VastuShastra can be typically referred to be as the backbone of Indian Traditional Architecture which involves the planning and designing of a space in accordance with the cardinal directions. Vastu is basically a science of directions which manages to combine the five elements of nature typically referred as the Panchmahabhutas (Prithvi, Jal, Vayu, Tej, Aakash &Mahatatva) with the cosmos. The designing according to the vastu shastra is based on utilizing the different types of energies available at free of cost in the atmosphere.
The designing in relation to the vastu shastra takes up directions in accordance, therefore buildings designed as per the vastu shastra have proved to be climate responsive in nature hence, also limiting the use of mechanical energy.
Since Vastu Shastra manages to bridge the relationship between the man, material and the nature, therefore, according to this logic of the vastu shastra, the building design plays a major role in defining the health and the well being of the persons residing in the building.
As directions play a major role in the designing the building according to the vastu shastra, therefore, the theory of vastu shastra is totally rational and permanent and logical in nature since the directions are also permanent and unchangeable in nature.