Optimization of building envelopes using indigenous materials to achieve thermal comfort and affordable housing in Abuja, Nigeria

Purpose: This paper aims to demonstrate the optimization of an existing residential building in a tropical climate using indigenous materials as an alternative to conventional building envelopes to achieve thermal comfort and affordable housing. Design/methodology/approach: This study mainly adopted a quantitative research methodology through a comprehensive simulation study on a selected prototype building. The energy plus simulation tool in DesignBuilder was used to predict the average monthly and annual thermal comfort of a typical residential building in the study area. Also, a cost analysis of the final optimization interventions was conducted to estimate the construction cost savings. Findings: The comparative analysis of simulation results for the base-case and optimized models indicates potential advantages in replacing conventional building envelope materials with indigenous materials. The base-case simulation results showed that the annual operative temperature is more than the adaptive thermal comfort set points in tropical climates, by 8.26%. This often leads to interventions using mechanical cooling systems, thus triggering overconsumption of energy and increase in CO2 emissions. The building envelope materials for floor, walls and roof were replaced with low U-values indigenous materials until considerable results in terms of thermal comfort and overall building construction cost were achieved. The final simulation results showed that using indigenous materials for the ground floor, external walls and roof could substantially reduce the annual operative temperature by 8%, thereby increasing the predicted three months of thermal comfort in the base-case to nine months annually. Likewise, there was a 32.31%, 35.78% and 41.81% reduction in the annual CO2 emissions, cooling loads and construction costs, respectively. Originality/value: The knowledge of indigenous materials as an alternative to conventional materials for sustainable buildings is not new. However, most of the available research is focused on achieving affordable housing. There is a dearth of research showing the extent that these indigenous materials can be used to improve indoor thermal comfort in developing countries with tropical climates such as Nigeria.