing energy-efficient challenges. “In South Africa, unlike many other parts of the world, the main heat gain is through the roof rather than the walls, because of high radiation levels at a predominantly vertical angle,” explains Van Wyk. “The challenge for insulation is to find solutions that will provide the same kind of performance as offered upon installation, year in and year out.”

One such innovation is plasterboard that incorporates a phase-changing material such as microscopically small polymers with a wax core. As the room reaches a certain temperature threshold (21°C, 23°C, 26°C), the wax starts melting while absorbing the excessive heat energy. When the temperature drops, this energy is released while the capsule solidifies.

“All these developments progress towards squashing the temperature curve to reduce the time and energy required to maintain interior comfort levels,” Van Wyk concludes.

Full thanks and acknowledgement are given to VDMMA, Boogertman + Partners Architects, the CSIR, www.basf.co.za and www.glasstec-online.com.

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