This paper summarizes the work within the EU RESHYVENT project in regard to design parameters for the performance assessment of hybrid ventilation systems. A framework for performance assessment based on simulation was developed. Performance criteria were defined for air flows, indoor air quality, thermal comfort, acoustics, energy, and emissions. These criteria were adapted to the time dependant performance of hybrid systems and were applied in the performance assessment of the systems developed within the project, together with a reference set of design constraints (boundary conditions) and building parameters. Probabilistic methods were evaluated and are proposed to account for uncertainties in the input parameters.