Achieving net zero life cycle primary energy and greenhouse gas emissions apartment buildings in a Mediterranean climate

Abstract

Achieving net zero life cycle energy and greenhouse gas emissions buildings is rare. This would entail not only covering operational energy use, but also embodied energy and displacing embodied greenhouse gas emissions in construction materials and renewable energy systems, across their supply chains.The aim of this paper is to evaluate the feasibility of achieving net zero life cycle primary energy and greenhouse gas emissions (NZLCPEGHG) buildings. We use a case study apartment building in Sehaileh, Lebanon and conduct a life cycle cost, energy and greenhouse gas emissions analysis over 50 years of a business-as-usual building and its NZLCPEGHG counterpart.Results show that a 6.5 kWp solar photovoltaic array, solar hot water, an improved operational energy efficiency, an all-electric operational energy demand, and a reduced embodied energy, can achieve a NZLCPEGHG apartment unit (154 m2, 4 occupants) in a four-storey building. Installing battery storage (or not) is critical regarding life cycle cost, swinging the net present value from −46 to +47 USD2020/(m2-of-gross-floor-area) over 50 years. The greenhouse gas emissions factor of the electricity grid is key to achieving a NZLCPEGHG building, with cleaner grids making it harder to displace embodied greenhouse gas emissions. We argue, inter alia, for a more transparent and comprehensive definition of NZLCPEGHG buildings, policy that subsidises this level of performance to cover additional capital costs, and reducing the initial embodied energy and greenhouse gas emissions that might never be paid-back or displaced. These measures will help address the current climate emergency.