When you step into an ancient home, you feel fresh cool air all over. Have you ever wondered, how can such houses be so cool without air conditioning? The people in those days focused on building houses that adapt to the surrounding climate. For example, in warmer climatic regions they made stepwells and enclosed ponds adjacent to the the main building. The evaporating water from them cooled the surrounding air, making the building interiors pleasant. And many such time tested techniques form the backbone of passive house construction.