Thermal performance evaluation of vernacular roofing systems in contemporary buildings

Abstract

This study explores the thermal performance of three vernacular roofing systems—Filler Slab, Hourdi Roof, and Jack Arch Roof—in the moderate climate of Bangalore, India. The objective was to evaluate and compare the thermal performance of these roofing systems under peak summer conditions. Temperature data were continuously monitored during the hottest month, April, using an eight-channel data logger that recorded outdoor air temperature, indoor air temperature, and roof surface temperatures. To evaluate thermal performance, two indicators were used: Maximum Temperature Difference (MTD), which measures the largest temperature difference between the outer and inner roof surfaces, and Temperature Difference Ratio (TDR), which reflects the roof’s ability to reduce the impact of outdoor temperature fluctuations. The results showed clear differences in the thermal behavior of the three roofing systems. The Filler Slab Roof achieved the highest average TDR (0.451) and MTD (25.85°C), indicating the strongest resistance to heat transfer and the greatest ability to moderate external heat gains. The Jack Arch Roof also performed well, with a comparable TDR and MTD. The Hourdi Roof, however, recorded the lowest TDR and MTD, suggesting a comparatively lower capacity to resist heat flow under the climatic conditions studied. Overall, the findings indicate that the Filler Slab Roof offers the best thermal performance among the three vernacular roofing systems. These results highlight the continued relevance of vernacular roofing strategies and their potential application in contemporary sustainable architecture and energy-efficient building design.