Sustainable Integrated Project Control for Prefabricated Construction: A Synchronization-Loss Metric Linking Multi-Stage Scheduling, Cost, and Delivery Risk

Prefabricated construction couples factory production, buffer storage, transportation, on-site installation, and workforce resources. Desynchronization across these stages creates waiting, idle labor, standby, and buffer pressure—non-value-adding losses that local schedule and cost controls leave hidden. This study takes a project-control view of multi-stage prefabricated delivery and develops a full multi-stage synchronization model that makes these losses explicit and controllable during schedule evaluation. From a sustainable-construction perspective, the framework targets operational resource efficiency by reducing non-value-adding waiting, idle labor, buffer burden, and standby, rather than claiming direct carbon or life-cycle effects. The model optimizes three objectives: makespan, total cost, and a resource-efficiency synchronization loss (RESL) that aggregates waiting, crew-idle, buffer, and standby losses; RESL is a schedule-based resource-efficiency proxy, not a carbon or life-cycle measure. A SPEA2-based solver, SI-SAR-SPEA2, adds structured initialization and synchronization-aware light repair. Using project-inspired semi-realistic prefabricated building-delivery instances, the evaluation compares alternative model scopes, algorithm baselines, a pre-fixed fresh-seed extension, ablation variants, and sensitivity settings. The full model exposes cross-stage synchronization losses and substantially reduces RESL relative to a production–transport model, whereas its relative performance against a production–transport–installation model remains marginal, instance-dependent, and weight-dependent. Under the formal benchmark protocol, SI-SAR-SPEA2 improves hypervolume, average rank, and RESL compared with the SPEA2 backbone, but this quality gain requires additional runtime. The results position RESL as an integrated project-control indicator for comparing schedule alternatives in terms of delivery timing, cost exposure, workforce utilization, and synchronization risk.