What is adaptive thermal comfort ?

Overview

Field studies of thermal comfort have been conducted intensively at various climatic locations to define the range of acceptable thermal environment for air-conditioned and naturally conditioned buildings that led to the development of Adaptive Thermal Comfort (ATC) model. 

Research on adaptive thermal comfort revealed a higher range of acceptable temperatures, which depend on climate, building type, behavioral controls, and other similar factors. Field studies have also revealed the role of thermal adaptation to conserve energy in air-conditioned buildings, and this concept is also useful for building design, and operation of naturally conditioned buildings as per the outdoor conditions. 

Higher bandwidth of comfort temperature and energy conservation opportunities encouraged researchers to carry out intensive field studies of thermal comfort to propose robust adaptive thermal comfort model.

Definition

Adaptive principle states that if a change occurs such as to produce discomfort, people react in ways which tend to restore their comfort. The fundamental assumption of the adaptive approach of thermal comfort was expressed by Nicol and Humphreys in 1973 and by Humphreys in 1978. It implies that human beings have tendency to adopt the variable environment conditions for making themselves thermally comfortable. 

Adaptive approach of thermal comfort is based on the findings of field survey of thermal comfort conducted into the building of particular climate. Responses regarding the indoor thermal environment are recorded from the building occupants along with the measurement of indoor environment variables. The purpose of conducting field studies of thermal comfort is to evaluate thermal variability in different climatic conditions. The results of the studies are used to determine the thermal neutrality and acceptable temperature bandwidth.

Below figure shows the acceptable temperature limits (80 % and 90 % thermal acceptability) for various cities across the globe. Difference in acceptable temperatures for New Delhi and Stockolm can be seen clearly as variation in mean monthly temperature is large for both the cities, hence variation in acceptable temperature. 

Acceptable temperature in naturally conditioned spaces for different climates

(Source: Olesen, 2005. International standards for the indoor environment. Where are we and do they apply worldwide? Denmark: Danish Technical University.)