Microclimate Prediction Model For Thermal Conditions In Sheet Metal Clad Residential Buildings -Case Study for Uthiru, Kiambu County

Abstract

Kenya has had an acute shortage of affordable housing which has led to low cost housing developments in the form of sheet metal clad residential building settlements around major urban centers. This study aimed at conducting a field investigation on sheet metal clad residential buildings’ internal thermal comfort and humidity levels. This was to determine if their internal microclimates have acceptable levels of thermal comfort, are safe from internal condensation formation and if they can be predicted using a microclimate thermal prediction model. The study was done in the same geographical area of Uthiru, Kiambu County at an altitude of 1940 m above sea level. Data was collected using three temperature and humidity data loggers. A web based application software (Thermal Comfort Tool for ASHRAE-55) based on ASHRAE Standard 55-2020 was used to assess for thermal comfort in the naturally ventilated sheet metal clad residential buildings. The internal thermal conditions in the buildings at the time (8 pm) of 100% occupancy in the living room never fell below 20 °C and nor exceed 27 °C. The thermal conditions met the requirements of ASHRAE Standard 55-2020. Condensation risk of the sheet metal clad residential buildings was found to be high in the warm season than in the cold season. This was at times of cooking, heating bathing water or occupants were shut in the buildings. The empirical microclimate predicting model derived from computer learning process using Microsoft Excel software predicted with over 69% accuracy. The model showed that poorly ventilated sheet metal clad residential buildings are less predictable than those with effective ventilation. The computer derived model overpredicted on an average of 1.8 °C while the standard mechanistic model underpredicted on an average of 1.4 °C. It was recommended that sheet metal clad buildings are suitable for human habitation in the highland areas of Uthiru, Kiambu County. Occupants of sheet metal clad residential buildings in Uthiru, Kiambu County are recommended to open windows and doors when cooking or heating bathing water in the warm season so as to reduce the risk of condensation formation. The developed microclimate thermal prediction model can be adopted for predicting indoor thermal conditions expected in sheet metal clad residential buildings at Uthiru, Kiambu County.