Improving Indoor Air Quality with Green Walls: An Experimental Study

Poor indoor air quality (IAQ), particularly elevated CO2 concentrations, is known to impair cognitive function and comfort. In sealed or energy-efficient buildings, natural air exchange is limited, increasing the need for passive pollutant removal strategies. This study evaluates the CO2 removal capacity of a living wall system installed in a full-scale climatic chamber (38 m3). Controlled CO2 decay tests were performed under two conditions: with LED illumination (photosynthesis active) and without lighting. The temporal evolution of CO2 concentration was modeled using a first-order exponential decay function, and equivalent air change rates (ACHe) were calculated. Under illumination, the half-life of CO2 decreased from 90 to 63 minutes (- 30%), with an additional removal of approximately 6 g of CO2 over 6 hours. The ACHe increased from 0.46 h-1 (LED OFF) to 0.66 h-1 (LED ON), representing a 43% improvement in effective air renewal attributable to photosynthesis. The findings confirm the synergistic role of lighting and vegetation in enhancing passive indoor air purification. Properly illuminated living walls (LWs) can achieve substantial CO2 removal rates, offering a sustainable strategy for improving IAQ in energy-efficient buildings.