Analysis of ventilation strategies for the nearly zero energy retrofit of a day care center

The scientific literature often reports examples of educational buildings with extremely poor ventilation performance. An in-field investigation for the environmental and energy assessment of a day care center in Italy in Milano, confirmed that operable windows were not opened on days when the average daily outdoor temperature was below 15°C, seriously affecting indoor air quality and potentially affecting the wellbeing and learning process of the children. A numerical model for the dynamic energy simulation of the school building was developed to optimize the thermal insulation of opaque and transparent envelope, the solar control strategy, reducing energy needs and uses to implement a nearly zero-energy approach to the retrofit. Different ventilation strategies were therefore simulated, in order to evaluate the one(s) that best fit the deep energy retrofit of the building, including building envelope and systems. A control logic for hybrid ventilation was simulated and analyzed, with the aim to develop a strategy suited for replication and effective in ameliorating both energy performance and indoor environmental quality. Daytime and nighttime natural ventilation showed to be extremely effective in improving thermal comfort conditions, during the cooling season, performing better than mechanical ventilation