• El Cuartel de Ballajá, Vegetated Green Roof  
While the green roof market in Puerto Rico has grown by 25% in recent years, El Cuartel de Ballajá is the first historic structure to feature one.

    Credit: photo: Edmundo Colon-Izquierdo

    El Cuartel de Ballajá, Vegetated Green Roof While the green roof market in Puerto Rico has grown by 25% in recent years, El Cuartel de Ballajá is the first historic structure to feature one.

On the rocky edge of San Juan, where a finger of land stretches into the Atlantic Ocean, sit two of the most historic structures in Puerto Rico. The better-known of the pair is Fort San Felipe del Morro, the 16th-century fortification that is now a UNESCO World Heritage Site. Not far away, however, is the lesser-known El Cuartel de Ballajá, a large military barracks dating from the 1850s. With its striking, formal courtyard and Neoclassical arcades, one would never guess that the building is now a platform for groundbreaking sustainable technology.

Puerto Rico has a long history of poor urban planning. Currently, municipalities can make land-use decisions without the benefit of any overarching master plan, leading to a mishmash of development and sprawl. A recent report on Puerto Rico’s land use published by the EPA reported that “if current practices continue at the same rate they have in the last five decades, the whole island of Puerto Rico will become a suburban megalopolis in less than 75 years.”

Yet a growing number of architects and environmental engineers are working to stem that tide through historic preservation, adaptive reuse, and green building. The Cuartel de Ballajá project is a prime example. Two decades after the Puerto Rican government began restoring and adapting the formerly abandoned building for cultural purposes, the Cuartel now houses the Museo de los Americas, music and dance studios, and other educational and cultural organizations.

All of this was welcome, but given the Cuartel’s prominent location as a tourism gateway for the rest of the island, government officials realized that more could be done. Led by the Puerto Rico State Historic Preservation Office, the Cuartel is in the process of a complete energy-saving retrofit to include a solar array with more than 700 photovoltaic panels, mechanical and electrical system upgrades, and a new air-conditioning system.

The showpiece, however, is a 24,000-square-foot vegetated green roof. Designed by Edmundo Colón-Izquierdo, senior designer for ECo, a San Juan–based architecture and engineering firm—with David Aponte, an environmental engineer and Green Roof Professional and a principal of PRGD, serving as an engineering consultant—the roof is one of the largest ever built in Puerto Rico and the only such roof installed on a historic building in that country.

The green-roof market in Puerto Rico has grown by about 25 percent in recent years, according to Aponte. Still, when general contractor Jorge Castellanos of WTI assembled a project team, Puerto Ricans knew little about green roofs. “In Puerto Rico, the lack of understanding of what green roofs are and can be makes most people immediately think of a green roof as just grass,” Colón-Izquierdo says. The designers convinced their client and the contractor to develop a much more ambitious scheme that includes a complex plant palette and a 1,800-square-foot wetland pond that serves as water storage and an on-site irrigation source. “Our goal was to have a roof that worked to cool the building and could also be an almost self-sustaining ecosystem on its own,” Colón-Izquierdo says.

  • Credit: Courtesy of ECo

The green-roof structure includes a thin, protective mat-and-drain system, and about 4 inches of growing medium comprised of a lightweight soil aggregate (manufactured by Rooflite) mixed with local compost and pea gravel. The designers created this mix to stretch the amount of Rooflite material used and to cut costs because of the fairly tight budget, Colón-Izquierdo says. The addition of gravel required careful calculations of the saturated weight and eventual distribution.

The planting palette consisted of drought-tolerant vegetation, an unexpected choice, given Puerto Rico’s tropical climate. Yet the site’s microclimate and shallow planting environment required a range of succulents—some from as far away as Israel, that would be likely to survive. The irrigation system has a sensor that, when the roof reaches critical drought conditions, takes water from the wetland and uses it for irrigation. Circulation systems aerate the water and provide irrigation for a planted living wall. The wall, in turn, serves as a biofilter for the lake, which is stocked with fish.

Observers say that the work has relevance for all of Puerto Rico and beyond. Last November, during its annual convention, AIA Puerto Rico offered a seminar and tour of the project in order to showcase its systems and share lessons learned with local architects.

“The Cuartel de Ballajá project is very significant to Puerto Rico,” says Jaime E. Sobrino, AIA, immediate past president of AIA Puerto Rico. “Its execution required surpassing technical difficulties, regulations, code compliance, historic preservation, costs, and other issues that were successfully addressed.”

Aponte hopes that the project will help people realize that green roofs offer more than energy efficiency. “This project shows that green roofs are more than an R-value,” he says. “There are the ecological benefits, the water-resource benefits, the impacts on the heat-island effect, and, most important, bringing nature back to life. I hope we’ll see a lot more architects play around with this scenario in the near future.”