Optimizing Adaptive Displacement Ventilation for Sustainable Office Retrofits : Integrated Strategies for Thermal Stratification Control, Circular Material Utilization, and Occupant-Centric Airflow in Swedish Landscape Offices

With increased emphasis on sustainability and occupant well-being, displacement ventilation (DV) has gained recognition as a viable strategy for retrofitting office environments. This thesis investigates the energy and environmental performance of adaptive DV configurations in Swedish landscape offices through a combination of dynamic thermal simulations and life cycle assessment (LCA). The study explores multiple ventilation strategies including demand-controlled ventilation using CO₂ sensors, heat and energy recovery (HRV and ERV), radiant floor heating, and night ventilation, under both current and projected climate conditions. A series of simulations conducted using the stratification model in IDA ICE 5.1 evaluated six HVAC scenarios based on energy use, thermal comfort, and indoor air quality. Parallel LCA modeling using One Click LCA, supported by a hybrid dataset of generic and product-specific environmental product declarations (EPDs), quantified life cycle carbon emissions across stages A1–A5, C1–C4, D, and operation emissions. The results identify DV+HRV+Floor heating – NV 0 as the most environmentally favorable scenario. When assessed with the 2022 Swedish electricity mix, this configuration achieved the lowest total life cycle emissions at 18.59 tons CO₂e over 25 years. The system combined efficient thermal stratification, reduced auxiliary HVAC loads, and improved energy efficiency through floor-integrated preheating. However, under the 2023 residual electricity mix reflecting higher grid carbon intensity, the same scenario's emissions increased to 27.69 tons CO₂e. This sensitivity analysis underscores the importance of grid emission factors and electricity sourcing in shaping the environmental performance of HVAC retrofits. Overall, the findings demonstrate that integrating DV with HRV and radiant floor heating delivers superior performance in winter conditions simultaneously without having worse performance in summer. The night ventilation strategy improves both thermal comfort and IAQ. The study also emphasizes the need for early-stage HVAC design decisions that consider future energy mixes and material circularity, enabling low-carbon, occupant-centric office retrofits aligned with long-term climate targets