We will need to build more than four million new Australian homes by 2036, a greater than 50 per cent increase in dwelling stock from 2011. The prosperity and wellbeing of future generations will rely on those buildings being well designed and efficient to live in. There should be a lot of debate about how we are going to do that.

As Hagrid said to Harry Potter (’cause it’s very important), not all wizards are good. Similarly, not all stakeholders want more efficient buildings – and those stakeholders have the most to gain from influencing government regulations. It is very important that those who believe in building efficiency stand up to be counted and keep a watchful eye on the discussion.

The recent The Fifth Estate article on net zero high rise resi discussed the important work being done by pitt&sherry and included some discussion of NSW’s BASIX sustainability framework and how it compares to Victorian building controls.

The report provides some much needed critical comment on the performance of building controls across Australia and some wonderful opportunities for building efficiency improvement. The way that BASIX applies to high-rise apartment buildings may need review, however it is important to keep in mind the underlying strengths of BASIX.

BASIX is a State Environmental Planning Policy, which is a land use planning control. That means BASIX integrates land use planning with energy and water management and is regulated differently to the narrower focus of building controls. It also means that the performance of the building is considered at the design stage prior to planning approval rather than when a building permit is required.

BASIX was designed to set performance based targets for both water use and greenhouse gas generation, which is a consideration of energy use. These performance targets were based on rigorous data analysis of energy and water use at the postcode level and consider the performance of the whole house, not just the building shell.

The target is a 25 per cent reduction on greenhouse gas emissions and 40 per cent reduction water use from 2004 levels. This equates to a target of about 90,000 litres of potable water and 3300 kilograms of greenhouse gas per person in the dwelling. These targets apply to all new houses in NSW and renovations worth over $50,000.

Later BASIX was extended to assess thermal performance of buildings. BASIX has two separate mechanisms addressing heating and cooling. First, the building envelope must meet separate thermal performance criteria for summer and winter. This can use the NatHERS rating tools or simplified tools offered by BASIX. Second, those thermal ratings are integrated with the heating and cooling appliance efficiencies to feed into the calculation of the greenhouse gas target compliance using the performance-based points approach.

Performance-based measures are important

Why are performance outcome controls that people can understand – like litres per person and kilograms of greenhouse gas – so important? Because these sorts of performance controls can be measured and verified at a system level. That is very rare for planning and building controls. Specification of performance outcomes includes all the elements that contribute to the outcomes. BASIX considers what is happening inside the house, heating, cooking, cooling, lighting, pools, water efficiency, water efficient appliances and landscape, as well as design and materials. Similarly by specifying a performance outcome that people can understand, the whole population has a standard they can relate to. This influences behaviour far beyond the planning or building control.

The BASIX targets specify a performance outcome, but importantly they are non-prescriptive. Prescriptive regulations that require a particular design component can restrict the best design for a house. Specifying a solar hot water system or double-glazed windows or a rainwater tank doesn’t suit every house and every home owner. Using the performance measure of an energy or water use target and letting the designer work out which solution is best allows the market to operate more freely, allows for individual choice and for new, more efficient technologies.

Original projections by the NSW Department of Planning were that BASIX would apply to 120,000 new dwellings by 2050, saving three million litres of water and 100 million tonnes of greenhouse gas. Compliance with the regulations has a positive cost-benefit assessment and savings are projected between $800 million and 1.2 billion by 2050, shared between households and government utilities.

The difference down south

Victoria, by comparison, uses the NatHERS (National Home Energy Rating System) six star rating for new homes applied as a building control under the National Construction Code. The six star rating applies to the thermal energy performance of the building envelope. It is not immediately clear what level of energy performance the star rating refers to and, as noted below, the six star energy requirement can double or triple between different cities.

The rating does not take into account actual appliances or fittings within the house such as heating or cooling or refrigeration or hot water. In the driest inhabited continent on earth, the national building code does not provide a measurable target for water use.

Using the pitt&sherry comparison of Melbourne and Sydney apartments as an example shows the problem of not using clear performance outcomes.

