Environmental sustainability assessment of single-family modular homes using performance benchmarks of conventional homes: case studies in British Columbia, Canada

Modular construction has become exceedingly relevant against the current scenario of increasing housing demand and can respond to this need in Canada due to its advantages of rapid construction. However, a holistic environmental sustainability framework for this construction method is still lacking. This paper proposes a hierarchical-based framework to benchmark the environmental performance of modular buildings versus conventional buildings. The framework identifies criteria and indicators affecting environmental sustainability, makes composite indicators, and establishes performance benchmarks. Based on expert survey, six criteria (construction waste management, energy performance and efficiency strategies, site disruption and appropriate strategies, renewable and environmentally preferable products, regional materials, and renewable energy use) are first identified. The related indicators and sub-indicators are combined to develop indices using Technique for Order of Preference by Similarity to Ideal Solution. Robust benchmark scales were established through application of Monte Carlo analysis on data collected through experts. Finally, the developed indices were compared against the benchmark scales at different assessment levels. The proposed framework was examined for two single-family modular buildings in British Columbia, Canada. The overall environmental performance benchmarking informs the policy makers on the usefulness of modular buildings, while the criteria-level indices direct the construction industry practitioners to improve the low performing indicators. The proposed framework will enhance the sustainability of modular and offsite construction in Canada.