- Sustainable architecture is one of the most popular trends today. With dense urban living and less green space available, green walls and roofs are helping to fill that gap. These living structures can be created with vegetation, which helps to absorb rainwater, provide insulation, and lower temperatures while creating a habitat for natural flora and fauna. Green Walls Green Roofs features projects from all over the world, showing how these elements work in various climates. Ranging from the tropical houses in Singapore to inner-city buildings in North America, this richly illustrated book will show you how living architecture can enrich our world.