Category: New Extensive, 2003

Project: 901 Cherry Offices for Gap Inc., San Bruno, California

Award Winner: William McDonough + Partners

Gensler & Associates, Executive Architect and Interior Design Architect
William Wilson and Associates, Construction Manager
Hargreaves & Associates, Landscape Architect
Paul Kephart, Grassland Specialist
Ove Arup & Partners, Engineers
Swinerton, General Contractor

Located in the hills above San Francisco International Airport, 901 Cherry Offices for Gap Inc. was designed to blend in almost seemlessly into its steeply sloping savannah foothills site. Designed first and formost as a great place to work, the building was completed in 1997 and incorporates diverse elements including a café, a fitness centre, a conference facility and other amenities. Its defining sustainable design feature is a 69,000 square foot green roof covered in native grasses and wildflowers. The design of this undulating green roof had a fundamental effect upon the building's design profile, its physical relationship to the surrounding environment, its mechanical performance, acoustical and thermal comfort and stormwater management. The system utilizes an American Hydrotech waterproofing membrane, and 6 inches of growing medium. Studies showed initial costs to be about 130% of a conventional base case, net first costs approximately 185% and annual operating costs of just 70% of a conventional roof. Annual energy cost saving projections demonstrated a simple payback of 11 years. Any excess rainfall is recycled back onto the roof for irrigation purposes. The mass of the roof attenuates sound transmission by up to 50 Db, providing an acoustic barrier to the air traffic above. Like other native grasslands, the roof is a highly self-sustaining ecosystem requiring minimal annual maintenance. The green roof not only allows the offices to blend into the landscape, but it also atones for the very space occupied by the building - for a bird flying overhead, nothing has changed!