When people envision green buildings, they typically think of state-of-the-art, energy-efficient, shiny, new buildings. Existing building stock is written off as inefficient, only good for demolition or recycling, and best left to heritage planners and architectural conservationists. Things are starting to change though. The Leadership in Energy and Environmental Design (LEED) Green Building Rating System recognizes the tremendous amount of energy embodied in existing building stock. It awards credits to those who reuse existing building structures.