Zhengen Ren

Thermal simulations of buildings play a critical role in optimizing energy efficiency, thermal comfort, and heating, ventilation and air conditioning (HVAC) systems design. Accurate weather data is essential for reliable simulations, as local weather and climate have a significant impact on energy requirements for space heating and cooling and thermal comfort. This study conducted a literature review regarding the sources, types, and uncertainties of weather data used for thermal simulations of buildings, including typical meteorological years (TMYs) and extreme weather files under current and future climates. Additionally, this paper evaluates methods for weather data processing, including interpolation, downscaling, and synthetic generation, to improve simulation accuracy. Finally, approaches are proposed for constructing weather files for the future and extreme conditions under a changing climate. This review aims to provide a guide for researchers and practitioners to enhance the reliability of thermal modeling through informed construction, selection, and application of weather data.

Australia aims to achieve net-zero emissions by 2050, and its building sector needs rapid change. The Nationwide House Energy Rating Scheme (NatHERS) is supported by the Australian Government to expand the current building envelope thermal performance energy star rating to a whole-of-home (WoH) energy rating. The NatHERS Administrator supports CSIRO to develop a benchmark WoH energy rating tool for new and existing housing, respectively. The tool for new housing was released in June 2023. This study presents the tool development for Australian existing housing. A case study was conducted using the tool for the eight capital cities of Australian states and territories. It shows that with a detached house built in the 1900s being updated to six or more stars and replacing old equipment and appliances with high-energy-efficient ones, more than 50% of energy can be saved in all the eight cities. To be zero-energy (carbon) housing, 5 kW solar PV needs be installed in Darwin and Hobart, 4 kW in Melbourne and Canberra, 3.5 kW in Adelaide and Sydney, and 3 kW in Brisbane and Perth. It demonstrates that this tool can be used for housing retrofitting to be low/zero-carbon emissions and low operational cost.

To manage energy-efficient indoor air quality, mechanical ventilation with a heat recovery system provides an effective measure to remove extra moisture and air contaminants, especially in bathrooms. Previous studies reveal that heat recovery technology can reduce energy consumption, and its calculation needs detailed information on the thermal performance of exhaust air. However, there are few studies on the thermal performance of bathroom exhaust air during and after showers. This study proposed a detailed thermal performance prediction model for bathroom exhaust air based on the coupled heat and mass transfer theory. The proposed model was implemented into the AccuRate Home engine to estimate the thermal performance of residential buildings with heat recovery systems. The time variation of the water film temperature and thickness on the bathroom floor can be estimated by the proposed model, which is helpful in determining whether the water has completely evaporated. Simulation results show that changing the airflow rate in the bathroom has little effect on drying the wet floor without additional heating. The additional air heater installed in the bathroom can improve floor water evaporation efficiency by 24.7% under an airflow rate of 507.6 m³/h. It also demonstrates that heat recovery can significantly decrease the building energy demand with the fresh air load increasing and contribute about 0.6 stars improvement for the houses in Hobart (heating-dominated region). It may be reduced by around 3.3 MJ/(m²·year) for the houses in other regions. With this study, guidelines for optimizing the control strategy of the dehumidification process are put forward.

Globally, buildings account for nearly 40% of the total primary energy consumption and are responsible for 20% of the total greenhouse gas emissions. Energy consumption in buildings is increasing with the increasing world population and improving standards of living. Current global warming conditions will inevitably impact building energy consumption. To address this issue, this report conducted a comprehensive study of the impact of climate change on residential building energy consumption. Using the methodology of morphing, the weather files were constructed based on the typical meteorological year (TMY) data and predicted data generated from eight typical global climate models (GCMs) for three representative concentration pathways (RCP2.6, RCP4.5, and RCP8.5) from 2020 to 2100. It was found that the most severe situation would occur in scenario RCP8.5, where the increase in temperature will reach 4.5 °C in eastern Australia from 2080–2099, which is 1 °C higher than that in other climate zones. With the construction of predicted weather files in 83 climate zones all across Australia, ten climate zones (cities)—ranging from heating-dominated to cooling-dominated regions—were selected as representative climate zones to illustrate the impact of climate change on heating and cooling energy consumption. The quantitative change in the energy requirements for space heating and cooling, along with the star rating, was simulated for two representative detached houses using the AccuRate software. It could be concluded that the RCP scenarios significantly affect the energy loads, which is consistent with changes in the ambient temperature. The heating load decreases for all climate zones, while the cooling load increases. Most regions in Australia will increase their energy consumption due to rising temperatures; however, the energy requirements of Adelaide and Perth would not change significantly, where the space heating and cooling loads are balanced due to decreasing heating and increasing cooling costs in most scenarios. The energy load in bigger houses will change more than that in smaller houses. Furthermore, Brisbane is the most sensitive region in terms of relative space energy changes, and Townsville appears to be the most sensitive area in terms of star rating change in this study. The impact of climate change on space building energy consumption in different climate zones should be considered in future design strategies due to the decades-long lifespans of Australian residential houses.

