Single-sided natural ventilation strategies for healthcare buildings

Control of airborne pathogens, while achieving comfort and energy efficiency, places strains on typical mechanical air-conditioning systems of hospitals. These buildings expend over 40% of their energy for heating of air and spaces (DoH, 2006) while still being challenged by the problem of airborne infection. Natural ventilation remains a largely unexplored alternative which could alleviate this problem; however, achieving acceptable indoor air quality (IAQ), thermal comfort and energy efficiency from this technique is challenging and requires careful design and modelling. Many hospitals appear to use same openings (windows) as both inlets and outlets, making the air exchange process inefficient. The aim of this study is therefore, to demonstrate the feasibility of using dual opening single-sided, buoyancy-driven natural ventilation for achieving low-energy comfort and reduction of airborne pathogens in 1-bed and 4-bed hospital wards that are designed or refurbished according to the Department of Health’s Activity Database (ADB). Conceptual design conditions were based on provisions of HTM-03 guidelines and openings were sized through empirical methods. The design conditions are tested using dynamic thermal simulation (DTS) to demonstrate the long-term airflow and comfort implications. Computational fluid dynamics simulations (CFD) are then used to provide an indepth steady-state prediction of the distribution and quality of air as well as pathogen dispersal, with respect to airflow patterns/directions for the selected strategies. These research findings provide insights into the airflow, and comfort performances of 1-bed and 4-bed wards for both existing and proposed healthcare buildings whose design or retrofit calls for single-sided natural ventilation.