• Energy Research

The design and assessment of net-zero buildings commonly focus exclusively on the operational phase, ignoring the embodied environmental impacts over the building life cycle. An analysis is presented on the consequences of integrating embodied impacts into the assessment of the environmental advantageousness of net-zero concepts. Fundamental issues needing consideration in the design process - based on the evaluation of primary energy use and related greenhouse gas emissions - are examined by comparing three net-zero building design and assessment cases: (1) no embodied impacts included, net balance limited to the operation stage only; (2) embodied impacts included but evaluated separately from the operation stage; and (3) embodied impacts included with the operation stage in a life cycle approach. A review of recent developments in research, standardization activities and design practice and the presentation of a case study of a residential building in Norway highlight the critical importance of performance indicator definitions and system boundaries. A practical checklist is presented to guide the process of incorporating embodied impacts across the building life cycle phases in net-zero design. Its implications are considered on overall environmental impact assessment of buildings. Research and development challenges, as well as recommendations for designers and other stakeholders, are identified.

Since existing residential buildings are a significant global contributor to energy consumption and greenhouse gas (GHG) emissions, any serious effort to reduce the actual energy and carbon emissions of the building sector should explicitly address the carbon mitigation challenges and opportunities in the building stock. This research investigates environmentally and economically sustainable retrofit methods to reduce the carbon footprint of existing residential buildings in the City of Greater Dandenong as a case study in Metropolitan Melbourne, Australia. By categorizing energy use into various building age brackets and dwelling types that align with changes in energy regulations, we identified various retrofit prototypes to achieve a targeted 6.5-star and 8-star energy efficiency rating (out of a maximum 10-star rating system). The corresponding operational energy savings through different retrofit options are examined while also considering the quantity of materials required for each option, along with their embodied energy and GHG emissions, thus allowing a more comprehensive lifecycle carbon analysis and exploration of their financial and environmental payback times. Results show that when buildings are upgraded with a combination of insulation and double-glazed windows, the environmental benefits rise faster than the financial benefits over a dwelling’s lifecycle. The size or percentage of a particular dwelling type within the building stock and the remaining lifecycle period are found to be the most important factors influencing the payback periods. Retrofitting the older single detached dwellings shows the greatest potential for lifecycle energy and carbon savings in the case suburb. These findings provide households, industry and governments some guidance on how to contribute most effectively to reduce the carbon footprint of the residential building sector.

PurposeA systematic approach is needed to engage a broad range of stakeholders to reduce greenhouse gas (GHG) emissions from energy use in the building sector. The purpose of this paper is to develop a systems‐based bottom‐up approach for this purpose, and to demonstrate its application in a case study of office building stock in the State of New South Wales (NSW) in Australia.Design/methodology/approachA conceptual framework for the general method is developed based on a cross‐typology matrix of energy consumption and supply on the one hand, and intervention schemes or policy instruments on the other. This is then tested and demonstrated using a case study of commercial office building stock, with building energy demand calculated using a validated computer energy simulation tool for a representative set of office buildings within a local government area (LGA). The energy consumption and associated GHG emissions are then aggregated up from LGA to the whole State. The impact projections of different intervention schemes are compared and mapped spatially across the State.FindingsResults have demonstrated the significance and capability of the proposed approach, in allowing quantitative comparisons of the relative effectiveness of a specific set of regulatory, technical and behavioral scenario settings on the spatial distribution and trends in energy consumption and GHG emissions of the NSW office building stock to 2020.Research limitations/implicationsFurther case studies involving mixed building types and specific building types with greater granularity of modelling details, energy use and supply options, and spatial resolution are needed.Originality/valueThe structured cross‐typology approach is a novel contribution to bottom‐up modelling approaches to designing and/or assessing the effectiveness of specific policy instruments, alone or in combination. It will enable policy makers, property portfolio owners, utility companies and building tenants to assess the broader impacts of their specific actions towards a common goal.

Abstract Aiming to achieve net-zero operational greenhouse gas emissions at the community level is a valuable endeavour because of synergies and efficiency gains through mixed energy uses, the economy of scale, and a broader range of technological options. Nevertheless, there are several challenges in the planning and design process of the energy infrastructure towards this goal for whole communities. The preponderance of the zero emission concepts at community scale, including unclear definitions of key terms, the availability of supporting tools, and the energy planning approaches could affect the design and decision-making process of stakeholders. In this paper, the state of the art and the state of practice of energy master planning of net-zero emission communities are critically reviewed in order to identify the key research challenges and opportunities to enhance decision-making and hasten their wider adoption. Energy master planning approaches, tools, technologies and decision-making indicators used towards net-zero emission targets are evaluated in selected case studies worldwide. The analysis and research findings show an inconsistency in the scope, definition and approaches in energy master planning of net-zero emission communities. In addition, energy resilience and social metrics and criteria are rarely included in the energy master planning of net-zero emission communities. A conceptual energy master planning framework is proposed that can support performance-based decision-making in the design and planning of net-zero emission communities. A more integrated energy master planning approach and tools, as well as more comprehensive and multi-dimensional assessment metrics, are required for improved and effective decision-making.

