Designing buildings that rely on natural ventilation for temperature control is a relatively new science. Due to limited analytical tools, such buildings to date have too often resulted in uncomfortable occupants. This work seeks to improve the design and operation of such buildings to yield increased overall building efficiency (in mixed-mode ventilation) without sacrificing comfort. The researchers will use high-fidelity simulations and rigorous sensitivity analysis based on available weather and building data to inform designers on the amount of time in a year the building is not operating in the mode expected. The tools developed will also evaluate and incorporate mitigation strategies, and identify what to monitor in order to assure building performance.