Comparison of the Embodied Carbon Emissions and Direct Construction Costs for Modular and Conventional Residential Buildings in South Korea

Modular construction is an innovative new construction method that minimizes waste and improves efficiency within the construction industry. However, practitioners are hampered by the lack of environmental and economic sustainability analysis methods in this area. This study analyzes the embodied carbon emissions and direct construction costs incurred during the production phase of a modular residential building and provides comparison to an equivalent conventional residential building. Major drawings and design details for a modular residential building in South Korea were obtained, and the quantity take-off data for the major construction materials were analyzed for a modular construction method and a conventional construction method using a reinforced concrete structure under the same conditions. Focusing on major construction materials during the production phase, the embodied carbon emissions assessment revealed that adopting a modular construction approach reduced the environmental impact by approximately 36%, as compared to the conventional reinforced concrete method. However, in terms of the direct construction cost, the modular construction was approximately 8% more expensive than the conventional reinforced concrete construction method.

Shared Responsibility for Carbon Emission Based on Embodied Carbon Emission in China-US Trade

Traditional Production-Based Accounting (PBA) principle does not consider the embodied carbon emissions in export and import trade. A multiregional input-output (MRIO) model is constructed to estimate the embodied carbon dioxide emissions of 41 countries and regions worldwide, based on the PBA and shared responsibility approach in this paper. The results indicate that the embodied carbon emissions in 2018 in China's export trade were 1326.1 million tons higher than that of import trade. Through the empirical analysis of the embodied carbon emissions in China's import and export trade, it can be seen that China is a major producer of carbon emissions, not a consumer country, and has taken more carbon emissions responsibility for the world. And it is more reasonable and impartial to assign developed and developing country’s carbon emissions responsibility in the light of the shared responsibility method.

Comparative LCAs of Conventional and Mass Timber Buildings in Regions with Potential for Mass Timber Penetration

Manufacturing of building materials and construction of buildings make up 11% of the global greenhouse gas emission by sector. Mass timber construction has the potential to reduce greenhouse gas emissions by moving wood into buildings with designs that have traditionally been dominated by steel and concrete. The environmental impacts of mass timber buildings were compared against those of functionally equivalent conventional buildings. Three pairs of buildings were designed for the Pacific Northwest, Northeast and Southeast regions in the United States to conform to mass timber building types with 8, 12, or 18 stories. Conventional buildings constructed with concrete and steel were designed for comparisons with the mass timber buildings. Over all regions and building heights, the mass timber buildings exhibited a reduction in the embodied carbon varying between 22% and 50% compared to the concrete buildings. Embodied carbon per unit of area increased with building height as the quantity of concrete, metals, and other nonrenewable materials increased. Total embodied energy to produce, transport, and construct A1–A5 materials was higher in all mass timber buildings compared to equivalent concrete. Further research is needed to predict the long-term carbon emissions and carbon mitigation potential of mass timber buildings to conventional building materials.

Embodied Energy and Cost Assessments of a Concentrating Photovoltaic Module

This paper focuses on the embodied energy and cost assessments of a static concentrating photovoltaic (CPV) module in comparison to the flat photovoltaic (PV) module. The CPV module employs a specific concentrator design from the Genetically Optimised Circular Rotational Square Hyperboloid (GOCRSH) concentrators, labelled as GOCRSH_A. Firstly, it discussed previous research on life cycle analyses for PV and CPV modules. Next, it compared the energy embodied in the materials of the GOCRSH_A module to the energy embodied in the materials of a flat PV module of the same electrical output. Lastly, a comparison in terms of cost is presented between the analysed GOCRSH_A module and the flat PV module. It was found that the GOCRSH_A module showed a reduction in embodied energy of 17% which indicates a reduction in embodied carbon. In terms of cost, the costs for the GOCRSH_A module were calculated to be 1.71 times higher than the flat PV module of the same electrical output. It is concluded that a trade-off is required between the embodied energy and cost impacts in order to bring this CPV technology into the market.

A Conceptual Framework for Estimating Building Embodied Carbon Based on Digital Twin Technology and Life Cycle Assessment

Low-carbon building design requests an estimation of total embodied carbon as the environmental performance metric for comparison of different design options in early design stages. Due to a lack of consensus on the system boundaries in building life cycle assessment (LCA), the carbon estimation results obtained by the current methods are often disputable. In this regard, this paper proposes a method for estimating building embodied carbon based on digital twin technology and LCA. The proposed method is advantageous over others by providing (1) a cradle-to-cradle LCA and (2) an automated data communication between LCA and building information modelling (BIM) databases. Because data for the processes in the life cycle are collected via digital twin technology in a standard and consistent way, the obtained results will be considered credible. So far, a conceptual framework is developed based on a comprehensive literature review, which consists of three parts. In the first part, formulas for LCA are given. In the second part, a hybrid approach combining semantic web with a relational database for BIM and radio-frequency identification (RFID) integration is described. In the third part, how to design the LCA database and how to link LCA with BIM are described. The conceptual framework proposed is tested for its reasonableness by a small hypothetical case study.

The Status of Embodied Carbon in Building Practice and Research in the United States: A Systematic Investigation

The building construction industry accounts for 5% of global energy use and 10% of global greenhouse gas (GHG) emissions. A primary source of these emissions is the manufacture of building construction materials such as steel, cement, and glass. As aggressive building energy codes push new construction towards net-zero-energy and net-zero-carbon operations, corresponding efforts to reduce embodied energy and carbon from building construction materials must be pursued to achieve the decarbonization goals of the building sector. In the past few decades, progressive building energy codes as well as the underlying research on reducing the operational energy and its related greenhouse gas emissions have stimulated changes of practice in building design and operation. In contrast, strategies to reduce embodied carbon in the substitute remaining life-cycle stages of a building are less defined and studied. The selection of building materials and systems is largely unregulated, as long as minimum health, safety, and performance standards are met. In addition, it is unclear whether we have adequate knowledge infrastructure to incorporate embodied carbon into national model codes. This study provides a comprehensive review of the current state of knowledge of existing methods, databases, and tools on embodied carbon studies, and identifies the knowledge gaps. It provides a basis for the governments, academia, industry, and other institutes to collaboratively fill in these gaps and develop standards and codes to decarbonize buildings and their interface with other sectors.