Comparative Life-Cycle Assessment (LCA) Analysis of Timber and Reinforced Concrete Multi-story Buildings. State-of-the-Art Review

Being the building sector responsible of 30–40% of total greenhouse gases’ emissions and being some administrations (e.g., EU and Canada) targeting net-zero carbon emissions by 2050, a proper assessment of building sustainability is no more an option but an essential requirement. To the scope, Life-Cycle Assessment (LCA) analysis results an unavoidable tool to be adopted during building design process: by carrying out targeted sensitivity analysis on different aspects (e.g., materials, geometry, construction techniques), the optimal solution may be identified. To the scope, LCA cradle-to-grave analysis should include all the processes involved in building construction, use and decommissioning, in order to provide relevant and robust results through a comprehensive approach. Existing literature is reviewed highlighting, for those aspects that generally represent standardized analysis steps, items that naturally involve uncertainties in their estimation. Strengths and weaknesses in current estimation procedures are identified and discussed, to the scope of guaranteeing the reliability of Life-Cycle Assessment as a tool to evaluate sustainability of building works. It is found that Operational Energy Use phase (commonly referred to as B6) is generally disregarded or estimated as a given constant value, disregarding that operational energy, which contributes in a significant way to GWP emissions of the whole structure, may be highly influenced by the specific material or construction system. Additionally, other phases of stage B should require specific attention as seismic strengthening, service life extension, renovation, considering their remarkable contribution to emissions and their high values of embodied energy. Finally, such aspects also impact on End-of-Life (D) Phase, which again is analyzed by low-standardized methods.