A Parametric Simulation-Integrated Framework for External Insulation Evaluation in Early Phase Design Decision-Making

Energy burden is one of the major challenges facing Baltimore City, where residential buildings consume more energy than the Maryland state average. This condition is largely driven by the city's aging housing stock and deficiencies in building envelope performance, which result in excessive heating and cooling demand and high energy costs. Building retrofitting, particularly envelope upgrading through the addition of external thermal insulation, represents an effective strategy for improving energy efficiency and reducing household energy expenses. Beyond insulation material properties, insulation thickness plays a critical role in determining retrofit performance and cost. However, effective insulation thickness adjustment and optimization require moving beyond prescriptive code requirements to incorporate project-specific conditions and performance criteria. This study proposes a parametric, simulation-integrated framework for external insulation thickness upgrading that enables efficient, transparent, and user-friendly evaluation during early design decision-making. The proposed framework integrates three interconnected workflows—building energy simulation, parametric construction assembly modeling, and insulation thickness determination—within a unified computational environment. External insulation is incorporated directly into the construction assembly, allowing its thickness to be adjusted parametrically while continuously evaluating impacts on energy performance and cost. The framework supports both code-compliant and cost-optimal thickness determination and enables rapid comparison of alternative insulation materials and thickness scenarios. A residential-scale case study in Baltimore is used to demonstrate the application of the framework and its ability to support informed retrofit decisions. By embedding insulation thickness upgrading within a parametric simulation environment, this study provides a transferable decision-support approach that bridges the gap between prescriptive insulation requirements and performance-driven residential retrofit design.