Green roofs are the new community
From mitigation to production to connection
I often see great stories profiling unique green rooftop applications, accompanied by a sweeping photo and a data statistic - usually a number representing the diversity of trees/plants, the massive amount of carbon capture, food production, etc. Nothing wrong with those; they’re factual representations of input/output.
Perhaps I’m nitpicking, but I see two potential issues:
If the rooftop project has made it into design copy, I’d be willing to guess it was a reasonably complex and expensive one
Most of the climate impacts of such projects get distilled into numbers that are easily disassociated from reality, and what remains is a glossy image of a swanky rooftop
The first may seem harmless enough, but I believe these types of communications may unintentionally do more harm than good. Why? Because they foster a belief, an erroneous one, that rooftop green space is reserved for the few with deep pockets. Sure there are plenty of public rooftops, but while they appear open to all, they retain an ‘out of reach’ air for the common citizen.
In reality, this couldn’t be further from the truth. Several cities across Europe have set sweeping legislation mandating green roofs across their cities and have benefited from widespread visibility and adoption. In Basel, Switzerland they’ve become so ubiquitous that nearly 1 million square meters or 247 acres of green roofs have been constructed. They’re more common than front lawns.
In North America, many public rooftop projects, despite being designed specifically for general access, suffer from an “out of sight, out of mind” dilemma. They tend to be one of a few green roof projects sprinkled across different regions, lending to an air of exclusivity. But with changing policy across US cities, we’re betting rooftop farms will become as commonplace and accessible as your neighborhood coffee shop.
That brings us to issue number two. Too few articles distill climate impact information into digestible and relatable sound bites. What does 1 ton of produce look like?
How many people does that feed in my community? For how long? People relate to numbers when they’re used to illuminate clear visual connections.
Roughly 12k people could meet their daily intake requirements of 2.5 cups of vegetables (look away kids) and 2.5 cups of fruit for a day, from a single relatively small rooftop like the one below (1 acre / 4k m2).
Ten rooftops (10 acres / 40.5k m2) could feed the entire communities of:
Borough Park or Central Harlem in NYC for a day, or
West Ridge and Bridgeport in Chicago for a day, or
Midtown, Morningside/Lenox Park, North Buckhead, Pine Hills, and Home Park in Atlanta for a day.
Estimates have suggested there are >1.2M viable rooftops in the US, ranging between a few thousand square feet to well over 1 acre. Rooftop agriculture on that scale could see nearly the entire US population meeting their daily intake requirements for a day. From city rooftops.
You may be asking yourself, only a day’s worth of produce? That’s not going to make a significant dent in food security. I’d challenge you to think about the knock-on effects. Imagine how many gallons of fuel you’d save in that one day without deliveries nationwide - no idling, no traffic jams, no smog, and perhaps as important, no double parking (looking at you Brooklyn) and incessant horns. These represent both tangible and intangible health benefits.
Urban production can lead to significant stress reduction for rural farmers and big changes to fossil fuel consumption in shipping, refrigeration, and packaging through the movement of produce from rural areas to inner cities. It can also create community food exchange opportunities, diversification in options based on community needs and new carbon-free delivery businesses between rooftops and restaurants, schools, and offices.
But that’s not all.
More than just a pretty face
Rooftop farms at the scale I mentioned (1.2M strong) can not only feed >300M people, but also:
help prevent severe flooding → all that soil absorbs excess rainfall in a storm event and prevents it from reaching and overwhelming older storm drains at street level
affect ambient temperatures by >5° F → all those plants release cool moisture into the surrounding areas in a process called evapotranspiration (ET) - the more plants you have and the denser their canopy, the greater the effect, potentially reducing heat-related stroke and mortality
reduce energy usage in the buildings they adorn between 3-10% → thermal mass of the soil, plus ET means cooler indoor temps in summer and warmer temps in winter, along with lighter loads on the HVAC systems, avoiding GHG emissions in the process
increase biodiversity for pollinators along heavily depleted city corridors
add 5x the number of local jobs per rooftop vs. solar application
Then there are the intangibles, those things that are hard to quantify or attach a monetary value to, but nevertheless, make very tangible impacts on health. Many have had the opportunity to visit a rooftop farm in densely packed cities like NYC, Shanghai, Johannesburg, or Buenos Aires. It’s an immediately visceral experience, but one that remains largely inaccessible to the majority of urban dwellers.
The intangible encapsulates a concept floated by an architecture professor of mine from grad school. It’s the reverse juxtaposition, but I think it still works: the technological sublime.
The idea is that objects representing technology or the built environment, be it infrastructure, connectivity, etc. can be found in remote and strikingly beautiful natural areas (think the Hoover dam). The juxtaposition of machinery against natural landscapes provides this odd but beautiful backdrop, with the differences between the two accentuating the stark beauty.
Often it is categorized as humans defiling nature, but I see it as extreme opposites existing in tandem - we may not be able to avoid building in beautiful landscapes, but we can choose to do so with care.
In the urban context, seeing verdant fields thriving atop concrete, glass and steel feels like nature reasserting itself, green is the new black.
A farm on every rooftop?
It’s an audacious goal, but DirtSat is developing a platform to facilitate building farms on a city-wide scale.
It isn’t practical to expect every rooftop will be viable for farming, but we’ve been working on models that show roughly 15-19% of the rooftops per city are tenable. And we’ve also been working out pretty significant ROIs for rooftop agriculture that meet, and in some cases, exceed that of a solar deployment — a popular choice for open rooftop space on commercial buildings.
New green financing options for property owners are gaining traction, makes the decision to add a rooftop farm or green roof a substantially easier one. Property values go up due to climate mitigation measures, tenants gain health benefits with access to the outdoors, and healthy, fresh food is grown sustainably right where it’s needed most - in communities.
Triple bottom line win.
As always, thanks for reading. Until next time, feel free to reach out to us with any thoughts.
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