The green movement has embraced the global marketplace and captured the attention of consumers, companies, architects, and facility managers like never before. From sustainable building designs to alternative fuels to water conservation, “going green” is causing businesses and industries to take notice and change the way they’re constructing and operating their institutional and commercial facilities.
Of course, “green” means different things to different people. It also has different meanings based on location. In hot, dry climes, water conservation is top of mind. In northern states, where wind chills rattle windows and doors, energy saving measures play a key role in commercial buildings. There also are more sustainable options available to organizations than most realize. Quite simply, there’s no one way to be “green.”
However, one facet of “going green” that seems to appeal to many building owners and managers across a myriad of environs includes the ever-popular “green roof” trend whereby communities are seeking sustainable and eco-friendly solutions within their commercial building infrastructure. And that’s where the Nashville Music City Center (or simply, the Music City Center) in Nashville, Tennessee, comes in.
According to Elisa Putman, senior vice president and chief operating officer for Music City Center, sustainability is part of the organization’s mission. In fact, the Music City Center has been committed to reducing its carbon footprint since construction of its facility in 2010, when they set a goal for LEED Silver Certification, a globally recognized rating.
“The green roof was an integral part of that goal. Thanks to several sustainability initiatives, including the green roof, we ultimately achieved LEED Gold Certification,” Putman says.
The Music City Center is a 1.2 million-square-foot convention center, spanning three city blocks. As part of the complex, the building includes an expansive exhibition hall, 60 meeting rooms, a large grand ballroom, a junior ballroom, and a parking garage.
TVS (formerly tvsdesign) of Atlanta, Clark Construction, and Greenrise Technologies worked in concert to design and install the green roof, which was part of the original design and construction of the building. Five stories high, the green roof is approximately four acres, covering 175,000 square feet, and it was completed in 2013. At the time, the biggest factor in the construction of the green roof was slope stabilization.
“The design is considered an extensive green roof, constructed for shallow plants, minimal watering, and no public access,” Putman says. “The four-acre sprawl has undulating surfaces with pitches ranging from 16 to 25 percent to allow for stormwater collection.”
The roof consists of several layers including grounding screens, which protect against leaks; capillary fabric, which stabilizes plants and distributes water; drainage layers, pavers and membranes, which provide a low-flow drip irrigation system and overhead irrigation; and growing medium, which consists of clay, soil and compost. Vegetation completes the layered effect.
As the Music City Center’s green roof is made up of multiple layers including a waterproof membrane, less than three-inch soil depth, and native plants, the soil is a lightweight, free-draining clay-compost-sand mix. As part of the green roof environment, the Music City Center grows 14 types of sedums, as well as fescue, clover, and wildflowers. Pre-vegetated sedum mats offer slope stabilization and prevent soil erosion. The sloped design allows for stormwater retention and water is collected in a 360,000-gallon cistern, filtered, and then reused to irrigate vegetation outside the facility and to flush toilets and urinals inside the facility.
In the 10 years since the green roof was installed, the Music City Center has introduced native wildflowers to the rooftop vegetation, and they also set up four beehives. The Center works with volunteers from the Nashville Area Beekeepers Association, along with the Music City Center’s own in-house bee team to manage the hives.
“The hives are home to honeybees that produce roughly 100 pounds of honey annually, which is then used in our kitchen,” Putman says.
At its core, a green roof helps manage stormwater runoff, can provide some insulation to the building, and reduces the urban heat island effect as green roofs can help moderate the temperature of a building and its surroundings. These roofs can also help reduce greenhouse gas emissions and air pollution, which is vital in urban areas where lack of vegetation can lead to a build-up of carbon dioxide and other harmful pollutants. In addition, the vegetation and soil on the roof act as additional insulation, helping to regulate indoor temperatures and reducing energy consumption of both cooling and heating.
Externally, the green roof is part of the Music City Center’s identity as it was designed to mimic the rolling hills of Tennessee and has become an identifiable building in downtown Nashville. As Putman explains, it is an iconic fixture in the Nashville city skyline, and it’s become a symbol of the organization’s commitment to sustainability. Indeed, there is a visual appeal of the building that enhances the overall aesthetic of Nashville’s urban area.
“Internally, we reap the benefits many times over. It reduces heat by lowering the roof temperature and insulating the building. It improves air quality by capturing pollutants, reducing greenhouse gases, and increasing oxygen,” Putman says. “It also provides a natural habitat by adding green space, attracting birds and insects, and promoting pollination. It’s difficult to associate a dollar amount with those things, but we feel like it’s well worth it.”
Currently, the Music City Center’s fixed annual maintenance for the green roof is $75,000. Like any other facility, they also have a roof maintenance contract for the surface area below the dirt. That contract would also include repairs for any roof leaks. Currently, the waterproofing membrane that was originally installed extends the life of the roof by protecting it from UV rays, wind, and stormwater runoff.
“Additionally, a top dressing of compost to sustain the vegetation is required every 8 to 10 years at a cost of approximately $35,000,” Putman says.
As noted, one of the much-celebrated facets of the Music City Center’s green roof is its expansive rainwater collection procedure. Specifically, rainwater filters through the roof’s plants and along the waterproofing membrane atop the Center’s exhibit halls. The water is drained into the building’s 360,000-gallon underground cistern to be pumped throughout the building and in the facility’s landscape irrigation system. According to the Music City Center, since its opening, they have used over 16 million gallons of rainwater, accounting for approximately 48 percent of the facility’s total water usage.
To complement the Music City Center’s green roof initiatives, the facility also boasts an expansive solar power system, which is comprised of 845 solar panels in an effort to reduce energy costs. These solar panels are located on the roof above the facility’s Grand Ballroom. Since the installation of these solar panels, the Music City Center has experienced an average monthly cost savings of about $2,025 in energy savings.
Since the green roof installation, the Nashville Music City Center has received numerous awards for its sustainability efforts. In 2014, the Center received the Green Roofs for Health Cities Green Roof Special Recognition Award; in 2015 the Center earned the Nashville Downtown Partnership Award in the LIVE category for the addition of bee hives on the green roof; and they were awarded the Governor’s Environmental Stewardship Award in the Building Green category in 2013.
As with any type of roof, the Music City Center’s green roof does require continuous maintenance, but it is far less maintenance than a typical asphalt roof. For example, green roofs boast shallow soil depth and are planted with hardy, drought-tolerant plants. The vegetation is watered with reclaimed water about three times per week, especially in the hotter, drier months. No lawn mowers are allowed, so weeds are handpicked.
“We contract with Greenrise Technologies for monthly maintenance that includes weeding, trimming, inspections, etc.,” Putman says. “In December 2021, we applied a top dressing of nutrient-rich soil to compensate for natural soil erosion and to support the plant life.”
Maura Keller is a freelance writer based in Plymouth, Minnesota.
