When Lend Lease built what was then the world’s tallest timber building at the Forte apartment complex in Melbourne’s Docklands in 2012, the company had some ‘interesting’ discussions with the Metropolitan Fire Brigade.
The MFB raised eyebrows at the idea of a 10-storey timber building in the middle of the city.
Moreover, the building went far beyond what had been allowed for under what are known as deemed to satisfy (DTS) solutions to achieving compliance with what was then the Building Code of Australia (BCA, now the National Construction Code or NCC). Whereas Forte was 10 storeys in height, the highest anyone could go using DTS at the time was three storeys (this has since been raised to eight storeys).
Instead, the building was delivered using what was then known as an alternative solutions (now known as performance solutions) – a method by which the requirements of the Code are met through a solution which is unique to the context of a particular situation.
Whilst awareness about performance solutions has grown, several misconceptions about them and the performance based nature of the NCC remain. To explore these, Sourceable spoke with Neil Savery, chief executive officer of the Australian Building Codes Board (ABCB) and Mark Brentnall, managing director of Sydney based building consultancy and certification group Brentnall Consulting.
At the outset, it is important to clarify how the performance based nature of the NCC works.
Prior to 1996, the then BCA (like state based codes before it) dictated that buildings be constructed in a prescriptive manner. From 1996 onward, however, the BCA and now NCC has adopted what is known as a performance based approach. This is intended to provide the building sector with greater flexibility to embrace innovation and to select the most appropriate building solution given the particular context of an individual building in question.
Under this approach, there are performance requirements, DTS solutions and performance solutions.
Performance requirements specify the minimum standards by which the building is expected to perform. They are the outcomes which the building design must deliver. They are mandatory and must be satisfied if the building is to comply with the NCC.
Performance requirements can be achieved by either a DTS solution, a performance solution, or a combination of both.
DTS solutions essentially represent a ‘cookbook’ approach and describe a set recipe of materials, components, design factors and construction methods which, if used, are deemed to satisfy the performance requirements of the NCC.
Performance solutions are building solutions which are specifically designed to form an appropriate solution in the context of each individual situation. These directly address the performance requirements of the Code by using one or more of the assessment methods available under the Code. Whereas DTS solutions are prescriptive in nature, performance solutions offer a flexible alternative to meeting the Code’s performance requirements.
Neither DTS solutions or performance solutions are mandatory. The performance requirements are mandatory. Both DTS solutions and performance solutions simply offer a means to achieving the performance requirements. Neither is mandatory and both are valid as a pathway to achieve compliance.
According to Savery, misconceptions fall into seven areas.
First, there is a myth that industry does not want a performance based National Construction Code.
In fact, Savery says, it was industry itself which came together in the late 1980s to request that governments introduce a performance based code to facilitated delivery of new buildings, construction techniques and products. The outcome of this was that state and federal governments introduced the performance based Building Code of Australia to facilitate this.
More than 20 years later, he says the industry remains committed to and embraces the performance based nature of the Code.
Second, Savery says there are myths about performance solutions cutting costs.
To be sure, he says, cost savings and efficiencies may be achievable through the design optimisation which performance solutions enable. However, he says that flexibility also enables the industry to meet multiple (sometimes competing) objectives and to provide greater functionality and amenity whilst still achieving the mandatory performance requirements.
Indeed, Savery says, there are many examples of how performance solutions were used to deliver improved building performance.
In Perth’s Matlock Street in 2013, for example, eco-effective architect and Curtain University Academic Sid Thoo RAIA was engaged to renovate an existing single-story home built in the early 20th century. The clients wanted to preserve the dwelling’s character while adding a second storey consisting of a new kitchen, living, dining and upstairs parents’ retreat towards the rear of the block.
The DTS approach to energy efficiency restricts opportunities to test and specify different combinations of wall types, insulation and windows so as to produce an energy compliance outcome. An additional consideration revolved around using the Nationwide House Energy Rating Scheme (NatHERS) Technical Note1, which requires house energy ratings to be assessed against the entire home. This therefore required the thermal performance assessment to include an assessment of rooms and spaces that would remain unchanged during the renovation.
Primarily through the use of double glazed windows with timber frames, however, the architects were able to demonstrate compliance with the performance requirements through verification method V188.8.131.52 by demonstrating that the heating and cooling loads in the proposed building were lower compared with a reference building – the proposed design being modelled using the Autodesk Ecotect Analysis software tool.
As a result, energy modelling of the proposed design allowed multiple options such as thermal mass, insulation and ventilation, and how they could be combined to improve the heating and cooling load performance, as opposed to just minimum compliance or a star rating. The clients were able to optimise the thermal performance of the proposed addition without the need to assess parts of the existing house that would remain unchanged.
A third misconception involves notions that performance solutions are an inferior way of building which inevitably deliver lower performance compared with DTS solutions. DTS solutions, Savery says, are simply one of the available pathways to achieving the performance requirements of the NCC. Provided that they deliver a solution which meets the performance requirements of the Code, Savery says performance solutions represent an equally valid pathway to achieving compliance.
