Lots of Vastu sources speak about energy / electric / magnetic forces / ions coming from the north. This is based on the polarities of our north and south pole. 

The Sun has a big impact on all live on earth and is therefore an important factor in how you implement Vastu knowledge when your designing your house or rooms. Lots of sources discuss the benefit and the harm of the different rays (ultra violet and infrared) of the sun.

The Bṛhat Saṃhitā is an old sanskrit text written by Varahamihira (Varaha or Mihira) in the sixth century and contains a variety of subjects including astrology, architecture and gemstones.

When your desiging your living room make sure that you have one couch or chair facing eastwards. Vastu says sitting facing eastward balances thinking.
If your room is very dark, use light colors and hang a big mirror on the wall where there is some sun coming in your house. With the mirror you can reflect back the light and make your room much brighter.

According to Vastu sofas should be placed in the south east, south and west of a room.   

The colors of a room have big impact on the way you feel. Modern science found out that blue for example makes your relaxed red makes you alert, impulsive but also passionate.

What does Vastu say about the entrance of a House ?

According to Vastu the ideal location for a kitchen is south east the direction of the god of fire.

The Sthapatyaveda is one the ancient texts that form the Vaastu Shastra's.