A study on hygrothermal conditions in intermittently heated or unheated bedrooms in southern Europe

Abstract

Indoor hygrothermal parameters have an important role in the assessment of indoor air quality (IAQ) and comfort. In fact, the perception of air quality is strongly influenced by temperature (T) and relative humidity (RH). In Northern Europe, due to the severe climate conditions during winter, it is common to adopt continuous heating to guarantee sufficient thermal comfort in residential buildings. On the contrary, in Southern European countries, due to the specific climate, economy and culture, a permanent heating practice in winter is generally not adopted. Consequently, the indoor climate in Northern and Southern Europe is expected to be quite different, and this discrepancy should be taken into account when designing retrofit interventions aimed at improving indoor comfort and lowering energy demands. In particular, when studying the properties of interior coating materials, T is commonly set between 20-25 °C and RH in the range 33-75%. These are considered acceptable and common indoor conditions for continuously heated buildings, but they might be not representative of Southern European reality. For the present study, four residential buildings were chosen in the city of Lisbon. The indoor air T and RH were continuously recorded for one bedroom in each building during wintertime. The bedrooms are characterized by a floor surface of 7.5-10 m2, the occupancy of one person during an average of eight hours, natural ventilation and the presence of one window North/Northwest oriented and with manually-regulated shading. All rooms were monitored under operational conditions, with users adopting intermittent heating (room heaters) or no heating at all. The main differences between the case studies concern the floor where the apartments are located and the constructive characteristics of the buildings. The indoor hygrothermal conditions obtained in the monitoring campaign are discussed in this paper and indoor thermal comfort is evaluated. Finally, despite the differences between the case studies, an approximation of the overall indoor T and RH fluctuations is provided.