What are green roofs, and what are their advantages?
A green roof is a special type of roof that has plants instead of traditional coverings such as concrete slabs or shingles. There are various types of green roofs, including intensive (soil depth greater than 6 inches) and extensive (soil depth less than 6 inches). Green roofs provide many advantages, such as:
- Stormwater runoff reduction
- Reducing energy consumption by HVAC systems
- Increasing biodiversity
- Improved aesthetics
- Reducing the heat island effect
Through a combination of specially engineered soil and water management systems, green roofs can dramatically decrease the water run-off from a building, holding it on the roof instead of letting it go down into the municipal stormwater system. In the summer, as this water evapotranspires off the roof, it carries heat with it keeping the roof cool, and in the winter the green roof provides an extra layer of insulation to keep heat in the building. Because of these numerous benefits, the Green Roof Committee wants to see Purdue’s buildings utilize them, and is working to make this an ever-improving reality.
What has the Green Roof Committee done in the past?
The Schleman Hall green roof was installed by BGI members in May of 2009. This roof was the center piece for BGI when the club was just beginning. The three main goals for the roof were:
- Publicly accessibility
- Centrally located on campus
- Structurally able to support the extra load of a green roof without any reinforcement
Before the actual installation, however, the roof needed to be physically prepared for going green. That preparation included covering the roof with a 100% water-proof membrane, extending the safety rails on the roof, and adding handicapped accessible ramps from the hallway inside the building to the roof. The surface of the roof is a combination of highly reflective pavers and sedum plant mixtures. The pavers were placed on the roof to optimize the amount of green space while maintaining a completely usable area.
The sedum plants, a close relative to the cactus, are highly adaptable perennials – capable of surviving long droughts in the summer and even the harsh winters of Indiana. In addition, they are planted in an engineered soil that is designed to retain nutrients and volume over time. The plants were placed in 1 x 2 ft modules that are easy to remove for maintenance and lock and grow together for a uniform look. Because the effects of green roofs are highly variable by geographic location, BGI monitors the Schleman Hall green roof. Powered completely by solar energy, a datalogger automatically records the temperature, soil moisture, rainfall, and runoff in various locations on the roof. This data is continuously uploaded here. The Schleman Hall green roof has also been used in research and publications, such as this. You can also visit the Schleman Hall green roof! It is outside the second floor, and there are signs posted for a self-guided tour of the roof.
What is the Green Roof Committee doing now?
Following the success of Schleman Hall, BGI worked for a few years on a project to install a roof on Knoy Hall of Technology, to have been installed in summer 2014. However, this project was very ambitious and eventually was cancelled by the College of Technology due to a lack of funds. So, the Green Roof Committee is now under way with planning for a new project. Our current goals for this second roof are to demonstrate higher efficiency by dedicating more roof space to plants, to investigate the use of larger plants by having deeper soil, and to use additional types of monitoring sensors. After a selection process where we considered the pros and cons of individual roofs, we believe that Shreve Hall is the best location for our project. This building is an H-shaped residence hall with large visible and possibly accessible roof spaces located behind the lounges on the main floor. We are currently in the process of fundraising and commissioning a study for the project, and we hope to be allowed to place our monitoring equipment on one of the roofs soon. By measuring conditions before the installation of the green roof, we will be able to compare results with the post-green roof data and more accurately evaluate the benefits.
Like Schleman Hall before it, we would like to have a student-led installation of the green roof. This will save on construction costs and provide opportunities for greater involvement in the project. Upon completion, if the roof is accessible, we will have benches and tables to make the roof inviting for people to use for lunch, study, or even formal events. And of course, BGI will offer informational signage and tours. If you have any questions about Schleman Hall, our current project, or green roofs in general, do not hesitate to contact us. Also, we are continuously looking for grants and sponsorship opportunities, as well as outside contacts and resources. If you can assist us in any way, it will be greatly appreciated.