This study highlights thermal underperformance in key spaces of a vernacular granite masonry building in Portugal, where winter monitoring revealed critically low air temperatures (9.5 °C in the bedroom at 06h30), failing adaptive comfort standards despite passive strategies like thick walls and wood stoves. A localised analysis of external walls and slate roofs evaluates agglomerated cork insulation (5 cm 10 cm) through simplified thermal calculations. Results show 10 cm cork reduces wall U-values by 82 % (0.387 W/m²·K) and roof U-values by 93 % (0.439 W/m²·K), while 5 cm balances insulation (0.658 W/m²·K) with retained thermal mass. Long-term data correlates inherent passive designs, namely thermal mass from granite walls and shared party walls, with limited buffering capacity during extreme cold, necessitating targeted retrofitting. Despite moderate solar gains and stove heating, the building’s thermal inertia proves insufficient without intervention. The findings reveal context-sensitive retrofitting: thicker cork for stable climates, moderate layers for regions requiring thermal mass. By aligning cork insulation with traditional strategies, this approach enhances energy efficiency without compromising heritage integrity, supporting SDG 11. Future work should integrate dynamic simulations to optimise solutions for vernacular architecture.
Khei et al. (Wed,) studied this question.