According to Vaastu, the movement of energy through a 4-sided building is similar to the flow of energy across the Earth. In Vaastu Shastra, it is believed that 'prana' or positive energy flows into the house early in the morning from the North-East direction and meanders towards the South-East and North-West corners before heading out through the South-West corner at night.
The main aim of Vaastu Shastra is that humans should strive to absorb positive energy or 'prana' throughout the day as it is beneficial to our bodies and our health. So in Vaastu, the layout plan of a house is based on the position of prana during the day and the functions of each room. Thus, the rooms that are mostly used in the morning like the Pooja room, Bathrooms etc are placed in the North-East and the Bedrooms to which we retire at night are placed in the South-West.