Bulk airflow measurements in a large naturally ventilated atrium in a mild climate

In recent years, concerns about global warming and greenhouse gas emissions have motivated designers to reduce building energy consumption through the implementation of passive solutions without compromising users’ thermal comfort. This evidence has stimulated a renewed interest in designers for the exploitation of natural ventilation as means of passive cooling solutions. The adoption of ventilative cooling is particularly suitable for large spaces (non-residential buildings) as a measure to reduce the HVAC system high cooling loads. Due the inability to control and ensure a constant airflow rate through natural ventilation most of the times designers choice goes towards mixed-mode buildings. Mixed-mode buildings are designed in such a way that the HVAC system acts as backup to prevent uncomfortable conditions when natural ventilation is not sufficient to guarantee a comfortable environment. Unfortunately, information about the actual performance of mixed-mode buildings is difficult to obtain due the difficulties to set up measurements in naturally ventilated buildings that highly depend on building geometry and outdoor conditions (weather, pollution and noise). This limitation leads designers to follow a traditional design approach based on mechanical air conditioned systems. With the aim of reducing the lack of information about the actual performance of mixed-mode non-residential buildings, this paper presents a full-scale bulk air flow measurements for a large naturally ventilated atrium in a mild climate. The methodology and the results presented in this paper refers at the first step of a more complete and complex work which aims at assessing the performance of the large mixed-mode atrium. The general performance of the atrium are tested through a long term measurement campaign which is indeed ongoing. The final aim is to quantify the effect of ventilative night cooling in term of cooling energy reduction and indoor thermal environment.