Section J Energy Efficiency

The Objective of this Section is to reduce greenhouse gas emissions.

Basis of Objective

This Objective reflects the Council Of Australian Governments (COAG) decision in 2009 that a building is to be capable of reducing its greenhouse gas emissions.

National Commitment

In November 1998, all jurisdictions demonstrated their commitment to an effective national greenhouse response by endorsing the National Greenhouse Strategy, a part of which recognised the importance of energy efficiency standards for housing and commercial buildings. An option outlined in the National Greenhouse Strategy was to introduce measures in the BCA to reduce greenhouse gas emissions by efficiently using energy.

On 19 July 2000, the Commonwealth Government announced that agreement had been reached between it and the State and Territory Governments to examine and develop suitable national energy efficiency provisions for domestic and commercial buildings. After taking account of the views of industry, the Commonwealth Government also announced its intention to pursue a strategy that included two elements: firstly, the encouragement of voluntary measures by industry, and secondly, the introduction of minimum mandatory requirements in the BCA.

As a result of the Commonwealth Government’s initiative, the Australian Greenhouse Office (AGO) and the Australian Building Codes Board (ABCB) entered into an agreement on 5 January 2001 to develop energy efficiency measures for inclusion in the BCA. Industry was supportive of the need to eliminate worst practice and accepted a minimum mandatory approach because it provides a level playing field. Further, industry took the view that any building-related regulations should be consolidated in the BCA wherever possible.

In 2003, energy efficiency provisions were introduced into the BCA for housing. In 2005, energy efficiency provisions were introduced for other residential buildings. In 2006, the provisions were expanded to include all other building classifications, as well as enhancing the stringency for houses to a target of 5 stars. In 2010, all measures were further strengthened for both commercial and residential buildings as part of the National Strategy on Energy Efficiency. For houses and apartments the stringency was increased to the equivalent of 6 stars.

In 2016, the COAG Energy Council requested a review of the provisions as part of the National Energy Productivity Plan. For commercial buildings this was to involve an economically feasible stringency increase in NCC 2019. For residential buildings this was to involve strengthening the intent and interpretation of the current provisions in preparation for future stringency increase, possibly in NCC 2022.

Goal.

The underlying goal of the energy efficiency provisions is to reduce greenhouse gas emissions. Initially this was achieved by efficiently using energy. In BCA 2010, this was broadened to include consideration of the greenhouse intensity of the energy used for the building's services.

It should also be noted that the goal is not focused on occupant comfort. The measures are based on achieving an internal environment in which the conditions are sufficiently tolerable for occupants to minimise their use of services including artificial heating, cooling or lighting.

The energy used over the life of a building has an operational energy component and an embodied energy component. Operational energy, and the related greenhouse gas emissions, is the focus of the NCC at this time; broader environmental sustainability measures may be considered in the future.

To reduce greenhouse gas emissions, to the degree necessary—

JF1 refines the intention of JO1.

The Functional Statement has two parts.The first outlines that a building is to be capable of efficiently using energy.The word“capable”is important, as energy consumption in a building is highly dependent on how the building is used. Energy efficiency cannot be assured simply by ‘building-in’ appropriate measures, as the building also needs to be operated, managed and maintained in an appropriate way.

The second part addresses the need for a low greenhouse gas intensity source or a renewable source of energy for the building’s services.

The greenhouse gas intensity of energy sources vary. For example, natural gas has a low greenhouse gas intensity compared with electricity generated from coal.

For the purposes of Section J, the renewable energy source must be generated and used on-site (so cannot be GreenPower or include energy that is exported to the grid) and includes solar,geothermal, wind and bio-fuels.

Heat reclaimed from another source includes the heat recovered for water heating and water chilling from co-generation type processes as well as other industrial processes.

Importantly, the lead-in words “to the degree necessary” qualify that the use of such energy sources may not always be appropriate or required.

This Verification Method allows the use of the modelling protocols and schedules of the National Building Environment Rating System for energy efficiency (known as NABERS Energy) to demonstrate compliance with JP1 for Class 5 buildings. NABERS Energy has a well-established energy modelling framework, which is used primarily to benchmark a building's energy use against a 6-star scale based on its actual energy consumption over a 12-month period. However under JV1 compliance is shown when an energy model of the building design predicts the energy consumption to be less than 67% of 5.5 stars on the NABERS Energy for Offices base-building scale. 67% of 5.5 stars is roughly equivalent to a 6-star NABERS Energy rating.

In addition to the energy model, the Verification Method requires a NABERS Energy for Offices base-building Commitment Agreement to be obtained. This ensures that the necessary rating has been verified through the NABERS Energy process, committing to the design being followed through to the building's operation.

