The façade sector is a dynamic, constantly evolving industry driven by a number of trends from technology to materials to costs.
So what does this mean for tall buildings in the Asian and Australian markets?
The sector, however, continues to rise to these challenges through clever thinking.
We have seen and been part of innovations like four-part unitised systems to accommodate double curvature curtain walls.
We have also been involved with extreme cold bending for curtain walls by developing in-house parametric modelling that considers all aspects of cold bend glass, including structural and fabrication limitations, as well as appearance. A specific testing method to validate numerical models for this has been developed as well.
The tall building market in Australia has historically been predominantly influenced by the residential market. These projects were often developed with the expectation of large cash returns with architecture and sustainability held in less regard. This saw a trend for cheaper and cheaper materials, simple designs and mass production options as a driving force for facades. Innovative solutions and opportunities for R&D were very limited.
This, though, has led to more design scrutiny as a common expectation from builders when providing these cost effective solutions nowadays. They have learned from the past as remedial façade works have started to pick up, similar to the post-Olympic era in the 1990s, caused by fast and in-experienced construction.
From a systems perspective in Australia we note the following key trends:
- Monumental awning windows on residential buildings to improve natural ventilation. This saves costs on air-conditioning but needs to be considered in tandem with wind implications, which isn’t always being done
- A move away from BMUs and a tendency toward rope access – a potentially worrying trend putting cost before safety
- Stage-by-stage construction which creates opportunities for wind engineers and other specialists
In terms of materials, the propensity for glass continues.
The technology for glass fabricated and processed in China is advancing to meet the European and American supply and it is very competitive in terms of cost. Even Europe and the US are now allowing their products to be processed in China for export use, and they are selling their coating technology to Chinese factories in order to remain competitive in the market.
Factored into this are architects who also want larger and larger glass size panels and for clearer and clearer glass, pushing the boundaries in terms of glass selection criteria.
Technology has also contributed to the sustainability of the materials driven, in tandem, by the increased demand for green certification of projects. Technology has also opened up new techniques and possibilities for application. For example, we are currently proposing to use an 80 millimetre thick single piece of carbon reinforced plastic (CRP) that is 15 metres by 15 metres on a project.
In Australia, as well as glass, there is also a trend toward other cheaper material options.
These include light weight steel, as this avoids the need for specialist trades, and the use of weaker stones like travertine stone, which, as well as the cost benefits, is also locally available and Green Star rated.
As we continue to go higher, there are three particular trends that we have identified as key to the next evolution of tall buildings:
- The magnification of issues on small buildings is exacerbated as you go higher. For example, there is the elastic shortening on columns as you build higher, so the stack joints need to cater for that by being installed with bigger joints.
- Although there are examples, like the 568 Collins Street project in Melbourne, where transfer structures have been avoided, inevitably in most buildings as we go higher these will have to be made at some point. This means careful consideration must be made for the deflection of the façade members to the floor above and below the transfer floor.
- Greater heights will lead to greater variation in wind loads and so optimising frame sizes will test façade engineers.
In terms of costs for a low-rise building, one could expect the façade cost to be in the range of 10 per cent or less of the total construction cost. With a super high-rise building, the façade cost can easily exceed 20 per cent, which is more than the cost of the superstructure, but simply because there is more surface area.
Savings can be made by having robust coordination between the design consultants; not only with the architect, but also the structural engineer (for reasons mentioned above), the MEP engineer, the specialist lighting consultant and the BMU consultant.
Other savings can be made by understanding your materials properly in order to optimise the cross-size of members and to minimise wastage by choosing appropriate modulations for the façade.
Building Physics Modelling can also help generate significant value. Energy modelling helps ensure appropriate glass selection to reduce loading on the HVAC systems, while daylighting and glare studies can help optimize façade additives and the overuse of artificial lighting. We have a live example where this approach saved the client a million dollars by halving the original depth of the sunshades.
From a developer’s perspective, it is all about risk and reliability.
Nearly all façades are produced based on façade contractor’s shop drawings. Construction risk can be minimised via a systematic QA/QC approach and contractual risk can be managed via specification.
The future presents a key challenge in the maintenance or façade access of a building. As buildings become taller and more intricate, ensuring that all parts of the façade can be accessible is a huge challenge that is often overlooked or left to the last minute.
With buildings being so tall, the duration of the cleaning cycle could mean that once you finish, it may be time to start again.
The maintenance of artificial lighting on a taller façade needs also to be considered as well as the replacement of glass and/or components on the façade (ie. gaskets, sealants, etc).
Staying on top of all the trends we have referenced is crucial to ensure the fostering of creativity but also an understanding of how these can be delivered without compromising the final design outcome for the sake of short-term financial gain.