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BASIX – What is it?

HIA’s Building Services team is often about BASIX requirements in NSW and how various inputs to achieve compliance affects the design and materials used on projects. The information below has been developed to provide you with an outline of what BASIX is and how it may affect your projects.

What is BASIX?

The Building Code of Australia (BCA) contains energy efficiency provisions that apply to all new buildings. However, in NSW the national provisions don’t apply. Instead, the Building and Sustainability Index (BASIX) applies to all NSW residential dwellings so they meet the BCA’s energy efficiency requirements. 

BASIX is a web-based planning tool designed to assess potential performance against a range of sustainability indices including thermal comfort, energy and water use. 

The requirements apply to Class 1 and 2 buildings, Class 4 parts of a building (i.e. caretaker's flat within a building) and Class 10 buildings with a conditioned space. 

Commitments made under BASIX become a condition of the relevant development consent or complying development certificate and applies to any new building work – or alterations and additions to an existing dwelling where the value of the works is over $50,000. 

A BASIX Certificate is the formal evidence that the project achieves compliance with the required targets for energy, water and thermal comfort. 

Overall, the objective of the BASIX scheme is to reduce greenhouse gas emissions and lower water use across NSW. To enable the objective to be met, targets are set by the NSW Government. 

What are BASIX targets?

BASIX targets are the benchmarks that must be achieved to receive a pass score within the BASIX tool and are split into three categories: 

  1. Energy – This gives a ‘target score’ according to the energy consumption of fixed appliances such as cooktops, hot water systems, air conditioners, ceiling fans, lighting etc. that are to be installed in the building. 
  2. Thermal comfort heating and cooling loads – Heating and cooling loads are capped, based on the energy required to either heat or cool a building to keep it at a comfortable temperature. This takes into account the climate zone the building is located in, the size and orientation of the building, building form, insulation, glazing and ventilation, etc. 
  3. Water – The tool rates the water usage of fixtures and fittings such as taps, shower heads and toilets and gives a ‘score’ for water saving measures such as low water use landscaping and rainwater tanks. 

Targets for energy and water are expressed as a percentage. The percentage is the reduction in usage compared to a pre-BASIX home. 
So, for example, a detached dwelling in Sydney has an energy target of 50, and a water target of 40 – that is to say a new building in Sydney must use 40% less water and 50% less energy than a pre-BASIX era building. 

Maximum heating and cooling loads are expressed as a number (load). The smaller the numbers (loads) the less energy is permitted to either heat or cool the dwelling. 
The targets applicable to each project vary according to the location of the building and whether the building is detached, low-rise, medium-rise or high-rise. 
To view targets relevant to a particular postcode or region, click on the following: 

What changed in July 2017?

BASIX energy and thermal comfort targets increased on 1 July 2017. 

Since 2005 the benchmark target had been 40 for houses. However, the changes that took effect resulted in an increase in energy targets by typically 10% for houses and low-rise units and 5% for mid and high-rise units. 

Essentially, thermal comfort heating and cooling load caps increased in stringency to bring NSW thermal comfort scores to a 5.5-6 star (NatHERS) equivalent. 
Water targets remain unchanged and the renovation and extensions part of the BASIX tool has also remained unchanged. 

Changes were also made within the BASIX tool. Prior to the changes, there were three methods for demonstrating compliance with thermal comfort targets: DIY, Rapid and Simulation. 

The ‘Rapid Method’ was removed meaning DIY and Simulation methods are now the only options for demonstrating compliance with thermal comfort targets. 

The resulting stringency increase in the targets has also impacted on the application of DIY method, and given its limited scope (outlined below), in most instances the DIY method is unlikely to provide a cost-effective solution. 

Therefore, in most situations using the simulation method, which involves using an accredited energy assessor with relevant experience in energy assessments for residential buildings, will be an effective means of meeting the new requirements and be able to develop cost effective design solutions. 

A simple example of a comparison between DIY and simulation might be: 

A bedroom over a garage in a two-storey home will lose heat through the floor of the bedroom into the garage. To accommodate for this heat loss you can install insulation in between the floor joist over the garage. This will often lead to a much better outcome when completing a simulation. However, the DIY method does not allow for this; the only option it will give to account for the heat loss is to improve the glazing of that room which may result in an adverse outcome for the project. 

Achieving compliance with BASIX

While the best options for each project will vary, the following tips may assist in achieving compliance with the BASIX targets. 

