Variation of Natural Ventilation with Floor Level and Orientation of Classrooms

Abstract

In recent times, the multi-story school building has emerged as a new trend in Nigeria due to land cost in the urban area and population increase due to urban migration resulting from insecurity in rural areas. Among other factors, the floor level and space orientation are believed to affect its natural ventilation. Electricity per capita consumption in Nigeria is very low, suggesting passive ventilation in the building. The ventilation in the classroom is usually through wind-driven systems (windows). The study sought to establish the variation of natural ventilation among classrooms on different floor levels and orientations. In the ex-post facto design, instruments were employed to observe wind speeds and directions in and around selected classrooms in a school building block with two wings on three-floor levels, a perimeter fence, and a built-up residential area. The classrooms on the ground floor were half-opened casement windows, while those on the upper floors had sliding windows. Data generated were subjected to descriptive statistical analysis. In the longer wing classrooms, the mean wind speed and standard deviation obtained were 0.17m/s and 0.123 on the ground floor; 0.15m/s and 0.104 on the first floor; and 0.18m/s 0.126 on the second floor. Corresponding results in the shorter wing classrooms were 0.12m/s and 0,077 on the ground floor; 0.11m/s and 0.095 on the first floor; and 0.17m/s and 0.126 on the second floor. Ventilation coefficients were 0.13, 0.11, and 0.13 respectively on the ground, first, and second floors in the longer wing classrooms, while those in the shorter wing classrooms were 0.13, 0.12, and 0.19 respectively. The findings revealed some direct variation in natural ventilation with the floor level in the studied classrooms, which was more manifested as the floor level increased upwards. In conclusion, the floor level and orientation affect wind-driven ventilation. There is also a need for further field studies on more suitable cases (higher floor levels) to ascertain the level of significance of this variation and the optimisation window area based on floor levels for orientation for wind-driven natural ventilation.