Investigation of the daylighting and the thermal environment of Nigeria's low-income housing: the case of Abuja

The housing schemes that were developed as part of Abuja’s master plan over 30 years ago are still in use today as prototypes for low-income housing developments. At the early stage of the city’s development, the designers involved in the process were mainly focused on providing the required quantity of dwellings to accommodate those involved in the construction. There were no weather stations set up to monitor the climatic conditions of the area and no urban areas within a hundred kilometres of the city’s location. Thus, the value of the region’s unique climatic conditions received only cursory consideration during the early phases of development. More records of the climate of the region have become available since the mid-1990s. Yet, despite the availability of such data and the global interest in an energy efficient approach to building design, it is still not clear whether the concern about energy conservation has led to a different design practice in the housing sector. On the contrary, recent statistics on energy consumption in Nigerian residential buildings indicate an increase in energy use due to the growing use of mechanical air conditioning units for meeting comfort requirements. Previous studies have shown that space air conditioning and lighting have been accounting for some 80% of domestic energy consumption in Nigeria. Given that the region is already struggling to meet its current energy demands, it is important to examine whether improvements made to the design approach for future buildings can assist in reducing overheating indoors and energy consumption. The aim of this study is to develop passive design guidelines that will help improve the thermal and daylighting conditions in residential buildings in Nigeria, thereby reducing the need for active energy sources to keep occupants comfortable. To achieve this, the study has four main parts. Firstly, the literature relating to the environment and phases of architectural development in Abuja, Nigeria is reviewed in order to identify the unique elements of the climate and socio-economic context of the city. Secondly, the literature relating to human comfort as well as the thermal and visual performance of buildings, is reviewed in order to identify the design parameters that are crucial for improving occupants' comfort in dwellings, especially in tropical regions. Thirdly, using computer based simulations, the research investigated the performance of eight housing types in Abuja in their current state and examined the impact changing key design parameter has on occupants comfort. Finally, the findings from the investigations are used to deduce which passive design approaches are more relevant for improving the thermal and visual conditions in residential buildings in the region. Evaluating the performance of the buildings in their existing state revealed clear overheating problems and excessive natural lighting for most of the year. However, among the key findings from the investigation, it was found that a 6-11% decrease in the frequency of thermal discomfort and a 16-54% decrease in the frequency of visual discomfort can be achieved by adjusting the orientation of the facades. The results also showed that the frequency of thermal and visual discomfort can be reduced by about 6.5% and 71% respectively, using façade and window shading components.