Building materials are the primary factors along with socio-cultural structure, climate, technology and economy that influence architectural forms. Vernacular construction techniques using Kadapa stone are used in the hot semi-arid region of Kadapa, India. However, no quantitative or qualitative evaluation has been used to establish its thermal performance. This study compares the indoor environmental conditions of vernacular dwellings with kadapa-lime roof and a modern house with RCC roof using qualitative and quantitative analyses. Both the houses have walls made of 0.6 M thick Kadapa stone. Field measurements of indoor air temperature and humidity are analysed and compared based on adaptive thermal comfort model in the vernacular house and a modern house simultaneously. A post-occupancy evaluation is performed using a questionnaire survey to compare the outcomes of the field study’s findings. Results of the study are plotted based on adaptive thermal comfort model with an indoor operative temperature range of 28.95–33.71 ℃. Temperatures inside the vernacular house are the closest to the comfort range with a deviation of only 0.1–1 ℃ above the upper comfort limit whereas the temperatures inside the modern house have a deviation of 1–3.6 ℃ above the upper comfort limit. All the occupants in modern houses voted for uncomfortable or very uncomfortable conditions and 57% of the occupants from vernacular houses voted for slightly comfortable and comfortable conditions. It is also found that RCC roof slabs are not an appropriate choice for roof construction in hot semi-arid conditions as it did not perform well thermally as compared to the kadapa-lime roof. Vernacular buildings with local materials like Kadapa stone, lime concrete roof and other passive strategies helped in achieving close to comfort conditions during the summer time in the hot semi-arid climate.