A Window into Scotland’s Heritage: Evaluating the Role of Sash and CaseWindows in Historic Preservation and Sustainability

This paper explores the intersection of heritage preservation and sustainable retrofitting through a thermal performance analysis of Scotland’s iconic sash and case windows. Rooted in the country’s architectural history, these windows are widely recognized for their aesthetic and cultural significance but face increasing scrutiny under modern energy efficiency standards. This study examines how retrofitting techniques, particularly the application of advanced vacuum glazing, can improve thermal performance without compromising the historic integrity. A positivist, quantitative approach was employed within a case study of a typical Scottish detached house to simulate and evaluate different window types against selected energy efficiency metrics. A Building Information Model (BIM) of the case study was developed in Autodesk Revit 2025, incorporating five window configurations: (1) original single-glazed sash; (2) new sash with double glazing; (3) new sash with vacuum glazing; (4) refurbished sash with vacuum glazing; and (5) a modern tilt-and-turn window. The BIM was populated with material and energy parameters, enabling annual simulations of energy use and heat transfer to evaluate each configuration. Energy simulations were conducted using the Autodesk Revit Insight 365 plugin, which assessed thermal performance by analysing annual energy use and heat transfer rates to evaluate the effectiveness of each glazing option. A comparative analysis was performed using u-values and annual thermal performance data. Results show that vacuum-glazed retrofits reduce heating demand by over 70%, achieving U-values consistent with modern regulation (1.4 W/m²K). However, these high-performance refurbishments slightly increased cooling needs due to reduced ventilation. The findings echo existing concerns about traditional single-glazed sash inefficiency while reinforcing the potential of smart retrofit solutions to reconcile heritage conservation with sustainability goals. Despite limitations such as modelling assumptions, limited variety, and climatic variability, this research provides a strong foundation for the future use of vacuum glazing in heritage windows. The results support retrofitting as a compelling strategy to reconcile the preservation of built cultural heritage with the urgent need to reduce carbon emissions in the built environment.