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Purpose: This study conducts a comparative analysis of Displacement Ventilation (DV) and Mixed Ventilation (MV) strategies in landscape offices, considering thermal comfort, indoor air quality, energy performance, and life cycle assessment (LCA) in HVAC design. Methods: IDA-ICE 5 software was used for air stratification analysis of the indoor environment, Magi-CAD for ventilation system design, One Click LCA for calculating the environmental impact, hand calculations and an extensive literature review. Results: The energy performance simulations indicate that DV is more energy efficient than MV. This efficiency is largely attributed to the higher heat exchange capacity of the DV system´s air handling unit, benefiting from the stratification of indoor air temperatures, because for the DV case, the exhaust air temperature is higher than in the MV system, enabling more effective heat recovery. Conversely, the MV system exhibit a more homogeneous air temperature distribution, resulting in a lower exhaust air temperature and consequently less effective heat recovery. Additionally, the supply air temperature for MVS is lower (16°C) than DVS (19°C), leading to increased energy consumption for indoor heating. Regarding environmental impact, the LCA results from stages A1 to A5 (“cradle to practical completion”) show that DVS has a higher Global Warming Potential (GWP) compared to MVS. However, when considering the complete LCA (“cradle to grave”), including energy consumption over the entire lifespan, DVS has a lower GWP than MVS. This outcome is due to the operational energy efficiency of DV, leading to a lower overall environmental impact over the system´s lifetime. Sensitivity analysis confirms also that DV has a lower overall environmental impact, even when accounting for future climate scenarios. Regarding indoor air quality, DV delivers better indoor air quality for the same airflow rate compared to the MV system. MVS requires a higher airflow rate to meet the WELL Building Standard's CO2 level requirements, leading to higher energy consumption and global warming potential. Thus, the DV system maintain better indoor air quality at lower airflow rates, contributing to greater energy efficiency and reduced environmental impact. However, MV systems demonstrate better performance in thermal comfort. The homogeneous air distribution of MV systems results in lower Predicted Percentage of Dissatisfied (PPD) values, enhancing overall occupant comfort. In contrast, DV systems' air temperature stratification characteristics result in cooler temperatures at the floor level, increasing PPD values, and decreasing thermal comfort, particularly in the summertime when temperature differences are more pronounced. Conclusion: DV is more energy-efficient due to higher heat recovery from stratified air temperatures. DV is more environmentally friendly over its lifespan due to lower operational energy use. DV provides better air quality at lower airflow rates, reducing energy consumption and GWP. MV offers a slightly better thermal comfort with more uniform air distribution.