Performance-Based Design: Benefits and Pitfalls

Thursday, June 23rd, 2016
liked this article
Engineering Education Australia – 300 x 250 (expire Nov 30 2016)
performance based design
FavoriteLoadingsave article

Performance-based building codes are dedicated to allowing industry to tailor design solutions to achieve requirements and boost productivity.

They allow us greater flexibility in terms of what we can build, leading to more interesting and/or efficient designs and allowing us to increase our overall building output.

For the uninitiated, performance-based regulation is simply an approach that allows designers to demonstrate via analysis of known risks and design environments that construction will meet certain performance requirements (energy efficiency, load, fire safety performance and the like) without prescribing exactly how these outcomes are achieved.

Performance-based design has slowly emerged across the Australian building and construction landscape since it was introduced into the national Building Code in 1996 (the first Building Code of Australia was introduced in 1990 but contained only prescriptive DTS options).

Today, many new buildings feature some level of performance-based design (documented as ‘Performance Solutions’) and the NCC allows designers to demonstrate that their design complies with either traditional deemed to satisfy (prescriptive) elements or has been assessed to include appropriate elements to meet the performance requirements, or a combination of both.

On the surface, we have every reason to believe the current regulatory approach is contemporary, progressive and working well.

As the economy transitions from mining and resources, building and construction is poised to take its place as our major driver of economic growth. An Australian Industry Group study found that construction accounted for eight per cent of our gross domestic product (GDP). It comprises more than 330,000 businesses nationwide and directly employs over one million people (around nine per cent of the total workforce).

When applied correctly, performance-based design can deliver buildings that are more aesthetically pleasing faster and at a lower cost than might be possible under a paint-by-numbers or “deemed to satisfy” model.

So what’s the problem?

The problem with performance

It should come as no surprise that the use of performance-based design introduces a need for increased understanding, not just of design professionals but the entire supply, installation, routine service and maintenance chain. With performance, a gradual increase in the competence of practitioners involved in design through to implementation of such designs is necessary in order to achieve compliance.

Let’s start with the designers. Of all the engineering disciplines, fire safety engineering is considered to be adolescent. We know a lot about fire science and strategies, techniques and technology used to apply it to commercial projects are evolving rapidly.

Performance-based solutions for fire immediately require expertise from a fire safety engineer, who must make value judgements about the validity of design decisions and their relationship with occupant safety in the event of fire. Unlike structural engineering (which could be considered a grandfather by comparison), fire safety engineers are still debating the criteria on tenability and acceptable methods to demonstrate their designs are safe. Introducing performance-based design as an option has accelerated the profession, but there are still plenty of questions regarding appropriateness of assessment rigour and inputs.

Installers do not have a performance-based mindset. They focus on delivering prescribed solutions as contracted and are used to establishing price and system performance targets based on traditional prescriptive codes. Introducing “one off” bespoke or custom variants to these prescriptive approaches rubs against the grain and needs dedicated directions as to what is required when suddenly one size does not fit all.

For the Authority Having Jurisdiction (such as a building surveyor) approving the performance based design, they too are suddenly left without the security of checking against prescribed requirements. This means they will likely need to call in experts with fire safety engineering design skills to provide an independent check on their behalf regarding complex fire safety engineering.

Owners are unlikely to have any awareness of the impact of performance-based designs, especially if they were not involved in the construction approval. Without knowing the way a building’s use has been assessed and when certain safety features have been installed or are required to be maintained, it is more than likely that owners will be oblivious to requirements that could jeopardise their legal obligations and safety if not maintained, and this can include the implementation of tailored emergency management plans.

For any routine servicing or maintenance company to operate competently, they need to know what they need to service and maintain, as well as why and how, in order to be sure it remains effective. Without the prescriptive code as a manual, they must hope designers have been diligent enough to document what is expected for their design to function and how to measure this.

The key factor across of these roles is – without prescribed requirements, how do we know we’ve hit the target and will continue to meet it?

The solutions

Performance-based design is not going away any time soon, unless it is determined to have a negative impact on public safety.

To continue to reap the benefits of performance and avoid a return to being locked in to antiquated prescriptive codes, the Australian Building Codes Board must continue its stated objective of “engendering a performance mindset” via the development of verification methods. There are already a few of these in the Building Code, but not many.

Verification methods introduce more quantifiable targets that performance-based designers can meet without prescribing how to get there – a sort of halfway house between performance requirements and deemed-to-satisfy requirements. This gives clear direction to designers as to what their analysis should be able to demonstrate. It also gives Authorities Having Jurisdiction more confidence that designs meeting these quantifiable targets should be approved and increases consistency.

Importantly, unlike methods introduced in New Zealand, the ABCB approach is being developed to ensure methods used by fire safety engineers to meet these targets are not limited, allowing good engineering and ingenuity to continue to evolve. It is becoming clear that introduction of more quantifiable verification methods will make the target much clearer and in turn easier for designers to hit.  But if these designs don’t include clear, albeit bespoke, requirements for what systems to install, how to install them, how to integrate them without systems and how to measure that they are operating as intended, we will miss the target.

This is not helped by the uniquely Australian situation of having eight different variations of building and construction regulation, each with differing expectations for administrative processes for the review and approval of performance based designs and the competency of individuals required to do this.

Whole cottage industries of experts have sprung up just to unravel the labyrinth of these requirements for end users. However, the outcome too often is individuals simply forging ahead in confusion, creating non-compliant and potentially dangerous scenarios for the eventual occupants of these buildings without ever being held accountable.

We must address these issues now if we are to avoid a similar scenario to the New Zealand “leaky building” experience, where the use of cheap building products that were signed off under the auspices of performance-based design have now been found to have caused millions of dollars worth of defects in residential homes.

Which leaves us with one question: where is the benefit in producing more buildings, more cheaply now if they come to haunt us down the road?

To restore and support ongoing confidence in the performance-based process, education and enforcement of consistent processes needs to be agreed upon and supported by regulatory requirements that are nationally applicable. Such requirements should include clarification of who can design, who can approve design, referral to other stakeholders and documentation requirements for installation and maintenance.

We can’t afford to leave safety objectives in the passenger seat.

We need a building and construction sector where trained, competent individuals are making quality decisions at each phase of design and construction. Performance-based design is not going away and we all need to work together to ensure compliance so that safety is prioritised along with efficiency and productivity.

FavoriteLoadingsave article


 characters available
*Please refer to our comment policy before submitting