The report includes a comment that in the two apartment buildings modelled by pitt&sherry, the Sydney apartments approved under BASIX received a NatHERS rating of 4.5 stars versus a 6.5 star NatHERS rating for the Melbourne apartments.

A quick look at Figure 1 shows that the Sydney apartments approved under BASIX were actually using a bit more than half the energy of the Melbourne apartments. A six star building in Melbourne uses three times as much energy per square metre as a six star building in Sydney, on the rationale that this allows for climate difference.

This difference in apparently comparable energy ratings goes a long way to explaining the differences between NSW and Victorian energy uses in Figure 4.

Figure 1: NatHERS star rating scales for Melbourne and Sydney relative to the NCC minimum (pitt&sherry draft for consultation 2016)

We do agree there may be problems with the way NatHERS is implemented, presentations delivered to the MEFL Spark conference on climate action, renewables and charting a path on energy transition proposed that Melbourne’s existing housing was operating at a two-star standard in a six star regulatory regime. One would have expected that after this period of time NatHERS would have had more of a cumulative impact on existing housing stock.

A lot has changed since 2004 – 12 years later we can look back at high level performance data for NSW and compare it to Victoria and see how they fare.

The utility operating costs to supply water to households in NSW is substantially different to utilities in other states and Victoria as shown in Figure 2. Operating costs reflect distribution and treatment costs and are usually strongly related to volume. The comparison here is between major water utilities in NSW compared to all major water utilities in Australia, Victoria and Queensland. Since 2009-10 large water utilities in NSW have had much lower operating costs than Victoria, Queensland and the national average.

Figure 2: Water operating costs for utilities operating with mandates for sustainable buildings versus costs of other utilities

An important element of sustainability is household affordability, which is partially represented by household expenditure for mains water services as shown in Figure 3. Household expenditure on water has increased by 93 per cent since 2007/8, but household bills in NSW for major water utilities are $200 less each year compared to the rest of the country.

Figure 3: Household expenditure for mains water supply

Figure 3 highlights that household expenditure on mains water supply has been steady since 2009-10 in NSW, whereas the average costs of households supplied by other utilities has continued to increase.

Sustainable buildings provide benefits across the entire biosphere. In 2013/14, Sydney dwellings also contributed to protecting waterways by reducing discharges of nitrogen in stormwater by 55 tonnes, and reduced greenhouse gas emissions by 151,400 tonnes for heating water and avoided mains water supply. In comparison, the Melbourne dwellings reduced nitrogen discharges by 52 tonnes and greenhouse gas emissions by 73,600 tonnes. The BASIX policy in NSW appears to have provided greater systemic change in impacts than Victorian dwellings. However one of the original proposals for BASIX was to include stormwater controls and a target of a 30 per cent reduction in the volume stormwater generation is an obvious consideration for the future of BASIX.

The Australian Bureau of Statistics and the Commonwealth Office of the Chief Economist provide some interesting macro data that can reveal the total energy and electricity use of dwellings in NSW and Victoria as shown in Figure 4.

Figure 4: Total energy and electricity use of dwellings in NSW and Victoria

Figure 4 reveals that the total energy use per person in Victorian dwellings is substantially higher than the total energy use in NSW. While Victoria has a cooler climate than NSW this should be grounds for better building performance rather than higher energy use.

Comparison of total energy use of people in dwellings since the commencement of BASIX in 2004-5 reveals that NSW total energy use has reduced by nine per cent and Victorian total energy use has reduced by eight per cent. The NSW dwellings are performing slightly better.

However, the profiles of electricity use per person in dwellings are somewhat different for each state. These differences are explained by the energy mix used in each state. A large proportion of Victorian household energy use is sourced from gas and only a small proportion of NSW household energy use is sourced from gas. As such a sole focus on electricity use can create a misleading comparison between the performances of buildings in each state. For example, since 2014-5 the electricity use of dwellings in Victoria reduced by 25 per cent and in NSW by 12 per cent. However, the reductions in electricity use in Victoria were simply replaced by gas supply for limited overall reduction in total energy demand. If gas is more efficient than electricity than the energy use in Victoria may be due more to a shift in the energy source rather than a change of actual performance.

