Full length articleMaterial intensity in single-family dwellings: Variability between locations, functional unit and drivers of material use in Toronto, Perth, and Luzon
Introduction
This research examines the material intensity (MI) of single-family dwellings (SFD) in Toronto, Canada, Perth Metropolitan Region, Australia, and Luzon, Philippines. MI describes the type, quantity, and functional purpose of construction materials in a building (Gontia et al., 2018). The paper investigates how MI varies both within and between cities, explores the impact of functional unit selection in the study of residential MI and comparisons, identifies opportunities for building light-weighting, and contributes to public data available on residential MI.
From 1970 to 2017, global consumption of resources grew from 27 billion tons to 100 billion tons (Circle Economy, 2021; Oberle et al., 2019). This scale of resource use stresses the planetary boundaries, increasingly destabilizing biophysical processes that maintain a stable Earth system (Rockström et al., 2009a, 2009b). The construction industry accounts for a huge share of resource use, in large part through the use of concrete (Cao et al., 2017) and steel (Pauliuk et al., 2013), which are considerable contributors to greenhouse gas (GHG) emissions and other negative environmental impacts. Global production of cement and steel are responsible for an estimated 5–8% and 8%, respectively, of GHG emissions (Gerres et al., 2021; Shanks et al., 2019). Mining activities associated with material production further negatively impact local ecosystems, particularly in terms of water use, land use, and biodiversity (Bringezu et al., 2017).
Buildings are voracious consumers of construction materials; they store the single largest stock of anthropogenic resources (Haberl et al., 2021; Tanikawa et al., 2015). At a unit level, buildings consume between 115 and 3860 kg of materials per m2 floor area with this large range mainly driven by type of construction (e.g., highrise vs low rise), material choice, building function and building form (De Wolf et al., 2015; Guven et al., 2022; Heeren and Fishman, 2019). Historically, GHG emissions embodied in building materials have received less attention in research and public policy compared to operational energy use. However, with decreasing operational GHG emissions due to more efficient building operation and the use of lower GHG fuels, embodied emissions (highly correlated with MI) represent a larger portion of life cycle emissions (up to 90% of life cycle building GHG emissions) (Birgisdottir et al., 2017; Moncaster et al., 2019). Due to population growth, changes in patterns of household formation, and growing per capita demand for space, construction material use in residential buildings, and its associated environmental impacts, is increasing (Kleemann et al., 2017; Ortlepp et al., 2018; Yang et al., 2020). Without dramatic changes in material stewardship, resource use related to housing construction alone will make meeting climate commitments, for example, almost impossible (Soonsawad et al., 2022; Yang et al., 2022).
Existing efforts to quantify building material use and inform improved material stewardship have been challenged by a lack of detailed information on material use (Guven et al., 2022), limited consideration of variability in material use (Arceo et al., 2021), a focus on material replacement rather than material reduction (Hertwich et al., 2019), and the widespread use of a 1 m2 functional unit in MI and life cycle assessment studies, which obscures total material use (Koutamanis et al., 2018; Norman et al., 2006). This study contributes toward addressing these gaps by examining the variability in MI within and between cities, investigating the influence of selected functional units on the interpretation of results, and examining the drivers of material use in SFDs across three very different geographical locations.
Section snippets
Material flow analysis of urban material cycles and building material intensity
Increasing attention to mitigating negative environmental impacts has accelerated the study and use of building MI. For example MI studies: 1) support bottom-up understanding of urban construction material cycles (e.g., Augiseau and Barles (2017)); 2) identify urban mining potential as part of efforts toward a more circular economy in the construction sector (e.g., Yang et al. (2022)); 3) inform building designs that reduce material use (light-weighting) (e.g., Hertwich et al. (2019)); and 4)
Case study areas
The case study areas in this paper include the City of Toronto in Canada, Perth Metropolitan Region in Australia, and Luzon in the Philippines. These areas were selected based on data availability, the different construction traditions in each area, and the authors’ familiarity and knowledge of each area. Design drawings and relevant references (e.g., local building codes, construction product brochures) were available in English, facilitating access and ease of comprehension. The case study
Materials, material intensity and variability in material intensity of single-family dwellings
Fig. 2 shows the total MI of the SFDs in Toronto, Perth Metropolitan Region, and Luzon on a mass basis per 1 m2 gross floor area, 1 building, and 1 bedroom. Table S8 in Supplementary Information shows the corresponding values for Fig. 2. The total MIs on a volume basis across the three functional units have similar findings to those on a mass basis and are presented in Supplementary Information, Fig. S2. The contributions of the different materials to total MI considering both mass and volume
Conclusion
This research improves the availability of data on MI in SFDs, examines variability in SFD MI within and between different locations, examines the impact of functional unit choice on the perception of MI, and identifies the largest drivers of material use within SFDs.
