This study investigates the relationships between air temperature, radiant heat and subject ratings of comfort in both transient and steady-state conditions when an infrared-reflective (IRR) treatment has been used on automotive glass. In the study, IRR films were systematically applied to the driver-side window of an outdoor stationary vehicle. In the first phase of the experiment, cabin air temperature was controlled while participants rated their thermal comfort. In the second phase, air temperature was adjusted according to participants' responses. Results in Phase 1 showed that the IRR treatment improved thermal comfort on the left forearm, which was exposed to direct solar irradiance, but not whole-body thermal comfort. In Phase 2, participants indicated that they were comfortable at a higher air temperature (mean of 2.5A.F [1.4A.C]) with the IRR treatment than in the untreated condition. These findings indicate that reducing radiant heat via IRR treatment affects subjective assessments of thermal comfort and allows occupants to maintain the same level of comfort in a warmer vehicle cabin. These findings suggest that the IRR treatment can improve fuel economy, since an IRR-treated vehicle's air conditioning would not need to work as hard in achieving high levels of air temperature reduction if the lower radiant heat is already mitigating occupant discomfort. Directions for future research are discussed.
Abstract