The considerable environmental impacts, resource consumption and waste generation emanating from buildings are a cause of great concern and political attention. Interest in the circular economy (CE) concept of slowing, narrowing and closing material loops through CE strategies (reuse, repair, refurbish, recycle and recover) has grown in recent years to facilitate minimising these unresolved issues emanating from the building industry. Although CE initiatives are proliferating within the industry, wide-scale adoption of CE is still lacking, and the current development and implementation of CE building design and construction strategies is fragmented. Through a systematic literature review (SLR), this study assesses which design and construction strategies are being linked to the concept of CE for new buildings, and their level of application and readiness in a building context. On this basis, the study offers insight into how this field of research is developing and provides directions for future research. From the SLR, a taxonomy is presented that groups the strategies together into 16 overarching building design and construction strategies. An important gap preventing a greater CE uptake within the industry was found to include the lack of knowledge about the environmental performance and related benefits of the various building design and construction strategies. Thus, it is suggested that conveying more comprehensive and uniform adoption of CE in the building industry requires the development of a new design typology to facilitate CE-oriented decision-making in a building context and that prioritises the strategies according to their potential in terms of minimising building-related environmental impacts.

The building industry is responsible for a large proportion of anthropogenic environmental impacts. Circular economy (CE) is a restorative and regenerative industrial economic approach that promotes resource efficiency to reduce waste and environmental burdens. Transitioning from a linear approach to a CE within the building industry will be a significant challenge. However, an insufficient number of quantitative studies exist to confirm the potential (positive) environmental effects of CE within the built environment as well as a consistent method for characterizing these effects. This paper considers key methodological issues for quantifying the environmental implications of CE principles and proposes a life cycle assessment (LCA) allocation method to address these issues. The proposed method is applied to a case study of a Danish office building where the concrete structure is designed for disassembly (DfD) for subsequent reuse. The potential environmental impact savings vary between the different impact categories. The savings are significantly influenced by the building’s material composition, particularly the number of component-use cycles as well as the service life of the building and its components. The substitution of other material choices (e.g. glass and wood) for the concrete structure exhibited a potential increase in impact savings.

Transitioning the built environment to a circular economy (CE) is vital to achieve sustainability goals but requires metrics. Life cycle assessment (LCA) can analyse the environmental performance of CE. However, conventional LCA methods assess individual products and single life cycles whereas circular assessment requires a systems perspective as buildings, components and materials potentially have multiple use and life cycles. How should benefits and burdens be allocated between life cycles? This study compares four different LCA allocation approaches: (a) the EN 15804/15978 cut-off approach, (b) the Circular Footprint Formula (CFF), (c) the 50:50 approach, and (d) the linearly degressive (LD) approach. The environmental impacts of four ‘circular building components’ is calculated: (1) a concrete column and (2) a timber column both designed for direct reuse, (3) a recyclable roof felt and (4) a window with a reusable frame. Notable differences in impact distributions between the allocation approaches were found, thus incentivising different CE principles. The LD approach was found to be promising for open and closed-loop systems within a closed loop supply chain (such as the ones assessed here). A CE LD approach was developed to enhance the LD approach’s applicability, to closer align it with the CE concept, and to create an incentive for CE in the industry.

Transitioning to a circular built environment can reduce the environmental impacts, resource consumption and waste generation emanating from buildings. However, there are many options to design circular building components, and limited knowledge on which options lead to the best environmental performance. Few guidelines exist and they build on conventional environmental performance assessments that focus on single life cycles, whereas the circular economy (CE) focuses on a sequence of multiple use- and life cycles. In this article, environmental design guidelines for circular building components were developed in five steps. First, examples of circular variants of a building structure were synthesized. Second, the environmental performance of these variants was compared with a business-as-usual variant through Life Cycle Assessments (LCA) and Material Flow Analysis (MFA) respectively. Circular parameters of these variants were tested using a scenario-specific approach. Third, from 24 LCAs and MFAs, a scorecard, rules-of-thumb and nine environmental design guidelines for designing circular building components were developed that provide guidance on which circular pathways and variants lead to the best environmental performance. For components with a long functional–technical lifespan, the following are promoted: resource efficiency, longer use through adaptable design, low-impact biomaterials and facilitating multiple cycles after and of use. Fourth, the design guidelines were evaluated by 49 experts from academia, industry and government in seven expert sessions. Further research is needed to validate the generalizability of the design guidelines. However, this research makes an important step in supporting the development of circular building components and, subsequently, the transition to a circular built environment.

As the construction industry consumes vast amounts of natural resources and in return produces large waste quantities, interest in circular economy has emerged as the means to reduce sector specific environmental impacts meanwhile ensuring continued economic growth. Life cycle assessment is a scientifically based and ISO standardized method for assessing resource consumptions and environmental impacts of products, systems or services over its entire life cycle and has been increasingly used in the construction industry and in some recently published circular economy studies. However, circular economy brings about 'rethinking' present well established building systems as well as the future life cycle scenario of these. Hence, this also means rethinking how life cycle assessments are performed on these building systems as it is suggested by some that life cycle assessment is a linear environmental impact assessment approach that misfits the circular economy idea of multiple product life cycles. The paper at hand aims at visually demonstrating variations in life cycle environmental impacts and material flows when supplying buildings with linear components compared to prospective circular designed building components for reuse and recycling and how they are modelled in life cycle assessments.