Figure 4 highlights that local behaviour change of energy use within buildings commenced in the 1990s and has gained momentum in recent times. The behaviour of buildings (and their residents) shown in Figure 4 has delivered substantial change since the mid-1990s, which seems to be little understood, but it seems BASIX targets fosters these types of behaviours.

However, the impact of buildings or their overall sustainability is not limited to the direct energy demand of the buildings – it also includes impacts of operating the buildings as shown for energy use per person to supply water. Since 2004-5, the energy demand of water supply decreased by 38 per cent in NSW and increased by 10 per cent in Victoria.

A paper being presented by Professor Peter Coombes and others at this week’s Stormwater2016 Conference reveals that in 2013-14 sustainable dwellings in Sydney reduced water demands by 43,450 million litres, and by 30,030 million litres in Melbourne. That difference can be explained by BASIX.

There is also evidence that the cumulative reductions in water demand from dwellings in NSW have created strong reductions in utility energy use.

What would we do if we had a magic wand? We need independent governance and enforcement of BASIX, further consideration of how high-rise apartments are dealt with, stormwater and green infrastructure should be put on the BASIX agenda, and the BASIX approach should be upgraded and rolled out nationally.

Michael Smit is executive officer of the Rainwater Harvesting Association of Australia. Professor Peter Coombes is managing director of Urban Water Cycle Solutions.

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  1. Hello Philip, I have enjoyed your various discussions on this topic. However, I cannot agree with you that the transparent use of real data is somehow misleading. Similarly the difference in climate between Melbourne and Sydney is not so dramatic as to justify the outcome from NatHERS that a six star building in Melbourne uses 2-3 times more energy than a six star building in Sydney. This result does not make sense. Analysis of the relative climate processes also does not support this outcome.

    However, we have argued that BASIX has transparent targets that operate via the planning scheme and NatHERS (and other tools) apply as building controls using outcomes that are not obvious (or plausable?). The performance relative to climate that you discuss seems to be excessive. We understand the real climate differences as do most, but the outcomes from NatHERS and related commentary during recent times is curious. The data does not support some of the claims.

    Nevertheless, application of a BASIX type approach to other cities (such as Melbourne) requires an evidence based approach – as you imply, the planning targets for Melbourne are different than the targets for Sydney and are influenced by climate (and many other factors). But these targets are not as dramatically different as suggested by NatHERS. For example, Sydney also has cold winters and Melbourne also has hot summers!

    Finally it would seem from the data and various commentary that BASIX is working and NatHERS has had limited success. We attempted to included targets for sustainable buildings in the Victoria planning schemes and this action was strongly resisted by the bureacracy. Perhaps application of sustainable building form solely via building controls is too late for significant beneficial outcomes? And the benefits easily gamed away?. In any event, the direct impacts of buildings is substantial. From a total systems perspective, the direct and indirect impacts of buildings on the biosphere is the dominant emissions impact in Australia. This is our concern, a scheme that only focuses on the building at the building stage cannot account for the substantial systems challenge that we face to manage our scarce resources and climate impacts

  2. I fear this article is somewhat misleading, at least on energy performance. It’s great that BASIX looks at water efficiency – it would be good if the National Construction Code did that as well. But this article fundamentally ignores the impact of climate on energy consumption. NSW, and Sydney in particular, has some of the mildest climates in Australia. That’s not a reason for patting yourselves on the back. Your call that Melbourne houses should be more efficient because they are in a colder climate is exactly what the research finds to be the case. They use more energy, as they are subjected to greater thermal loads, but their performance, relative to the climate, is better than in NSW on average. That is what a higher star rating means, and that is what Figure 1 in your article shows – at least the theoretical relativities. BASIX would have more supporters around Australia if it led to at least comparable energy performance outcomes as NatHERS, but that is not currently the case. If it adopted a leadership position, on energy performance, we’d welcome it with open arms.