Does energy-efficient renovation positively impact thermal comfort and air quality in university buildings?

The University Institute of Technology (IUT) buildings in France were primarily built in the late 1960s without considering the energy issues that were not relevant at the time. At the IUT of Nîmes, during winter and summer, rooms within the same building can be either very hot or very cold, causing discomfort for the users. One of the solutions is the renovation of the building and its systems. This research aims to evaluate the energy-efficient renovation performance associated with thermal comfort and indoor air quality. Modifications to the building envelope and systems were recommended by thermal engineers based on simulations that did not consider the occupants’ behavior and operational uncertainties. Therefore, this analysis relies on physical measurements of CO2 concentrations, humidity, and temperature during the heating period, along with a thermal comfort survey. The analytical result showed no significant change in CO2 level and humidity, but the temperature reduced up to 3 °C as a consequence of adjusting the heating temperature threshold. However, in certain post-renovation classrooms, the CO2 concentrations increase by 11.7% with an incorrect airflow rate. Although there is no change in measured values, according to the French thermal building code for renovated buildings, these values are on the border of their comfort zone. Overall, thermal renovation saves 85 MWh while maintaining satisfactory thermal comfort and air quality. However, caution should be exercised regarding the air exchange rate. •Ideal temperature threshold in offices and workshops is higher than in classrooms•The heating temperature threshold can be lowered to 18 °C without affecting user comfort•Post-renovation indoor climate falls short of the renovated building standard values•Ventilation rate lower than 9 m3/h per increases CO2 levels by 11.7% in average.