As a wise man once told me, “It is easy to deceive yourself, it’s just all of the others you need to convince - that’s the real challenge!”

On the same note, is it time the Australian construction industry admitted that the NatHERS system is fundamentally flawed for assessing multi-residential (Class 2 buildings) Section J compliance?

With a renewed interest in greenhouse gas emission reductions on the back of COP21, can we honestly say this cornerstone objective of Section J compliance is being met and will be a tool for improvement in Class 2 buildings?

The Nationwide House Energy Rating Scheme (NatHERS), the national framework for the thermal performance, has been much-discussed and debated over the past year. Sadly, most of the comments from industry were born of frustrations with the system and process. While it sometimes doesn’t feel like it, when running the models and hoping to hit the magic number of stars to tick that compliance box, great strides have been made within the NatHERS rating system by talented and enthusiastic people that should not be simply forgotten.

However, today we seem to be at a crossroads regarding the value of this approach to the built environment. After years of administrative tension during the rapid rise in multi-residential developments across Australia, particularly in Sydney and Melbourne, we need to ask ourselves if the glass is half full, half empty or has it a gaping hole in the side.

Beyond a revenue stream for consultants and presumably for the administrators, with over 16,000 dwellings approved for construction each month last year all requiring a rating, can we say that the NatHERS rating system is leading to an improved quality in our multi-residential built environment or are we simply lost in a convoluted mess of self-interest?

Disjointed management

First and foremost, the administration and number of stakeholders in the process over the last 15 years has become a bloated who’s who of government departments, a scientific research agency, software tools/developers, assessor accrediting organisations and industry bodies, all with a claim in the discussion. With minimal industry engagement, it is no wonder that the reporting methodology and state-specific requirements are an ongoing source of pain for the modelling community.

nathers chart

A system of gaming

It only takes a short period of time working on the deliver end of the NatHERS rating system to realise that the system is being gamed for results and not performance. In my view, this is partly commercially driven but equally a component of the unpredictability of the modelling software and a lack of user confidence that sustainable design principles will actually provide benefit to the build.

Where it really matters, in the built form, there is little evidence that what is being specified within the modelling process is not being transferred into the actual building. In a recent report by the National Energy Efficient Building Project (NEEBP), 50 per cent of homes reviewed (albeit from a tiny population sample that is likely statistically irrelevant) could not confirm if they were compliant with the NatHERS rating system.

A calculation engine that needs improvement

Beneath the hood and focusing on the energy modelling tools, the CSIRO-developed Chenath engine has proved suitable for Class 1 buildings and meets the internationally recognised BESTEST protocol (northern hemisphere) for software testing.

While tested for Class 1 buildings back in 2004, can we really state that this methodology can be readily transferred to multi-residential (Class 2) buildings with fundamentally different flows and storage of energy? Given the recent Chenath engine updates to account for bugs and improvements, which has taken over a year to integrate into the various software tools, should we not have seen a BESTEST update illustrating continual compliance against the protocol? Paid for by the tax payer, should this not be an open source engine, as the equivalent (Standard Assessment Procedure) is in the UK?

Simplification of glazing

Another technical question that cannot be ignored is the simplified treatment of windows or glazing systems. Using the supporting technical compliance documentation to ensure all NatHERS modelling is undertaken under the same assumptions, we are directed to use a default database for window performance; the Window Energy Rating Scheme (WERS).

Representing a list of default values within the NatHERS modelling software that enables windows to be rated and labelled for their annual energy performance, WERS neither reflects the custom window products being procured on most Class 2 multi-residential projects nor their performance as it is primarily a function of the frame quality. As such, we are adding values to models to ‘make it work’ for glazing systems that are not those used in the built form. We don’t make up values for lighting, HVAC, walls or other features, so why do we do this for windows?

No opportunity to peer review

Another deeply frustrating element of multi-residential compliance is the lack of opportunity available to larger projects for a peer review to be undertaken from design to construction.

The commercial reality of the design and construction process most commonly used in Australia is that the same assessors are often not carried through the entire project to the built form that may be as long as three years. As a result, in the event of design changes post tender, it is often difficult to assess the full set of assumptions made by another assessor and if they are accurate to a set of drawings and specifications. This generates far more work and confusion than is necessary.

No communication with the market

Getting to the business end of the NatHERS ratings, until we mandate that the number of stars in the rating are made available to all buyers and renters of new and existing properties, similar to the Energy Performance Certificates in Europe, we are not allowing benefits to be gained by theoretically higher performing buildings. Without this driver, as we do for NABERS, how are we to convince market-driven construction teams that the effort required for higher performance buildings are worthwhile and carry a bottom-line economic benefit?

A future in question

After five years of development and consultation, from July 1, 2015, all existing accredited assessors have been required to upgrade their skills to the Certificate IV in NatHERS Assessment. The aim of this professional development has been to achieve ‘consistent and reliable outcomes’ by assessors that require a minimum level of understanding of building construction, building thermal performance and applicable building regulations.

Early feedback from the NatHERS modelling community suggests that this onerous undertaking – expect two to three weeks of full-time training at a significant cost to your business through lost revenue – fails to engage in developing an understanding of how to improve sustainable design skills. Rather, it achieves ‘consistent and reliable outcomes’ by teaching the assessor how to game the system to ‘make it work’ within assessment scenarios that are fundamentally detached from commercial reality. With an unclear outcome for our built environment, this process represents a very real risk that it will harness resentment of the NatHERS assessment process rather than engaging our industry and further reduce the body of assessors nationally.

Are we ready to face a few home truths to plan for a more effective solution for multi-residential buildings? A gaping hole has appeared in the NatHERS system that may very well ensure the vast majority of our multi-residential buildings stand as a legacy of poor performance and oversight.

Until we fix the administration, technical, construction and end-user issues, collectively raising our voice against a system that simply doesn’t work, the NatHERS framework may provide little more than a drawn-out process with no real benefits to the built environment. Change is difficult, but without it our industry will be stuck in a rut and only have ourselves to blame.