Optimal design guidelines for net zero energy residential buildings in cooling-dominated climates: Case study of Ghana

Net-zero energy buildings (NZEBs) are regarded as an achievable solution for reducing energy use and carbon emissions in the built environment and addressing climate change. However, the ultimate objective of NZEBs is to enhance the energy performance of buildings by changing how they are designed and constructed. Consequently, identifying cost-effective energy efficiency strategies at the early design stages of buildings has become imperative and often required in several countries. This study describes a systematic analysis approach to optimize the design of residential facilities considering both energy efficiency and renewable energy systems. The design optimization is based on life cycle cost (LCC) analysis, which considers capital and energy costs over the life cycle of the building. The analysis consistently shows that LCC-based optimal designs significantly reduced the building’s annual energy consumption, achieving 34-35% energy-saving across the various climates compared to the baseline case. The most cost-effective energy efficiency measures that proved effective across all the climate zones include north orientation of the building at 180 azimuth degrees, natural ventilation, adequate window-to-wall ratio, minimal façade air leakage (i.e., about 5-7ACH @50 Pa), and high efficient fans, air conditioning, and dehumidification. The integration of the PV system indicates that the net-zero energy (NZE) design for the building is technically feasible and cost-effective across the climate zones considered. The sensitivity analysis further shows that the cost of integrating PV systems is even more cost-effective over a more extended period of the building’s lifecycle. The study provides an optimal path for designing NZEBs and offers guidelines to achieve NZE across the building’s lifecycle.