The Life Cycle of Materials and Its Importance in Sustainable Construction

The life cycle of materials and its importance in sustainable construction rests on a rigorous quantitative framework: Life Cycle Assessment (LCA). Codified in ISO 14040:2006 and ISO 14044:2006, LCA evaluates the environmental burdens associated with a product from raw material extraction through manufacturing, transport, use, maintenance and end-of-life treatment. For buildings specifically, EN 15978:2011 translates this framework into a modular structure spanning the entire building lifecycle: modules A1-A3 (product stage: raw material supply, transport to manufacturer, manufacturing), A4-A5 (construction process stage), B1-B7 (use stage: maintenance, repair, replacement, refurbishment, operational energy and water), C1-C4 (end-of-life stage: deconstruction, transport, waste processing, disposal) and D (benefits and loads beyond the system boundary, including reuse and recycling credits).

The importance of this structured approach is evident in the numbers. According to Roeck et al. (2020), the building sector accounts for 37% of global energy-related CO2 emissions, of which approximately 28% derive from operational energy and 11% from materials and construction processes — the so-called embodied carbon. As operational energy efficiency improves through stricter building codes (nZEB requirements under the EPBD recast 2024), the relative share of embodied carbon grows: in a contemporary near-zero-energy building, modules A1-A5 can represent 50-80% of total lifecycle emissions over a 50-year reference study period. This shift makes LCA not merely an academic exercise but a practical necessity for architects, engineers and policymakers who must quantify and reduce the upfront carbon locked into buildings at the moment of construction.

Embodied energy measures the total primary energy consumed across all manufacturing stages of a material (MJ/kg), while embodied carbon expresses the associated greenhouse gas emissions (kgCO2eq/kg). The ICE Database (Inventory of Carbon and Energy, University of Bath, Hammond and Jones 2011) remains the most widely cited open-access source, covering over 200 materials with peer-reviewed data. The differences between materials are stark and consequential for design decisions.

Cement and concrete: ordinary Portland cement (OPC) has an embodied carbon of 0.80-0.95 kgCO2/kg, of which approximately 60% originates from the calcination of limestone (process emissions) and 40% from fuel combustion in the kiln. A cubic metre of C30/37 concrete contains roughly 300-350 kg of cement and emits 250-400 kgCO2/m3. Clinker substitution with supplementary cementitious materials — ground granulated blast-furnace slag (GGBS) at 50-70% replacement or fly ash at 25-40% — reduces concrete embodied carbon by 30-60% (Cabeza et al. 2014).

Steel: basic oxygen furnace (BOF) steel, produced from iron ore, carries an embodied carbon of 2.0-2.5 kgCO2/kg and an embodied energy of 20-35 MJ/kg. Electric arc furnace (EAF) steel, using 80-100% recycled scrap, drops to 0.4-0.8 kgCO2/kg — a reduction of 60-85%. Global steel production in 2022 reached 1,878 million tonnes (World Steel Association), of which 28% was EAF-produced, a share growing at 1-2 percentage points per year.

Timber: sustainably harvested structural timber has a biogenic carbon content of -1.0 to -1.6 kgCO2/kg, meaning that carbon dioxide absorbed during tree growth is temporarily stored in the building. Cross-laminated timber (CLT) extends this benefit to multi-storey construction: Churkina et al. (2020) estimated that a global shift to mid-rise timber construction could store 0.01-0.68 GtCO2/year in buildings. The embodied energy of sawn softwood is 7-10 MJ/kg, predominantly from kiln drying.

Aluminum: primary aluminum carries the highest embodied carbon of any common construction material at 8.0-12.0 kgCO2/kg (Ashby 2012), driven by the energy-intensive Hall-Heroult electrolysis process consuming 13-16 kWh/kg. Recycled aluminum requires only 5% of the primary energy, reducing embodied carbon to 0.4-0.6 kgCO2/kg. Given that aluminum curtain wall systems can contribute 15-25% of a commercial building's total embodied carbon, the specification of recycled content is a high-leverage design decision.

Environmental Product Declarations (EPDs), standardized under EN 15804+A2:2019, provide manufacturer-specific, third-party-verified environmental data for construction products. An EPD reports impact indicators across all EN 15978 modules: Global Warming Potential (GWP in kgCO2eq), Acidification Potential (AP), Eutrophication Potential (EP), Ozone Depletion Potential (ODP) and Abiotic Depletion Potential (ADP), among others. The ECO Platform, the European umbrella organization for EPD programme operators, lists over 8,000 verified EPDs as of 2024, covering products from 35+ programme operators including IBU (Germany), INIES (France), EPD International (Sweden) and GlobalEPD (Spain).

The difference between generic database values and manufacturer-specific EPDs can be substantial: a study by Roeck et al. (2020) found variations of 30-50% for the same product category depending on manufacturing location, energy source and raw material origin. For example, the GWP of flat glass ranges from 0.8 kgCO2/kg (manufacturer using natural gas and high recycled cullet content) to 1.5 kgCO2/kg (manufacturer using heavy fuel oil with low cullet content). This variability underscores the importance of specifying products by EPD rather than by generic material type.

