A reliable and simplified whole-of-home energy rating tool for housing retrofitting

In Australia, there are around 11 million dwellings and millions of them were constructed before building energy standards were introduced. As a result, significant energy is wasted in these houses, leading to high energy bills for households. Retrofitting these houses can save significant energy and lead to cost savings over time. Building energy simulation plays a critical role in this retrofitting process. A challenge for existing housing energy simulation is the requirement of detailed input data, which is often time-consuming to collect and might be unavailable. This study proposed simplifying methods to address this issue.

The simplified methods consist of two components: the building shell’s thermal performance and the installed equipment and appliances. This paper proposes a new zoning method for assessing building shell thermal performance. Based on similar functions and thermostat settings for space heating and cooling, three virtual zones (family/kitchen, bedroom and unconditioned) were proposed to reduce the zone number and simplify input data for a dwelling. When accurate information on insulation, shading, and air tightness is unavailable, simplified data inputs are used. For installed equipment and appliances, energy efficiency is estimated based on factors such as age and type.

Case studies were conducted using both the standard multizone model and the proposed three-zone model for detached houses across eight capital cities in Australia. These cases were tested under two input data scenarios: precise input data and estimated data using the proposed method for both building shell’s thermal performance and installed equipment and appliances. The results indicate that, for both scenarios, the outputs of the proposed three-zone model and the standard multizone model are very close, with a maximum difference of 0.5 stars in building shell energy performance star rating and 5% in whole-of-home energy consumption.

This study offers a simplified method that provides a quick and reliable tool for housing retrofitting in Australia, significantly reducing the time needed for both on-site data collection and building energy performance simulation. The results confirm that the simplified zoning model can perform as effectively as the multizone model for energy benchmarking purposes.

Overall, this study could expedite the process of generating upgrade advices for retrofitting homes in Australia.