Impact of thermal behaviour on outdoor human thermal comfort in tropical climate

Abstract

In recent years, the challenges of the urban environment have been identified as urban heat island phenomenon due to the impacts of thermal behaviour from the surrounding built-up environment, with a low surface albedo. Their impacts on individuals are getting worse due to improper urban building designs with albedo modification that changed thermal behaviour in cities which in turn affects the quality of thermal comfort, especially in tropical countries. Therefore, this research aims to evaluate human thermal comfort by developing a preferable range of Discomfort Index (DI) interpretation for tropical climate. Next, the study integrates the application of a Surrogate Human Sensor (SHS) with measurements of climatic variables. Following this, Heat Stress Index (HSI) and Thermal Comfort Index (TCI) are established, using the correlation of the thermal perception with SHS and climatic variables measurement for evaluating thermal comfort in outdoor spaces. In-situ field measurements were carried out to analyse the impacts of thermal behaviour and its relationship to human discomfort. Human discomfort levels were evaluated using Thom's DI and a new extended DI range of 20°C to 28.9°C for “partially comfortable”. It was proposed in association with local climate as a result of thermal adaptability. Outdoor thermal sensations for the outdoor environment can be assessed using questionnaire surveys and a SHS model that was initially developed as a sensor to receive data on the impacts of thermal behaviour. SHS significantly reflects the impacts of thermal behaviour from the surrounding ambient environment towards human skin surface and found to be useful as a simple sensor, or indicator, for pre-assessing thermal conditions and comfort. In this study, two factors, i.e. climatic and psychological factors, are taken into consideration. Within this combination, SHS acts like a sensor to predict the thermal responses of people with respect to the influence from climatic variables. Thermal perception regression models, which represent the HSI, and SHS temperature regression models were developed based on the local microclimate environment. With this correlation, TCI was established where it enhances the understanding of the relationship between human psychologies and the climatic environment using SHS. Then, the SHS can be used to identify the perception level of the people as the SHS correlated with the thermal perception and surrounding climate measurements. All the regressions established were verified through execution in the real case scenarios by comparing the observed and predicted outputs. These verifications have shown that the regressions may be suitably applied in all tropical climate locations, especially in Malaysia, to evaluate correctly outdoor thermal comfort.