Adaptative thermal comfort analysis in the elderly based on Fried frailty classification in residential buildings during summer

Due to differences in aging levels resulting from physiological functions, there are individual variations in the needs and adaptabilities of the elderly toward their environment. To explore the adaptive thermal comfort of different frailty elderly individuals, summer household surveys were conducted on 394 elderly individuals residing in 58 residential apartment buildings in Chongqing, China. Their behavioral habits and subjective thermal sensations were recorded, and environmental parameters were measured. Additionally, the elderly population was categorized based on frailty levels as defined in geriatrics, with relevant physical parameters and self-assessments recorded. The results indicate that elderly individuals with different levels of frailty exhibit varying sensitivity to environmental factors. Frail elderly individuals exhibited heightened temperature sensitivity (slop of non-frailty = 0.1, pre-frailty = 0.15, frailty = 0.27) and often favored a slightly warm environment with low air velocity. The frailer the individual, the higher the outdoor temperature required to prompt them to use air conditioning (T-out = 32 degrees C) and close windows (T-out = 33.5 degrees C), and the higher the air temperature to prompt them to use electric fans (T-a = 28.4 degrees C). Frail elderly have higher clothing insulation and can improve their thermal comfort by adjusting their clothing, while non-frail older adults do not rely on clothing to enhance their thermal comfort during the summer season. In conclusion, frail elderly' psychological responses are influenced more by environmental factors and adaptive behaviors. This study found that differences in physiological aging levels among elderly people with different frailty levels lead to differences in their thermal needs and adaptive behavior, which should be considered in aging-friendly building design.