Assessment of Indoor Thermal Comfort in Residential Buildings During Harmattan Season in Kaduna State

Harmattan is a dry, dusty north-easterly trade wind that affects large parts of northern Nigeria between November and March, creating distinct indoor thermal comfort challenges due to low humidity, elevated dust loading, and wide diurnal temperature swings. This study assesses indoor thermal comfort conditions in forty low-cost residential buildings across three urban districts in Kaduna State, North West Nigeria, during the harmattan season. Measurements of dry bulb temperature, relative humidity, mean radiant temperature, and air velocity were taken using calibrated instruments at three times of day in occupied rooms. The predicted mean vote index and predicted percentage dissatisfied values were calculated using ISO 7730 thermal comfort standards, accounting for metabolic rate and clothing insulation typical of Nigerian indoor occupants. Results indicate that 72 percent of sampled rooms recorded predicted mean vote values outside the acceptable range of negative 0.5 to positive 0.5, with the majority indicating thermally dry, cool conditions during early morning hours. Buildings with mud brick walls showed more stable indoor temperature profiles compared to those with sandcrete block construction. The study finds that roof material, window orientation, and wall thickness are statistically significant predictors of harmattan thermal comfort. Practical recommendations for passive design improvements and community education on adaptive thermal comfort strategies are provided. Keywords: thermal comfort, harmattan, Kaduna, indoor climate, building physics