Fourth and fifth, Savery talks of ideas that performance solutions are too costly and also that use of performance solutions leads to time delays. To be sure, Savery acknowledges that greater effort is necessary to support performance solutions compared with a DTS approach. In cases where this delivers better outcomes, however, he says this should be seen as an investment which delivers net positive outcomes overall rather than a cost. Indeed, he says an industry survey undertaken by the ABCB indicated 68 per cent support for performance solutions justifying their investment overall.
Sixth, Savery talks of misconceptions about practitioners needing only to comply with the DTS solutions. Indeed, he says notions about satisfying DTS solutions necessarily achieving compliance with the NCC are dangerous and ones which the ABCB has been trying to debunk.
Rather, Savery says it is the performance requirements of the Code which need to be satisfied. These must be satisfied using either performance solutions, DTS solutions or a combination of both.
On a related note, Savery says some have fallen under a misconception about the ABCB promoting the use of performance solutions over that of DTS solutions. This, he says, is not the case. Rather, the Board’s education initiatives have revolved around promoting understanding about how the Code operates in general. As part of this, it has promoted awareness about the merits of performance solutions in cases where no DTS solutions are available or the complexities of the project are such that performance solutions are warranted.
Indeed, Savery says, the performance based nature of the Code allows the industry greater flexibility to innovate and move forward as technological change progresses. In fact, writing and maintaining a prescriptive code which is able to keep up with change is not feasible.
Finally, Savery says there is a misconception about a lack of information and material in regard to performance solutions. In fact, he says, there is a wealth of material on the regulator’s web site.
Brentnall agrees that there are misconceptions in several areas.
First, he says there is a notion that DTS requirements are the best possible solution in every situation. Under this misconception, Brentnall says there can be presumptions that the DTS solutions have been based around scientific analysis and/or historic evidence and have been demonstrated to represent the best possible way forward. Following on from this, he says there is a misplaced belief that performance solutions represent a form of compromise and an inferior alternative.
This, he says, is wrong. DTS solutions, he says, are rarely based around scientific analysis and in many cases have been developed through trial and error.
Moreover, DTS requirements are limited and cannot apply to every conceivable building design. Accordingly, in many instances, Brentnall says DTS provisions have been put in place on the presumption of a worst case scenario in design. These represent a ‘big hammer’ approach which is overly conservative and unduly onerous where designs are better than worst-case.
Brentnall says performance solutions reflect consideration of the most suitable approach given the context of the building in question.
Next, there are perceptions about performance solutions being applicable only to complex situations and applying primarily to more radical situations (such as the Forte apartment example).
Granted, Brentnall says, there are cases where you have large, complex buildings and fire engineering reports which extend for several hundred pages. Nevertheless, he says performance solutions can also be applied to more vanilla cases such as minor issues with balustrade configuration, small increases in exit travel distances or minor issues with fire resistance levels. Indeed, he says the most significant gains could arise from relatively small-scale performance solutions being applied over a large number of projects.
That said, he cautions that these opportunities often go unrealised as the process of gaining approval for these on each project is complex and costly. The substance of the subject matter being considered for many performance solutions is not difficult. The process of getting these approved, however, is costly.
Third, Brentnall says there is a misconception amongst property owners that performance solutions will reduce their flexibility in how they use the building in future leasing arrangements and/or will add to the complexity and cost of managing their building.
In most cases, Brentnall says performance solutions will consider and accommodate a range of potential future uses for the building and will afford owners flexibility in respect of changes in use and the type of tenant who is accommodated.
As for management complexity, Brentnall says in most cases annual fire checks will simply revolve around ensuring that the fire solution which was approved remains in place. Large-scale changes in how the building needs to be maintained, he said, are rare.
Going forward, Brentnall would like change to improve access to performance solutions. Certifiers could be afforded the ability to accept performance solutions based on relatively simple methods such as a comparison to DTS requirements within buildings which fall under their jurisdiction. Certifiers on relatively minor issues could also be allowed to carry out assessments for performance requirements themselves without needing an independent report.
In some cases, there could specific, basic and common performance solutions that can be adopted in the DTS provisions or be nominated as automatic performance solution – possibly with standard evaluation reports for common use.
Finally, an independent body could be created to provide analysis for performance solutions in cases where the certifier in question either does not have hold appropriate levels of accreditation or does not have sufficient skills in respect of the performance solution in question.
For his part, Savery says greater and competent use of performance solutions is a priority for the ABCB and that the regulator is undertaking a number of activities toward this end. These include:
- Targeted communications campaigns for specific sectors
- Active subject matter expert networks to advise industry on best practice and competent use of performance solutions
- Case studies to showcase the benefits of performance solutions, as well as FAQs and other resources to support the application of performance based design
- A guideline template for the development of performance based solutions
- Working in partnership with industry to increase engagement and deliver workshops and seminars
- Exploring opportunities to strengthen education requirements through the accreditation systems
- Exploring integration of performance-based design in continuing professional development programs.
Australia has a National Construction Code which is based around the performance of buildings.
For practitioners, understanding exactly how this works is imperative.