Throughout recent times, there has been a considerable degree of criticism with regard to the Nationwide House Energy Ratings Scheme (NatHERS).

Speaking particularly of its use in the multi-residential sector, for example, intelligent passive design advocate Darren O’Dea said the system had come a long way but suffered from disjointed management, potential to be ‘gamed,’ oversimplified treatment of windows or glazing systems and a lack of communication with the market at the end of the market due to a failure to mandate that the number of stars in the rating be made available to all buyers and renters of existing property.

Building façade system designer Fiona McKenzie, meanwhile, describes the program as ‘rudimentary’ compared with international standards and says that the system ‘assumes things that are not tested by law’ – especially with regard to air-tightness.

Perhaps most pointedly, challenges associated not so much with the system itself but rather the manner in which it is being implemented were laid bare by a Pitt & Sherry report in 2014, which found that there was a lack of verification and auditing activity surrounding the system, a ‘culture of sign-offs’ and a lack of compliance across multiple aspects of the building chain.

So what are the problems, and is NatHERS really working?

Clare Parry, principal sustainability consultant at Grun Consulting and CEO of the Australian Passive House Association, says the system is generally robust as a benchmarking tool to inform decisions about energy consumption. She added, however, that it suffers as a result of a lack of verification regarding the performance of the as-built product matching up with the design upon which the rating was based.

No matter how efficient the design is on paper, Parry says, what really matters is the as-built outcome.

“The main problems I and a number of others have with (NatHERS) are that the outcomes are not particularly great,” Parry said. “I think this goes back to the fact that the whole process doesn’t have any verification procedures around it.

“You might have something that rates really well in design and so it looks really good on paper, but the constructed building may not reflect that design. A star rating on paper does not necessarily translate into a good building.”

Aside from this, Parry is critical of the system for assuming a moderate to poor level of air-tightness and giving thermal mass a heavier weighting in terms of consideration than what she says is justified. She says all NatHERS rated buildings should be tested against the as-built product and that more broadly, Australia must lift its standards during the construction process to ensure the as-built product delivered strong performance outcomes.

Darryl Hargreaves, a director of outer-Melbourne based house design and energy rating outfit Harvan Design, applauds the broad direction of the system in trying to promote greater levels of environmental friendliness within house design but says a number of issues needed to be addressed.

As well as the lack of checking with regard to the as-built product, he says there are inaccuracies within the FirstRate software program (one of three software programs accredited by NatHERS for use by NatHERS assessors) and that the system can be manipulated in many ways to achieve what you want to achieve. For instance, even when loading plans into the program (from a PDF) and subsequently scaling it to size, there can be inaccuracies as there are no points to pick on and you are not given the size of the room and therefore left to guess where the corners are, he said.

Speaking particularly about the situation in Victoria, Hargreaves said the ability of anyone to gain certification as energy raters simply by completing a Certificate IV course means it is now possible for energy raters to become certified without any holistic understanding of building design or construction. Moreover, a lack of recognition of prior experience in building design and construction means that a number of designers would have a considerable depth of experience to bring to the table but are potentially being put off from becoming certified by the amount of cost and time associated with completing the course.

Finally, he said, there are limitations with the tool as an overall rating of household energy efficiency in that the NatHERS tool revolves around a rating of building fabric, and does not take into account heating and cooling or the energy efficiency of appliances within the home. Put evaporative cooling into a home, Hargreaves says, and the energy rating essentially goes out the window.

Others, however, defend the system. CSRIO Energy for Buildings manager Dr. Stephen White, for example, acknowledges that there are genuine issues associated with implementation and verifying that the as-built product lives up to the rating given by the NatHERS design, but says many criticisms of the tool stem from either misunderstandings of the role of the scheme or from people with an ‘axe to grind.’

Whilst some critics had wanted the tool to better represent airtight houses, he said, others had criticised it for supporting ‘sealed and insulated boxes.’ The industry can not have it both ways, he said.

As for arguments about the system could be ‘gamed,’ White says NatHERS was largely designed to eliminate poor practice as opposed to enforcing best practice. Moreover, builders should be using the flexibility of the tool to look for ways to build compliant homes as cheaply as possible, he added.

As for notions about the system being taxpayer funded, White says in fact the system is user paid and is funded by a small charge to enable assessors to use the software.

