Holistic Post-Occupancy Evaluation of The Harmless Home




Costa Sousa, Rafael Wildson

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Post-occupancy evaluation (POE) is a method that can provide feedback throughout a building's lifecycle from the initial concept to the occupation. From this feedback, it is possible to help stakeholders, designers, and policymakers with recommendations for future projects from the lessons learned in the previously evaluated building. Having that said, the research objective is to assess the performance of the Harmless Home and Just BioFiber holistically in order to help stakeholders, designers, and policymakers to have more options to achieve the carbon net-zero building requirement. A POE of the Harmless Home was conducted using the International Initiative for a Sustainable Built Environment (iiSBE) protocol to investigate and analyze the results. Four critical key performance indicators (KPIs) were analyzed in this paper: energy and emissions, water, indoor environmental quality (IEQ), and cost. Several lessons were taken for this, but the most significant one is for the energy and emissions, showing that the exterior wall had a higher R-value than predicted in the building energy modelling (BEM), resulting in less energy consumption. Furthermore, the solar panels were able to produce more energy than required in the house, enabling them to return energy to the grid and consequently saving CO2. More specifically, about the JBF, two evaluations were done regarding its performance: (1) hygrothermal performance analysis and (2) life cycle assessment. Hygrothermal performance analysis of the modified hempcrete used in the Harmless Home from Just BioFiber (JBF) in different Canadian climate zones and with different geographic orientations and exterior finishing to analyze where it would be possible to use the block without any additional vapour retarder. In order to analyze the hygrothermal performance, two main criteria were considered, the moisture content over time in different layers of the wall assembly and the improved model to predict mould growth revised and adopted by ASHRAE standard 160-2016. From the Canadian zones analyzed, climate zone 6 with a wind-driven oriented accumulated moisture over time, and climate zone 5 (both standard and wind-driven oriented) and 6 (non-wind-driven oriented) should have additional attention like the mould growth index (MGI). And last but not least, the environmental impact assessment of the Harmless Home and JBF LCA was conducted to analyze the embodied and operational carbon emissions. Two different construction methods were compared in the whole building life cycle assessment: (1) modified hempcrete block (JBF) for the exterior walls and insulated concrete forms (ICF) for the foundation compared to (2) the traditional construction method used in Canada with wood-frame for the exterior walls and reinforced concrete for the foundation in a whole-building LCA using One Click LCA as an LCA platform. Regarding the embodied carbon emissions, case (1) released 14% less greenhouse gas emissions than case (2), also having the ability to sequester 13 tons of CO2e. Regarding the operational carbon, both cases could save 11 tons of CO2e due to solar panels' energy production higher than the necessary usage of the house in 60 years. Thus, the main conclusion is that building material selection should be considered concerning the urgent need to mitigate global climate change impacts. CO2e. From the overall results across all the performances, the Harmless Home and JBF performed well regarding the POE, hygrothermal performance and LCA, which, based on the results, can contribute to minimizing environmental impacts and mitigating climate change.



Green Buildings, Sustainability, High-Performance Buildings, LCA, Hygrothermal Performance, Post-Occupancy Evaluation, Building Performance Evaluation