Ventilation, Thermal Comfort, and Energy Strategies for Underground Shelters

The compilation of findings in this literature review addresses ventilation performance, thermal comfort, humidity control, and energy-efficient heating, ventilation, and air conditioning (HVAC) design in underground shelter-type environments.This helps develop a comprehensive approach to passive, hybrid, and mechanical ventilation systems, as well as integrating renewable energy into low-carbon operation.Passive ventilation strategies utilize buoyancy and natural pressure differences to maintain acceptable air exchange rates.The application of hybrid systems, which involve integrated photovoltaic/thermal collectors and ground-source heat pumps (PVT-GSHPs), results in reduced energy consumption while maintaining temperature stability.Studies on thermal comfort in earth-sheltered buildings show that indoor temperatures are relatively stable; however, high humidity levels-often exceeding 80%-are common.As a result, mechanical dehumidification is typically required to maintain comfort.Both computational and experimental approaches, including Computational Fluid Dynamics (CFD) and Response Surface Methodology (RSM), are increasingly employed to optimize air distribution and enhance system efficiency.Overall, the reviewed studies highlight the importance of an integrated HVAC strategy that combines passive ventilation, renewable energy systems, and intelligent humidity control to achieve thermal comfort, occupant safety, and long-term sustainability in underground shelters.