Achieving a comfortable indoor environment that adheres to ISO 7730 [1] standards or similar benchmarks is a primary goal in HVAC design for human-centered spaces. Different HVAC components and systems lead to varying ventilation and air conditioning strategies. For example, ceiling-mounted fan coil units typically operate in mixed ventilation mode, while low-velocity air diffusers at floor level create a displacement flow. Indoor comfort should be a central factor in HVAC design and can serve as a starting point for system selection. This paper explores the impact of different HVAC systems and components on maintaining comfort while evaluating their efficiency. The focus is not only on thermal performance but also on how installation setups, such as piping and other construction needs, influence overall system efficiency. The first system analyzed is a fan coil unit installed in a suspended ceiling, which creates a mixed ventilation mode in a standard office environment. The second system is a trench cooling system embedded in the floor screed, providing a combination of displacement and mixed airflow in the occupied zone. Both ventilation strategies are examined and compared using Computational Fluid Dynamics (CFD) simulations. The carbon footprint of each system is assessed based on available Environmental Product Declarations (EPD) in accordance with ISO 14025 [2] standards, alongside construction-related considerations and energy consumption calculations based on efficiency findings.