There has been considerable opposition to the new requirements on the basis that adding more insulation, improving design and considering other environmental improvements costs money for the builders, which are then passed onto to new home occupiers. In fact, the costs have turned out to be minimal.  In Victoria, which has had the regulations for longest, the requirements have added around $1000-1500 to the cost of the average new house.  This is a drop in the ocean compared to other costs, and the new owners get the advantage of having lower bills for life. Of course, the environment also benefits, which very few people would now argue against.

The key question for this article is, do the regulations go far enough – and where next?

Background: sustainable housing in Australia

The development and application of ecologically sustainable development (ESD) principles to housing gained ground during the 1990s, with a range of ‘ecohome’ demonstration projects (for example, see Low et al ).  There is general consensus that a sustainable house, developed using ESD principles, will perform well in conserving water and energy and use low-impact materials, compared to an ‘average’ house.  Invariably, links to ecological carrying capacity are not drawn explicitly in guiding specific performance criteria.  One way to approach this in practical terms is to use Life Cycle Assessment (LCA) methods, using which, a sustainable house built today should satisfy the following general requirements:

• High thermal comfort;
• Maintain and enhance the health and wellbeing of building users;
• Consumption of minimal non-renewable energy;
• Cost-effective design, minimising life cycle operating costs;
• Low life cycle environmental impact; and
• Eco-design measures incorporated (location, orientation, passive design, appropriate materials and construction techniques, efficient appliances).

Clearly, more detail is required before houses can be assessed against such a list of criteria.  Terms such as ‘minimal’ and ‘low’ require definition, for example, in terms of environmental carrying capacity or what is deemed achievable in performance terms, while ‘cost-effective’ and ‘comfort’ are more related to human capacities and needs. 

The main metrics

Viewing the house as a system with a life cycle, we can identify the constituent parts of the life cycle and subsequent environmental burdens as indicated in Figure 1.  This shows that key input-related environmental factors include energy, water and materials depletion, and the related environmental impacts of mining, processing and supply of each.  Output factors include pollution and climate change, foul and stormwater discharge, and toxicity effects on humans and ecosystems.  All factors vary across the building life cycle.
 

Figure 1. Potential environmental burdens of an urban residential building.

For example, taking non-renewable energy use, it is clear that operational heating and cooling loads generally dominate.  Embodied energy of building materials (the energy required to produce materials) makes up typically 15-30% of the life cycle energy use, depending on the building materials used, and assuming typical heating and cooling equipment.  Most building materials are not as vulnerable as fossil fuels in depletion terms, although some have considerable environmental burdens associated with manufacture.  Thus steel and alloys use large amounts of energy compared to timber, where the main concern is biodiversity. 

International benchmarking

Since the main environmental concern facing humanity is climate change, it makes sense to prioritise our efforts in reducing greenhouse gas emissions from housing. In this regard, it is logical to start with heating and cooling loads, as the new 5-star requirements do, since these typically are a major factor in the total greenhouse gas emissions from housing. One way to establish whether the regulations go far enough is to compare new 5-star Australian homes with the equivalent heating and cooling requirements of typical homes being built overseas.

A study conducting such a comparison has been undertaken by the Centre for Design at RMIT University with Sustainable Built Environments and the School of Property, Construction and Project Management University for the Australian Federal Government Department of Environment and Heritage, Australian Greenhouse Office (the author wishes to acknowledge the co-authors and sponsors of the study).  In this study, energy ratings of new houses in Australia are compared with those currently being built overseas, using AccuRate software. Overseas locations in the UK, Canada and the USA, are mapped across to similar climate zones in Australia, and 51 house plans designed to comply with relevant local building codes are rated using AccuRate.  A review and analysis of the local ‘deemed to satisfy’ building codes is also undertaken as an aide to explaining any significant differences in house energy performance between different countries and locations. 

Results are presented in Table 3 showing a mean score of 6.843.  This indicates that the overseas equivalent housing is significantly out-performing the proposed Australian 5-star national requirements.  Within each climate zone, there are variations, although all mean climate zone comparison performance levels are above 5 stars and there is no significant pattern of performance according to warmer or cooler climates, or dry or humid climates.  Generally, apartments and townhouses perform better than detached houses, and the higher performing climate zones reflect comparison localities with more stringent local building codes.
 

The house designs obtained from the UK and Canada indicate that, in these countries, substantial houses are built to relatively very high standards, in compliance with relatively stringent building code requirements.  The more typical format of lightweight construction on slab seen in current new housing in Australia is also seen in the USA.  Neither country insists on sustainable design principles outside of high performance building elements.  However, according to the Deemed to Satisfy requirements in the building codes, houses in the USA are insulated to (on average) R2.5 in the walls, R5.5 in the ceilings, and have double or double low E glazing.  Some houses in Texas have single glazing, but otherwise all are double or double low E glazed.  In addition, the USA uses vinyl frames (PVC) with benefits in the energy ratings, despite raising questions over other environmental impacts.  Typically, from the USA designs used in this study and previous experience of the authors in rating Australian house designs, USA glass to floor area ratios are significantly lower than those in Australia.  On the basis of the comparisons in this study, the main exception within the USA is the building control regime in California.  This has a long history, and current standards are significantly advanced when compared to the other states, and to Australia.  The two climate zones which provide Californian comparisons in this study (Australian zones 5 and 6) show clear differences in the performance results from having more stringent building codes, adding further weight to the general conclusions that the higher performing climate zones reflect comparison localities with more stringent local building codes.

Conclusions and comments

5-star is an important and useful step forward for Australian homes and households. However, the comparison presented here indicates that we can do better, and the next generation of building code improvements should look to ‘7-stars’ to bring Australian housing up to international standards. However, these two extra stars need to consider other aspects of housing energy and environmental performance too in addition to further reductions in heating and cooling loads. For example, the growth in lighting energy demand (from halogens) and other electrical appliances is leading to ongoing increases in energy use in homes, and these issues as well as space efficiency need to be addressed.  Then there is embodied energy and other environmental issues. The there is the 98% of building stock that is not new – we need a set of retrofit and renovation environmental standards and measures to bring our existing homes up to spec.  In other words, 5-star has given us a good basis for improving our housing environmental performance. Now we need to build on this in a rolling programme of further housing performance improvements over the coming months and years.

References

Low, N., Gleeson, B., Green, R. & Radovic, D, The Green City: Sustainable Homes, Sustainable Suburbs. Routledge, 2005.

Horne, R. E., Hayles, C., Hes, D., Jensen, C., Opray, L., Wakefield, R., and Wasiluk, K., International comparison of building energy performance standards.  Report to Australian Greenhouse Office, Department of Environment and Heritage, 2005.