505 Brannan is a 6-story, 130,000 ft2 office building with a 50,000 ft2 underground garage. The building design includes provisions for expansion to 17 stories and a total of 430,000 ft2 of office area.

Mechanical systems include a unique underfloor air distribution system with all variable speed fans, zero reheat, zero damper losses, and warm supply air to maximize free cooling. This is the most efficient all-air HVAC system possible. An all variable speed water-cooled chilled water plant and condensing boiler heating system serves the air handlers. All systems are designed to be expanded when 11 stories are added in the future.