A FIELD STUDY ON THERMAL INSULATION PERFORMANCE OF GREEN ROOF FOR BUILDINGS IN HOT DRY CLIMATE OF ZARIA, NIGERIA

Although the practice of employing the use of green roof for thermal insulation is gaining a wideranging acceptance across the globe, its use in Nigeria and the sub Saharan Africa has remained unpopular. Study has shown that, although a vast literature on different approaches in the application of green roof system exists, there is substantial misrepresentation of inferences regarding its applications in Nigeria. The purpose of the study therefore, is to assess the thermal performance of green roof in facilitating thermal insulation for building interiors of hot dry climate in Nigeria. The study is carried out through an empirical field observation in the premises of Ahmadu Bello University Zaria, Nigeria. Two miniature live models were built and covered with galvanised iron roofing sheets on timber trusses; one of which was covered with green roof, while the other was left bare. This is with the view to determine the rate of thermal insulation a green roof system can offer over the bare roof in the building interiors of the study area. Using the experimental approach in green roof investigation, a data logging system was installed in the two thermal zones and readings of the temperature profile was taken. The results showed that; a reduction of 2.08°C in indoor air temperature was obtained on the diurnal ranges, while 19.78% of temperature fluctuation was achieved. Generally, the result showed that higher temperature ranges were recorded in the bare roofed case than the green roof. The maximum, mean and minimum record for the bare roof was 45.20°C, 32.03°C and 21.10°C respectively; while the recorded values for the green roof were 41.90°C, 29.95°C, and 21.00°C respectively. This implies that, the presence of vegetation on the green roofed case has offered a degree of thermal insulation required to achieve better passive cooling in order to attain thermal comfort in the interiors of the study area.