Installing a green roof is an essential part of the City of Chicago’s Sustainable Development Policy, which promotes strategies that help eliminate rainwater from flowing into the overburdened sewer system. While green roofs are a successful part of green building and sustainable design, they often can’t be seen or appreciated, which presents challenges to businesses wanting to publicly promote their sustainability efforts.
When RTM was awarded an urban retail project in Chicago, the design team came up with the idea of creating a living wall in place of a green roof, which was ultimately pitched to the City of Chicago. The team proposed to design a living wall on the side of a building to give the façade a softer look since the building is adjacent to a neighborhood. The design allows rainwater to be captured in an underground cistern and then used to irrigate the living wall. In addition to the beautification benefits for the neighborhood, the design team’s calculations and estimations also determined that a living wall is a cost-effective alternative in lieu of providing a green roof.
After meetings with the city’s Green Projects Administrator and stormwater engineer, the RTM team was given the green light on the concept of the living wall and now have entered the design phase of the project.
The biggest challenge the team faces is that they must design not only the underground rainwater harvesting system, but they also must design a separate underground water detention system. Both systems must work together in complex coordination to accommodate an overflow situation where one vault will flow into the other. Additionally, in the off-season, water won’t need to be used for irrigation so all collected water will be diverted into the detention system.
The living wall also will require that the right plants be put in the right location, and considerations such as what plants work well in shade or in direct sunlight must be taken into account. By following these best practices, the living wall will be self-sustaining in the long term.
The construction phase of this project is slated to begin by this fall.