Building on 40 SFDs previously studied in Toronto, this paper adds detailed bottom-up MI quantification for 40 new buildings (20 SFDs from Perth Metropolitan Region, Australia and 20 SFDs from Luzon, Philippines). Important
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors would like to thank EllisDon, BASF Canada, WSP, the NSERC Collaborative Research and Development (CRD) program, Ontario centre of Excellence (OCE) TargetGHG program, the University of Toronto, Faculty of Engineering Dean's Spark Professorship and the Canada Research Chair in Sustainable Infrastructure - grant number 232970 for funding and in-kind support. The authors thank Charles De Roxas for the data they shared with them.
References (94)
- et al.
Estimation of structural steel and concrete stocks and flows at urban scale–towards a prospective circular economy
Resour. Conserv. Recycl.
(2021) - et al.
Recent developments, future challenges and new research directions in LCA of buildings: a critical review
Renew. Sustain. Energy Rev.
(2017) - et al.
Capturing variability in material intensity of single-family dwellings : a case study of Toronto
Canada. Resour. Conserv. Recycl.
(2021) - et al.
Studying construction materials flows and stock: a review
Resour. Conserv. Recycl.
(2017) - et al.
Normalising and assessing carbon emissions in the building sector: a review on the embodied CO2 emissions of residential buildings
Build. Environ.
(2018) - et al.
Residential building facade segmentation in the urban environment
Build. Environ.
(2021) - et al.
Measuring embodied carbon dioxide equivalent of buildings: a review and critique of current industry practice
Energy Build
(2017) - et al.
Modelling global material stocks and flows for residential and service sector buildings towards 2050
J. Clean. Prod.
(2020) - et al.
Is practice aligned with the principles? Implementing new urbanism in Perth, Western Australia
Transp. Policy
(2010) - et al.
Material-intensity database of residential buildings: a case-study of Sweden in the international context
Resour. Conserv. Recycl.
(2018)
Buildings environmental impacts’ sensitivity related to LCA modelling choices of consstruction materials
J. Clean. Prod.
Uncertainty analysis for measuring greenhouse gas emissions in the building construction phase: a case study in China
J. Clean. Prod.
Urban mining and buildings: a review of possibilities and limitations
Resour. Conserv. Recycl.
Achieving environmentally friendly building envelope for Western Australia's housing sector: a life cycle assessment approach
Int. J. Sustain. Built Environ.
Raw materials consumption and demolition waste generation of the urban building sector 2016–2050: a scenario-based material flow analysis of Vienna
J. Clean. Prod.
Potentials for a circular economy of mineral construction materials and demolition waste in urban areas: a case study from Vienna
Resour. Conserv. Recycl.
A spatial analysis of material stock accumulation and demolition waste potential of buildings: a case study of Padua
Resour. Conserv. Recycl.
Estimating the construction material stocks in two canadian cities : a case study of Kitchener and Waterloo
J. Clean. Prod.
Widening understanding of low embodied impact buildings: results and recommendations from 80 multi-national quantitative and qualitative case studies
J. Clean. Prod.
Embodied greenhouse gas assessment of a bridge: a comparison of preconstruction Building Information Model and construction records
J. Clean. Prod.
Steel all over the world: estimating in-use stocks of iron for 200 countries
Resour. Conserv. Recycl.
A spatiotemporal urban metabolism model for the Canberra suburb of Braddon in Australia
J. Clean. Prod.
How much cement can we do without? Lessons from cement material flows in the UK. Resour
Conserv. Recycl.
Material demand, and environmental and climate implications of Australia's building stock: current status and outlook to 2060
Resour. Conserv. Recycl.
Towards a comprehensive life cycle energy analysis framework for residential buildings
Energy Build.
Urban buildings material intensity in China from 1949 to 2015
Resour. Conserv. Recycl.
Urban mining potential to reduce primary material use and carbon emissions in the Dutch residential building sector
Resour. Conserv. Recycl.
Perth's Urban Sprawl Driving our Love Affair with Cars [WWW Document]
A scalable data collection, characterization, and accounting framework for urban material stocks
J. Ind. Ecol.
Dreaming big and living small: examining motivations and satisfaction in tiny house living
J. Hous. Built Environ.
Elaborating the history of our cementing societies: an in-Use stock perspective
Environ. Sci. Technol.
Material quantities and embodied carbon in exemplary low-carbon case studies
Sustain. Built Environ. Zurich
Material quantities and embodied carbon dioxide in structures
Proc. Inst. Civ. Eng. - Eng. Sustain.
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