Part J1 Energy efficiency performance requirements

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.  J1O1 aims to achieve sustainable building design with the dual intent of promoting environmental stewardship and enhancing occupant well-being. It focuses on reducing both the operational and embodied energy consumption of buildings, minimising peak energy demand to ensure grid stability, and curbing greenhouse gas emissions. In addition to these environmental goals, J1O1 also emphasises the importance of improving the health, comfort, and overall amenity for building occupants.

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.

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

J1F1 refines the intention of J1O1.

The Functional Statement has five parts.

J1F1 mandates that buildings reduce energy consumption and peak demand, particularly regarding the operation of primary energy-using systems. This is critical not just for efficiency but also for reducing greenhouse gas emissions that result from the building's energy use and its sources. J1F1 also stresses the importance of occupant health and comfort, specifically within sole-occupancy units of Class 2 buildings or Class 4 parts of buildings, by ensuring these spaces can mitigate the effects of severe temperature fluctuations and power outages. For other spaces, the building's envelope must help maintain suitable internal conditions when occupied. Furthermore, J1F1 anticipates the integration of distributed energy resources, such as on-site renewable energy systems, by requiring the building to be adaptable to future installations.

J1P1 refines the intention of J1O1. A building, and its services, is required to use energy efficiently so that the greenhouse gas emissions associated with its operation are minimised. This is subject to the intended use of the building and the necessary level of occupant comfort. For buildings that are air-conditioned, the amount of energy has also been quantified.

The term “regulated energy consumption” has been defined to clarify the portion of a building’s energy use that is required to be less than the quantified value. This includes the energy used for air-conditioning, heated water, artificial lighting and lifts, minus the amount of renewable energy generated and used on site.

J1P2 focuses on the thermal performance of sole-occupancy units within Class 2 and Class 4 buildings. It mandates that the total heating, cooling, and thermal energy load of habitable rooms and conditioned spaces within these units must not exceed the specified limits outlined in Specification 44.

J1P3 pertains to the energy usage of domestic services within sole-occupancy units of Class 2 and Class 4 buildings. It restricts the energy value of domestic services, including heating, cooling, hot water, and lighting power density, with specific requirements for each aspect.

J1P4 requires buildings to incorporate features that enable the future installation of on-site renewable energy generation and storage, as well as electric vehicle charging equipment.

‘Verification Method’ is an NCC defined term and means a test, inspection, calculation or other method that determines whether a Performance Solution complies with the relevant Performance Requirements.

To help ensure a Performance Solution provides the level of intended performance, clause A2G2(4) of the NCC mandates a process for developing Performance Solutions. This process must be followed regardless of whether the Performance Solution is simple or complex in nature.

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 J1P1 for Class 5, Class 2, and Class 3 buildings, and Class 6 shopping centres. 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: 

For a Class 5 building: under J1V1 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.

For Class 2 buildings (other Than sole-occupancy units): under J1V1 compliance is shown when an energy model of the building design predicts the energy consumption to be less than 90% of 5 stars on the NABERS Energy for Offices base-building scale. 90% of 5 stars is roughly equivalent to a 6-star NABERS energy rating.

For Class 3 buildings: under J1V1 compliance is shown when an energy model of the building design predicts the energy consumption to be less than 70% of 5 stars on the NABERS Energy for Offices base-building scale. 70% of 5 stars is roughly equivalent to a 6-star NABERS energy rating.

For Class 6 shopping centres: under J1V1 compliance is shown when an energy model of the building design predicts the energy consumption to be less than 80% of 4.5 stars on the NABERS Energy for Offices base-building scale. 80% of 4.5 stars is roughly equivalent to a 6-star NABERS Energy rating.

All the above buildings must also comply with any additional requirements specified in Specification 33 and the calculation methods must adhere to ANSI/ASHRAE Standard 140.

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 Predicted 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 must be achieved across not less than 95% of the occupied floor area for not less than 98% of the hours of operation.

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 J1P1 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 J1V3 (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 J1V3, but are considered equivalent for the purpose of compliance with J1P1. Note, in fulfilling all of the sustainability categories for a Green Star rating a building exceeds the energy efficiency requirements of J1P1.

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 predictsthe occupant comfortof 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 J1P1 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.

J1V3 includes provisions in J1V3(1)(a)(ii) 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:

• 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 S34C2, S34C3 and S34C4.
• Calculate the theoretical annual greenhouse gas emissions of the proposed Performance Solution u sing the criteria in S34C3 and S34C4.
• 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.
• 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.

J1V3 can be used for all buildings using the occupancy profiles and other assumptions provided in Specifications 34 and 35.

Figure J1V3 illustrates how J1V3 can be used to assess different Performance Solutions.

Building sealing is essential for facilitating the energy efficiency of a building. J1V4 provides a method of demonstrating compliance with the building sealing requirements in J1P1(e). This provides an alternative compliance option to the prescriptive building sealing requirements in Part J5.

J1V4 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.

J1V4 also sets out mechanical ventilation requirements for a Class 2 buildings or a Class 4 part of a building where an air permeability rate less than 5 m3/hr.m2 at 50 Pa reference pressure is achieved. Further provisions ensure ventilation standards for spaces within buildings, particularly where combustion appliances are present. Compliance with AS/NZS 5061.1 is highlighted for gas-fuel combustion appliances.

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.

J1V5 covers the verification of Class 2 sole-occupancy units' compliance with J1P2 using reference buildings. For Class 2 sole-occupancy units, energy efficiency is gauged against a 'reference building'.

J1V5 evaluates the energy performance of Class 2 buildings' sole-occupancy units, addressing both J1P2 and J1P3 Performance Requirements. J1V5 enables compliance for either or both of these Performance Requirements through energy modelling, as outlined in Specification 45. 

J1V5 is particularly relevant for apartment blocks centralized hot water, heating, or cooling systems as specified in J1P3, allowing for the use of a single energy model to represent the entire building’s performance. Depending on the climate zones, the heating and cooling loads of the sole-occupancy units should either match or be better than those of a reference building. These loads also should not go beyond 120% of the values set in J1P2(1) for In climate zones 3 to 8, and J1P2(2) for climate zones 1 to 5 respectively.

This Verification Method ensures that the building's design and domestic services, like lighting and appliances, meet or exceed set benchmarks for energy efficiency. The calculation tools must align with the ANSI/ASHRAE Standard 140 and must not include house energy rating software.