Why Building Owners Are Going From ‘Gray to Green’ Roofs

Urban rooftops are too often only used by an occasional custodian or contractor. Imagine slipping out among the HVAC units and rain puddles for a mid-shift cigarette and having your own open-air observation deck commanding a panorama of Chicago, for instance.

Before JLL helped envision a new life for the Old Chicago Main Post Office, a smoke break or the odd air conditioner repair job were about the only things happening on the 2.5-million-square-foot building’s rooftop.

Now, the 10th-story terrace is an elevated, three-and-a-half-acre “meadow” hosting basketball leagues, tennis tournaments, swathes of wildflowers, bee colonies and mixology classes at its bar — all served up with a breathtaking, 360-degree vista of downtown.

Apart from being an absolute oasis amid a dense concrete jungle, where every spare square foot is premium real estate, the rooftop scores points in almost every building standard possible by doing its environmental duty, giving occupants access to the great outdoors and doubling as crucial infrastructure for the city.

To explain why and how developers, landlords, city officials and tenants are increasingly going from “gray to green,” LoopNet caught up with President and CEO Vanessa Keitges of Columbia Green Roof Technologies about its work on the nation’s largest private rooftop park and thousands of other “green roof” projects from coast to coast.

Visible, high-profile rooftops like the Old Chicago Main Post Office’s call attention to green roofs primarily because they spark what Keitges calls “green envy.”

“If you're going to rent an apartment or lease an office and you have a choice between one with a rooftop deck with a barbecue and swings and a place to hang out with your friends or coworkers and drink coffee and wine; and one that doesn’t …” Keitges said, “it’s a no-brainer. Green roofs add value to the asset.”

And that’s not just from a marketing perspective.

“Now there's this new standard around people’s wellness,” she continued. Similar to what LEED does for a building’s energy impact, WELL qualifications look at occupants’ access to fresh air, natural light, nature, fitness and other factors.

WELL certifications revolve around consumer demands, she added. “That’s what employees and residents want — and with these credentials, building owners are able to raise rents.”

Hospitals are also increasingly looking to green roofs — like Columbia’s work on the Fred & Pamela Buffett Cancer Center in Nebraska — thanks to research around biophilia’s association with reducing stress and recovery times. This not only benefits patients, she said, but also doctors and staff, as well as patients’ families who sometimes have to be at the hospital for weeks at a time. “For a child who might have to be in chemo for six or seven hours, hope often comes in the form of little things for them and their family — even looking out the window onto a green roof or terrace and seeing butterflies.”

Butterflies aren’t just pleasant to see floating around. Wildlife habitat restoration is crucial to scoring on LEED credentials, Keitges added. “You can’t really build a new park in the middle of the city, but you can build it on your roof. And when you do, it’s pretty remarkable to start to see natural habitat coming back.”

In this spirit, a lot of developers are even adding beehives to their green roofs, she continued. “Whether its Federal Realty Trust Fund, or Johns Hopkins University, Hines, JLL or Boston Properties, developers get really jazzed about the bees.”

These aren’t just warm-and-fuzzy flourishes, though. Shareholders care about this sort of thing from an Environmental, Social and Governance (ESG) standpoint — and with LEED status being crucial to a building’s competitiveness, an extra 16 to 20 points out the 100 they need for certification makes green roofs that much more attractive, Keitges said.

For comparison, she added, “white roofs,” which reflect light to reduce the heat island effect, score about two points.

But what makes green roofs white hot, propelling them to be part of a $14 billion “green infrastructure” business, according to Keitges, is a systemic effort to bring “nature-based solutions” to a series of issues cities are facing, led by stormwater management.

“Whether you’re in Virginia or Portland or New York City, the two-by-two pipe underneath the drain on the street dates back 50 to 100 years or more,” she explained.

