Many challenges are facing Egypt currently; two of them are water & energy shortage. Egypt is now in water scarcity level, and non-renewable energy sources have become insufficient for the needs of many sectors. Architectural design could contribute to these problems through Green Architecture concept, which encourages conservation and efficient use of such resources. Furthermore, since architects spend a lot of time at the early stages of architectural design doing trivial repetitive tasks, then the computer role as designer or assistant would be a precious aid to them. Generative Design Systems are computer applications which could produce automatically many alternatives of 3D digital models with different design solutions, depending on the designer's predefined rules. This book presents a new approach towards Green Architecture, by using the real capabilities of the computer through the Computer-Aided Architectural Design concept, to apply the Green Architecture principals on 3D digital models of office buildings generated automatically, based on the designer's input using a friendly simple GUI. This would solve the mentioned problems, beside saving architects' time & effort.