Green walls: A growing trend
Benefits of green walls, practical considerations for installation and maintenance

by Courtney C. McKay — Originally published in the May/June 2017 issue of BOMA Magazine — You may have noticed that some office walls are looking a little greener than usual these days.  Though they go by different names—living walls, green walls, vertical gardens—new hanging indoor plantscapes seem to be sprouting up in commercial lobbies everywhere. So, why has interior landscaping gone vertical?

The answer could be deceptively simple. “One of the reasons living walls are starting to be so popular is because, increasingly, horizontal space is at a premium,” explains Jim Mumford, president of Good Earth Plant Company in San Diego. “If you don’t have enough room to put plants on the floor, then the wall is the natural place to go.”

Most green walls are comprised of a collection of houseplants that gain sustenance from a system connected to the wall. They typically feature some type of growing medium—soil, fabric or foam, for example—as well as a support structure, an irrigation system and drainage. Installing a green wall earns commercial properties points towards both LEED and WELL Building Standard certifications, and, as is the case with any indoor landscaping, they offer a host of tangible benefits.

The Perks of Green Walls

“Nature is hot right now.” So says Joe Zazzera, founding principal of Scottsdale, Arizona-based Plant Solutions, Inc. “In the built environment, the use of natural elements has become much more prolific in recent years,” he shares. “There’s so much awareness of the benefits of indoor plants that people are really seeking us out.” What are some of these benefits?

Improved occupant wellbeing, for one. There is a scientific concept called biophilia, which means “love of nature.” Studies have shown that humans’ innate fondness of nature is more than just an aesthetic preference; a visual connection to nature can have a number of positive effects on wellbeing. As a result, biophilic design is being embraced in tandem with the growing wellness movement in the built environment. “Plants have a very positive psychological impact on building occupants,” says Mumford. Studies tie indoor plants to reduced stress levels and lower blood pressure, which can result in reduced absenteeism and increased productivity and creativity. Green walls also can help create a natural environment that lasts all year long, which is particularly helpful for places with long winters. “Indoor green walls are a lot more popular in places like Boston where people are trapped indoors for long periods of time,” adds Mumford.

Sound dampening—also linked to occupant wellness and productivity—is another benefit. “It’s been well known for some time that indoor plants improve acoustics,” explains Zazzera. “You have a lot more surface area in leaves to absorb sound, so it’s common for us to be asked to bring in plants for noise dampening.” Mumford recently completed a project in Orange County, California, where he installed a green wall to reduce noise in a pool enclosure where sound echoed. He notes that the same concept can be applied to a cavernous building lobby.

Living walls also can provide a significant “wow” factor. “We are certainly seeing an amenities arms race here in Arizona, where commercial properties are all competing to improve their interiors,” says Zazzera. “Tenants notice green walls right away, and it’s a real differentiator for a commercial building.”

In Phoenix, he worked with CBRE General Manager Jami Vallelonga, CPM, RPA, LEED AP O+M, to bring the Arizona desert landscape indoors by creating a succulent wall for the lobby of one of the buildings in the Esplanade office park. “Our living wall has been quite a hit with tenants and guests,” says Vallelonga. Not only did it become the hot topic of conversation in the building, but it also quickly caught on as a unique backdrop for many selfies and group photos. “It’s been a joy watching people’s faces light up when they encounter the wall,” she adds.

Clearing the Air on IAQ

A recent Harvard University study connecting better indoor air quality (IAQ) to higher human cognitive functioning has brought the conversation about the air in commercial buildings—and how to improve it—back to the forefront. While some may assume green walls will improve indoor air quality, the science does not back up the assertion that indoor plants can significantly reduce carbon dioxide in the air—even in the higher concentrations found in green walls. “Plants take in carbon dioxide and give off oxygen as part of their normal cycle, but they don’t absorb enough carbon dioxide to make a difference,” says Mumford.

Simon Turner, CEO of sustainability consulting firm Healthy Buildings, has been studying the effects of plants on IAQ since the 1990s, and he agrees. “The sheer volume of air that a building’s mechanical system brings in is really going to overwhelm any impact that plants are going to make directly on the air quality,” he states.

