View From The Top: Healthcare Green Roofs
No longer a novel, fringe feature, green roofs at healthcare facilities now have a good decade under their belt, during which time significant advances have been made in plant technology, installation systems, irrigation strategies, roofing structures, design processes, and maintenance protocols. By tapping into these advancements, as well as lessons learned from hundreds of healthcare green roof installations, today’s projects are yielding much better gains.
Inspired by both Roger Ulrich’s dictum that nature can positively influence well-being and E.O. Wilson’s biophilic effect theory that people have a strong affinity to living systems, early attempts at designing and installing rooftop gardens in the healthcare industry were focused on creating small, intimate garden spaces to which patients were brought, according to Mary Ann Uhlmann, president of The Rooftop Garden Firm (Atlanta). “From there, the trend to provide a healing aspect began with the advent of healing gardens, and in recent years, the trend has been to provide patients with a view from their room, thus realizing the full impact of nature for therapeutic improvement,” she says.
But beyond healing benefits and user enjoyment, green roofs also offer sustainability and cost savings benefits that are big draws for healthcare organizations. They help mitigate the urban heat island effect and offer extra insulation, thereby reducing building cooling loads. And according to the National Park Service, a well-maintained green roof can double a roofing system’s life expectancy, as compared to a standard roof.
Setting the scene
However, this process hasn’t been without its share of bumps in the road. For example, early attempts to transplant European methods, plants, and componentry to the U.S. were stifled by vast regional weather and environmental differences between the two continents, and exacerbated by inexperienced installers and designers. Furthermore, healthcare organizations suffered from a lack of knowledge and experience in maintaining vegetated green roofs.
Analyzing shortcomings of those first installations has now reshaped the way designers are approaching projects today, starting with addressing underutilization.
For example, lack of use can often be attributed to poor wayfinding or garden visibility, poor maintenance, a lack of seating arrangements, poor plant selection, too much pavement, not enough planting, and/or failing to provide users with a sense of control or engagement, says Matt Malone, landscape architect at Perkins+Will (San Francisco).
As for solutions, Malone says, “The seamless integration of outdoor space planning with the functional considerations of building structure, architectural detailing, wayfinding, and better understanding of the end user’s needs are paramount.” However, in order to achieve this level of integration, planning for a vegetated roof early in the design process is essential.
For example, at Nemours Children’s Hospital in Orlando, Fla., a green roof concept of a “hospital in a garden” was created, embedding gardens within the facility to provide direct access for the patients, visitors, and staff. One garden serves as an extension of the outpatient surgery waiting room and the second is an extension of the hospital’s rehab therapy activity space.
“From the beginning of the planning phase, we identified opportunities to use the healing power of nature by introducing garden spaces into the building massing, and that energy to prioritize gardens continued through design development, budget analysis, and construction phases,” says Michael S. Cluff, director of facility planning at The Nemours Foundation (Orlando). “We had a vision of the experience we wanted to create and did the research on product development, installation, and ongoing maintenance to select plant life and designed around what those plants needed to survive.”
Sharing a few lessons learned, Cluff says that several of the trees specified were taller than the design parameters of the lightning protection system, so they ultimately had to be replaced with shorter trees. Another misstep was failing to install sun shading over some artificial turf that was placed under a multistory curtainwall system. The consequence was some of the turf melting from the glare. “Add sun shading to any adjacent curtainwall system,” Cluff cautions.
One other challenging aspect of the Nemours green roof project was the fact that the authority having jurisdiction restricted reclaimed water from entering any facility, so it was an arduous public works process to bring reclaimed water to the roof gardens for irrigation and to meet the intended LEED credit.
Heads to tails
It’s important for healthcare providers to understand that rooftop gardens require regular maintenance with defined protocols and a functioning irrigation system.
Uhlmann says she often finds internal maintenance staffs fail to adequately water and weed the roof. She’s also seen a hesitance on the part of healthcare organizations to hire green roof professionals skilled in this type of maintenance. “While not always a welcome addition to what are typically lean operational budgets, regular, well-performed maintenance is far less expensive than the cost to renovate and restore a vegetated green roof,” she says.
At the same time, some well-considered design selections can help lower maintenance requirements, says Andrew Quirk, senior vice president of the healthcare center of excellence at Skanska (Nashville). For starters, proper vegetation for the climate—for example, drought-resistant native material in California—is the first course of action. “Also, tray system installations can help make the maintenance process easier because the system comes complete as a prefabricated element, including the drainage material, soil, and plants.” As opposed to a regular garden in soil, the tray works much more effectively to drain and filter the water as it enters the soil.
