Under current Australian building regulations, a new house, and in some cases renovations, are ‘energy rated’. This means the likely energy use of the house is calculated by using a combination of its location, construction materials and its orientation to the sun. The resulting ‘Star Rating’ that has become part of real-estate jargon is an indicator of the likely energy use. As of the first of May it is mandatory for a home to achieve a 6-star rating.
The system is by no means perfect. There are valid questions of the quality of energy ratings currently being performed as no audits have been conducted since 2006. Implementation is also an issue. You don’t have to look far to find dwellings where the designed energy saving measures specified by building designers are not actually being implemented on site.
How effective are the star ratings criteria?
Energy rating software allows building designers to meet rating standards with maximum flexibility. The elements of the building that are considered by the software include:
- building and window orientation
- size of window openings
- improved insulation of floor, walls and roof construction
- thermally improved and sealed doors and window frames
- thermally improved glazing –double glazing and low-e coatings
- effective external shading
- internal thermal mass.
- it only looks at the thermal performance of the building fabric
- the role of sealing the building against air leakage is not calculated or specified in any meaningful way
- it is based on a multitude of standardised occupancy and operation assumptions that may or may not reflect how occupants actually live in their home
- it takes no account of the efficiency of heating and cooling systems, and even whether they’re fitted or not
- hot water system efficiency is only considered in an add-on condition that allows the new home to have either a solar hot water system or a minimum 2,000 litre rainwater storage tank, connected to toilet flushing.
Amendments to the Building Code of Australia which came into force on the 1st May which will raise the minimum star rating of the building fabric to 6 stars and introduce limits on the amount of lights that can be fitted are a step in the right direction, but we have a long way to go. To really bring Australia up to speed with the US and Europe, and make real change for home owners, a more credible and holistic measure of the energy and water a house is likely to consume is desperately needed.
At Habitech, we have a solution so far ahead of the pack, that the development of rating tools able to measure the efficiencies we provide obviously is a passionate issue for us. Our sustainable building system is built around:
- design response & flexibility
- highly insulated and sealed building fabrics - such as outer shell - floor, walls, roof and windows
- smart, integrated and energy-building services – including heating, cooling, HW and lighting