Radiant vs. All-air cooling systems for highly glazed buildings: An experimental study on global and local thermal comfort

When integrating cooling systems into highly glazed buildings, the uneven radiation asymmetry caused by prolonged exposure to direct solar radiation becomes increasingly pronounced, thereby affecting indoor thermal comfort. This comprehensive experimental study analyzes and compares various cooling systems including radiant and all-air systems, used as single or combined, with an experimental focus on their effectiveness in providing thermal comfort in highly glazed buildings. The investigation, conducted in an outdoor experimental building, used a Newton Thermal Manikin and the Givoni Diagram to assess local and global thermal comfort. Key environmental parameters, such as air distribution, temperature stratification, and radiation temperature asymmetry, were adopted as comparison indicators. The main findings revealed that radiant systems are insufficient to mitigate overheating in spaces subject to a prolonged exposure to solar radiation, with an operative temperature exceeding the acceptable upper limit by 8degree celsius. Combined radiant systems might improve thermal comfort, however a pronounced thermal radiation asymmetry and temperature stratification were still noticed. Among the four different cooling methods, using Air handle units for air ventilation and cooling stands out more for ensuring good thermal comfort.