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Simulation Method FAQs

THERMAL HELP | Simulation Method

This page summarises the common queries and responses about the BASIX Simulation method.

QUESTION 1: Communications from the Department indicate that the BASIX energy targets are increased by up to 10% from July 2017, but I found that the heating and cooling caps are changed by more than 10%. Please clarify.

The ‘10%’ increase refers to the change in the BASIX energy targets. For single detached houses in coastal NSW, the energy target has increased from an energy target of 40 to 50.

The heating and cooling caps are related to the BASIX thermal comfort section and not the energy section. As part of the BASIX changes in July 2017, the thermal comfort stringency was increased to better align with the requirements imposed in other states and territories. Changes in heating and cooling caps in some climate zones are higher than 10% from their pre-July 2017 values.

QUESTION 2: Is the thermal comfort stringency in BASIX equivalent to NatHERS 6 stars, as required in other jurisdictions by the National Construction Code (NCC)?

The combined heating and cooling caps in BASIX are equivalent to NatHERS 5 stars for concrete slab on ground constructions of detached houses. The average heating and cooling caps applicable to multiple-dwellings projects are also equivalent to NatHERS 5 stars. Other jurisdictions do not have separate heating and cooling caps and evidence suggests that there is a 0.5 – 1 star over-compliance to satisfy the separate heating and cooling caps in BASIX.

Heating and cooling loads from the thermal comfort section will be carried over as the energy demand for space heating and cooling in the BASIX energy section. Due to this interaction between the thermal comfort and energy sections (which is unique to NSW), BASIX-affected dwellings passing both the thermal comfort and energy sections are regarded as having achieved the equivalent of 6 stars. 

QUESTION 3: My project cannot pass the heating and/or cooling caps using Simulation method. What should I do?

Simulation method provides more flexibility on design to pass the heating and cooling caps. You may need to discuss with the NatHERS accredited assessor and/or the architect to explore ways to improve the design and to reduce the resultant heating and cooling loads.

Alternatively, increasing the level of insulation and/or improving the specifications of the glazing will help reduce the heating and/or cooling load. In some cases, these upgrades may not be as cost-effective as changes in design. Increasing insulation levels may also increase the risks of condensation in buildings.

Last updated: 21/09/2023