Impact of Embodied Energy and Carbon on the Path to Nearly Zero Energy Residential Buildings

In recent decades, energy efficiency policies have increasingly focused on reducing buildings’ energy use and improving their performance. However, by overlooking the entire life cycle of a building, a considerable portion of its environmental impact has indeed been kept out of the process. As a result, even leading buildings that have advanced toward Zero-Energy status may not that as innocent as promised by evaluating environmental impacts during their whole life. Consequently, a logical method for achieving nearly Zero Energy Buildings (nZEBs) involves implementing energy-efficient measures and proper materials throughout the entire life cycle of buildings. This paper is one of its first kinds that includes all building systems and materials embodied energy and cost to explore the possibility of creating nearly zero residential buildings through their life cycle. Life-cycle energy consumptions, life-cycle CO₂ emissions and life-cycle cost of nZEB retrofit packages for a five-storey, 20-apartment residential building in Ankara, Turkey were evaluated. The methodology couples dynamic simulation (DesignBuilder/EnergyPlus) with an EN 15978-aligned boundary (A1–A5, B, C). The study highlights the critical role of both operational and embodied energy and carbon emissions in the pursuit of nZEBs. The best nZEB package reduces primary energy by ~55% and life-cycle CO₂ by ~45% relative to the reference building over 50 years, while cost-optimal packages deliver 6–7% lower global cost. These findings demonstrate the effectiveness of life cycle assessment in measuring building environmental impact, the utilization of renewable energy, and the optimization of building materials in reducing energy consumption and emissions, providing a sustainable and cost-efficient approach to residential building design.