In the frame of the project Flux50 smart ventilation, researchers and industrials aim at qualifying ventilation in mid-sized buildings through multidisciplinary consideration of sleep quality, user satisfaction, acoustic comfort, installation, maintenance, resilience and indoor air quality. As those factors may impact at different levels it is important to select a common metric for evaluation. Assessment of financial costs induced by the various categories will be used in that purpose. The major complexity of this task relies on identification and objective evaluation of each separate cost at building or individual scale. Identified impacts are divided into two categories, hard costs and soft costs. The first one include material, maintenance, operation and installation costs while the second gathers medical costs, productivity lost, learning disturbance and willingness to pay. Authors explain, for each concerned category, a generalization of medical cost calculated by Disability Adjusted Life Years (DALY) approach; and productivity lost function. Costs related to user satisfaction are assessed by a correlation between thermal comfort, energy consumption and productivity. This work is an early stage towards the next step of the project, which is a global optimization of ventilation according to all mentioned aspects. In this purpose, a case study is currently being investigated via a combination of multiple numerical environments of a floor of Antwerpen university.