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.

  • Well Said Darren, I was an assessor with ABSA, I am a Licenced building designer, a steel detailer and a licenced builder. I lament that peer review or at least cross referencing should be undertaken to paint a broader picture and narrow the accuracy.
    When wearing my Builders hat the local Council inspectors, the clients and other builders really don’t pay any homage to the thermal detail, as a thermal assessor the finer detail is within the reflective air spaces configuration and accuracy, I tell my clients that this is very important, because the fundamental ideology how insulation works is its ability to trap air, therefore the most cost effective way to gain high levels of insulation is to ensure the detail is stringently followed.
    The complications or counterproductive thermal outcomes arise from a twofold mechanism of; if the detail is not stringently followed, which in practice is proven not to be so, the lack of generic insulation makes for a very poor thermal design outcome and the fact that most tradespersons are fundamental to existing building methods.
    The other real issue is the whole approach to thermal efficiency & design, the technically accuracy is wasted, cumbersome & counterproductive if not looked at in its entirety, it is far better, simpler & more efficient to utilise standard building practices and address the real issues of the functionality and the over reliance on air-conditioning.
    An example of this is; following down one blind path way under the current regime ultimately leads to buildings with no or minimal windows with misleading high energy ratings outcomes.

  • Having been an accredited rater since 2002, I have opted not to accept the cost imposition in time & money to my business to complete the required Cert IV course to remain accredited. The net result of this new requirement is that many experienced building designers, who hold energy assessor accreditation, have opted to not renew, thereby reducing the construction knowledge in this sector significantly. What we now see is a preference for Cert IV accredited raters over industry experienced raters. The industry is poorer for this blanket decision to 'upskill' all raters without proper recognition of past experience. The little discussed fact is that the NCC provides performance criteria which can assure 6 star energy approval without accreditation when completed by a registered building practitioner. Given this the accreditation requirement is nothing short of a NatHERS money grab which has had the net effect of halving the number of experienced raters in Victoria alone.

    • Daryl, I am starting to hear this a lot recently, particularly from those with a lot of experience!

    • Absolutely Correct, it is not good business management for everyone concerned, including the end user and the environment, ultimately it indirectly affects everyone on the plant!

  • Hi Darren,
    I have a simple solution:
    Make it mandatory that all windows/doors must be double glazed, have the max R-values in walls and roofs as the min requirements. Cost of double glazed windows will be reduced due to volume as everyone must install double glazed and the Energy Raters jobs to be re-adjusted making it mandatory for accredited energy raters only to do inspections during construction and at the end of construction. The other area of concern is the user, no point having a 10 Star house if the user keeps all the windows open whilst the air conditioner/heater is on and plasma TV's in every room, and a fridge for every occasion etc.

  • Having just bumped into NatHERS it hit me quickly that here is a cumbersome expensive system that pretends to meet environmental needs but actually is pulled and pushed to meet political and commercial needs and never will. NatHERS is NOT about sustainability and MOST IMPORTANTLY fails the people who will occupy the buildings. NatHERS ignores the most important parameters for a healthy built environment for the inhabitants – no IAQ requirement for just one example.

  • Dear Darren,
    Firstly I will state that I believe there is significant room for improvment and advancement when we compare current minimum performance requirements in Australia to that of other developed nations. However, there a few items that require a bit more information and clarification.
    Management Diagram: This is very wrong. NatHERS is managed through COAG based on industry and government guidance from the state level. This is the same as the NCC. A state by state agreed approach to a national direction. Many of the groups you have listed respond to or lobby the relevant state goverment body. Naturally each state has its own view on what is imporatnt due to current political and industry influences. NatHERS does have a technical advisory committee who provide guidance to the Administrator and COAG recommendations.
    Software testing: Researchers at Tas, SA, Vic & NSW have provided empirical data on real building performance for the last 20 years. Ths data has been used to provide ongoing improvment and calibration to the software. This practice occurs in every country and every software has good and bad points. Many northern hemisphere programs may be inappropriate in AU due to our climate that requires both heating and cooling on a regular, if not daily basis.
    Building materials: compared to other international tools, our material library is limited, but this is in response to an industry that does not provide adequate documentation and in many cases the sigificant difference between design documentation and the cheaper choices made at the time of construction. in the early 20's many houses in ACT had double glazing on plans but single glazing as built.
    Peer review – There is a lot
    happy to discuss…

