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.
On avarage the light that comes from the sun takes 8 minutes and 19th seconds to reach the earth. (This varies because the earth doesn't make a perfect circle but an elips arround the sun).
The power of (bright) sunlight on 1 square meter on sealevel is 1000 w. Of this 1000 km 552 w contains Infrared, 445 vissible light, and 32 w is UltraViolet.
Current science found out that ultraviolet sunrays helps to start a chemical proces in your body that produces vitamine D, Ultra Violet is also antsceptic (kind of purifier, that can kill bacteria, and for example is also used to purify water). To much Ultra Violet is dangerous, it burns the skin. The effect of UV rays of the Sun on the planet earth differce per lattitude on planet earth. (The more north or south you are). The beneficial UV sunrays are more beneficial at the tropics than at the artic. If your skin is exposed to long to the sun the vitamin D fades away.
Sources:
Sun Wikipedia
Infrared Wikipedia
Vitamin D Wikipedia