On the impact of night ventilation through motorized windows on the energy and thermal performance of office buildings

Global and local climate changes affect the energy performance of buildings, especially during the warm season, with relevant increase of cooling uses in mechanically cooled buildings and discomfort hours in naturally ventilated ones. The ventilative cooling is proved to be a promising strategy to tackle this threat, however installing new ventilation systems in existing buildings is challenging in technical and economic terms. The strategy can be also pursued by motorized windows duly operated. This solution is tested in a living lab in the northern outskirts of Rome, Italy. The living lab consists of seven rooms of an office building, planned to be upgraded to more four rooms and services during the present year. The energy and environmental performances of the living lab are continuously monitored and operated by a smart energy management system. Four of the seven rooms are equipped with motorized windows to provide free cooling and adequate indoor air quality through the implementation of different control rules. These windows are 200cm wide and 160cm high, the width of the manually and monetized sashes are 130 and 67.5cm, respectively. The latter opens/closes thanks a developing chain (30cm long) that allows 30° as maximum angle opening. As the living lab is expanding in the number of rooms, new solutions are screened to exploit the free cooling potential for windows to be replaced. Field measurements were carried out to assess the impact of night ventilation under real operative conditions, as well as to calibrate the living lab model in TRNSYS 17. In this study, starting from the calibrated model, a parametric analysis is carried out to evaluate the impact of different aperture angles of the motorized sash on the ventilative cooling potential. Simulations are run for the case of the active cooling installed in the office rooms. Based on the numerical analyses outcomes, the partner industries designed a prototypal windows, in which the developing chain is stretched so to allow 45° opening angle of the motorized sash. The new windows are currently under production, and it is planned to be installed and tested on site in summer 2024.