Thermal Comfort:

  • Keep main living areas on the north side of the building to help maximise north-faced glazing
  • Position garage, laundry, and similar ‘service rooms’ to west and or south
  • 20–40% of the building’s floor space should equal the amount of glazing – this is the most economical 

  • Windows are approximately 90% of a home’s heat gain and 50% of a home’s heat loss. Therefore aim to have: 
  • the majority of glazing on the north façade, with up to 50% of the façade glazed 
  • up to 15% of the east and west elevations glazed
  • 10% of the southern elevation glazed
  • Fixed windows (not opening) tend to perform poorly, particularly when placed high such as in voids or at the top of gables
    • Thermal mass acts like a temperature battery and helps to reduce drastic changes in temperature. Slab on ground with floor tiles and one or two internal brick walls in rooms with large amounts of glazing can help with thermal comfort 
    • 450–900mm eaves (including gutter) are best for shading
    • Large eaves or an alfresco over sliding doors can block winter sun from the opening, making the opening perform poorly due to heat loss
    • Use sealed LED down lights and self-closing exhaust fans to reduce air leakage
    • Insulate walls with R2.0 or R2.5 insulation and ceiling with R3.0 or R3.5 insulation and install ‘roof blanket’ under metal roofs or R3.5 - R4.0 insulation with sarking for tiled roofs. 


  • In many cases designs will pass the energy targets by using typical 6-star gas instantaneous Hot water service, reverse-cycle air-conditioning, LED/Fluro lighting, gas cooktop and the installation of a clothesline
  • If the design fails by under 5% of meeting the targets using some of the following may help: 
    • Well-ventilated fridge space achieves 2%
    • External clothesline achieves 4%
    • Indoor clothesline achieves 1%
    • Utilise natural lighting and ventilation as much as possible
    • Adding ceiling fans in a living room will achieve 1%
    • Check air-conditioning performance EER/COP most 3.0-3.5 for both, some 3.5-4.0 for heating, achieves 1%
  • If failing by more than 5–6% consider removing other commitments and use a 3-4.5 KW PV system or add a 1.5KW PV system. 


  • Keep landscaped areas to a minimum and use low-water plants such as natives

  • Most projects will pass using WELS-rated 7.5 - 9 litre/min showerhead, 4-star toilets and 3-star basin and kitchen taps

  • Upgrading to 5 star tapware achieves another 1% and 6-7.5 litre/min showerhead achieves another 2% (high-rated shower heads give a score for energy as less hot water is used)

  • Use rainwater tanks with 50–100% of roof draining to it connected to irrigation, clothes washing and toilet flushing.

To gain the most benefit from these tips, they should be taken into consideration at the design stage of the project rather than after plans have been completed. 

Demonstrating compliance with BASIX

When making an application for development consent, a BASIX certificate must accompany other relevant documentation such as architectural plans. 

BASIX certificates are generated using the BASIX tool. No formal qualifications are required to generate a BAISX certificate (must be accredited to input a simulation) and anyone can open an account to access the online tool. 

Once logged on the user inputs all the relevant data from the project plans into each section of the tool. 

The energy and water sections of tool are relatively straightforward with the user inputting the chosen appliances (tapware, light fitting types, cooktop type, etc.) while the tool keeps the user updated with the relevant score. 

There are two options for demonstrating compliance with the maximum thermal comfort heating and cooling loads. 

Do it yourself (DIY) is a fairly simple but very limited option for demonstrating compliance with the targets.

The DIY method can only be used if: 

a. the conditioned floor area is not more than 300 square metres 
b. the dwelling is either single or double storey 
c. the dwelling must not contain open mezzanine area exceeding 25 square metres 
d. the dwelling must not contain a third-level habitable attic room 
e. the glazing area is between 10% and 40% of the conditioned floor area 
f. there are no more than 40 windows and glazed doors in the dwelling (combining windows of the same orientation is not allowed) 
g. the total area of skylights is not more than 3 square metres. 

Insulation is automatically set according to the region the building is located in and reflects the insulation requirements found in part 3.12 of the BCA Volume Two. Building materials and each individual window, eave and verandah must be input in the tool, which then calculates the heating and cooling caps as you go, displaying either a pass or fail at the top. 

The DIY method only contains the most common building materials and is mostly only favourable for single-storey, slab-on-ground dwellings with reasonably favourable solar orientation. 

The Simulation method allows for a wider selection of building materials, shading devices and insulation, often reducing the need for improved glazing and other added building costs. 

The simulation method involves an accredited energy assessor using computer modelling (i.e. NatHERS ‘second-generation’ simulation tools (namely AccuRate, BERS Pro and FirstRate 5) to simulate how the building performs thermally. This computer modelling allows the assessor to input details for almost any technology and building material. There is no limit on the size of the building. 

Through the simulation, while it requires the use of an accredited assessor the broader scope allows the assessor to achieve compliance in often a more affordable way rather than the limited options provided in DIY. 

For further information visit:

Note: The above information is general advice only. HIA recommends that as part of demonstrating compliance with the requirements of BASIX that builders, designers, etc. discuss it with the relevant energy assessor, building certifier and regulator to ensure project requirements are being met. 

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

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