Feasibility and retrofit guidelines towards net-zero energy buildings in tropical climates: A case of Ghana

Abstract

Constructing and retrofitting buildings into net-zero energy has become an important strategy for reducing greenhouse gas emissions; however, its implementation remains a critical challenge, particularly with existing buildings retrofit. This study investigates the feasibility and proposes retrofit guidelines that achieve net-zero energy targets for existing buildings in a tropical climate. A two-storey residential building, a typical archetype model in Ghana, was analyzed systematically using parametric simulation. The calibrated model was used to determine energy efficiency interventions and renewable energy potential for achieving Net-Zero Energy Building (NZEB) across four major climate zones. The results showed that passive design strategies such as natural ventilation, sun-shading, daylighting, and envelope airtightness transformed the case building with an Energy Use Intensity (EUI) of 136–138 kWh/m2/yr to 68–70 kWh/m2/yr, therefore reducing 48–50% of total energy demand. Subsequently, a solar PV system was scaled to cover the remaining energy needs with a payback period of 6–10 years, thus transforming the building into NZEB and even to “net-positive energy” (i.e., building generating more energy than it consumes). The study demonstrates that it is feasible to achieve the NZEB target in existing residential buildings in the tropical climate of Ghana. This study’s novelty is that it offers retrofit interventions and adequate retrofit guidelines for renovating residential buildings into NZEBs.