the other large exporters are hvac and building control systems followed by biofuels green consumer products air and water purification technologies green chemicals and organic food brookings institution lb prominent city indexes increasingly include sustainability as a factor of attractiveness or specifically rank cities by their greenness including the siemens green city index forbes world s smallest cities the chicago tristate metroregion has the potential to build on its reputation as a leader in innovative architecture and green building design to sustain this reputation there is a need to increase the scale of efforts like the city of chicago s green roofs and alleyway repaving initiatives