Many countries across the globe have set targets for different economic sectors, aiming to tackle global warming by reducing the overall carbon footprint of human-related activities. Among these sectors, the building industry stands out as a major consumer of materials and energy resources, making it a key player in achieving carbon neutrality. It is one of the main contributors responsible for energy-related greenhouse gas (GHG) emissions, including both operational emissions and embodied emissions in materials and equipment manufacturing. Nature-based design solutions, such as planting trees in urban spaces, or incorporating the use of wood products, have regained attention in recent years due to their potential to mitigate carbon emissions from buildings. Within this context, this paper presents a comprehensive life cycle assessment (LCA) of a recently built research facility, with a focus on demonstrating how the benefits of nature-based solutions, specifically carbon sequestration from trees and biogenic carbon content in wood products, can be quantified and reported using the latest LCA standards and tools. The analysis is provided under three end-of-life scenarios for wood products: wood incineration with energy recovery, wood landfilling, and wood recycling/repurposing. The results indicate that the set of strategies adopted in this building, i.e., tree planting, the use of wood products, and the end-of-life treatment of materials, can potentially offset carbon emission by 37.2% up to 83.9% when included in the LCA, depending on the scenario considered. By continuing to refine LCA standards and tools, and fostering collaboration between researchers, policymakers, and industry professionals, we can advance our understanding and ultimately achieve the widespread adoption of carbon-neutral buildings.

In response to Canada’s commitment to reducing greenhouse gas emissions and to making pathways to achieve carbon neutral buildings, this paper presents two real case studies. The paper first outlines the potential of trees to absorb CO2 emissions through photosynthesis, and the methods used for the estimation of their annual carbon sequestration rates. The net annual carbon sequestration rate of 0.575 kgCO2eq/m² of tree cover area is considered in our study. Then, this paper presents the carbon life cycle assessment of an all-electric laboratory at Concordia University and of a single-detached house, both located in Montreal. The life cycle assessment (LCA) calculations were performed using two software tools, One Click LCA and Athena Impact Estimator for Buildings. The results in terms of Global Warming Potential (GWP) over 60 years for the laboratory were found to be 83,521 kgCO2eq using One Click LCA, and 82,666 kgCO2eq using Athena. For the single-detached house that uses natural gas for space heating and domestic hot water, the GWP was found to be 544,907 kgCO2eq using One Click LCA, and 566,856 kgCO2eq using Athena. For the all-electric laboratory, a garden fully covered with representative urban trees could offset around 17% of the total life cycle carbon emissions. For the natural gas-powered single-detached house, the sequestration by trees is around 3% of the total life cycle carbon emission. This paper presents limits for achieving carbon neutral buildings when only the emissions sequestration by trees is applied, and discusses the main findings regarding LCA calculations under different scenarios.