17 November 2011 – Does it sound strange that we are still reviewing NABERS? The energy (and other environmental metric) rating system that started out so long ago is currently being re-reviewed, this time by the Australian Institute of Refrigeration Air Conditioning and Heating. Separately, however, it is also under review by the Property Council of Australia and in another work, by AIRAH, to see if elements such as its energy modelling can be harmonised with the Green Star rating tool and the Building Code of Australia, Section J in particular.


Yes, we’ve had reviews of NABERS before. Some of the inconsistencies in the methodology have been fixed and the star rating moved up a notch to six stars.

But it seems there is more to do.

This time NABERS stakeholders’ advisory committee has asked AIRAH to do the impartial technical thing. (Instead of the heavy handed political thing that has the practioners perplexed).

Chief executive officer of AIRAH Phil Wilkinson said the work would complement the review already undertaken recently but hopefully bring a more technical and impartial view to the process given that his members are generally the engineering consultants who undertake the NABERS assessments.

Here’s the website for input, which is strongly urged by Wilkinson.

Wilkinson says, “one of the things that came out with the NABERS stakeholders advisory committee was that the industry hadn’t had a good say. What was found was there was more will to have the industry more involved in the development process So things are starting to open up.”

The advisory committee, by the way, is composed of mainly non-technical people.

According to Wilkinson the sense coming out of the committee deliberations was that “NABERS is broke.”

So what needs fixing?

In theory at least, says Wilkinson, the AIRAH review should complement the PCA’s.

“We have no agenda, we’re not aligned with any of the tools and it’s our members are the ones who use the tools and do the ratings,” he says.

“They’re the guys who can tell if it’s really broke or not.”

Wilkinson says that the sense is starting to seep to the top echelons of the property world, that “the industry really does love NABERS.”

So it seems there’s more to this issue.

Some of it came out during a casual chat to one of the chiefs at the NSW Department of Environment and Heritage after the CitySwitch Awards in Sydney on Tuesday night.

All the angst and reviews are perfectly understandable, he said. It’s all very well when NABERS is a voluntary tool but now that there is a regulatory imperative, through mandatory disclosure of energy efficiency, the tool has  some serious commercial ramifications.

It’s understandable the industry investors want to ensure it’s fair and working well for them from a governance point of view as well as technical, our source said.


The other bit of work under way for NABERS also involves Green Star and the Building Code of Australia.

Wilkinson says, “We did some work with the Building Code with compliance with Section J …and we thought let’s put all this (work) in one place and consolidate it.”

A word to the NSW Office of Environment and Heritage, which manages NABERS, encouragement from Canberra, and it was decided to start to look at this massive project.

In steps.

It’s complex of course, being an engineering issue, but as we understand it AIRAH will start with a look at an energy simulation models and how they line up with the three approaches. Currently ¬¬– you guessed it ¬– they don’t.

“So get different inputs for the same thing,” Wilkinson says.

But then, he adds, it’s a bit naïve to think all three could correlate, simply because they measure different things

The BCA is about minimum standards, for instance while NABERS and Green Star are about aspirational targets and world’s best practice.

So the work is to see what can be harmonised; where to start.

And Wilkinson says some of the work will be strategic, to see how the tools should shape up over the next five years.

See below* for some highlights of the discussion paper around the energy modelling protocols for the tools and code.

Discussion paper highlights
Following are highlights from discussion paper, Australian Energy Modelling Protocols ¬– potential for harmonisation and alignment

This paper summarises the issues identified when considering the proposed alignment and potential harmonisation of the three energy modelling protocols in current use in the Australian non-residential building industry namely:

  • NCC 2011 Volume 1 (Building Code of Australia) –Verification method JV3
  • Green Star Greenhouse Gas Emissions Calculator Guide – Public Building PILOT
  • NABERS Energy – Guide to Building Energy Estimation (for commitment agreements)

The core issues are:

  1. Each modelling protocol has been developed and managed by different organisations and for different purposes and so the three individual protocols have diverged in some areas and duplicated in others.
  2. Retaining three separate protocols with different default values and profiles is causing some frustration, confusion and additional expense to industry.
  3. Each modelling methodology has slightly different goals and outcomes so default values cannot be automatically standardised.
  4. There is potential for alignment of specified defaults, schedules and requirements and also potential for further harmonisation between the three modelling protocols.
  5. Harmonisation will only occur after detailed consultation and negotiations with the owners of the three protocols.

There are several energy modelling protocols currently in use by the Australian building industry to simulate the energy performance of non-residential buildings. These include protocols required to undertake energy modelling for; BCA minimum energy efficiency standards compliance using the JV3 approach, NABERS Energy Commitment Agreements for offices, and Green Star building rating schemes.

While all of these energy modelling protocols have differing applications and goals, there are some opportunities for alignment between the energy simulation requirements, particularly with regards to default input values that are specified for input into the simulation programs. Default values such as climate conditions, building schedules, internal loads, occupancy profiles and the like can have a significant effect on the modelling outcomes. The specification of different defaults in each protocol can cause confusion and frustration for protocol users leading to error or inaccuracy in modelling results and duplication of modelling work
The alignment of requirements and practices where possible, has the potential to improve the Australian building industry’s understanding of the various energy modelling requirements. A more complete understanding of the requirements, including the reasons underlying the remaining differences between protocols has the potential to improve the standard of energy modelling outcomes, as well as reduce compliance and implementation costs to industry.

