Duke LEEDS in Parking

Duke University is no stranger to commissioning sustainable structures. With 290 buildings on more than 8,000 acres, the Durham, NC-based University boasts 25 U.S. Green Building Council (USGBC) Leadership in Energy and Environmental Design (LEED) certified buildings. The latest to join the University’s growing body of environmentally responsible projects is the Sands Parking Garage, the first freestanding, single-use parking structure to achieve LEED certification in the U.S.

Prior to the Duke certification, the USGBC had not recognized a freestanding, single-use parking garage as a certifiable building type. Finally, a sustainable standalone parking garage can join the pantheon of sustainable structures.

Challenging Perceptions
Generally, parking structures are considered to have a negative impact on the environment. Apart from housing gas-powered vehicles that produce harmful emissions, large areas of paved surface lots contribute to the heat island effect in cities, altering local weather. At the pedestrian level, parking lots and garage façades can disrupt the continuity of a city block or neighborhood. Impervious pavement absorbs and then releases oil, fuel, road salts, and other fluids that contribute to polluted rainwater runoff.

Recent parking trends indicate that structured garages can positively respond to environmental concerns by providing a significant number of parking spaces in a small site on vertically stacked levels. Grouping parking in this fashion reduces urban heat islands and urban sprawl.

For this precedent-setting project, the University chose RATIO Architects, Inc. and Walker Parking Consultants to design the $35M, 1,900-car sustainable parking garage within its medical research campus. Duke challenged the team to enlighten the USGBC and other sustainable design advocates as to the benefits of adding freestanding garages to the list of LEED certifiable structures. Up to the challenge, the RATIO/Walker Parking team’s design successfully incorporated 31 LEED-NC rating system points and ultimately convinced USGBC to award certification.

Garage Design
From an architectural designer’s perspective, this project offered a unique challenge — creating a structure that is simultaneously sustainable, functional, and an integral part of the existing campus fabric. RATIO’s design used complementary materials and patterned the facility’s façade to emulate fenestration so as to integrate the building into the medical campus context. To assimilate the project site into the heavily wooded campus, native and adapted vegetation were used to restore more than 75 percent of the site to natural woodland. Planted trellises on the garage roof and exterior walls further soften the garage aesthetic.

The architectural style of the Sands Parking Garage respects the University’s design language. Architectural pre-cast concrete, terra cotta wall tiles, and blended stone in an ashlar pattern commonly referred to as “Duke stone” humanizes the large parking structure’s scale. Architecturally distinctive towers call attention to circulation from the facility to the campus and enhance the connection between the garage and the streetscape. Dark-sky compliant LED light fixtures with unique shields maintain ample lighting levels to ensure the safety of students, staff, and visitors using the garage and prevent glare at the street level.

The garage’s functional design takes advantage of the topography. The efficient cast-in-place, post-tensioned concrete structure utilizes an outboard express ramp and flat floor plates, allowing for clear unobstructed views and enhanced security. Entry/exit locations on the ground tier are for University students, staff, and faculty. The garage’s second tier is reserved for University visitors and features a separate entry/exit.

The Sands Parking Garage’s functional design also provides interior access controls at certain levels to maximize future operational flexibility. All of the parking attendant rooms use energy-efficient HVAC and gray-water systems. The cast-in-place structure incorporates several recyclable materials, including recycled steel, fly ash, and ground-blasted slag.

University students, staff, and faculty are given automotive vehicle identification tags for efficient garage access. This identification control system for frequent parkers processes transactions in half the time of traditional insertion cards and about 25 percent faster than proximity cards, nearly eliminating idling at the garage entrance. Upon exiting the facility, visitors use a pay-on-foot system with a central cashier rather than from an idling car — which is increasingly becoming the standard — reducing processing time at exits by 60 percent.

