Sectors: Designers
Building facades are an under-appreciated facet of the design and construction process whose importance will only grow because of climate change, according to Beres Dowdle.
Gone are the days when the façade stood as a rigid, static singular item that represented nothing more than a barrier to keeping the world out. The façade of today freely interacts with other elements of a building. It is the filter that connects occupants to the outside environment.
Today’s façade stands as the focal point of what we now know as bioclimatic design.
The way in which façades have been designed and procured has changed significantly over the past 20 years, and the understanding of how they impact on a building – be it commercial or residential – is now far greater.
As this understanding has developed, so too has the façade’s influence on the building’s overall performance. Once seen as an impost on delivery (through its cost, critical path and possible source of risk) it is now recognised that the building fabric or building envelope, considered as a whole, impacts directly on the use of a building through operational cost (both energy and maintenance) and on the comfort and health of the occupants.
This altered perception has largely been influenced by the impacts of climate change, and the way in which owners, occupants and regulators have responded has forced us, as designers, to produce a better outcome and gain a more holistic understanding.
Taking a longer view
The design of many buildings is presently focused on their delivery and operation so that they meet a set of criteria based on the past or present experience. These criteria are derived from commercial equations, tenant expectations, market perception and historical climatic conditions.
Unless specifically required, façade design typically has limited impact on the building’s operation and none on its performance into the future, either in response to changes in the world climate or on the end of the building’s original life and how it may be reused. Considerations of future-proofing and adaptation requirements are also typically overlooked as they have not been required in the past, making them hard to specify and even more difficult to procure.
Only in PPP (public private partnerships) and PFI (private financing initiatives) projects has it really dawned on the delivery and operation team that the future cost and performance of a building needs to be dealt with during the initial procurement – at least for the initial change-of-use in the building’s first 25 to 30 years.
The typical method of delivery strives for the lowest immediate cost and time delivery option, which therefore sees the whole-of-life cost, measured either in dollars or by environmental impact, excluded from the equation. How a building may be operated or easily adapted for future reuse is hardly considered.
Experience gained in the re-generation of buildings confirms there is a disconnect between the 15- to 40-year product cycle of a building and the technology and products which are embedded or used within it. Current time scales will see many generations of embedded technology through the first life of a building and façade.
The way in which some building envelopes are currently procured is very much a symptom of the “rip, tear, bust” delivery method – one where the very best of design intent may have been developed as a whole, paying careful attention to the façade’s integrated performance/nature, acting in unison with the structure, mechanical systems and the sustainable design initiatives. This may be compromised by the decomposition of the building envelope into a number of discrete façade elements and prices based on the lowest common denominator.
And the result of this type of procurement? A building fabric that is as disconnected as the individual elements of the façade. It is also counter-productive, particularly when considering the whole-of-building integrated performance required to meet the demands of both the regulatory and sustainable objectives being incorporated into the design. This is particularly true when designing high performance building fabric systems such as ventilated double skin facades, hybrid ventilation strategies or building integrated photovoltaic systems.
The fragmentation of façade elements into the lowest cost option not only reduces performance through uncoordinated assembly such as air infiltration – which greatly influences energy transfer, vapour migration and indoor environmental quality – but also results in a reduction in the overall quality of materials, in turn reducing the durability, life span and opportunity to adapt the building and increase its future usefulness. The fragmented façade thus has little opportunity for easy reuse in the future when the building may be regenerated.
Considering climate change
Changes in climate will result in higher average temperatures (anywhere from 2 to 4 degrees Celsius), higher extremes in temperature, higher temperatures from heat island effects, greater extreme weather events including higher intensity and variability in rainfall, and higher wind loads in some locations. For the property industry, this means a need to consider the greater stresses on the building fabric design of yesterday.
If the ‘now’ design model considers the delivery of buildings at today’s cost, the ‘future’ model must reflect the additional strain the environment will place on the performance, along with alternative ways of assessing the economic performance of their asset – in both dollars and carbon.
We can no longer assume that conditions will remain as they currently are, and that with regular and appropriate maintenance and use, a building façade will continue to perform ad infinitum as on day one.
The model needs to consider the whole-of-life aspects and already we are seeing a number of clients asking for assessments that cater to this need. These assessments imply both durability and life cycle analysis, along with whole-of-life embodied energy and embodied carbon.
But these are still quite formative as the methods of procurement remain “rip, tear, bust” and rarely is the end-of-life reuse, its flexibility and adaptability really considered.
One of the questions we face when developing whole-of-life and life cycle assessments is how to establish an acceptable recurrent period for when items need to be upgraded or replaced. This decision in mechanical systems is relatively simple as items are more mission critical – if something doesn’t work, the system doesn’t work. However, with façade systems, the decision is often emotional and subjective as the level of tolerance and acceptance of defective items varies from client to client.
So, how do you design for adaptation to climate change?
- Should you design for higher winds?
- Should materials be more durable and longer lasting?
- Should designs cater for retro fitting of shades, renewable energy sources or operable windows?
- Should whole of life costing be used instead of low capital investment?
- Should there be a services agreement for the façade?
The questions are many and there are areas yet to be fully explored. How will innovation in delivery be addressed to ensure we move on from performance now to performance tomorrow? We are yet to see. But one thing is certain – this approach will define the buildings of the future.
Beres Dowdle is building sciences leader – Asia Pacific for Aurecon.
