Plant efficacy in biophilic design: A novel three-tiered assessment framework

Integrating plants in biophilic design can improve indoor air and environmental quality (IAQ/IEQ), yet field studies remain difficult to compare due to environmental variability and inconsistent analytical methods. To address this gap, this field study investigated the impact of plants on indoor air quality (IAQ) in an office environment using two different CO 2 sensors and a total volatile organic compounds (TVOCs) sensor. To isolate plant-related IAQ effects from environmental variability, a three-tier framework was developed: low-interference day selection, temporal sampling, and advanced statistical analysis including Spearman correlation and dynamic time warping (DTW). The framework was verified using linear mixed-effects modelling (LMM). In unventilated environments, TVOCs-based IAQ values (TVOCs_IAQ) reached 250 (severely polluted), while CO 2 frequently exceeded 1000 ppm. Conversely, potted plants under artificial or natural sunlight reduced CO 2 to a mean value of 651.2 ppm and 763.8 ppm, respectively, maintaining levels below critical exposure thresholds. Under optimal conditions, plants reduced TVOCs_IAQ to levels comparable to mechanical ventilation (96.72). However, DTW analysis revealed substantial day-to-day variability, indicating that simple statistical averaging may mask these dynamics. These findings suggest that plant-related IAQ improvements depend on pollutant type and environmental conditions and are most effective when combined with sustainable building practices.