The Thermal Balance Challenge - How Efficient is Your Design?

Aiming to achieve either a 6 or 7 Star NatHERS rating?

Achieving a Thermally Balanced building design offers an easy passing solution to the NatHERS rating requirements and will assist towards achieving compliance with the Energy Efficiency provisions of the National Construction Code of Australia. A Thermally Balanced building design reduces operational energy usage, minimises construction costs and creates enhanced thermal comfort for occupants throughout the usable life of the building.

What is Thermal Balance?

A Thermal Comfort NatHERS rating is required to demonstrate your development's Sustainability credentials to a local council. Your building is computer modelled to simulate the Heating and Cooling loads that are required to keep the interior temperature within a nominal 20-25 degree temperature range. This is typically measured in Mj/m² or in other words the amount of energy used per square metre over a calendar year. It's measured separately with both Heating and Cooling energy loads that account for the energy required to both heat and cool the building to maintain a comfortable living environment for the occupants all year round. 

Thermal Balance is achieved when both Heating and Cooling loads for a building are aligned with the stipulated maximum regulation threshold targets set by legislation and should seek to address the constructability of any Thermal treatments while maintaining original design integrity. When optimising or “value engineering” a project to achieve a favourable outcome for all stakeholders the following needs to be considered: overall energy efficiency, cost of any additional building elements, the inherit Thermal Properties of those building elements and how they relate to the overall Star Rating for the development.

The Thermal Rubiks Cube

Juggling the Thermal Balance of a project or its Heating and Cooling loads simultaneously can be a bit like solving a Rubik’s Cube where many scenarios are tested with multiple simulations against the CSIRO’s Chenneth NatHERS engine to determine the most optimal solution to achieve the desired Thermal Balance for the project. 

When applying a Thermal cosmetic or building fabric treatment, for example to achieve either a lowering of a Heating load to a building we may add additional insulation. There are many instances where after simulating the proposed change there is also an unintended consequence of this building improvement or colour choice which results in an increase to the Cooling load for the project. 

In this example the building has been treated with additional insulation which may be to the wall, underfloor or exposed cantilevered floors, ceiling and in some cases roof spaces, which will likely result in keeping the building warmer in Winter but could also make it harder to cool a building in the middle of summer at very high or extreme ambient temperatures. 

9 Thermal Comfort Passive Design Strategies

This can be achieved through 9 Thermal Comfort Passive Design Strategies which are used by Architects and Building designers to achieve an optimised Thermally Balanced design outcome: