The retrofitting strategies in European school buildings are usually focused on reducing the heating demand since it represents the major energy consumption. Nevertheless, the rise in outdoor temperatures shows that the risk of overheating during the summer is increasing. When planning such processes, decision-makers need to take into account the different building typologies, the effect of the potential measures in the future conditions and their costs. This study integrates these factors and provides specific guidance on the most appropriate measures to improve indoor thermal comfort in classrooms in the city of Karlsruhe, Germany. The simulations suggested that current overheating of the studied buildings represents up to 27% of the occupied time. The heavyweight buildings could prevent overheating by means of good ventilation, while lightweight buildings require more sun protection. With the appropriate natural ventilation strategy and with the help of ceiling fans, overheating can be avoided in most of the building types in the near future. In the case of lightweight buildings, overheating can be reduced to less than 10% of discomfort during occupied time; however, it would be required to significantly reduce the solar gains through technologies such as electrochromic glazing or a combination of other passive measures.

Understanding humans’ perception of the thermal built environment is one of the prerequisites for designing satisfactory workplaces and related to their energy use. This paper compares the predictive performance of nine thermal comfort indices with respect to the population mean and individual votes together with the effect of false assumptions of metabolic rate, clothing level, and air velocity on this performance. In addition, the potential to customize the indices to the building level, e.g. by means of the coefficient for psychological adaptation, PSYCH, included in the adaptive thermal heat-balance (ATHB) model is analysed. The analysis of field data from two naturally ventilated and four mixed-mode office buildings showed that the ATHB indices outperform the other indices in terms of predicting thermal sensation. The effect of false assumption is larger for predicted mean vote (PMV)-based models compared with standard effective temperature (SET)-based models. In addition, customization revealed no clear distinction between naturally and mixed-mode buildings, which suggests that other factors are more influential. These results are discussed with respect to the potential of the ATHB approach to account for differences in building control characteristics and the way thermal comfort is addressed in related standards.

Data was collected in the field, from an office building located in Frankfurt, Germany, over the period of 4 years. The building was designed as a low-energy building and featured natural ventilation for individual control of air quality as well as buoyancy-driven night ventilation in combination with a central atrium as a passive cooling strategy. The monitored data include in total 116 data points related to outdoor and indoor environmental data, energy related data, and data related to occupancy and occupant behaviour. Data points representing a state were logged with the real timestamp of the event taking place, all other data points were recorded in 10 minute intervals. Data were collected in 17 cell offices with a size of ~20 m², facing either east or west). Each office has one fixed and two operable windows, internal top light windows between office and corridor (to allow for night ventilation into the atrium) and sun protection elements (operated both manually and automatically). Each office is occupied by one or two persons.