The environmental and energetic impact of prefabricated envelope components with bio-based materials for deep renovation

The construction sector increasingly adopts off-site prefabricated systems for deep retrofitting due to their low waste, fast installation, adaptability to specific building requirements, and reduced occupant disruption. Additionally, these systems utilize fewer and/or bio-based materials. Off-site prefabricated envelope components, integrating Heating Ventilation & Air Conditioning (HVAC) and renewable energy systems, are a promising strategy for achieving Near Zero Energy Buildings (NZEB). Beyond enhanced energy performance, assessing the environmental footprint of these retrofits is crucial. This study examines a prefabricated façade panel designed for the deep renovation of a residential building in Berlin to meet NZEB standards. The façade features a timber-based frame, bio-based insulation, advanced windows and a compact fan coil unit. The analysis evaluates energy savings from the reduced heat loss through the envelope and the improved HVAC efficiency. An adjusted cradle-to-gate Life-Cycle Assessment (LCA) calculates the embodied energy of the retrofitting components and compares it to the operational phase's primary energy use. Findings reveal a substantial reduction in total primary energy consumption, indicating that the NZEB state is attainable. Although the retrofit's initial embodied energy is occasionally significant, this is offset by the operational energy savings in the early years post-installation.