>>sager: the building sector is the single largest contributor to global greenhouse gas emission with one-third of global energy use taking place in offices and homes, a number that is expected to double by 2030 unless urgent action takes place. the united nations environment programme has done just that: building an energy neutral showcase it hopes will be copied far and wide. >>reporter: the $19 million office facility takes environmental sustainability to a new level... incorporating cutting-edge eco-architecture and energy neutral designs. >>perhaps, most surprisingly, it was built in africa... by local architects and contractors. >>kibaki: it is remarkable that unep and un habitat, both of which are at the heart of global efforts towards sustainable environment and human settlements, are pioneering this milestone project in our region and africa. >>reporter: situated almost 1,800 meters above sea level just south of the equator... nairobi was deemed the perfect location for the new building... as it enjoys warm, sunny days and cool evenings. >>the building's data center benefits