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High-resolution combined building stock and building energy modeling to evaluate whole-life carbon emissions and saving potentials at the building and urban scale

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Abstract

As global and local actors seek to address climate concerns, municipalities, regions, and countries are developing policies for the built environment to reach carbon neutrality. In most cases, however, current policies target new construction and operational carbon emissions only, thus omitting the significant carbon emission saving potential resulting from the reactivation of embodied carbon in existing buildings. This article describes the development of a high-resolution combined building stock model (BSM) and building energy model (BEM) on both building and urban scale using all residential buildings of Ithaca, NY, USA as a case study. The model offers a holistic, detailed and local perspective on operational and embodied carbon emissions, associated saving potentials at both the building and urban scale, and the linkages, trade-offs and synergies between buildings and energy use as a basis for decision-making. A circular economy (CE) in construction posited on the reuse and recycling of existing building materials, necessitates a detailed material inventory of the current building stock. However, the scale and nature of this endeavor preclude traditional survey methods. The modeling process described in this article instead engages a bottom-up data aggregation and analysis approach that combines detailed construction archetypes (CAs) and publicly available, higher-level municipal geospatial data with building metadata defining occupancy and systems to create an autogenerated, detailed 3D geometry. The resulting BSM and BEM can simulate both embodied carbon content and operational carbon emissions of individual buildings within a municipal study with minimal required input data and a feasible computational effort. This provides modelers with a new spatial and geometric fidelity to simulate holistic renewal efforts, and inform carbon neutrality policies and incentives towards the decarbonization of the built environment.

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The potential of urban mining is getting greater. From the global view, the potential of urban mining, namely the estimated amount of on-surface stock which has been mine form the geo-sphere into the techno-sphere, is comparative to natural resource which is still in geo-sphere as underground stock. However, practical recycling of metals are still in the stage of developing, and depending on the country. As an example, ultimate potential of urban mine in Japan was estimated. The differences between input of each metal contents and output of it were considered to be accumulated. I/O method was combined to estimate the metal contents in exported products. Japan, which is considered a typical exporter of materials, has great potential of urban mining which comes from domestic demand of products. However, real activity of development of urban mine, namely recycling, is not so effective, especially for minor metals which sometime called rare metals from the viewpoint of the importance in industries. We need to develop the technology and system for urban mining, just now.
Article
Urban residential buildings are formed, maintained and reformed by different external material and energy flows, and their behaviors of input, accumulation and output are characterized by their architectural factors and modes of use that usually determine the consumption of material and energy of a building at its overall life cycle.In this research, we took Beijing city, a rapid developing city as a case study, and examined material flows of urban residential building system based on a survey of typical residential buildings in the urban areas of Beijing city. The quantitative analysis were made to describe the input, transformation/accumulation, and output of building materials from the year 1949 to 2008, and a comparative analysis was done to identify the differences of material uses among the buildings with different architectural structures as masonry–concrete, and steel–concrete.During the period from 1949 to 2008, there were six main materials of cement, sand, gravel, steel, bricks and timber used in urban residential building system in Beijing. The total amount of material imported into the system was 5.1 × 108 t, among which the accumulated amount was 4.7 × 108 t, an accumulation rate of 92.5%, and the total of building wastes reached 3.9 × 107 t. Among the buildings with two architectural structures, the total amount of material use for buildings with steel–concrete structure was larger than masonry–concrete. It was found that the buildings with steel–concrete structure experienced a rapid increase since the year 1979 in Beijing. As a result of rapid urban development, the large-scale reformation and demolishment of urban old buildings also led to a rapid growth of the amount of building wastes. And the building wastes generated in the process of reformation and demolition began to exceed that produced in the process of new buildings construction. The amount of building wastes generated from 2004 to 2008 accounted for 52.2% of the total that generated from 1949 to 2008.From this research, the rapid development of Beijing's residential building system in the past 60 years became a big ecological pressure for urban sustainable building development. It is important to change the traditional model of urban construction, and develop some sustainable or ecologically friendly construction technologies to enhance the capacity of recycling and reuse of residential building wastes for realizing a sustainable urban building construction and management in Beijing.
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