Is mixed-mode ventilation a comfortable low-energy solution? A literature review

Despite a wide range of energy efficiency measures being implemented, carbon emissions from the building sector continues to rise. Against the backdrop of rapidly increasing cooling energy demand, mixed-mode (MM) ventilation approach has extensively been studied by the building science community as a way to lift comfort indoors whilst minimising energy use associated with air-conditioning. This paper presents a literature review of important research themes within the context of thermal comfort and energy use in mixed-mode buildings. The findings from our focused review suggest that occupant perception of, or attitudes toward indoor thermal environment can differ, depending on the mode of operation within a MM building. The comfort zone of occupants in MM buildings are consistently estimated to be wider than that of fully air-conditioned building counterparts. Although the scale of benefit greatly depends on climate characteristics, the MM strategy demonstrates significant energy saving potential especially when coupled with a 'moving comfort target' approach based on the adaptive comfort model. The focus of future research should be on how to optimise comfort, level of control (automated vs. manual), and the associated energy demands.