VALIDATING A SIMULATION STUDY OF GREEN ROOF'S THERMAL PERFORMANCE IN BUILDINGS OF THE HOT-DRY CLIMATE OF ZARIA, NIGERIA

The study is an effort to expand the frontier of green roof knowledge in response to the limited technical and general knowledge on the thermal benefits of using green roofs as an external insulation technique against excessive solar radiation on the roof system of the study area. Therefore, the sole purpose of the study is to assess the thermal performance of green roofs used as a passive technique in facilitating temperature reduction in building interiors of the hot dry climate of Nigeria. The was carried out through Building Energy Simulation; where two miniature models covered with galvanised iron roofing sheets on timber trusses were modeled in DesignBuilder 4.0 software in conjunction with Energyplus Version 8.3. For comparative evaluation, one of the models was covered with a green roof, while the other was left bare as the reference case; after which a validation exercise was carried out against physical models in an empirical field experiment. The results revealed that; higher temperatures were recorded in the bare roofed thermal zone, which indicates that the presence of vegetation on the green roofed cases offers a degree of thermal insulation against heat flux seeping into the building’s interior. Records in both simulated and field observation were taken in maximum, mean, and minimum ranges. Where, the record of the mean values showed that the field observation for the bare roof was 32.97°C, while the recorded values for the green roof was 31.37°C. On the other hand, the record of the mean values for the simulation exercise for the bare roof was 32.68°C; while the recorded value for the green roof was 31.85°C. A correlation analysis carried out after the field and simulation exercise showed that; there is a strong correlation between the measured data in the field observation and that of the simulated scenario; it established that the results are valid, reliable, and can be used for further green roof studies.