Devastating storms hit urban clusters harder and harder every year, she continued, and when those pipes get backed up, they interfere with both clean and sewage water systems going into and out of a building, Keitges said. “It’s called combined sewage overflow, resulting in sewage in the streets and in the basements — and all of that flooding becomes a real hazard.”

Cities around the country are increasingly requiring developers to submit stormwater management plans, and green roofs are progressively being approved as technology capable of retaining water, she purports — showing in tests an ability to capture up to 80% of stormwater runoff that would otherwise drain to the streets or have to be detained in a building’s water tanks.

One of the goals of green roofs, Keitges continued, is to reduce the number of water tanks necessary in the basement of a building. “We value-engineer the green roof into the design to out-price the costs of the tanks in a city environment, because it's just too expensive in an urban environment in New York or Chicago, or even Omaha. Space for tanks inflict an opportunity cost as well, she added. “That is valuable space for a parking lot or a bottom floor.”

So, what goes into planting vegetation on your roof?

First off, it doesn’t have to be all-or-nothing.

Projects like the Meadow on the Old Chicago Main Post Office are exemplary of green roof parks. But there’s no way around some designs that require space for mechanical components on the roof, especially for existing buildings.

Good news, she continued, is that even when only 25% to 50% of the roof is “green,” environmental benefits come into play.

She also said that the process doesn’t have to be part of an intensive overhaul. The bulk of what Columbia delivers, for instance, is a pre-grown product that’s installed in trays over waterproof membranes. “It's very simple,” Keitges explained.

“Certified installers basically come and roll out [insulation] and essentially a mat, like you would with turf, made up of trays of pre-grown sedum succulents embedded in our engineered growing media with built-in irrigation and a root barrier,” she said. “The media has drainage, but doesn’t require rocks and worms or dirt or soil. We want something that retains water but doesn't become a muddy mess.”

Costs for this “green on day one” product come in at around $10 per square foot, she said, and is meant to be easy to maintain. “Low maintenance is important, especially because our installers are contracted for lifetime maintenance.”

That’s one of the primary reasons Columbia uses sedum, which Keitges says naturally soaks up water and is hardy in extreme wind, heat and even snow — unlike grass, for example, which also requires mowing and “a ton of water.”

Given said simplicity and purported benefits, it’s easy to wonder why every building’s roof isn’t “green.”

Well, there are tons of ways it can go wrong, Keitges explained. “Technology matters. There have been tons of failures in the marketplace, sadly, because it's an emerging market and there are so few standards.”

Green roofs have swiftly gone from a hippie movement in northern European cities and in places like Portland, Oregon, where Columbia is based, to an international infrastructure imperative, she said.

Associations like Green Roofs for Healthy Cities work on educating the market and creating standards. A lot of people will use gravel for drainage, for example, but that doesn’t support foliage, Keitges said. “If the plants are brown and dead, or will take two years to grow, it’s not working.”

A lot can go wrong structurally as well, she said. New buildings are engineered to handle the weight of snow loads other intense demands of nature, she said, but existing buildings will sometimes have to upgrade their structural elements to manage the additional weight required for adding additional layers of vegetation and supporting systems. Columbia’s products are on the relatively lightweight side, she said, at around 30 pounds per square foot.

“Our goal is to make this multi-billion-dollar business not scary,” Keitges continued.

The more designers, general contractors, building owners and installers get comfortable and knowledgeable about the benefits of green roofs, she said, the more green roofs are becoming an integral part of the built environment.

Westbank Development has planned to incorporate green infrastructure from “roof to roots” on five huge developments in San Jose, for example. The City of Houston, as part of an initiative guided by its newly appointed chief resilience and sustainability officer, is incorporating green infrastructure incentives to combat stormwater flooding.

Columbia also worked on Capital One’s The Perch project at its headquarters in northern Virginia, which is open to the public. “All of a sudden they've got thousands of people up there listening to music, drinking at the beer garden and shopping [at Tyson’s Corner Center]. It’s become a destination,” Keitges said.