LCA software tools have matured to support practical design workflows. One Click LCA (Finland) integrates with BIM platforms (Revit, ArchiCAD, IFC) and accesses over 80,000 EPD datasets, enabling automated calculation of whole-building LCA from the architectural model. eLCA (Germany, by BBSR) provides a free online tool with the OEKOBAUDAT database (1,300+ datasets) compliant with German regulations. OpenLCA is an open-source desktop application supporting multiple databases including ecoinvent (18,000+ datasets) for researchers and consultants requiring full methodological transparency. The accessibility of these tools has transformed LCA from a specialist consultancy exercise into a routine part of the design process: a whole-building LCA using One Click LCA and a BIM model can be completed in 4-8 hours of analyst time, compared to 40-80 hours a decade ago.

The transition from voluntary LCA to mandatory embodied carbon regulation is accelerating across Europe and beyond. Denmark introduced the world's first mandatory whole-life carbon limit for new buildings in January 2023: 12 kgCO2eq/m2/year over a 50-year reference study period for buildings exceeding 1,000 m2, with a planned reduction to 7.5 kgCO2eq/m2/year by 2029. This limit covers modules A1-A3, B4, C3-C4 and D, effectively capping the embodied carbon of materials at the design stage.

France's RE2020 regulation (effective since 2022) sets carbon budgets for new residential buildings: 640 kgCO2eq/m2 for modules A1-A5 in single-family houses and 740 kgCO2eq/m2 for multi-family buildings, decreasing to 415 kgCO2eq/m2 and 490 kgCO2eq/m2 respectively by 2031 — a reduction trajectory of approximately 35% over nine years. The Netherlands mandates a whole-life carbon declaration (MPG) for all new buildings and requires a maximum Environmental Performance score of 0.5 points/m2/year for residential buildings. Finland has published a voluntary carbon footprint assessment method and is preparing mandatory limits for 2025.

At the EU level, the EPBD recast 2024 (Energy Performance of Buildings Directive, 2024/1275) requires member states to integrate lifecycle GWP assessment into building energy performance certificates and establishes a roadmap toward mandatory whole-life carbon limits by 2030. The World Green Building Council (WGBC) targets are more ambitious: 40% reduction in embodied carbon of new buildings by 2030 and net-zero whole-life carbon for all buildings by 2050. These targets are adopted by national Green Building Councils across 77 countries representing 40% of global construction output.

Reducing the lifecycle impact of materials requires action across every EN 15978 module. At the design stage, structural optimization — reducing material quantities through efficient geometry, appropriate safety factors and computational design — can lower embodied carbon by 10-30% without changing material specifications (Cabeza et al. 2014). Material substitution adds further reductions: replacing a reinforced concrete frame with CLT in a 6-storey residential building reduces structural embodied carbon by 40-60%, while replacing aluminum cladding with timber cladding reduces facade embodied carbon by 70-85%.

Design for disassembly (DfD) maximizes the value recovered in module D by enabling the reuse rather than recycling or disposal of building components. Key principles include: mechanical rather than chemical connections (bolted steel joints, screwed timber connections), modular dimensions compatible with standard transport, avoidance of composite materials that cannot be separated, and comprehensive documentation through material passports (platforms such as Madaster). A building designed for disassembly can achieve a module D credit of -50 to -150 kgCO2eq/m2, offsetting 10-20% of total lifecycle emissions.

At the operational stage, material durability directly affects modules B3-B5: specifying a zinc roof (service life 60-100 years) instead of bituminous felt (service life 20-30 years) eliminates 2-4 replacement cycles over a 60-year reference study period, reducing B4 emissions by 60-75% for that component. At end of life, the choice between demolition and selective deconstruction determines whether materials enter the recycling stream at high or low quality: selective deconstruction recovers 80-95% of materials in reusable condition, compared to 30-50% recovery as downcycled aggregate from conventional demolition.

The lifecycle of materials in sustainable construction ultimately points toward a circular economy model where buildings function as temporary material banks rather than permanent waste generators. The combination of EPD-informed material selection, structural optimization, clinker substitution in concrete, EAF steel specification, timber construction where structurally appropriate, design for disassembly and material passports creates a pathway to reducing whole-life carbon by 50-70% relative to current practice. With Denmark, France and the Netherlands already enforcing mandatory carbon limits and the EPBD recast 2024 requiring all EU member states to follow, the life cycle of materials has moved from an academic concern to a central regulatory and commercial driver of building design. Professionals who master LCA methodology and the associated tools — One Click LCA, eLCA, OpenLCA — and databases — ICE, OEKOBAUDAT, ecoinvent — hold a decisive advantage in this rapidly evolving regulatory landscape.