Climate change and the urgency of decarbonizing the built environment are driving technological innovation in the way we deliver thermal comfort to occupants. These changes, in turn, seem to be setting the directions for contemporary thermal comfort research. This article presents a literature review of major changes, developments, and trends in the field of thermal comfort research over the last 20 years. One of the main paradigm shift was the fundamental conceptual reorientation that has taken place in thermal comfort thinking over the last 20 years; a shift away from the physically based determinism of Fanger's comfort model toward the mainstream and acceptance of the adaptive comfort model. Another noticeable shift has been from the undesirable toward the desirable qualities of air movement. Additionally, sophisticated models covering the physics and physiology of the human body were developed, driven by the continuous challenge to model thermal comfort at the same anatomical resolution and to combine these localized signals into a coherent, global thermal perception. Finally, the demand for ever increasing building energy efficiency is pushing technological innovation in the way we deliver comfortable indoor environments. These trends, in turn, continue setting the directions for contemporary thermal comfort research for the next decades.

Results from naturally ventilated buildings show that allowing the indoor temperature to drift does not necessarily result in thermal discomfort and may allow for a reduction in energy use. However, for stationary conditions, several studies indicate that the thermal neutral temperature and optimum thermal condition differ between young adults and elderly. There is a lack of studies that describe the effect of aging on thermal comfort and productivity during a moderate temperature drift. In this study, the effect of a moderate temperature drift on physiological responses, thermal comfort, and productivity of eight young adults (age 22-25 year) and eight older subjects (age 67-73 year) was investigated. They were exposed to two different conditions: S1-a control condition; constant temperature of 21.5 degrees C; duration: 8 h; and S2-a transient condition; temperature range: 17-25 degrees C, duration: 8 h, temperature drift: first 4 h: +2 K/h, last 4 h: -2 K/h. The results indicate that thermal sensation of the elderly was, in general, 0.5 scale units lower in comparison with their younger counterparts. Furthermore, the elderly showed more distal vasoconstriction during both conditions. Nevertheless, TS of the elderly was related to air temperature only, while TS of the younger adults also was related to skin temperature. During the constant temperature session, the elderly preferred a higher temperature in comparison with the young adults. Because the stock of fossil fuels is limited, energy savings play an important role. Thermal comfort is one of the most important performance indicators to successfully apply measures to reduce the energy need in buildings. Allowing drifts in indoor temperature is one of the options to reduce the energy demand. This study contributes to the knowledge concerning the effects of a moderate temperature drift and the age of the inhabitants on their thermal comfort.