Abstract A common starting point in assessing greenhouse gas (GHG) reduction policy implications in the built environment is to look at industry specific policies. This paper addressed the glaring gap between national all-economy policy options that actually determine industry-specific programs, and their downstream impacts and implications to the building and construction sector. National carbon policy schemes were organised into two basic types: indirect pricing mechanisms, and direct pricing mechanisms. Their features and comparative strengths and limitations were critically reviewed under a common framework, drawing from a wide body of literature. The status of the application of the GHG reduction policies in China was reviewed. A green building case is studied to quantitatively present the effectiveness and deficiencies of the current GHG mitigation policies in the building sector of China, and their implications to a building's life cycle. Based on China's current status of the policy system, this paper identifies the future direction of building's GHG mitigation policies of China. Policies directly aiming to GHG mitigation in the building sector should be implemented in holistic and comprehensive pathway, to balance the costs and benefits of the stakeholders for the promotion of building GHG mitigation technologies.

Abstract The building sector is regarded as having one of the highest benefit–cost ratios from greenhouse gas (GHG) emission reduction strategies. However, because of uncertainties around household behaviour patterns, it is very difficult to assess and compare the GHG reduction impacts of different intervention schemes for whole housing stock. Intervention schemes include policy instruments such as incentives or rebates for energy efficient appliances or renewable energy, and regulatory building code requirements for energy efficiency. This paper presents a decision support tool based on mathematical diffusion that evaluates the adoption levels of different schemes or pathways towards reducing GHG emissions in housing stock. It is an extension of the Bass diffusion model that accommodates financial and non-financial benefits, ceilings of adoption and interactions between intervention options. The model capability was tested using a case study of seven suburbs in Brisbane, Australia, comprising of 25,000 houses and units. Estimates of GHG emission reductions to 2019 of a household rebate scheme for solar panels and a rebate scheme for solar hot water compared to a base case of no rebates were presented and analysed. Modelling also allowed identification of important characteristics of adoption trends that could assist policy makers and industry to substantially improve the design of effective intervention options.

Abstract Energy retrofits of buildings usually ignore the amount of embodied energy and greenhouse gas (GHG) emissions needed to reduce the operating energy and related emissions. Focusing on the Greater Melbourne Area (GMA), the fastest growing capital city in Australia, this paper analyses the embodied impacts of different dwelling stock retrofit programs using a combination of a top-down and a bottom-up approach. We look at dwelling stocks that have been built before 2005 (i.e., before a minimum 5-star rating in energy performance was introduced in Australia) because these are expected to consume, without any retrofit or upgrade, about 34.9 TWh of energy or emit 8.57 × 106 t-CO2eq GHG for heating and cooling every year. Retrofit options to improve their energy star rating range from relatively cheap and easy options (e.g., draught sealing) to relatively expensive options (e.g. double glazing of windows). If all these buildings' energy efficiency is improved to the level of a 6-energy rated dwelling across the metropolitan region, we can save about 25.5 TWh per year in heating and cooling energy (or 6.25 × 106 t-CO2eq GHG each year). However, the retrofit program is estimated to consume 4.75 TWh of embodied energy, or have 1.89 × 106 t-CO2eq embodied GHG emissions. This is equivalent to 50% of the annual heating and cooling energy for the stock, or 81% of operational GHG emissions due to heating and cooling of existing dwellings. Considering the total life cycle energy and GHG emissions over the life of the buildings, although reducing the operational heating and cooling energy will remain to be the primary driver for action, the proportion of the embodied impacts’ contribution is expected to increase in the coming years especially as the implementation of net-zero energy/emissions concepts become more commonplace.

Electricity network investment and asset management require accurate estimation of future demand in energy consumption within specified service areas. For this purpose, simple models are typically developed to predict future trends in electricity consumption using various methods and assumptions. This paper presents a statistical model to predict electricity consumption in the residential sector at the Census Collection District (CCD) level over the state of New South Wales, Australia, based on spatial building and household characteristics. Residential household demographic and building data from the Australian Bureau of Statistics (ABS) and actual electricity consumption data from electricity companies are merged for 74 % of the 12,000 CCDs in the state. Eighty percent of the merged dataset is randomly set aside to establish the model using regression analysis, and the remaining 20 % is used to independently test the accuracy of model prediction against actual consumption. In 90 % of the cases, the predicted consumption is shown to be within 5 kWh per dwelling per day from actual values, with an overall state accuracy of −1.15 %. Given a future scenario with a shift in climate zone and a growth in population, the model is used to identify the geographical or service areas that are most likely to have increased electricity consumption. Such geographical representation can be of great benefit when assessing alternatives to the centralised generation of energy; having such a model gives a quantifiable method to selecting the ‘most’ appropriate system when a review or upgrade of the network infrastructure is required.