As a principle to reduce the use of energy and use of natural resources, rainwater harvesting has been encouraged in all houses through the provision of circular Ferro cement rainwater harvesting tanks supported on brick legs about 60cm high. The capacity is 1200lts. In Kerala we have an average of 140 days of rain. On these days without relying on the municipal water supply the inhabitants can use this water. The water tanks of corresponding houses are to be provided on its corresponding terraces or on ground level for units in the ground floors.