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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.
BASIX targets are the benchmarks that must be achieved to receive a pass score within the BASIX tool and are split into three categories:
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:
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.
While the best options for each project will vary, the following tips may assist in achieving compliance with the BASIX targets.
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.
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.
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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.
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