Physiological responses to indoor climates in tropical cities: The Lagos Experience

The significance of the climatic environment on urban planning and building design has increased the awareness for the need to have maximum benefits of the indoor climates in addition to having accurate knowledge of the external climate, as this affects the behaviour of buildings and the constituents parts. In particular, planners, architects and building engineers are for example usually faced with the problems of designing against rain, sunshine and wind such that the buildings can provide comfortable indoor conditions. Unfortunately, in spite of the significance of indoor climate, not much has been done to carry out studies on the characteristics of indoor climates in the tropical areas in general, and West Africa and Nigeria in particular. Thus, many building designers have not been able to provide functional, pleasant building environment, which will enhance the quality of life of the inhabitant. This is for example, the case in Lagos metropolitan area (Nigeria), where very few studies of thermal stress and thermal comfort are available. Much less available still, are studies related to physiological responses of the society to thermal conditions and the extent to which buildings have been able to perform one of their main functions, namely, to create indoor climates which would be suitable for comfortable accommodation.

In the present paper, therefore, a pioneering effort is being made to examine the extent to which some buildings in Lagos metropolitan area have been able to create indoor climates that are suitable for comfortable living. Eight buildings were selected for the purpose of this paper, which also applies two thermal indices, namely, the Effective Temperature (ET) and the Relative Strain Index (RSI), for computing the thermal stress values and for objectively evaluating the degree of sensation in the study area. The study also utilises human subjective responses obtained by using questionnaires during field investigations in order to assess the human perception of the thermal environment.

The results showed that a lot of variations occur in the characteristics of the indoor thermal environment, thermal comfort level and human physiological responses. In particular, the results showed that the environmental conditions were generally uncomfortable for most of the subjects used, when measured against the human physiological responses obtained by using the thermal index scales for the middle latitude countries. However, when measured against the subjective responses as obtained for the indoor thermal environment in Lagos, the results showed relatively comfortable levels of thermal sensation for relatively higher values of the thermal index values. This indicates the relatively higher levels of adaptability for people in the study area than for those in the middle latitudes. It also indicates differences in other physiological differences in human requirements between people in the middle latitudes and those in the tropical areas. The study therefore advocates for the need to modify the existing thermal comfort index scales for different regions in the world, and the hot humid tropics of Africa in particular, in order to accurately apply any developed thermal indices to obtain thermal indoor requirements for the different regions.