Four-Star Certified Pilot Project

Location: Pittsburgh, Pennsylvania
Project Size: 2.9 acres
Project Type: Open Space - Garden / Arboretum
Site Context: Urban
Former Land Use: Brownfield
Terrestrial Biome: Temperate Broadleaf & Mixed Forests
Budget: $15,000,000
photo by Denmarsh Photography, Inc.

Project Overview

The Center for Sustainable Landscapes (CSL) at Phipps Conservatory and Botanical Gardens was designed to be the first project in the world to simultaneously achieve LEED Platinum, SITES four-star certification, and The Living Building Challenge. Built on a previously paved-over city maintenance yard and documented brownfield, the nearly 3-acre site supports a new 24,350-square foot education, research, and administrative building; manages all sanitary waste and a 10-year storm event on site using a range of green infrastructure strategies; has successfully reintroduced 150 native plant species; and is designed to be net-zero energy and water. The CSL is open to the public and its building and landscape performance is being extensively researched and monitored to inform the design and construction of similar projects that restore ecosystem services, generate their own energy, and clean and re-use their own waste water.

Regional Context

The CSL is located in Pittsburgh, Pennsylvania, a temperate region characterized by rolling hills and steep slopes, river valleys, clay soils, a legacy of resource extraction, and exceptional biological diversity in its mixed-mesophytic forests. The average annual rainfall is 39 inches. Center for Sustainable Landscapes green roof with Tropical Forest Conservatory

SITES Features + Practices

The most notable strategies we used to earn SITES credit include: development on an existing brownfield; managing stormwater on site; using primarily all native plants; responsibly sourcing landscape materials from appropriate distances and origin; and sustainably managing the project's waste stream.

To achieve net-zero energy, on-site solar photovoltaics are used to meet 99 percent of the CSL’s annual energy demand, a single wind turbine meets about 1 percent, and 14 geothermal wells significantly offset the building's HVAC energy requirements. The CSL was also designed to use 50 percent less energy than a comparable conventional office building. To achieve net-zero water, all grey water and black water is treated on site using passive systems and UV filters, then reused as toilet flushing water or converted to distilled water for orchid irrigation. The 2.9-acre site's severely degraded soils were almost entirely paved over but can now manage a 10-year storm event on site (3.3 inches in 24 hours).

A 4,000-square foot stormwater lagoon, surrounded by a boardwalk, is central to the landscape design. The lagoon is fed by captured runoff from the neighboring 12,000-square foot Tropical Forest Conservatory roof, is stocked with native wildlife, and also feeds three additional water features that draw in visitors and provide pleasant background noise.

Additionally, 150 native plant species have been reintroduced to the 1.5 acres of new green space. Underground storage also enables the project to harvest an estimated 500,000 gallons of stormwater runoff annually from the roofs of neighboring buildings and re-use it as irrigation water in the conservatories.


The integrative design process was invaluable. The challenging site constraints and requirements —degraded, compacted, and contaminated soils; steep slopes; limited access; and designing to the highest goals of LEED, SITES, and the Living Building Challenge — required an interdisciplinary team to assure a successful outcome. The integration of building, landscape, circulation, and abrupt elevation changes was exceptionally done, as was weaving together a complex underground network of infrastructure to accommodate the movement, treatment, and storage of storm and sanitary water, as well as geothermal wells.

Local health codes do not allow Phipps to capture rainwater and treat it to potable water standards for use in the building, so the project relied on municipal water supply for potable water needs and sought an exemption from the Living Building Challenge on this aspect of being a net-zero water facility. The project is required to perform bi-quarterly water quality testing by an EPA-certified lab to prove the effectiveness of the onsite sanitary treatment system.

Maintenance + Stewardship

Pursuing the trifecta of green building certifications - LEED Platinum, SITES four-star certification, and the Living Building Challenge - has garnered a lot of attention from the design and environmental community. As part of our educational mission we regularly host tours and guests, and actively engage regional stakeholders to promote the merits of the CSL site to help inform other like-minded projects.

As a public garden, Phipps Conservatory and Botanical Gardens is well equipped to handle the maintenance requirements of building and landscape in house. Phipps' CSL and campus maintenance policies adhere to the highest standards of sustainability and are reviewed annually to assure effective execution and inclusion of current best practices.

Landscape performance is being closely analyzed to assess the effectiveness of the CSL's green infrastructure strategies. Phipps is working in concert with Civil and Environmental Consultants to monitor performance of the rain gardens and green roof to absorb and filter stormwater. Decagon brand sensors take measurements every five minutes on a range of performance variables and several on-site data loggers communicate the data to a server every four to six hours. We are also working with Ecological Landscape Management and Earthfort Laboratories to monitor the effectiveness of compost teas as soil amendments for building soil biology and aiding plant establishment in developing landscapes. Phipps is the project lead on all of these programs and the CSL's building performance is also being monitored in collaboration with the University of Pittsburgh and Carnegie Mellon University.

Site Challenges

The existing CSL site posed a great challenge. The soils were severely degraded and it was nearly entirely paved over except for the steep bluff slopes along the entire northern perimeter. These northern slopes were prone to erosion and filled with construction spoils and urban fill soils. The southern and western perimeters are bound by steep forested slopes that are part of neighboring Schenley Park. The site is accessible from only one entry drive to the east and it is essentially hemmed in by steep slopes on all sides. Creating a pedestrian-friendly and vehicle-accessible site, while also accommodating a new 24,350-square foot building, and making the entire site net-zero energy and water, was exceptionally tricky. Portions of the site were also characterized as brownfield due to leaking underground storage tanks owned by the site's former occupant, the City of Pittsburgh Department of Public Works.

Project Goals + Successes

The top goals of the CSL project were to meet The Living Building Challenge, SITES four-star certification, and LEED Platinum standards; to showcase Pittsburgh and Pennsylvania talent, innovations, and materials; to create a healthy, productive, biophilic work environment for Phipps staff; and to serve as a center of research on sustainable building and landscape performance.

Pursuing SITES aligns with the mission of Phipps as an environmental organization. The Conservatory has a legacy of pushing the envelope in green building and site design, and has earned a reputation as one of the most sustainably operated public gardens in the world. The SITES guidelines informed design from day one to meet the lofty standards of SITES four-star certification.

LEED NC Platinum has been achieved, and The Living Building Challenge certification will be another milestone on the project. The Pittsburgh- and Pennsylvania-based design team was also a condition of the owner to showcase regional talent and become an accomplishment of which the region can be proud. Overall, achieving a net-zero water and energy facility on a former grey- and brownfield while overcoming site constraints, such as limited access, degraded soils, and steep slopes on all sides, was a great success. Additionally, the integration and accessibility of building, landscape, circulation patterns, and abrupt elevation changes is exceptional.

Lessons Learned

Simultaneously seeking LEED Platinum, SITES four-star certification, and the Living Building Challenge is a valuable exercise in the rigorous documentation required to vet all project materials for sourcing requirements. We have learned to allot more time than originally projected for vetting across three rating systems.

Project Team

Phipps Conservatory and Botanical Gardens

The Design Alliance

Landscape Architect
Andropogon Associates


Civil Engineer

Construction Manager
Turner Construction

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