Performance evaluation of an office-integrated cultivation room utilizing human-emitted CO

Integrating plant racks into office buildings enhances indoor environmental quality (IEQ) and supports sustainable building-integrated agriculture (BIA), yet balancing crop energy demands with building conditioning remains a critical challenge. This study explores a novel carbon capture and utilization (CCU) strategy by recycling human-emitted CO2 from office zones for crop photosynthesis. We propose a 'cultivation room' located in the southern perimeter zone of an office model in Nagoya, Japan, utilizing plant racks for hydroponic lettuce production. High-intensity artificial lighting (193 W/m2) was modeled to supplement natural daylight to ensure sufficient photosynthetic photon flux density (PPFD). To evaluate the environmental and energy impacts of this integration, a simulation model was developed using Rhinoceros and the Grasshopper plug-ins, Ladybug and Honeybee. Two operational scenarios were compared: (1) a combined system in which the cultivation room is ventilated with CO2-rich exhaust air from the office zone to utilize indoor thermal and gaseous resources, and (2) an independent system in which the cultivation room is ventilated exclusively with outdoor air. Ventilation rates were dynamically controlled to prioritize latent heat removal from plant transpiration. Simulation results revealed a distinct seasonal trade-off between energy efficiency and carbon reuse. In summer, the combined system significantly outperformed the baseline, reducing the total thermal load by 32% by utilizing cool office exhaust air. Conversely, in winter, the independent system proved thermally advantageous, functioning as an economizer to offset significant internal heat gains from artificial lighting. Notably, regarding CCU performance, the combined system reduced the external CO2 supply requirement to just 8% in summer and 17-20% in winter compared to the independent system. Consequently, this study proposes a seasonal hybrid operation strategy—switching between combined operation in summer and independent operation in winter—to maximize overall building sustainability.