Evaluation of thermal comfort of naturally ventilated residential buildings in the informal settlements in Kampala city, Uganda.

Abstract

The hot conditions in the tropics where Uganda lies affects the indoor thermal comfort conditions due to the prevalence of the use of natural ventilation in many residential buildings to obtain thermal comfort. This necessitates the need to evaluate the parameters such as air temperature, air speed, and relative humidity that influence the indoor thermal comfort of these buildings due to the hot weather conditions. This study presents the results of a thermal comfort study in naturally ventilated residential buildings in Kawempe 1. Indoor and outdoor measurements for air temperature, air speed and relative humidity were done for seven buildings for a period of eight days according to ASHRAE 55 in the month of June, 2019 in Kawempe division, Kampala city. Questionnaire surveys were used for obtaining occupant subjective thermal sensation votes and DesignBuilder software was used for generating the building model and for performing thermal comfort simulations. Survey results showed that 67.8% of the respondents were comfortable with the thermal environment. From field measurements, the acceptable indoor operative temperature range was 22.7°C – 29.5°C which lies within the 80% acceptable limits by ASHRAE 55. Indoor PM2.5 and PM10 levels were found to almost double and triple the WHO limits, and ASHRAE 62.1 guidelines, respectively. The CO₂ concentrations were found to be lower than the limits set by ASHRAE 62.1 guidelines. The average monthly indoor operative temperature range from the model simulation results was 23.63°C - 25.3°C which predicts comfortable indoor conditions based on the 80% acceptable limits set by ASHRAE 55 guidelines. Lighting control, Mechanical ventilation without cooling, and Mechanical ventilation with cooling strategies improved thermal comfort hours by 0.5%, 3.8%, and 9.3% respectively. The results of the present study reveal that occupants have become tolerant of the hot indoor conditions through the use of adaptive means.