Comfort-based control for mixed-mode buildings

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• A control framework for mixed-mode buildings was proposed. • Different framework configurations were tested using dynamic simulations. • Energy use, thermal comfort and air quality were analyzed for five locations. • The proposed framework used between 12 and 51 % lower energy than mechanical cooling. • Using the proposed framework led to satisfactory thermal comfort and indoor air quality. International thermal comfort standards are applicable for the design and operation of either mechanically cooled or naturally cooled buildings and limited guidance is given for mixed-mode buildings. In this study, a control framework for mixed-mode buildings was defined based on the adaptive comfort model and PMV-PPD method. The proposed framework was tested using a simulation-based analysis of a central module of an office building. The results were compared with a mechanically cooled building. The objective was to characterize how to control mixed-mode buildings optimally, regarding both energy use and thermal comfort. Five locations were considered: Copenhagen - DK, Edinburgh - UK, Palermo - IT, Tokyo - JPN, and Zurich - CH. The mixed-mode control strategy had a primary energy use between 12 and 51 % lower than the mechanically cooled case. In this context, using the upper limit of the adaptive comfort zone as cooling set point rather than the upper limit of the PMV-based comfort zone showed nearly 20 % more energy savings and fewer switchovers between operation modes. Night cooling led to lower operative temperatures and fewer switchovers between operation modes as well as additional energy savings of 10 % only in Palermo. The results show that a mixed-mode building operated based on the adaptive comfort criteria can have a large reduction of energy use without compromising thermal comfort or indoor air quality, compared to a mechanically cooled building.