Green cost premium for attaining energy-efficiency rating in Nigeria's hot-humid residential buildings

Purpose: The dearth of green standards (GS) in sub-Saharan Africa is alarming and the green cost premiums (GCP) in seeking certification in emerging markets are scanty. This paper studied the Building Energy-Efficiency Code of Nigeria (BEEC) and estimated the potential GCPs associated with the various energy-efficiency ratings. Design/methodology/approach: The study retrofitted 150 conventional residential bungalow and maisonette buildings using BEEC's energy-efficiency interventions and performed analytical estimating of the retrofitted designs. The mean cost premium associated with each energy-efficiency intervention is presented as well as their financial benefits and payback periods. The benefits are achievable financial-savings due to a reduction in energy consumption and savings in electricity payment estimated from the average energy demands of each building. An independent t-test was further conducted to determine the cost differential between energy-efficient design (ED) and conventional design over a five-year period. Findings: The potential GCPs and their payback periods are actually less than feared. The study showed that less than 5% and 21% extra funding would be required to achieve 1 to 4-Star and 5-Star energy-efficiency ratings involving passive design interventions and photovoltaic systems. Passive and active design interventions produced a financial savings of $8.08/m2 in electricity payment and $2.84/m2 per annum in energy consumption reduction. The financial-savings ($10.92/m2) was objective to pay-off the GCPs in less than four years. The independent t-test analysis showed the cost of ED is more economical after four years into the project lifecycle. Originality/value: The research provides cost benchmarks for navigating cost planning and budgetary decisions during ED implementation and births a departure point for advancing energy-efficient construction in developing markets from the rational economic decision perspective.