Among the green elements which have come into use over the last twenty years to soften the impacts of buildings on the environment are green roofs. More recently this concept has been extended to vertical surfaces with the use of green walls, both interior and exterior. Both of these elements have potential and both come with caveats -in terms of their value to the environment and their relationship to the buildings on which they are located. A well designed green envelope can make a contribution to a sustainable building; a poorly designed green envelope can seriously damage a building. This course will examine the many choices available for designing, constructing and maintaining green roofs and green walls, the pros and cons of each in any given location from an environmental standpoint, and the critical things to be aware of as you design and construct them.