The various green features that helped the Duke garage to achieve 31 points and LEED certification are:
  • It replaced an existing surface parking lot, reducing the area of new hardscape surfaces on campus. Because stormwater from parking facilities tends to have a high level of pollutants, cisterns treat and store gray water for irrigation and sewage conveyance.
  • Green trellis canopies on the roof and green screen exterior walls provide vegetated surfaces to reduce heat-island effect, filter airborne emissions, and provide aesthetic appeal.
  • Rain gardens planted with native plants naturally clean runoff water.
  • Garage accepts discounted parking passes to owners of low-emission, fuel-efficient, carpool, and vanpool vehicles.
  • Energy-efficient LED light fixtures and daylight harvesting reduced energy consumption by 50 percent.
  • Building materials include recycled content and local/regional products.
  • The revenue control systems processes vehicles much faster than traditional systems, reducing vehicle idling.
  • The project’s specified concrete provides high solar reflectance, reducing the building’s heat absorption.
  • Waste generated by the construction process was sorted and partially recycled to reduce landfill waste by 75 percent.
Materials Disposal and Resource Efforts
While the RATIO/Walker Parking team worked diligently to incorporate sustainable elements into the Sands Parking Garage’s design, construction manager Bovis Lend Lease managed the materials disposal and monitored the use of construction resources. The garage project generated 288.36 tons of total construction waste. Of that, 218.12 tons of non-hazardous construction, demolition, and land-clearing construction waste —just over 75 percent total — was diverted from landfills. Based on the total construction costs, the project’s combined recycled content value is 11.8 percent, with 24.3 percent of local material used in the garage’s construction.

The Sands Parking Garage’s waste management plan included using WCA Waste Corporation of North Carolina to haul, sort, and then recycle or send to landfills all of the project’s waste. WCA then followed up with monthly reports to reflect their sorting.

Because the Sands Parking Garage is a large cast-in-place, post-tensioned structure, the project team had to plan early for concrete washout and removal. Trucks were not permitted to wash out at the project site, reducing concrete and water runoff. Concrete trucks with any remaining concrete were sent back to the concrete plant (six miles from the project site), where the concrete was poured and crushed to make gravel. Every truck's concrete was tested just outside the project site to ensure concrete met specifications. In the event an entire truck did not meet specifications, the truck was sent back to the batch plant where the concrete was used to make reinforced concrete pipe, concrete drain boxes, and septic tanks.

As a result of these efforts, Duke’s garage received two exemplary credits for recycled material and waste management.

Duke’s Sustainability Commitment
Sustainability was part of Duke’s mission long before the word became fashionable. In 1993, Duke University adopted a set of design guidelines to direct all future building on campus. The original design guidelines contained many sustainable development principles, including a commitment to planning for 50 years rather than the industry standard of 20 years. In 2003, at the request of students in the Duke University Greening Initiative, the University solidified its commitment to green building, specifically the LEED rating system. Embracing sustainable practices permeates the University fabric:
  • The campus master plan celebrates and protects “the University in the forest.”
  • Each fall, Duke hosts an Eco-Olympics competition for first-year students.
  • Nine full-time staff members are dedicated to sustainability.
  • The University drives sustainable efforts in the community, including DukeEngage, a program that provides community service opportunities in Durham and beyond.
  • Duke University recently signed the American Colleges and University Presidents Climate Commitment, pledging to become a climate-neutral institution in the future.
In addition, the University has made significant commitments to green design and construction: incorporating environmentally responsible design and construction practices are a primary objective on all University building projects. At minimum, Duke strives to have all new construction and renovations LEED certified. Every reasonable effort is made to certify projects at Silver certification or beyond. The University has been successful in their endeavors, as all new constructions since the West Edens Link project have been registered with the USGBC.

As Duke University continues to expand in population and footprint, any new project designs must be functional, aesthetically seamless, and sustainable. The challenges parking designers face in “greening” a parking garage are great, but through this project, Duke University and the RATIO/Walker Parking team have shown that it can be done.

Paul O. Manning is director, Project Management, for Duke University. William A. Browne, Jr., FAIA, LEED-AP, is a principal for RATIO Architects, Inc.