“I think NatHERS is working well,” White said. “Builders are voting with the feet (over 70 per cent of houses use NatHERS to comply with the code) and evidence shows that consumers are getting better quality houses at a more affordable price.”

White acknowledges that the system did suffer from under-investment in continuous improvement in its first decade of use, especially in terms of the fact that it has only recently gone into the cloud. He adds that interfaces are not yet as they could be and integration of the software with CAD has only recently started to occur.

Nevertheless, he says any alternative system will require ongoing investment to ensure it remains relevant and responsive to industry.

“Glib assertions of easy low cost alternatives frustrate the hell out of me for their complete ignorance and/or disingenuousness,” White said.

The NatHERS energy rating system in Australia is coming under sharp criticism.

Whether or not some of it is justified, it seems there are issued regarding implementation which need to be addressed.

  • With the majority of building projects or even small renovations required to comply with an energy rating it is no wonder so many are using NatHERS, there is little if any choice. This does not reflect acceptance unless you count enforced acceptance. The questions being asked about NatHERS should reflect what is desired in the country from a rating system meant to support more energy efficient housing construction. Does NatHERS achieve this? In a word NO. The question then is why not and what to do about it.
    My greatest problem with NatHERS is that it is actually way too restrictive, heavily biased to current common construction, i.e. the status-quo and as such provides no real lasting benefit and adds only paperwork and expensive processes.
    More over building standards and performance requirements are I would have thought, meant to produce healthy environments for people. NatHERS fails miserably to support this ideal and in fact encourages the construction of some downright unhealthy structures. There are no effective Indoor Air Quality (IAQ) requirements that consider human health in NatHERS. That should be enough in itself to provoke a complete review. So I will leave it there. Enough said.

  • Many multi level high rise residential project ESD consultants use NatHERS. The algorithms weigh heavily in favour of passive solar design and thermal mass. A high aspect ratio building with a very high wall to roof ratio is contrary to the building concept assumed for the Algorithms. Using NatHERS for high rise is delivering high solar heat gain coefficient numbers for glass. This is counter to the building needs as evidenced by Commercial high rise, not rated under NatHERS, recommending low SHGC numbers to reduce HVAC and improve occupant comfort. Using NatHERS for residential high rise is clearly delivering the wrong outcome.

  • NatHERS has some issues but the biggest one in my opinion is that the system is not policed. As in the third paragraph of this blog: 'a lack of verification and auditing activity surrounding the system, a ‘culture of sign-offs’.' Once this is sorted, it has definitely possibilities to increase the quality of our building stock.

  • This article would have really been boosted if we had more practitioners supporting the NatHERS system as opposed to the natural defence by the CSIRO. If anyone thinks NatHERS is working well, they are not connecting to industry or delivery. It is a disruptive process, but not by GBCA definition. On large projects, proving 1000's of certificates before DA in NSW and after is a cash cow, nothing more!

  • Official response from the owner of FirstRate5 – Sustainability Victoria

    FirstRate5 is a NatHERS accredited software tool and it has met all requirements set out in the NatHERS Software Accreditation Protocol. This means that the administrator of the NatHERS scheme has verified that FirstRate5 is as accurate as the other accredited NatHERS tools on the market (i.e. BERS Pro and AccuRate).

    The Certificate IV in NatHERS Assessment shows thermal performance assessors (TPAs) how correctly use FirstRate5 to complete accurate energy ratings. There are a number of simple approaches TPAs can utilise to ensure the accurate scaling of plans and drawing of zones.

    The claim made in the article that there are inaccuracies in FirstRate5 and that the software can be manipulated is unsubstantiated and unfounded.

    • What other response would you expect from NatHERS. The claim is not that the software is inaccurate but that the input of a PDF file on which to base the rating zones can never be referred to as accurate. The claim that PDF files are not an accurate file medium to use for energy assessments is well founded & substantiated by every rater using the software. Now if they could allow cad files to be uploaded & used as a base for the rating tool then we might be approaching some form of accuracy.

  • While indeed the industry cannot have it both ways, someone issuing a certificate should know whether improved airtightness is a worthwhile goal or not. Balancing good with untenable arguments to justify a shaky middle ground is probably one source of the problem with rating tools.

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