Heat loss from a building through the ground becomes relatively important as the above-grade components of the building fabric are built more energy efficient. For annual space heating and cooling load calculations that require short computation time, with reasonable accuracy, for modelling heat losses to ground through the foundations, this study presents a new correlation-based model. The correlation algorithms were derived from the results of a commercial 3D transient heat transfer program using Artificial Neural Network. We demonstrate that for steady-state heat loss through slab-on-ground, the proposed correlation model agrees with the CSIRO analytical solution within 6.8%, and for transient heat loss through slab-on-ground and basement the new model agrees with a well validated commercial 3D heat transfer program. The new simplified approach presented covers most foundation configurations of interest, with low processing requirements, and is ideal for use in building energy performance simulations due to the short computation time.

To evaluate potential air infiltration model improvement for residential building energy simulation, three infiltration models have been developed and implemented into AccuRate, a housing energy star rating tool widely used in Australia. This paper presents a comparison of the calculated air infiltration rates and building energy performance using the three models. Case studies are made for eight houses with various envelope leakages under different weathers Australia (Melbourne – heating dominated, Sydney – balanced heating and cooling, and Cairns – cooling dominated). The results show that there are up to 37% differences in the calculated average infiltration rates between these three models for both Melbourne and Sydney, and 40% in Cairns. Up to 13% and 6.7% differences were observed in the modelled annual energy needs for space heating/cooling in Melbourne and Sydney, respectively, among the three models, and up to 20% differences in the simulated energy needs for cooling in Cairns. The simple approaches ignored impact factors such as system operation, envelope leakage and stack effect variation due to indoor–outdoor temperature differences. The multizone model accounted all these factors and should be used for predicting infiltration in the future. However, the executing speed using multizone model will need to be improved.

This study presents an integrated air flow model for AccuRate, a benchmark housing energy star-rating tool widely used in Australia. The model was developed by implementing a network multi-zonal infiltration model into an existing large opening model. Case studies using 10 houses in Melbourne, Australia, showed that on average the predicted infiltration rates are within 12.6% of the blower-door test results with a standard deviation of 1.6%. The model study also showed that on average the infiltration rates of the 10 houses could be reduced around 52% by sealing major air leakage pathways, which can result in an average of 7% reduction in the annual space heating and cooling loads for the 10 houses. It was also found that an annual hourly energy performance simulation using the new air flow model requires around 15 min in comparison with around 1 min using the existing simple infiltration model in the AccuRate engine.

A new tool for predicting the total energy consumption and associated greenhouse gas (GHG) emissions of Australian households is developed by integrating the thermal efficiency of the building envelope, installed equipment and appliances, and different occupancy profiles with energy end-use modules for space heating, space cooling, water heating, lighting, and plug-in appliances. Space heating and cooling energy consumption are simulated by an enhanced version of a house energy rating tool - AccuRate, modified to account for specific heating, ventilation and air-conditioning (HVAC) system efficiency and occupancy profile. Individual modules for hot water, lighting and appliances are developed, calibrated and assessed against available published end-use data in Australia and New Zealand. The tool's integrated capability to predict the annual energy consumption of a tenant-occupied house in Melbourne is validated with actual data measured over a 12-month period.