Comprehensive assessment method for building environmental performance: Trade-off between indoor environmental quality and life cycle carbon emissions

Indoor environmental quality (IEQ) significantly influences occupants' comfort and health, yet enhancing IEQ often leads to higher carbon emissions, exacerbating global warming. Striking a trade-off between IEQ and carbon emissions without sacrificing human well-being remains challenging. However, most studies focused on either IEQ or carbon emissions, lacking an integrated approach. To address this gap, a comprehensive assessment method was proposed to evaluate a building's environmental performance by considering both aspects simultaneously. This method assessed IEQ through a holistic approach, considering physical factors (thermal environment, air quality, lighting, and acoustics) and non-physical factors (personal environmental control, space design as well as maintenance and cleanliness). Both subjective data (questionnaires) and objective data (on-site equipment measurements) were collected. Carbon emissions were assessed from a life cycle perspective and contextualized by comparing them to emissions from similar buildings in the region, accounting for regional differences and building types. By integrating these assessments, the building carbon emission efficiency (BCEE) metric was introduced, which measured overall environmental performance. Data from case buildings in the Yangtze River Delta region of China were analyzed. The BCEE values for these buildings were determined to be 1.10 for O1, 1.16 for O2, 0.86 for O3, and 1.58 for O4. Based on these values, O1 and O2 were categorized as Grade C, while O3 was classified as Grade D and O4 as Grade B. The method's advantages are clarified through comparisons with other assessment methods. The approach offers valuable guidance for designing highperformance buildings with high IEQ and low carbon emissions.