Hungary’s building stock, mostly built in the nineteenth and twentieth centuries, consists mainly of traditional masonry, including bricks with varying quality and material properties. Today’s renovation regulations require strict thermal performance, but the thermal and material characteristics of older structures are often unknown, making it hard to verify energy compliance. This research focuses on analyzing historical masonry bricks from Hungarian brickworks from the early twentieth century, with the goal of creating a detailed database in the future to help understand and preserve the energy performance of heritage buildings. Key thermal properties such as thermal diffusivity, conductivity, and volumetric heat capacity were measured using the modified transient plane source method. The bricks’ density and material composition were also studied, with detailed analysis performed using SEM-EDS (Scanning Electron Microscopy with Energy Dispersive Spectroscopy). The study also compares traditional bricks to modern masonry elements, showing how advancements in material engineering affect thermal behavior and performance. The results provide important data for energy simulations and digital modeling, helping architects and engineers make better decisions during renovations and energy upgrades of both historical and modern buildings. The research highlights the importance of using material-specific data in building energy calculations and provides a basis for future analyses of masonry in the context of changing energy efficiency requirements.