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Item Dynamic carbon budgets and carbon debts for Aotearoa New Zealand and its building sector(Elsevier Ltd, 2026-01-01) Weerasinghe SN; McLaren SJ; Boulic M; Dowdell D; Chandrakumar CThe remaining carbon budget (RCB) is a crucial parameter when setting climate budgets for nations and economic sectors that want to measure their progress in climate change mitigation. The Paris Agreement is the most widely used and accepted climate change mitigation target, and the global RCB specified by the Intergovernmental Panel for Climate Change (IPCC) provides the carbon budget remaining from the beginning of 2020 that can be emitted as CO2 before the Paris Agreement’s target is exceeded. This research investigates the global RCB allocation to the national and building sector level in Aotearoa New Zealand, including consideration of different sharing approaches and modelling of potential future dynamic parameters for the RCB allocation, that are required to stay below 1.5 °C warming between the years 2024 and 2050. The average national RCB ranges from 159 to 339 MtCO₂ from year 2024; based on an average annual emissions rate of 38 MtCO₂, it will be depleted in 4–8 years. Therefore, this study proposed a dynamic carbon debt framework that provides a more realistic representation of dynamic RCBs and the carbon debt over future years. Key findings include the urgency of timely interventions, the need for additional mitigation strategies beyond the current policy approach which is largely focused on increased plantation forestry, and the usefulness of time-disaggregated carbon budgeting to address exhaustion of the RCB. Overall, this study demonstrates the relevance of dynamic budgeting to guide effective climate policy at both the national and building sector levels.Item Application of absolute sustainability assessment to new zealand residential dwellings(IOP Publishing Ltd, 2020-11-20) McLaren SJ; Chandrakumar C; Dowdell D; Bullen L; Jaques ROne approach to supporting the implementation of sustainable activities by industry sectors is the use of climate targets. Such climate targets have potential to be used in design and rating tools for buildings and to support government regulation for the building and construction sector. In this study, the climate targets for New Zealand residential dwellings were calculated based on assigning the global carbon budget (for limiting temperature increase to 1.5 or 2.0 °C during 2018-2050) to three building typologies: detached, medium-density housing and apartments. These budgets were assigned to the pre-existing and new-built dwellings using building stock projections for the nominated period. Separately, the climate impact of new-built dwellings in each of the three residential typologies were assessed using Life Cycle Assessment methodology. For New Zealand residential buildings, new-built dwellings exceed their 1.5 °C climate targets by a factor of 6.7, 6.8 and 10.9 for detached, medium-density housing, and apartments respectively. For the 2.0 °C climate target, these factors are 4.8, 4.8 and 7.7 for detached, medium-density housing, and apartments respectively. The results show that about two-thirds of the climate impact of residential dwellings for the period 2018-2050 is associated with preexisting dwellings rather than new-builds. The operational energy used for space heating, water heating, lighting and plug loads makes the biggest contribution to the climate impact for all typologies of pre-built residential dwellings. For new-built residential dwellings, both the operational energy and the construction materials/products contribute most of the climate impact.Item A top-down approach for setting climate targets for buildings: The case of a New Zealand detached house(IOP Publishing Ltd, 2019-09-05) Chandrakumar C; McLaren SJ; Dowdell D; Jaques RClimate change mitigation requires the construction of low/zero-carbon buildings, and this is a challenge for designers. The use of Life Cycle Assessment (LCA) provides useful information to support eco-efficiency improvements and therefore, to reduce the climate impacts of building designs. However, it does not provide information about whether a proposed design aligns with achieving the global climate target of limiting global warming to below 1.5C or 2C. This study, therefore, introduces an LCA-based top-down approach for setting climate targets for the whole life cycle of buildings in terms of greenhouse gas emissions. It involves assigning a share of the 2C global carbon budget for 2018-2050 to a country, to the construction sector of the country, and finally to a building. The approach includes a stock model that accounts for the projected growth in the number of buildings and associated climate impacts in a country up to 2050. The proposed approach was applied to a detached house in New Zealand, the most common residential building type in the country; it was found that the climate target of a New Zealand detached house over a 90-year lifetime is 71 tCO2eq. This modelling approach has potential to guide designers and other interested stakeholders in development of building designs enabling the building sector to operate within a selected global climate target (such as the 1.5C or 2C target).Item Policy implications of time-differentiated climate change analysis in life cycle assessment of building elements in Aotearoa New Zealand(Springer-Verlag GmbH, 2025-03-21) McLaren SJ; Elliot T; Dowdell D; Wakelin S; Kouchaki-Penchah H; Levasseur A; Hoxha EPurpose: Climate change policies are increasingly including time-dependent carbon targets for different economic activities. However, current standards and guidelines for climate change assessment of buildings ignore these dynamic aspects and require use of static life cycle assessment (LCA). This research investigates how to better account for the timing of greenhouse gas (GHG) emissions and removals in LCAs of buildings and construction products, using a static and dynamic LCA case study of roofs, walls and floors in Aotearoa New Zealand residential dwellings. Methods: Static and dynamic LCA methods were used to assess the climate change impact of two assemblies each for external walls, ground floors and roofs used in stand-alone residential dwellings in Aotearoa New Zealand. Each assembly was modelled for a life cycle extending from material production, through to element construction, operational use, and final end-of-life treatment. Results were calculated as total GWP100 results for each life cycle stage, GWP100 results disaggregated into time periods, and as instantaneous and cumulative radiative forcing up to year 190. Sensitivity analysis was undertaken for the building reference service life, exposure zone, location, and end-of-life treatment. Results and discussion: Four time-related aspects were found to be particularly significant as regards their contribution to the final static LCA (sLCA) climate change results: -Inclusion versus exclusion of biogenic carbon storage in landfill -Modelling of end-of-life recycling activities using current versus future low or net zero carbon technologies (in module D) -Building reference service life (50 versus 90 years) -Choice of modelling parameters for landfilled timber and engineered wood products. Use of dynamic LCA (dLCA) enabled priorities to be identified for climate change mitigation actions in the shorter and longer term, and showed that half of the assemblies achieved net zero carbon by year 190 (timber wall, steel wall, timber floor). Conclusions: Timing of GHG emissions and removals should be included in LCAs to support decision-making in the context of achieving targets set in climate change policies. In particular, LCA results should show ongoing biogenic carbon storage in landfilled timber and engineered wood products. Carbon footprint standards, guidelines and calculation tools should be prescriptive about building and construction product reference service lives, the EofL fate for different materials/products, and modelling of forestry and landfill activities, to provide a level playing field for stakeholders.