Providers must also determine if the roof will be accessible as a space where patients, families, and staff can find respite, or what’s called an extensive rooftop that’s for viewing only. While accessible roofs more fully tap into the healing and biophilic benefits of providing access to nature, they do come with larger structural requirements and capital costs. “The best way to make a selection is to balance first cost versus whole life cost in order to achieve a desirable return on investment (ROI),” Quirk says. “The second way to address cost is to verify expectations for the green roof. What does a facility want the roof to do? For example: reduce operating costs, conserve and manage resources, or serve as a healing garden for staff and patients?”
Overall, Jeffrey Keilman, senior associate at Perkins+Will (Boston), says that the decision over which roofing system to select relates to aesthetics regarding planting choices, required maintenance, and even upfront costs with structure and waterproofing considerations. In particular, waterproofing relates to reliability and warranty, so it’s vital to select the correct roofing/waterproofing system, as access is usually limited once the green roof is installed. “In my experience, one system [accessible versus in-accessible] is not mor
e common than another,” he says. “This is due to each project having its own particular goals and constraints.”
Although costs will vary significantly for new construction, Quirk offers a general rule of thumb of $30 to $40 per square foot for an extensive roof and $50 to $100 per square foot for an intensive, or accessible, roof. To help owners best calculate ROI, it’s important to take into account gains from reduced heating, cooling, and maintenance costs. For example, a U.S. General Services Administration “Green Roof Benefits and Challenges” study documented $14.10 per square foot of green roof savings from reduced infrastructure improvements and fees, and $6.60 per square foot of savings from decreased cooling and heating energy expenses for a 5,000-square-foot green roof.
In terms of the structural component, the roof deck and support must be able to handle the dead load weight of the rooftop garden. Because green roof depth can vary from 3 inches to 12 inches, the dead load can be as little as 20 pounds per square foot to as much as 80 pounds per square foot. For accessible gardens, the roof must also support the live load added by occupants. Adding a green roof to an existing structure will require a study to understand the bearing capacity, Quirk adds.
As for putting the green into these green spaces, the industry has seen significant improvement in the selection, propagation, and maintenance protocols for commonly used sedums, expanding the plant palette available today. Also of note, native plant species—driven by regulatory efforts spurring stormwater management—more commonly include native grasses and wild flowers in the rooftop mix thanks to their water-absorbing properties. “Their root systems are vast, soaking up large quantities of rainwater and removing pollutants from the resulting run-off,” Uhlmann explains.
While local and federal stormwater run-off and management requirements vary, cities located near oceans, rivers, lakes, and subsurface ground water are generally more regulated.
Another noted area of development is the art and science of growing vast acres of pre-grown mats, which are similar to sod. Here, soil blend improvements and moisture retention fabrics—providing more moisture control to help plants survive heat and stress—are leading to more reliable plant environments.
Uhlmann says that early vegetated roof irrigation systems relied on sub-surface emitter technology, which delivered moisture directly to the plant roots and were mainly used in shallow, extensive green roofs. Although they worked well when installed correctly, the systems were challenging to troubleshoot and didn’t provide a total package solution. On the contrary, today’s comprehensive, high-performing systems also offer weather stations and remote operating capabilities, providing a much more reliable method of managing hydration for hard-to-access roof landscapes.
A worthwhile endeavor
While healthcare green roofs have come a long way in the past few years, the process is a demanding one, requiring lots of collaboration to make it work. “The challenges associated with green roof design are primarily in the complexity of the detailing, documentation, and coordination of several design and engineering disciplines, contractors, and installers,” Malone says. “Although green roofs are becoming more familiar and understood in the realm of healthcare design and construction, coordination throughout the entire design and installation process is still the most important strategy to ensure the successful implementation of any system.”
In order to achieve this, clearly delimitating which professional is detailing and specifying each system is key. Another determination is whether to divide or combine this information in the drawings and specifications. “What we do as an in-house team is combine the green roof system specification into the architectural roofing specification for clarity, and the landscape drawings detail everything above the waterproofing,” Malone says.
While not without planning, design, and maintenance challenges, healthcare green roofs come with plenty of benefits and provide a comfortable, quiet environment or soothing view that contrasts with the often highly stressful clinical setting.