Investigation of Thermal Comfort Conditions in a Secondary School Classroom in the Hot-Dry Climate of Yobe State

Extreme indoor temperatures in unventilated or inadequately ventilated secondary school classrooms in North East Nigeria are known to impair student cognitive performance and attendance, yet the thermal conditions in rural school buildings in Yobe State have received little systematic engineering investigation. This study investigates thermal comfort conditions in a representative secondary school classroom in Potiskum, Yobe State, during the hot dry season using field measurement and established thermal comfort indices. Indoor and outdoor dry-bulb temperatures, relative humidity, air velocity, and mean radiant temperature were measured at 15-minute intervals over 20 school days using calibrated environmental sensors. Predicted mean vote and predicted percentage dissatisfied indices were computed from measured data using the ISO 7730 standard methodology. Mean indoor temperatures during peak lesson hours ranged from 37.2 to 41.8 degrees Celsius, with predicted mean vote values consistently above plus 2.5 on the ASHRAE thermal sensation scale, indicating conditions rated as hot to very hot by more than 90 percent of occupants. Roof type was identified as the primary determinant of indoor temperature, with corrugated iron roof classrooms averaging 4.1 degrees Celsius warmer than those with aluminium-foil-lined ceiling boards. The study recommends the adoption of thermal insulating ceiling liners and cross-ventilation openings as minimum-cost interventions for improving classroom thermal comfort in the region. Keywords: thermal comfort, classroom environment, hot-dry climate, Yobe State, predicted mean vote.