Buildings represent the major energy consuming sector in India. Sustainable and climate responsive architecture offers possible solutions to this high energy demand. Vernacular buildings, in contrast to modern 20th century buildings, are more climate receptive to the environment and are based on principles evolved over many generations. The traditional architecture of housing in Chettinadu, Tamil Nadu, India is known for its use of natural and passive methods for a comfortable indoor environment. However, it has not been proved by a detailed and quantitative evaluation method so far. A summer field study was thus conducted to investigate the indoor environmental conditions in such housing. The objective of the investigation was to understand the solar passive features in Chettinadu housing by qualitative and quantitative analysis of thermal comfort parameters. This was undertaken by continuously monitoring the indoor and outdoor conditions using a custom made instrument called the "Architectural Evaluation System". The results showed that the natural and passive climate control system of this traditional housing style provides a comfortable indoor environment irrespective of the outdoor climatic conditions.