from: http://en.wikipedia.org/wiki/Historic_preservation 03/30/09

Historic preservation or heritage conservation is a professional endeavor that seeks to preserve the ability of older (e.g., "historic") objects to communicate an intended meaning. This meaning is rooted in cultural and social processes that negotiate how the authenticity of the historical object should be expressed. More recently historic preservation has subsumed issues of healthy living, sustainability, and green building to justify the retention of the older built environment.