New buildings need to meet mandatory minimum energy efficiency performance levels. These standards are set out in the Building Code of Australia.

When requirements are demonstrated

The energy performance of a new building must be demonstrated when applying for building approval. The building certifier will require proof that a building will meet the mandatory minimum energy efficiency standards as part of determining whether to give building approval. There are several methods for assessing this. Before advancing with your design and preparation of plans, you may like to discuss with your designer the method of assessment that would be most appropriate.

How requirements can be demonstrated 

Energy efficiency requirements for building approval can be demonstrated in a variety of ways. Before advancing with your design and preparation of plans, you may like to discuss with your designer the method of assessment that would be most appropriate.

Different methods may be more appropriate for some designs than others. Some of the methods that may be appropriate involve:

• use of a currently accredited software model - this calculation can be made by an accredited energy assessor;
• comparison with a reference building - this method involves verifying that the plans for the new building are the same as those for a reference building which complies with the energy efficiency requirements;
• the deemed-to-satisfy method - the Building Code of Australia specifies design features which, when adopted in the design of a building, are sufficient to meet the energy efficiency requirements; and
• acceptance of a nominated expert's report.

In the case of most residential buildings, certifiers are likely to accept the first method - a currently accredited software model. This requires you to employ an accredited energy assessor who will interpret the various energy efficiency factors specific to your design and will produce an Energy Efficiency Rating Statement for the property.

If using software assessment

If you are demonstrating energy efficiency through the use of a currently accredited software model, you should be aware that energy efficiency ratings are undertaken using a software assessment tool which rates the thermal performance of the building fabric and is performance-based rather than prescriptive. That is, it does not prescribe the types of building elements (such as double glaxing, insulation etc) required to achieve a certain rating. Instead, it uses the building elements present in a building design and models the thermal performance based on those elements.

This means that in theory, where one building may require double glazing and high level of insulation to achieve a high star rating, another design may, for example, be able to achieve a similar star rating without double-glazing by reducing the size of the windows and increasing the insulation levels. On the other hand, if large windows were oriented to the south or west for example, a house may struggle to achieve a high rating even with double-glazing and high levels of insulation.

The software also do not currently take into account hot water systems, photovoltaic systems, lighting or other energy-generating or consuming appliances. 

The software used for undertaking energy efficiency ratings was developed under the Nationwide House Energy Rating Scheme.

The Building Code of Australia recognises first and second generation software - first generation software being able to rate up to six stars, and second generation software being able to rate up to 10 stars.