The different targets set for the Commitment Agreement and energy modelling recognises that it is common industry practice to commit to a lower NABERS Energy rating than is likely to be achieved. This is to allow for factors outside the control of the designer relating to the building's operation, which can impact on its ability to achieve a higher rating.

To ensure that occupant comfort is not compromised in the pursuit of energy efficiency, an assessment of the Percentage Mean Vote (PMV) is also a requirement of the Verification Method. PMV predicts the occupant comfort of a given design. The calculation of PMV uses much of the same information that is used in the creation of energy models.

The PMV metric is designed for fully mechanically ventilated buildings. In situations where a building uses mix-mode or naturally ventilating air-conditioning systems, the Adaptive Thermal Comfort metric may be more appropriate. This can be used as a Performance Solution subject to the approval of the building regulatory authority. Adaptive Thermal Comfort can also be used in combination with PMV in buildings that have both fully mechanical and partially naturally ventilated spaces.

To demonstrate compliance, it is suggested that the equivalent result produced by an Adaptive Thermal Comfort Model should be not less than 80% acceptability achieved across not less than 95% of the floor area of all occupied zones not less than 98% of the hours of operation of the building. Note, this is likely to be appropriate for buildings that meet the applicability criterion in Section 5.4.1 of ASHRAE 55-2013.

This Verification Method allows the use of the Green Star rating tool to demonstrate compliance with JP1 for Class 3, 5, 6, 7, 8 and 9 buildings, or common areas of a Class 2 building. Green Star rates buildings across a range of sustainability categories, including energy efficiency. As with JV3 (below), the energy efficiency category of Green Star is based on comparing the proposed building to a reference building compliant with the Deemed-to-Satisfy Provisions in Section J. The schedules and assumptions in the Green Star protocols are different to those of JV3, but are considered equivalent for the purpose of compliance with JP1. Note, in fulfilling all of the sustainability categories for a Green Star rating a building exceeds the energy efficiency requirements of JP1.

The project is required to be registered for a Green Star – Design & As-Built rating to confirm its compliance with the Green Star modelling requirements.

To ensure that occupant comfort is not compromised in the pursuit of energy efficiency, an assessment of the Percentage Mean Vote (PMV) is also a requirement of the Verification Method. PMV predicts the occupant comfort of a given design. Its calculation is based on factors that are used to predict energy consumption.

This Verification Method compares the greenhouse gas emissions of a proposed building to that of a reference building which is based on the Deemed-to-Satisfy Provisions. If the greenhouse gas emissions of the proposed building do not exceed that of the reference building, compliance with JP1 is achieved.

Through this modelling process, it must be demonstrated that the Performance Solution is equivalent to, or better than, the Deemed-to-Satisfy Provisions. This equivalency is also one of the Assessment Methods recognised in the NCC.

JV3 includes provisions in JV3(a)(i)(B) which are designed to protect the thermal performance of the building’s envelope from "trading" off its performance with that of the building services.

The steps to using this Verification Method are:

1. Determine the annual greenhouse gas emissions allowance by modelling a reference building, i.e. a Deemed-to-Satisfy complying building based on the criteria in clauses 2, 3 and 4 of Specification JVb .
2. Calculate the theoretical annual greenhouse gas emissions of the proposed Performance Solution using the criteria in clauses 3 and 4 of Specification JVb .
3. Calculate the theoretical annual greenhouse gas emissions of the proposed Performance Solution, with the services modelled as if they were the same as that of the reference building. This tests the performance of the facade.
4. Compare the theoretical annual greenhouse gas emissions calculated in steps 2 and 3 to the annual greenhouse gas emissions allowance calculated in step 1 to ensure that in both cases, the annual greenhouse gas emissions are not more than that allowed.

The same software must be used in all modelling runs.

JV3 can be used for all buildings using the occupancy profiles and other assumptions provided in Specifications JVb and JVc .

The following flowchart illustrates how JV3 can be used to assess different Performance Solutions.

Building sealing is essential for facilitating the energy efficiency of a building. JV 4 provides a method of demonstrating compliance with the building sealing requirements in JP1(e). This provides an alternative compliance option to the prescriptive building sealing requirements in Part J3.

JV4 quantifies the level of sealing (expressed as an air permeability rate) appropriate for different building classifications and climate zones. The method for testing the sealing level is through a blower door test carried out in accordance with Method 1 of AS/NZS ISO 9972.

Envelope sealing has less impact on buildings that do not operate overnight and which are located within relatively mild climates (i.e. climates zones 2 and 5). Envelope sealing can have a reduced benefit in these circumstances as these buildings are less likely to cool naturally overnight and may require additional cooling energy than necessary the next day. However, if buildings in these climate zones are operated in a manner that expels warm air and draws in cool air overnight as part of its cooling regime (typically known as night purging), then a lower air permeability rate could be beneficial.