There is still much evidence to be gathered and work to be done on current energy rating tools in order to develop the next generation for regulating and assessing low to zero carbon buildings.
In Australia and around the world, a number of building energy simulation packages and environmental performance indexes are used including GreenStar, BASIX and NatHERS in Australia; BREEM and SAP in the United Kingdom; and LEED and EnergyPlus in the United States.
Multi-indicator rating tools such as GreenStar and LEED encourage environmental design quality beyond minimum standards, and evidence shows that voluntary take up of these tools has enabled significant improvements in non-residential building environmental performance, now evidenced in many buildings (see the Green Building Council of Australia website for examples).
Tools have improved over the years to become more reliable, especially as users become better trained. A few years ago when I was head of the house energy rating management body, I oversaw Australia's first government-led use of the CSIRO-developed ‘AccuRate’ tool for compliance. This initiative helped take ‘tool confidence’ a step further, providing a springboard for national uptake of compliance checking tools. Such schemes have evidently improved building energy performance.
However, recent Australian analysis of current tools (see Viable integrated systems for zero carbon housing) for use in the National Construction Code showed they were not successful in testing compliance for zero carbon performance. The level of error in tool-based assessments can also be quite significant depending on the extent to which they are simplified to get faster results, and according to the design stage of the project. Current tools cannot provide absolute answers and are at best good for comparative performance studies or 'what-ifs,' leaving much room for improvement.
Research is now underway to develop evidence-based building energy modelling tools to address these gaps by providing data and evidence about building types, technologies, climates and the behaviour of occupants.
The need to better understand the impact of post-occupancy behaviour on building performance is clear. Experiments using the same simulator, tool and house have compared results with post-occupancy data from actual houses, and have shown that models are only as good as the assumptions about building user behaviour.
In the end, actual energy use is determined by the way people use buildings, and that’s not easy to predict. In Singapore for example, where the GreenMark tool is mandatory, a five-year review found a lack of consistency and correlation between design ratings and post occupancy performance.
Surveys have shown that metaphorical ‘black balloons’ and the concept of energy megajoules do not significantly influence consumer decisions. However, promoting good design principles through comfort and well-being can deliver low carbon and energy outcomes. Next generation tools for residential buildings need to acknowledge the importance of occupants’ comfort and well-being in influencing design and purchasing decisions, and provide information to help consumers find the right products. This can go beyond space heating and cooling to include, for example, acoustic and visual comfort and air quality guidance.
In a country that has taken to rooftop solar technologies faster than any other, and with household-scale batteries likely to make a huge impact in managing energy supply and demand very soon, new tools must also recognise the consumer and environmental benefits of incorporating renewable energy technologies and be ready to provide feedback on these.
Non-residential buildings also present a challenge in better integrating technological systems, architectural design and occupant well-being. It is now well understood that there is a strong link between indoor environment quality in office buildings and occupant satisfaction and productivity, as is the case with healing in hospitals and learning in school buildings. Interestingly, in non-residential buildings, a focused energy manager is shown to be more influential in delivering results than the inclusion of design features alone.
The expertise of those using tools can also have a significant impact. Current high performance building design tools either simulate building performance based on fundamental laws of physics, or correlate performance and design variability. Their success depends on the quality of analysis performed and the confidence of those undertaking it, with assessments by qualified practitioners showing better quality results. Experiments conducted over the years using the same tool and same house with different simulators have shown tool-user expertise can significantly impact assessment quality.
The connectivity of next generation tools will also determine their success. Effective links with building information models (BIMs) and, as development-scale projects grow, with precinct information models (PIMs) are vital, as is inter-operability between tools and the use of common data platforms (so there can be consistency in comparison).
As we move forward and tackle the need to go beyond an easy 30 per cent energy reduction to zero carbon output, we must have tools that show clear evidence of the building performance, and which are not just predictive. This necessitates consideration of the whole building life cycle, with checks on post-occupancy performance and rewards for good results.
With the help of effective tools, zero carbon scenarios for all buildings can be presented at design stage to enable continuous improvement and the ongoing measurement of ratings. The matter of prediction risk and uncertainty will remain, but good tools with well-trained users can deliver on high performance buildings.