Renzo Piano, in collaboration with Mark Cavagnero Associates, has unveiled plans for a new mixed-use tower for San Francisco. Assuming it goes ahead, the building will seek LEED Platinum certification, the leading green building standard's highest award.

Slated for San Francisco's Transbay neighborhood, 555 Howard would rise to 36 stories and though one building, would actually look like two large towers and one smaller tower lined up in a row.

Inside, the building would include 69 residential units (15 percent of which will be rated "affordable"), a 255-room luxury hotel, meeting and ballroom facilities, a spa and fitness center, and a restaurant. 555 Howard would also be topped by a bar and cafe and a rooftop garden, offering choice views of the city to the public.

Though we expect the sustainable design to be relatively significant on this build, details are slim at this early stage.

A representative told us that the tower would offer excellent public transit links and bicycle facilities. Certainly, other LEED Platinum projects we've seen have boasted impressive energy-efficiency, so features like grey water recycling, low-flow taps, and an energy-efficient building envelope seem likely.

555 Howard is being developed by Pacific Eagle Holdings. As of writing, it's awaiting planning permission.

View gallery - 6 images