In particular this paper should help to:

  • Facilitate a clear understanding, by all parties, of the fundamental objective of each modelling methodology.
  • Provide a comparison of the “requirements” of the various modelling protocols for all stakeholders.
  • Highlight any apparent inconsistencies between the protocols (and their defaults) that may not be absolutely necessary.
  • Investigate areas where these requirements (and associated default values) can be aligned or rationalised between the protocols and provide recommendations on the options for alignment where applicable and appropriate. (This may require a sensitivity analysis to be undertaken on the input variables for each approach to quantify their effect on modelling outcomes.)
  • Acknowledge areas where modelling cannot be aligned due to the different goals of the individual modelling protocols.
  • Facilitate the consultation process with industry experts and key stakeholder groups, including the owners of the modelling protocols, to build consensus on an agreed set of recommendations for alignment.
  • Document these recommendations for consideration in stage two.

Associated issues
The associated issues that need to be addressed are:

  • he future format of the three protocols.
  • Whether a single model can be adapted with enough variations built in to meet the varying needs (minimum requirements, good/best practice and actual performance).

Energy Simulation Objectives

Objectives of individual protocols
It should be noted that none of the three modelling protocols under consideration claim to provide an accurate model of the building’s energy consumption. Safety margins are used in these protocols so that the modelling outcomes will be conservative rather than accurate. The different approaches either set a compliance standard independent of likely operation (in the case of the NCC and Green Star protocols), or attempt to predict likely operation (in the case of the NABERS Guide).

The goals of the three modelling protocols are different and hence the inputs may also need to be different to reflect these goals. However, there are opportunities for alignment of method and defaults and also opportunities to ensure that future developments in individual protocols are convergent rather than divergent.

It is a useful first step in the discussion to clearly state the purpose or objectives of each individual protocol.
NCC Volume 1 JV3

The National Construction Code Volume 1 (The BCA Volume 1) sets a minimum standard of construction/energy efficiency for new buildings and uses a verification methodology based on a comparison of the proposed building and its services with a reference (deemed to satisfy) building and its services. Hence it is important that the parameters on which the compliance is based upon are fixed.

Verification is by method JV3 which requires that the modelled energy consumption of the proposed building (modelled with both the proposed building services and with the reference building services) is not more than the modelled energy consumption of the reference building. The aim of these two assessments is to test the energy efficiency of both the building services and the building fabric independently. Deficiencies in one cannot be hidden by good performance in the other. Both aspects of the building, its services and its fabric/layout/orientation must meet the minimum standard specified.

The JV3 verification methodology requires that the proposed and reference building are assessed using the same calculation method, physical model, internal heat gains, occupancy and operational profiles, geographic location, climate and with the same HVAC zoning and internal environmental conditions.

The intent of the modelling is to assess the building design for compliance with the minimum energy performance specified within the NCC Volume 1 Section J. Compliance is assessed on a pass/fail basis, i.e. there is no recognition for exceeding the specified minimum requirements.

Green Star
The Green Star Greenhouse Gas Emissions Calculator Guide was developed for the Green Building Council of Australia Public Building PILOT, Healthcare V1 and Industrial V1 rating tools. This document specifies how to undertake energy simulations for the purpose of these Green Star rating schemes. It is intended that this protocol (revised as appropriate after the pilot stage) will be applied to all green star rating tools in the future.

Under this protocol the assessment of the energy performance of a proposed new (or refurbished) building is based on the comparison of the modelled greenhouse gas emissions of the proposed building during operation with that of a ‘standard practice building’. The characteristics of the standard practice building are specified within the calculator guide.
The intent of the green star protocol is to measure the ability of the building to be energy efficient in operation, not to predict or assess the actual energy or environmental performance of the building.

NABERS differ from the two schemes above in that the data used in an Energy rating is extracted from the building in use. NABERS ratings assess actual energy consumption from the building in operation, and therefore, are always based on actual parameters rather than default or specified parameters.

The operational focus of the NABERS program is reflected in the NABERS Energy Commitment Agreements for offices. Under these arrangements developers of new and refurbished office premises can commit their building to achieving a 4, 4.5, 5, 5.5 or 6 Star NABERS Energy performance rating. Energy performance simulations are recommended for 4 star commitments and are mandatory for commitments of 4.5 Stars and above. All simulations used for commitment agreements must be in accordance with the NABERS Energy Guide to Building Energy Estimation and for whole buildings the NABERS Guide to Tenancy Energy estimation must also be used.

Under the Commitment Agreement process the energy use of the building in operation will be verified using a NABERS rating. Consequently, the intent of the Nabers Energy simulation is to accurately predict the energy consumption of the building in operation, within the limitations of theoretical computer simulation. This provides useful and realistic assistance to the design and construction process and specifically helps achieving the target NABERS rating.

The Guide requires modelling the building as it is expected to operate. Default values are only intended to be used when actual data, or realistic estimates, are unknown. These default figures provide a conservative estimate of likely building consumption and were established with reference to the extensive NABERS database of rated office buildings

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