In fact, if not properly maintained, green walls and other indoor plants could even decrease IAQ. “It’s important to keep them from degrading air quality,” says Turner. Indoor plants can become dusty, especially if underwatered, or moldy if overwatered. Overwatering also can lead to excess water sitting in a tray or drainage system, which can cause decomposition.

Alan Darlington, PhD, a botanist by training and founder of the Canadian-based Nedlaw Living Walls, has come up with a different solution: using plants as a biofiltration system by incorporating them into the HVAC system of a building. This unique living wall technology came out of research he did in the 1990s at the University of Guelph outside Toronto, where they were exploring long-term space habitation. “We were studying how to use biological systems to remove waste and rubbish in the air, and we realized that what we created had much more application here on Earth than in outer space,” Darlington explains. “After all, they’re constructing many more office buildings down here than they are on the moon.” So, in the early 2000s, he commercialized the biofiltration system.

He says the real magic takes place in the roots of plants, not the leaves—roots have beneficial microbes that break down volatile organic compounds (VOCs) like formaldehyde and benzene. His biofiltration system uses hydroponics to grow plants in a porous material similar to a scouring pad that goes over a return air duct and actively draws air through the wall, bringing contaminants in close proximity to these microbes in the root system. Typical buildings, Darlington describes, blow dirty air outside and bring fresh outdoor air inside through ventilation, but this new air usually needs to be heated or cooled for optimal indoor temperature, which consumes significant energy. Biofilters can “polish” existing air enough to reduce the amount of outdoor air needed by two-thirds, resulting in significant cost savings.

But, when it comes to IAQ, “the best strategy is to not bring VOCs and toxic materials into the built environment in the first place,” says Zazzera. “Having plants is a secondary strategy, and their biophilic benefits far surpass any IAQ improvements.”

Going Vertical with Your Landscaping

Installing a living wall in a property is a long-term investment that requires a lot of planning up front. Mumford offers this advice to property professionals: “Find an expert who knows what they’re doing, plan the project carefully and then don’t skimp on the maintenance.” To start, a vendor will need to visit the site to see what type of infrastructure is in place—water, electricity and especially lighting. “Light is a big deal, and 99.9 percent of the time, there’s not enough of it, even if the area is surrounded by glass walls or windows,” says Mumford. These factors limit what types of plants will thrive.

In some buildings, a moss wall or even an artificial installation might be a better option. Moss walls are, surprisingly, not usually alive. Except for in rare cases, they are made with real moss and lichen that are dehydrated, then “reanimated” with non-toxic, food-grade glycerin. Their biggest selling point is that they are about 20 percent less expensive than living walls, and they don’t require any ongoing maintenance except for the occasional dusting. Interestingly, some evidence suggests moss walls and artificial plants may provide many of the same biophilic benefits as real plants.

A green wall design is created based on many factors, such as budget, timing, size and scope, before installation can move forward. Moss walls, for example, are very low profile, so Mumford recommends having this type of installation recessed into the wall, if possible, or framed like artwork to hide the edges. However, unlike their living counterparts, moss walls cannot be in direct sunlight. “Moss walls might work where living walls won’t and vice versa,” adds Zazzera.

Then, it’s just a matter of maintenance. “Just about anybody can install a green wall that looks good on day one—that’s the easy part,” says Mumford. “But how’s it going to look in a month or a year?” Many vendors will draw up maintenance contracts as part of the installation process. Most of this maintenance is standard horticultural upkeep. “We’re dealing with a living, breathing product,” says Zazzera. “This is no different than caring for your landscaping.” Depending on the green wall, maintenance can take place every week or every month—or, in the case of moss or artificial walls, only when something is visibly amiss.

Regardless of the type of green wall installed, however, your tenants will enjoy the benefits of bringing the outdoors inside. “Investing in a natural indoor environment is always worth it,” says Zazzera. This is one design decision that can help your occupants flourish, and the trend doesn’t look to be dying out anytime soon.