NCC energy efficiency compliance pathways

Performance requirements for energy efficiency

People often refer to the National Construction Code (NCC) energy efficiency ’star rating’ requirements. However, the star rating pathway is actually one of a number of available pathways for compliance with the NCC’s energy efficiency requirements.

The NCC is a performance-based code, meaning that it allows other methods of demonstrating compliance with the mandatory performance requirements which set the stringency which must be achieved.

The objective of the performance requirements is to enable a building to facilitate the efficient use of energy for artificial heating and cooling, heated water and lighting taking into account its location and surrounds.

This means the floor, wall, roof, windows, etc. of the building shall be constructed so the house maintains a certain level of thermal comfort naturally. Artificial heating and cooling can still be installed but the building design and materials used must maintain a certain level of thermal comfort naturally, thus reducing the amount of artificially heating and cooling needed. Ultimately, the NCC’s requirements aim to:

• reduce heating and cooling demand at peak times
• improve occupant comfort and amenity 
• reduce greenhouse gas emissions.

Separate performance requirements describe the allowable energy use for fixed services installed and the thermal performance of the building fabric.

The requirements consider the geological or geographic conditions found at the building site. Therefore the actual stringency varies, as some areas will be heating dominated, others will be cooling dominated or temperate. 

Achieving compliance with performance requirements 

To meet the mandatory performance requirements, the NCC provides three different pathways, or an option to use a performance solution.

Using any of the pathways should result in a home achieving a similar level of efficiency and comfort for a given location.

These pathways include:

The Software Modelling or ‘Star’ pathway

This is the best-known method and uses accredited software programs under the Nationwide House Energy House Rating Scheme (NatHERS) scheme to assess the heating and cooling demands of a building to maintain an ambient internal temperature.

These demands are compared to performance bands that indicate the ‘star rating’ of that building.

The software outputs a certificate with a star rating and, how the building compares to specific summer, winter and overall heating and cooling load limits. The method also includes an assessment of energy used by the buildings fixed services.

The Elemental Deemed-to-Satisfy (DTS) pathway

This method provides as the name suggests a prescriptive minimum method to achieve the required level of performance. It contains two elements:

Thermal performance of the fabric

Solutions are generally based on an added nominal R-Value for walls, floors and ceilings. Essentially, this method is like the recipe or checklist approach that you work through, complying with the individual provisions of the NCC to achieve compliance.

The Whole of Home obligations

All the total operational energy use of a home’s fixed services to be calculated within a budget, including the energy used by:

• heating and cooling
• heated water systems
• artificial lighting
• pool/spa pumps
• minus the energy produced by any onsite energy generation.

This enables trading between more efficient systems and reduction in energy use where the building fabric is high performing. 

The Verification Using a Reference Building V2.6.2.2 ‘VURB’ pathway

This method compares the performance of the modelled proposed building against a similar building modelled to comply with the DTS Provisions (the ‘reference building’) using this method and assumption defined in the NCC.  Where the proposed building performs equivalent or better than a reference building, compliance is achieved. This method is technically a performance solution.

Another type of performance solution

The NCC also always allows a pathway for the development of another type of performance solution. This can be a unique solution that demonstrates the home meets the required performance of the NCC using:

• Evidence of suitability
• Verification methods
• Expert judgement
• Comparison with DTS Provisions.

Selecting which pathway to use 

These various pathways each have relative benefits, so selecting the appropriate pathways should be done on a case-by-case basis. One of the key areas to consider is the ability to achieve the required stringency using the proposed materials and building methods. Some buildings, blocks or materials may demand more flexibility and some pathways allow compensation between elements. 

NCC provisions that apply to all compliance paths 

When using any of the pathways for energy compliance, there are additional considerations relating to installation of insulation, thermal breaks, building sealing and air movement that require consideration when detailing the external envelope of the building.

State and territory variations 

New South Wales

Building Sustainability Index (BASIX) system is used in NSW. All residential developments must obtain a BASIX Certificate. BASIX assesses:

• Thermal performance - similar to NatHERS.
• Energy use - heating, cooling, and other fixed appliances.
• Water consumption.
• Embodied emissions targets - for larger dwellings.

Tasmania and the Northern Territory

NCC 2019 energy efficiency provisions apply in these jurisdictions.

There are also some other variations or additional provisions that apply in some states. As such, it is important to check with your local authority or administration for any specific state or territory provisions that may override the BCA/NCC provisions. 

Note: The above information is general advice only and HIA recommends that prior to using any method for demonstrating compliance with the NCC energy efficiency requirements, builders, designers, etc. Be consulted, to ensure the NCC requirements that apply and are being satisfied.