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Considering the significant consumption of energy in existing building stocks, effective retrofitting has great potential for reducing such consumption and promoting sustainability in existing buildings. This study aims to develop a sustainable retrofit decision-making mechanism for high-rise buildings in Hong Kong, China, by uncovering the optimum set of retrofit solutions based on the local climatic conditions, building features and cost. Based on a prototype building in Hong Kong, the study employed the net present value (NPV) to unveil the most suitable solutions to maximise the energy efficiency of existing buildings and minimise their retrofit costs, integrating the energy simulation. This study revealed that it is desirable to adopt an optimal set of measures for achieving a 40% energy improvement since the energy conservation can be as much as 82 (kWh/m2)/year with the optimal NPV of more than US$3300 over a 20 year life span. However, the cooling system, building energy management system and thickness of wall insulation are the most influential factors to the optimum NPV and energy conservation in Hong Kong. The identified optimal set of cost-effective retrofit measures can be effectively implemented for sustainable retrofit projects in the existing building, and the developed methodological framework can be suitably adapted for sustainable building retrofit projects in different climatic zones. The decision-making model is validated by the process of calculating energy consumption, selecting practical retrofit measures and analysing retrofit benefits when taking the local building standards into account. [ABSTRACT FROM AUTHOR]

The importance of the building industry on environmental impacts, especially global warming potential (GWP) impact due to greenhouse gases emissions is undisputed. Thus, significant efforts have been devoted to minimize environmental impacts and waste management problems from building construction globally. Numerous studies have particularly focused on assessing the environmental impacts of buildings based on materials, construction processes and whole building systems. However, less attention has been given on some critical features, especially on temporary works (e.g., hoarding system). But the temporary works also consume considerable amounts of materials and generate significant amounts of waste due to its short service life time. Therefore, this study evaluated the environmental impacts of hoarding systems as a case study in Hong Kong with the aim to identify the areas of impacts reduction and improvements in its waste management system. A case-specific structured questionnaire survey was conducted to the relevant stakeholders to identify the essential materials, and construction, deconstruction and waste management processes of hoarding systems, whereas life cycle assessment was employed to assess the associated environmental impacts. The findings demonstrated that more than 3 tonnes of CO 2 eq GWP and 39 GJ of non-renewable energy consumption impacts were associated with 1 m of hoarding construction. This is mainly due to the use of large amounts of steel products and concrete in the construction of the hoarding system. This results and analysis can help the building industry to identify the opportunity for reducing environmental impacts, and facilitate resource-efficient and effective design of hoarding systems. [ABSTRACT FROM AUTHOR]

• A food-energy-water-waste nexus analysis can aid in low carbon city design. • System dynamic modeling analysis synthesizes low carbon city initiative. • Scenario planning helps identify decarbonization pathways for prioritization. The retrofit of existing buildings at a community scale can provide a huge opportunity to reduce the community's energy consumption and subsequent greenhouse gas (GHG) emissions in support of the United Nations agenda for net-zero emissions and decarbonization. This study demonstrates a community-scale food-energy-water-waste nexus through 6 alternatives (A1–A6) by highlighting decarbonization pathways with system dynamics modeling. Several potential retrofit alternatives are proposed for analyzing building energy consumption, energy requirements for rooftop or greenhouse crop production, and potential energy and water savings from renewable energy harvesting. Such a nexus analysis is designed to integrate (1) building energy consumption, (2) waste management and water consumption, and (3) GHG emissions based on life-cycle assessment to prioritize alternatives. The incorporation of solar photovoltaic (PV) systems (i.e., rooftop, parking lot, parking garage, and floating solar PV) sustains approximately 72% of net energy demand (alternative A3), while the integration of all solar, wind, and anaerobic digestion alternatives provides around 41% of net energy demand (alternative A6). It is vital to emphasize decarbonization pathways through the use of renewable energy by 2030 in alternative A5 (i.e., solar and wind energy) and A6, both of which avoid energy consumption from the utility grid and result in 250% total carbon emissions offset. [ABSTRACT FROM AUTHOR]

Sustainable building retrofit can provide a great opportunity to reduce the energy consumption of existing buildings to commensurate the climate policies and enhance the building energy performance. Given it strategic importance, there is no shortage of research studies on sustainable building retrofit globally in particular the retrofit measures and technologies for different types of buildings. Despite that, sustainable building retrofit is climate and location specific, and decision-makers are still facing challenges to identify an optimum set of retrofit measures for different climatic conditions according to the trade-off between energy saving and retrofit cost. One reason for that is because of the lack of available information especially those related to the cost of sustainable building retrofit measures. This study aims to develop an integrated energy-cost model for selecting the optimal retrofit solutions for existing high-rise residential buildings in various climatic zones in China. Based on in-depth literature review and analysis of published reports, different alternative retrofit measures for wall, window, shading system, heating and cooling systems, and renewable energy technologies for buildings in different climate zones of China are identified. The retrofit costs related to the identified sustainable building retrofit measures are analyzed by referring to the local renovation techniques and cost in each zone through developing a set of equations. A total 28 practical sustainable building retrofit measures along with a set of retrofit options are identified. A deterministic decision framework is developed to facilitate decision-makers achieving a specific energy saving target and evaluating the associated costs based on the identified retrofit measures for high-rise residential buildings in the studied climatic zones. The practical implications of the deterministic decision framework are examined through the prototype buildings in climatic zones being studies. The findings not only actively support the selection of cost-effective sustainable retrofit measures for high-rise residential buildings in China, but the methodological framework and its implications are also equally applicable to other countries with diverse climatic characteristics and standards of living. • Developed integrated energy-cost model for finding optimal retrofit solutions. • Identified sustainable retrofit measures based on climates, building features and retrofit cost. • Developed 28 retrofit measures for wall, window, shading, HVAC, and renewable energy systems. • Optimum retrofit solutions can be adopted from identified set of retrofit options. [ABSTRACT FROM AUTHOR]