Articles written by the Certified Energy technical team covering NatHERS, BASIX and building performance in Australia.
21 min read
Two NatHERS Ratings Explained
The NatHERS thermal star rating and Whole of Home rating measure different parts of residential energy performance. One assesses the thermal response of the building shell. The other assesses major household energy uses, onsite generation and storage.
NatHERS and Whole of Home are sometimes described as competing assessment methods. This is no longer an accurate way to understand their relationship.
NatHERS is the wider residential energy-rating framework. Within that framework, a proposed home can receive a thermal star rating out of 10 and a separate Whole of Home rating out of 100. The two results answer different questions about the same dwelling.
The thermal star rating asks how much heating and cooling the home is likely to need because of its design and construction. The Whole of Home rating builds on those thermal loads and considers the energy performance of household systems, solar generation and battery storage.
20 min read
Reading a NatHERS Result
A NatHERS thermal star rating indicates how effectively a dwelling design is expected to manage heating and cooling in its local climate. It is a modelled building-shell result, not a percentage, appliance rating or direct prediction of future energy bills.
A NatHERS star rating is often treated as a simple pass-or-fail number. In practice, it communicates something more specific: the modelled heating and cooling demand created by the design and construction of a home.
Accredited NatHERS software models the proposed dwelling in its relevant climate and assesses how the building shell responds to seasonal heat gain, heat loss and internal comfort conditions. The resulting thermal loads are converted into a rating between 0 and 10 stars.
The rating is therefore best understood as an indicator of thermal design performance. It helps show whether orientation, glazing, insulation, shading, construction and room layout are working together effectively before heating and cooling equipment is considered.
