Meeting the energy efficiency requirements of the BCA
There are various routes to compliance with the energy efficiency requirements in the BCA that come under two broad headings – Deemed-to-satisfy provisions and alternative solutions.
Deemed-to-satisfy provisions (officially known as acceptable construction practice in the BCA), cover two compliance pathways:
- Elemental provisions (known previously as deemed-to-satisfy or DTS); or
- Energy Rating Method
The energy rating approach is mostly based on a computer simulation of the annual demand for heating and cooling using software accredited under the Nationwide House Energy Rating Scheme (NatHERS).
The Nationwide House Energy Rating Scheme (NatHERS) provides homes with a star rating out of ten based on an estimate of a home’s potential heating and cooling energy use.
Houses with higher star levels are considered more thermally comfortable than those of lower star levels. A zero star rating means the building shell does practically nothing to reduce the discomfort of hot or cold weather. A six star rating indicates good, but not outstanding, thermal performance. Occupants of a 10 star rated home are unlikely to need any artificial cooling or heating.
When performing the assessment, the size and function of rooms, size and specification of openings, type of construction and dwelling orientation and location are entered in the software to develop a simulation model of the house or apartment.
The energy rating approach aids in the development of unique building solutions, however it is limited to assessing the thermal efficiency of the building envelope only. For this reason, when undertaking a software rating, there are additional requirements for the services that must be satisfied to achieve full compliance to the building code of Australia.
The energy rating method is the most commonly used method for achieving compliance and provides the most energy efficiency solution. This method is very flexible and allows trade-off between different building elements.
In some cases, it is hard to get compliance using method including:
- Houses with light weight construction (Timber floor and steel or timber frame walls)
- Double or triple storey houses with narrow designs
- Houses with raised floors
In the above cases and when achieving compliance using Energy Rating Method is not possible or becomes very costly, other methods such as Verification Using a Reference Building method can be used to achieve compliance.