Performance-Based Design (or How to Bake a Cake)

Person mixing pastry

Access Insight Magazine March 2018 Cover PageAccess Insights Magazine – Feb/March 2018

The following is an extract of an article published in the above magazine today.

The full article can be read here.

This is the first of two separate posts each providing an extract of the article. A third post will discuss the Australian Building Codes Board (ABCB) readability initiative. These will be released over the coming three days.

Performance-Based Design in Australia

Since the release of BCA96, Australia has had a performance-based building code. This might come as a surprise to some building practitioners. However, after 21 years it is widely recognised that the uptake in the use of Performance Solutions across the construction industry has been limited.

This has been credited to a lack of acceptance across all sectors of the building industry and a reduced level of awareness and understanding of how compliance with the building codes can be achieved through a performance-based solution.

The objectives of a performance-based building code are to create an environment that has more flexibility to develop innovative and cost-effective solutions by focussing on the outcomes that the building is required to deliver.

National Construction Code 2016

The current National Construction Code or NCC now includes:

  • Volume One Amendment 1: Requirements for Class 2 to 9 (multi-residential, commercial, industrial and public) buildings and structures.
  • Volume Two: Requirements for Class 1 (residential) and Class 10 (non-habitable) buildings and structures.
  • Volume Three: Requirements for plumbing and drainage for all classes of buildings.
  • Guide to Volume One Amendment 1: Companion manual to Volume One providing clarification, illustration and examples for complex NCC provisions.
  • Consolidated Performance Requirements Amendment 1: A compilation of all NCC Performance Requirements.

Compliance with the NCC

For those not familiar with how compliance with the NCC is achieved, the following is a quick summary.

Ultimately, as a performance-based document, the legal compliance requirement in each part of the NCC is the applicable ‘Performance Requirement’. A Building Solution will only comply with the NCC if it satisfies the Performance Requirements. These Performance Requirements are outlined at the start of each part of the NCC (i.e. in Volume One these include structural, fire resistance, access and egress, services and equipment, health and amenity, and energy efficiency).

Compliance can be achieved by one of three paths when assessing a building design against the applicable Performance Requirements. This was best explained during the recent national NCC seminar series when the Australian Building Code Board representative used an analogy of baking a cake.

The first method of compliance is by strictly following the recipe. The NCC outlines a set of prescriptive requirements within the various parts of the NCC and following this recipe to compliance is referred to as being ‘Deemed-to-Satisfy’. This prescriptive path needs you to use all the same ingredients and follow the same instructions each time to meet the Performance Requirements (for example, baking a nice cake).

The second method is by way of a ‘Performance Solution’, which is defined as a building solution that complies with Performance Requirements, other than by satisfying the Deemed-to-Satisfy provisions. This path allows flexibility, innovation and industry expertise to deliver the same (or better) outcome. Performance-based design allows you to substitute some ingredients based on experience, follow a different recipe or use an alternate cooking method, to meet the Performance Requirements (i.e. an equally nice cake, but with perhaps a little less sugar).

The third method is through a blended approach, often seen in Australia, where compliance with many Deemed-to-Satisfy provisions is possible or desirable, but some aspects of the design will be developed as Performance Solutions. From experience, this is the approach most often used in accessibility-related Performance Solutions, particularly during upgrades of existing buildings.

Productivity Gains in Performance-Based Design

The fire engineering profession was an early adopter of performance-based design, but other professions have been slower to accept the use of performance solutions. As a result, the ABCB is now actively promoting the use of Performance Solutions and attempting to increase awareness and acceptance of their use as an accepted pathway to compliance.

There is evidence to support this approach. A 2013 report found that 70% of the $1.1 billion per annum productivity gains delivered by ABCB reforms was derived from the use of a performance-based code. The report also suggested that future gains would be increased with more acceptance and use of Performance Solutions. ABCB representatives have suggested that these benefits could, in fact, be doubled with the use of performance-based design.

Whilst the Australian Fire Code Reform Centre (FCRC) published the Fire Engineering Guidelines prior to the release of the first performance-based building code (BCA96), up until very recently there has been little guidance material available for other building disciplines developing Performance Solutions.

Moving Forward with Performance Solutions

To change this situation, the ABCB has a three-pronged approach to increase the use of Performance Solutions:

  1. Engendering a Performance Mindset
  2. Capacity Building
  3. Quantification (including Verification Methods)

These initiatives and the proposed changes to the NCC are discussed in the Access Insight article but will be released on this website as a separate post titled ‘The ABCB, NCC 2019 and What You Need to Know’.