The Living Roof
What is the purpose?
The urban environment is an ecosystem in itself. With this living roof, BRIT is bringing a functional, native Texas ecosystem back into the built environment. Rather than just looking for plants that can survive in hot environments, BRIT asked the question, “What are the environmental parameters of a roof and what are its analog and native environs?"
Bio-mimicked after a geology formation known as the Goodland Limestone Barrens, BRIT's roof represents one of only a few living roofs in Texas modeled after a true native ecosystem. Prairie barrens ecosystems are characterized by extremely shallow, limestone soils and low water throughout most of the year, perfect conditions for a roof in Fort Worth.
Most importantly, our living roof creates a usable ecosystem in space that would otherwise go unused by the biological community. When it's hot, the living roof also maintains a lower daytime temperature than the non-living roof, reducing heat island effect and insulating the inside of the building. During the winter, the roof insulates the building from the cold. The storm water collection system from the living roof allows for water to be reused for irrigation on the campus and helps to mitigate storm water surges during rain events.
Design and Construction
This ecosystem was not described until 2007, when researchers from BRIT and Texas Christian University began work on the project. As the compositions of these ecosystems were described, planting ideas were drawn up for the living roof, as well as design specifications for the planting medium. Similar to the prairie soil, the characteristics of the growing medium to be used on the roof needed to be defined and matched to topsoil with specific soil microbes and the seed bank. A matching topsoil was found and transplanted to the roof from a privately owned site in Cresson, TX.
BRIT's roof sits at a 9.5 degree angle to the south, mostly to facilitate viewing from ground-level but also to promote drainage. Biodegradable planting trays were used to prevent erosion during establishment and allowed for a modular design and easy installment. Each 2’ x 2’ tray was planted with six native Texas species (from a list of 38 total test species) within 7.5 cm of mixed native and engineered soil. The trays were initially grown in a sheltered spot under the tree canopy on the east side of the parking lot and delivered onto the roof using a conveyor belt.