Yesterday, McGraw-Hill Construction held a Green Building  Retrofit conference at the Michigan Avenue Marriott. Environmental Systems Design's  Andy Silverstein and Adrian Smith+Gordon Gill Architects'Kevin Nance  spoke on the greening of the Willis Tower, soon to be the world's largest LEED-EB building. The first step will be renovating the building's exterior by giving it double or triple glazed windows to increase efficiency. At 16,000 windows, that could take a while, but the panel is looking forward to the competition it will create with the Empire State Building  greening.

Adrian Smith + Gordon Gill's Gail Bothwick  said the tower's renovation could lead to more urban agriculture, pedestrian access to downtown, and the greening of the whole city (including the tunnel system). AS+GG created a plan to add mixed use projects and amenities, like schools, downtown to increase density and decrease waste. She presented a vision of green roofs on almost every building. After all, they're already experimenting with the world's highest green roof on Willis: the 8x20 ft garden is home to lady bugs and thriving plants, held down from the wind with netting.