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A key aspect of the reference building method is that it provides flexibility in meeting the BCA energy efficiency provisions. It allows trading between different elements of the building fabric to achieve the required heating load and/or cooling loads.

Energy Verification Reference Building Method

This information sheet has been developed to provide information regarding BCA Verification Method – V2.6.2.2 Verification using a reference building for demonstrating compliance with the energy efficiency requirements.

What is V2.6.2.2 - Verification using a reference building?

V2.6.2.2 is a method that can be used to comply with the BCA energy efficiency requirements for houses as an alternative to using the Part 3.12 elemental provisions or the NatHERS energy (star) rating modelling tools (using Accurate, First Rate 5 or BERS Pro).

V2.6.2.2 is a comparative approach that assesses the heating load and/or cooling load of the proposed building (typically measured in MJ/m2 annum) and compares it to the heating load and/or cooling load of that house’s design had it been built to the elemental provisions of Parts 3.12.1 to 3.12.4.

Similar to the NatHERS energy rating tools, V2.6.2.2 requires the use of a software/modelling tool to assess the energy efficiency of the building.

Appendix A includes an example of how this method can be followed.

When would you use the reference building method?

A key aspect of the reference building method is that it provides flexibility in meeting the BCA energy efficiency provisions. It allows trading between different elements of the building fabric to achieve the required heating load and/or cooling loads.

For example, the method could allow for a design that has a reduction of insulation in the walls whilst increasing the insulation in the roof or improving the energy performance of the glazing.

The method also allows for a wider range of windows and doors to be used including one off and unique windows. It also provides for a broader range of materials to be used for wall and roof cladding and for the use of new and innovative materials. These types of materials are not always listed in the NatHERS tools or the elemental provisions.

The method also enables the use of different energy software/modelling tools as part of the assessment that are not NatHERS based.

What modelling/software tools can be used?

Varying information has been published on the appropriateness of certain energy rating software/modelling tools that can be used for V2.6.2.2.

So what can be used?

V2.6.2.2 does not specify what modelling/software tools can be used.

This means various software tools may be used provided they are capable of assessing the heating loads and/or cooling loads within the defined temperature settings. It is essential to confirm that the software tool being used aligns with these defined temperature settings.

Defined temperature settings

V2.6.2.2 prescribes that the calculation method used must be capable of assessing the heating load and cooling load by modelling space temperatures settings in the range of 20°C to 21°C for heating and 25°C to 28°C for cooling, dependent on the relevant climate zone.

It is important to note that the temperature settings prescribed in V2.6.2.2 are different to the temperature settings used in the NatHERS energy (star) rating.

As such, in the majority of situations the NatHERS energy rating tools (BERS Pro, Accurate & First Rate 5) are not suitable to use for V2.6.2.2.

There are some software/modelling tools available, such as DesignBUILD that may be capable of assessing the heating loads and/or cooling loads within the defined temperature settings.

Additionally, there is potential to use the BERS Pro tool in a “BERS mode” (which is different to the mode used for NatHERS energy (star) rating) for modelling the building, as the tool in this mode allows for temperature settings to be adjusted to meet those prescribed in V2.6.2.2.

Further information:

The ABCB have also recently released an Advisory Note on the types of software/modelling tools that can be used as part of applying V2.6.2.2, which can be found here .

It is important to note that the information provided herein is of a general nature and it is recommended that prior to using V2.6.2.2 for any house design and energy assessment that advice is sought from an energy assessor or the relevant approval authority to ensure that the assessment will comply with the BCA.

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Appendix A

Step 1
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Step 1: Determine the energy efficiency requirements for the reference building

The design of the reference building is based on the plans for the proposed building. The energy efficiency features of the reference building are based on it complying with the BCA elemental provisions of Parts 3.12.1 - 3.12.4.

Using the roof as an example, the minimum R-Value for the roof construction to be used, including the insulation, for the reference building would be determined in accordance with Part This may be, for example, a minimum R-Value of R4.1.

This process would be repeated for all of the relevant Deemed-to-Satisfy Provisions that apply to the building to determine its energy efficiency specification.
Step 2
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Step 2: Assess the heating load and/or cooling load for the reference building via software/modelling

Using these specifications determined in step 1, calculate the heating load and/or cooling load for the reference building. This modelling is ‘software run 1’.
Step 3
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Step 3: Modify the reference building to reflect the preferred changes in the proposed building material specification

As the plans used for the reference building are based on the proposed building, changes can be made to material specifications used in ‘software run 1’. The new modelling is ‘software run 2’.

For example for the proposed building, the client would like to install unique one-off windows that are less efficient windows than those prescribed in the elemental provisions.

As the windows are less efficient than those prescribed, the heating load and cooling load for the proposed building will change in comparison to the reference building.
Step 4
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Step 4: Compare the heating load and/or cooling load of the reference building and the proposed building design

By comparing the outcome of step 2 and 3 it is now possible to determine whether the design complies with the Verification Method V2.6.2.2(a) which states that the heating load and/or cooling load of the proposed building must be equal to or less than that of the reference building.

Based on the client seeking to use less efficient windows, the proposed building is likely to have a higher heating load and/or cooling load than the reference building. Therefore the proposed design will require modifications to other building elements, such as increasing the roof, floor and/or wall insulation above the levels of the reference building, to compensate for the reduced performance of the windows.
Step 5
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Step 5: Model the modified design

The modified design with any compensatory material changes or other inclusions can now be model again to determine if the criteria in V2.6.2.2(a) is satisfied.

The modified building design ultimately satisfies the heating loads and/or cooling loads and therefore complies with V2.6.2.2. As such the home can incorporate unique one-off (less efficient) windows subject to design adjustments such as increased wall insulation.

To find out more, contact HIA’s Building Services team.

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