Partial Cost Information and Empirical Contingency in Building Retrofit Cost Prediction

This study retrospectively evaluated partial cost information and empirical contingency in an archived extract of public-building retrofits. The primary reporting sample comprised 246 records, with all 250 retained for sensitivity analysis. Adding four recorded component costs reduced total-cost mean absolute percentage error (MAPE) from 23.35% to 17.30% for genetic-algorithm-weighted case-based reasoning and from 23.05% to 14.68% for Extra Trees. The primary comparison did not establish a larger improvement for Extra Trees. Predicting the remaining cost and adding the observed subtotal produced 12.72% total-cost MAPE, but remaining-cost-weighted absolute percentage error was 19.28% and remaining-cost MAPE was 29.42%. The paired target-route difference also remained uncertain. Additional nested selection across 14 family-target routes yielded 12.64% total-cost MAPE within the same archive. The historical project-level 90th-percentile (P90) allowance was 35.47%; separate training/calibration/evaluation splits achieved 76–98% coverage with empirical P90 allowances calibrated on disjoint records. For the largest-area holdout, remaining-cost weighted error reached 46.74%, and the 35.47% historical allowance covered only 62% of cases. The selected extract differed from the other records in our 419-record research archive. Field timing and project dates were unavailable. The results support an evaluation framework, not demonstrated early-stage forecasting accuracy or a transferable contingency rate.