Optimizing Carbon Credit Strategies for Low-Energy-Efficient Buildings: Greener Alternatives for a Sustainable Future

A carbon credit represents the amount of carbon emissions avoided due to a building’s energy efficiency, as reflected in its Building Energy Rating (BER). In Dublin, buildings with low BERs, such as F and G, contribute significantly to carbon emissions, with annual energy demands exceeding 380 kWh and 450 kWh per square meter, respectively. CO₂ emissions from such properties range from 27.2 kg/m²/yr for an F-rated building to 34 kg/m²/yr for a G-rated one. For instance, a 300 m² house with a G rating could produce up to 10.2 tons of CO₂ annually, totalling 510 tons over 50 years—highlighting the long-term environmental impact. The debate over whether to retrofit or rebuild low-performing buildings has gained momentum, particularly in the context of net-zero targets. This study examines the trade-offs between retrofitting and rebuilding, focusing on both operational and embodied carbon emissions in Dublin’s low-energy-efficient buildings. The methodology integrates BER data from the GeoDirectory dataset and OpenStreetMap with the City Energy Analyst (CEA) tool—an open-source Urban Building Energy Modelling (UBEM) platform for simulating energy use and emissions across urban building stock. Through Life Cycle Analysis (LCA), this study assesses both embodied and operational carbon emissions to determine when retrofitting can achieve significant carbon savings to support net-zero goals and when rebuilding may be a more viable long-term strategy. Embodied carbon is quantified for each building component and amortized over the building’s lifecycle, while operational emissions are assessed annually by energy end-use. The spatial distribution of simulation results underscores the importance of retrofitting in dense urban environments like Dublin, where targeted interventions are crucial for reducing emissions. These findings provide a data-driven foundation for policymakers and urban planners, enabling informed decision-making on retrofitting initiatives and optimizing urban energy performance for a more sustainable and resilient city.