The Tai Chi (Yin-Yang) symbol is a circle split in half, with a thick white part narrowing into a black section which widens towards the white part on the other end. The black part represents feminine energy and the white part represents masculine, as in night verses day, cold verses hot.
The little dots in the center of each thick part, acknowledge that nothing is "all black or all white." There is a little bit of the opposite or polarity in everything, in the same way that men have some female hormones and women have some male hormones.
The black yin part is often associated with environments that are dark, cold, damp, closed in, small, narrow, still and quiet.
The white yang part of the Tai Chi symbol is associated with light, heat, dryness, openess, large, wide, movement and sound.
Just as a mountain is still (yin) and the ocean moves (yang), any environment can be categorized as basically yin or yang and when it gets extreme, it can throw a place out of balance.
As an example, we need wind and water movement as essential aspects of nature, but when the wind and water get extreme we can have hurricanes and tsunamis causing a lot of damage.
There is nothing inherently wrong with a dark space, but if a person lived in a chronically dark space they would get depressed. So the essence of the Tai Chi symbol is the essence of feng shui--to create and maintain balance of these two forces. Within the scope of feng shui, where the same environment can affect people differently, we also have to consider the function of the space.
The value we place on defining a space as yin or yang also has to do with what kinds of activities take place there and what may be appropriate for one location is not for another. As an example, if a residence is situated on a busy street, we can categorize that as "too yang." There is too much energy whipping by the house. It can cause arguments and discord in the house. But if that same structure was a store on a busy street, it can create more foot traffic, visibility, and therefore business. So all the exposure is not "too yang" for a business.
Yin-Yang theory can also be applied to colors, shapes of furniture pieces, even types of sound. As an example, water which makes a delicate tinkling sound compared to a raging river, which would be too "yang" to be relaxing.
Kartar Diamond, owner of Feng Shui Solutions, has been consulting on the feng shui of homes and businesses since 1992. She has auditted thousands of properties and has received very positive feedback regarding the analysis and remedies for environments that were initially deemed too yin or too yang.