    • As someone in the reflective foil insulation industry since 1985, and who gave extensive technical evidence to both the 2010 Senate Inquiry & 2014 Royal Commission – Home Insulation Program, I say that the House Energy Ratings are not based on real house testing data, across of range of differing houses., and vastly differing climates.
      Where is the differentiation for in-situ long duration testing of houses for both conditioned and unconditioned, ie free-running?
      The base BCA-NCC house model is conditioned! This is wrong. So many people have and want to have naturally ventilated houses.
      Again I say, that bulk insulation R-values are based on laboratory Steady State thermal testing for FOUR hours (only) between static plate temperatures of 33 & 13DegC, a USA test method. Buildings are not in Steady State across Australia – rather in Dynamic State.
      This thermal test method fails shockingly for the protection of chilled "conditioned" air traversing roof space ductwork. Catastrophic failure of airconditioning systems abound – I have them all on file. They are incredibly graphic. A total failure of Standards Australia to write truthful thermal test methods, which the public ultimately rely on.
      Currently, the public are stranded in ignorance about in-situ real-time thermal performance of many building materials and crucially insulation materials.
      And to think that legislation for Mandatory Disclosure of Energy Use in Buildings is in formulation right now.
      This will end up worse than the Home Insulation Program. Wrong data IN, wrong results OUT.

      Steering the vehicle over the cliff.

      Governments spout the line…."we can't tell Standards what to do". That is a lie. Why shouldn't they if the relevant Standards are failing.

    • Mark…thanks for the great response and clarifications. I appreciate your extensive research on the subject but many of my points remain valid. The system supports theory and not practical application in the Class 2 world. As our population continues to grow, driving more and more poor performing multi-resi buildings, the value of using an approach that is driving industry away or simply allowing gaming of the system to continue must be addressed.

  • Hi Darren,
    I have just come across your article and there seems to be some confusion about the use of window and glazing systems in the NatHERS modelling software. You have referenced a “default database for window performance; the Window Energy Rating Scheme” which highlights the extent of the mis-understanding, as the Window Energy Rating Scheme is a custom rating scheme for window products based on their real design and the default window database is a separate compliance path available within the regulated tools.
    To clarify, the NatHERS software currently has two different compliance mechanisms for glazing products, the first is the use of the default window database, which was developed by the AFRC for the NatHERS Administrator. This compliance path is intended for use where the final window product is not known and uses performance values as a stand in for real products until the final decisions on product procurement are made. This database is designed to allow a selection to be made that is required to be verified either through a re-assessment or by utilising a product that meets the performance of designated default window performance. This method does not use custom rated performance of products as it is designed to allow for flexibility in the system when final design choices have not been made.

    More to follow

    Richard Hamber
    Australian Window Association Sustainability Manager
    Window Energy Rating Scheme Manager

    • The second option for window selection is to use the full AFRC database, which currently comprises of products that have been certified for their energy performance by WERS. These are real product performances which have been calculated in accordance with the AFRC protocols and procedures, which are currently mandated by the NCC, and have been inputted into the software with a high level of detail. These products are to be called up in scenarios and will provide unparalleled levels of accuracy in terms of providing real frame and glass performance into the CHENATH engine.
      With these two different options for entering the performance of windows there are methods to allow flexibility for the assessor and designer to make informed design decisions in the design and construction of the building.
      You go on to state “We don't make up values for lighting, HVAC, walls or other features, so why do we do this for windows?” This is an over simplification of the methods for using window systems in the tools. The current method for using windows allows for the selection of custom rated windows, which are real performance values calculated from the simulation of the frame, glass and edge effects, and utilises world class research to provide real window performance.
      The AWA and its Window Energy Rating Scheme have been long term advocates for the use of custom only windows, as is common internationally, if the energy rating industry is ready to embrace them.

    • Richard, no confusion at all. I read the response on the WERS website. You are completely missing the point that in Class 2 buildings (Multi-Resi), we never use anything but custom windows and that those in the various databases overstates the performance of the system as they have much lower frame to window ratios. A 'planning value' taken from a database simply increases the risk of non-compliance later in the process when custom windows are assessed against it. Yes, the numbers are made up as they do not reflect that being installed. I recommend more industry engagement as opposed to industry protection. ABSA, WERS and Co are all going down the same route. We need a change and you guys refuse to illustrate enough motivation to suggest it could come from your direction.

    • Darren, I think that we are agreed that the use of the default windows is potentially dangerous as the substitution of product in the end can have serious impacts on the whole of building performance and that the best option in all cases is to use the real custom windows. You say that the frame to glass ratios are too low, I find this hard to accept as the WERS website (and the AFRC requirements) require that set standard sizes are used and this is common knowledge but the NatHERS tools have the functionality embedded in them to be area adjusted according to the real size of the product .