Whole Building Life Cycle Assessment of New Multi-Unit Residential Buildings in Southern Ontario

The built environment accounts for over one-third of global carbon emissions on an annual basis. Solutions for reducing carbon in the built environment typically focus on 'operational carbon' that is released during the day-to-day use of buildings. There is less understanding about how to reduce 'embodied carbon' that is released during the raw material manufacturing, transportation, construction and end of life phases of built assets. However, as operational carbon reduces, and the rate of new construction continues to increase, embodied carbon will grow to represent almost half of all emissions from new buildings. As a result, there is an urgent need to reduce embodied carbon to meet global climate change targets. This research paper begins with a literature review of embodied carbon in the built environment. This includes a review of the whole building life cycle assessment (WBLCA) methodology to calculate embodied carbon, assessment of outcomes from similar studies, consideration of key drivers of emissions and identification of potential reduction strategies. Based on this, a methodology and scope are defined for the WBLCA of 3 new multi-unit residential buildings located in southern Ontario. One Click LCA software is used to calculate the embodied carbon for each building. The baseline results ranged from 182 kg CO e/2 for the low-rise timber framed building up to 347 kg CO e/m fo2 the mid-rise concrete structure and 450 kg CO e/2 for the high-rise concrete structure. Cladding assemblies and floor finishes are identified as key drivers for embodied carbon in the timber frame, and horizontal structural slabs and foundations are the main contributors to emissions in the concrete structure. Six reduction strategies are identified to address the key contributors of embodied carbon in each building. Three of these measures are found to reduce the carbon footprint in the building by 10% or more. Replacement of the above grade concrete structure with timber frame and the use of low carbon concrete are found to be the most impactful reduction strategies. Combining several reduction strategies enables embodied carbon reductions of 20% or greater.