RP1017: Validating and Improving the BASIX Energy Assessment Tool for Low-Carbon Dwellings

_{CRCLCL Project Reports}

RP1017e: Validating and Improving the BASIX Energy Assessment Tool for Low-Carbon Dwellings - condensed final report

This report is a condensed version of a technical report completed as part of Validating and Improving the BASIX Assessment Tool for Low-Carbon Dwellings, a research project funded by the Cooperative Research Centre for Low Carbon Living (CRCLCL) Ltd and the NSW Office of Environment and Heritage (OEH), supported by the Cooperative Research Centres program, an Australian Government initiative.

Findings from this research show that the measured BASIX-compliant dwellings performed well in the overall reduction of greenhouse gas emissions and were close to BASIX estimations, thereby validating the effectiveness of BASIX tool in promoting low carbon dwellings. However, the breakdown of energy consumption measured by this project highlighted discrepancies in energy consumption for space heating and cooling, lighting and plug loads. An analysis of the attributes contributing to these discrepancies between BASIX estimates and actual energy consumption is discussed and recommendations for future improvements are presented in line with:

• Updating and improving the benchmarks utilised by the NatHERS and BASIX assessment models;
• Improving construction and building envelope quality control; and
• Encouraging sustainability awareness and behaviours.

basix short report final 26 03 19 (11521536 PDF)

RP1017: Interim report: Validating and Improving the BASIX Energy Assessment Tool for Low-Carbon Dwellings - interim report

This project interim report presents the initial outcomes of the research that consist of:

PART 1: Recruitment of participants from single dwellings and multi-unit dwellings, and initial data analysis of the stage 1 survey;

PART 2: Analysis of the BASIX assessment model, key variables and methods of data collection for the stage 2 energy performance monitoring.

The above initial outcomes contribute to the following overall project research activities:
1) Recruitment of participants from single dwellings and multi-unit dwellings;
2) Collection of real-time energy performance and behavioral data through metering, sensing and thermal imaging technologies as well as face-to-face interviews;
3) Development of a post-occupancy energy assessment model, including:
• Building envelope performance diagnostic modelling;
• Post-occupancy behavior modelling; and
• Modelling of the relationships between building design/condition, energy efficiency of appliances and consumer behaviour.
4) Generation of insights to inform future sustainability strategies and decision-making.

RP1017 Basix project interim report (6620643 PDF)

_{Peer Reviewed Research Publications}

RP1017: Journal Article: Post-occupancy energy consumption of BASIX affected dwellings in the Sydney metropolitan area

Australian residential sector contributes approximately 13 per cent of the total greenhouse gas (GHG) emissions. The New South Wales (NSW) government in Australia has introduced mandatory energy efficiency/ GHG emissions reduction target through the Building Sustainability Index (BASIX) assessment tool, which estimates the operational energy consumption and GHG emissions from new residential developments based on information available at the building design stage. However, post-occupancy energy consumption can be different from the estimated figures at the design stage. This research aims to disentangle the relationships between various attributes that influence energy consumption at the dwelling scale through a post-occupancy residential energy performance analysis model. The model combines multidimensional attributes which include building design features, construction quality, possession of household appliances and their usage, demographic and homeowners' energy use behaviour. The model allows comparing the estimated energy consumption/ GHG emissions from BASIX assessment with actual energy consumption/ GHG emissions in the real household environment. Data for this study has been collected from a sample of 48 BASIX affected dwellings located in the greater Sydney area which includes energy bill data, real-time monitoring of electricity consumption and indoor environment (temperature and humidity) data. This paper reports findings based on the data collected from late 2015 to mid-2016 from 16 dwellings. The initial results demonstrate discrepancies in energy consumption (therefore GHG emissions), household occupancy and breakdown of energy consumption for various services between BASIX estimates and the collected data. Given that BASIX assessment is based on information available at the design stage, the reported discrepancies are expected. More importantly, the initial results show that BASIX assessments under-estimated energy consumption for active cooling and over-estimated consumption for lighting and ventilation and other household plug loads.

This paper can be accessed here.

RP1017: Journal Article: The role of post occupation evaluation in achieving high performance buildings through diagnostics

Buildings are major consumers of energy for heating and cooling. The number of buildings is growing rapidly with demand for energy. To reduce consumption, governments worldwide have implemented codes, standards, and building practices. In New South Wales, Australia the planning department introduced a web-based energy-modelling tool intended to increase the thermal performance of the residential building's envelope prior to development applications. The modelling tool, Building Sustainability Index (BASIX) was introduced in 2004. Building codes and standards in them selfs are not perfect instruments but guidelines to achieve building objectives. However, there is evidence in literature stating that buildings are not achieving the predicted results in thermal performance leading to increased energy consumption. This research looks into the predicted modelling aspects to the BASIX program for thermal performance and undertaking a diagnostic study in verifying the building envelope meeting its objectives. This study considered the building envelope the key factor in thermal performance, in which building practices may undermine codes and standards delivering sub-optimal performance. The research justifies the need for diagnostics as a tool to evaluate building practices in reducing the performance gap between the modelled and the delivered results. This would provide building professionals, and government bodies in understanding and addressing the cause of performance gaps between the predicted and actual results for thermal performance in future buildings.

This paper can be accessed here.

RP1017: Journal Article: Modelling and analysis of post-occupancy behaviour in residential buildings to inform BASIX sustainability assessments in NSW

Sustainability assessment tools aim to promote high sustainability outcomes in residential buildings, ensuring less consumption of water, energy and less emission of greenhouse gases. However, existing literature often presents variations between the estimated outcomes from the assessment tools and actual outcomes after building occupation. Research suggests that actual energy consumption could be significantly influenced by resident behaviour in addition to the dwelling conditions and the energy efficiency of appliances. This qualitative study explores the nature of resident behaviour in achieving thermal comfort and how these influence the actual energy performance of BASIX-affected dwellings in NSW. A preliminary evidence-based behaviour model is developed to support the behavioural analysis. The model positions the heating and cooling effects of the dwellings’ design, the behaviour of residents in space heating and cooling, hot water consumption, etc. as well as multiple influential attributes such as resident’s perceptions, preferences, attitudes and knowledge towards energy efficiency in relationship to energy efficiency outcomes. The model not only identifies the key drivers that trigger energy consumption behaviour, but also investigates the potential inter-relationships among all the key influential attributes. The findings of this research will inform the BASIX assessment tool, sustainability policy, building designs and government educational programs on sustainability.

View paper