Pop-Up Pavilion

Divided into east and west campuses, St. Elizabeths Hospital opened in 1855 and had been been in operation for more than 100 years when it was closed in 1987 due to disrepair, despite its status as a National Historic Landmark. As part of the master plan to transform the former mental hospital into an inhabitable headquarters for the US Coast Guard and reconnect the site to the surrounding Congress Heights neighborhood, the District of Columbia Department of General Services held a design competition for an interim pavilion. Davis Brody Bond won, and here architect Cody McNeal explains how the St. Elizabeths East Gateway Pavilion will create new space for food trucks and open-air markets and still use no more energy than it makes.

gb&d: The planned pathways and sloping green roof planes of the pavilion encourage movement through the site. What was the idea behind this?

Cody McNeal: The hospital was closed off to the public for so many years, and when DC finally opened the gates, people immediately began circulating through the site to take shortcuts to the metro station. We asked ourselves, ‘Where are people coming from, where are they going, and how can we best facilitate that?’ With the relatively straightforward program in hand, we decided early on that the pavilion should retain a light footprint, keeping as much existing open and green space accessible to the public as possible. By lifting the land, we created an occupiable roofscape that shelters an outdoor marketplace, enclosed restaurant space, a farmer’s market, and food truck parking beneath.

gb&d: The pavilion incorporates a few out-of-the-box approaches in reducing energy and water use. Tell us about those.

McNeal: With the client embracing our net-zero strategy, this project provided opportunities to implement some sustainable measures that we’ve only toyed with on other projects.

The net-zero energy story starts with a cogeneration plant that runs on spent food oil from the enclosed restaurant space in addition to the food trucks that also serve the pavilion. Many kinds of food cooking oils, once filtered and used as biofuel, often contain more energy than petroleum-based gasoline. The cogeneration plant will provide enough energy to run the entire site and possibly excess. Waste heat from the cogeneration plant will allow for radiant slab heating for all enclosed spaces, providing a significant savings over installing a traditional HVAC system.

Rainwater will be captured on the roofscape, filtered, and stored in cisterns that sit below the market level. The cisterns will slowly release water throughout the year to avoid inundating the local ecosystem. We also plan on installing low- or no-flow urinals and self-composting toilets, eliminating the need to tie into the sewer system. Greywater and excess rainwater will be filtered naturally through a series of bioretention terraces at the north end of the site.

gb&d: The pavilion is temporary. How did that affect material selection?

McNeal: We chose to maintain modularity in our materials so that they can later be disassembled and repurposed elsewhere. Durability is also a must in a public environment, but shouldn’t come at the expense of one’s sensory experience. Ultra high-performance concrete panels provide us with a very modular, incredibly durable material but still offers an inviting texture. We’re working with Lafarge North America to incorporate their product, Ductal, a unique material that is extremely strong in compression because of its fiberglass reinforcement. The panels are only about an inch thick but allow us to span greater distances without using secondary framing, making them an economic choice.

We are also incorporating a lot of wood in the design of the pavilion. The master plan involves enlarging an avenue at the expense of several large, old trees, and we intend to upcycle the fallen trees to fabricate planking and sheet materials for use as both interior and exterior finishes. Finally, we are considering the use of salvaged materials such as concrete and brick from the demolition of historically non-contributing buildings on-site. These materials could be crushed up and repurposed as aggregate in the structure’s concrete or as loose gravel on the pavilion’s pathways.

gb&d: How do you imagine that the pavilion will impact the community over its lifespan?

McNeal: Historically, the Congress Heights community has been underserved with an unemployment rate that is higher than most other neighborhoods in the city. We hope to instill them with a sense of optimism in the form of dynamic public space that promotes their community activities and economic inclusion. To that end, the pavilion will include a 4,000-square-foot farm-to-table restaurant space that will allow local entrepreneurs, with the help of the pavilion’s operations team, to temporarily open their own sustainably sourced restaurant on a rotating basis.