Engineered bioclimatic responses in ancient settlements: a case study

The Mandya district of Karnataka, India, houses a unique Jain settlement constructed about 1000 years ago. Recent excavations by the Archaeological Survey of India (ASI) indicate a high degree of engineering skills among the builders of this settlement. Adapting to heat-stresses in a region where the Monsoons often failed was and is still a matter of concern. Ingenious methods were adopted to modulate bioclimatic responses to maintain thermal comfort indices. The Aretippurians used composite building fabrics which modulated heat transfer to the interiors. Indeed, the thermal transmittances for these composite fabrics were low to moderate for both the temple complexes as well as the dormitories; these were 0.27 Wm^-1K^-1 and 0.23 Wm^-1K^-1, respectively. A site visit revealed that a unique and engineered micro-climate was also made to prevail on this hilltop settlement housing several hundred Jain settlers. A granite skirted reservoir was indeed the pièce-de-résistance promoting hydraulic air-conditioning for eight months of the year around the premises with copious winds blowing over a large and exposed rain-fed reservoir. This fanned chilled air across the open plan temples, courtyards, and lived-in areas. This paper explores bioclimatic responses for around 120 residents to the prevailing indoor settings modulated by an engineered microclimate. This was possible because of the staggered layout, unique building forms, use of mixed building fabric, and carefully chosen glazing ratios which yielded salubrious settings. Clearly, this entailed a complex interplay between the intercepted solar insolation, structure-driven turbulence, and the transfer of heat across the original composite walls within and around the complex, requiring a systematic experimental as well as modelling study. The experimental part of the project involved the calculation of the thermal transmittivity across the walls made up of fired bricks, granite, and limestone, and the theoretical part involved the use of appropriate software to reconstruct air flow and heat distribution across floors, walls, and ceilings to proxy the original flow pattern yielding the comfortable PMV (predicted mean vote) and PET (physiological equivalent temperature) values within these premises. This exercise may well lead to further explorations on indoor comfort adaptations in tropical settings with the use of many edifying vernacular idioms in ancient settlements which prevail even in modern layouts.