Attention to Overheating in Curtainwall Buildings

Several years ago, Technoform and the Solar Energy Research Institute of Singapore (SERIS) researched the thermal performance of different aluminum window frames in a hot climate, and the study demonstrates the importance of having thermally broken aluminum window frames for desired thermal comfort. This paper focuses on a similar issue, but with curtainwall systems, by simulating typical shadow-box spandrels and obtaining each case's frame and glass temperatures.

The paper discusses that the overheating problem is as critical as the condensation problem; however, both are caused by the thermal bridging effect. Overheating may not only cause thermal discomfort but also affect the durability of the PVB interlayer if the laminated glass is used as the spandrel glass.

For the thermal simulation, summer outdoor temperature and solar irradiance referred to a subtropical climate (Shenzhen, China), and head transoms with different spandrel glass and frame types were modeled using THERM software. The results show that in the worst case, the maximum temperature of the frame and glass edge is 56°C (132°F) and 45.5°C (114°F), and the time duration of the frame temperature exceeding 40°C (104°F) is about 5.5 hours. The results also show that in the best case with external sunshades and high-performance thermal breaks, the frame and glass edge temperature is below 40°C (104°F) all the time.