Globally, the population has been aging in recent years, and this rate is expected to continue to increase, especially in developed countries. In addition, the elderly tend to spend more time in their houses than younger people. Therefore, indoor thermal environments are important for the health and well-being of older populations. In this chapter, we discuss the various influences of thermal conditions in residential environments on the elderly, focusing on room temperature, humidity, sleeping environment, and bathing environment. Although the comfortable temperature range for the elderly was almost the same as that of younger subjects, they had difficulty perceiving changes in room temperature and showed deterioration in sensitivity to cold and heat. The elderly showed greater cardiovascular stress due to room-temperature fluctuations than the young. Similarly, the physiological effects of high and low humidity on the eyes, throat, and skin are greater in the elderly than in the young; the elderly cannot perceive changes in humidity as much as the young. Adjustment of the thermal environment is especially important for the elderly compared to younger people because of their reduced ability to adapt to various environmental changes and subjective perceptions. The elderly people require a more appropriate temperature and humidity environment in their bedrooms to get a good night’s sleep. It has been reported that bathing in hot water in a cold bathroom during the winter causes large fluctuations in blood pressure in the elderly, leading to fainting and drowning. The adequate heating of dressing rooms and bathrooms is essential to ensure comfortable and safe winter bathing.