Greenroofs are smart for cities; they help the environment and draw a lot of attention. They manage to accomplish all of this by growing plants on an otherwise vacant space. By introducing plant life edible or not, a greenroof traps and uses rainwater, reducing the amount of water entering the sewer system. Therefore, water doesn’t run off the building and through the streets where it is mixed with pollutants. A greenroof also reduces the amount of energy that goes into regulating building temperature, by providing insulation in the winter, and evaporative cooling in the summer. Some sources claim that installing a greenroof reinforces the roof enough that it doubles to triples the roofs lifespan. Also, a greenroof provides many more plants who produce oxygen and remove pollutants from the air we breathe. In some cases a source of fresh local produce. If all of this is true, why aren’t there more plant-roofs?
The most daunting element with a greenroof project is creating a roof that can bear the weight added to the building. Unless the roof is already equipped with a strong system, the process requires reinforcing the roof with weight-bearing beams. Another solution could be to improvise, using a light-weight substrate. A company based in Hawaii, FarmRoof, has created a genus setup for growing on rooftops, reducing the amount of weight needed to produce edible produce.
A low maintenance greenroof containing a lot of sedums and a variety of native plants, can be left alone once it’s established. The majority of the work comes in the preparation, and maintenance for the first few years. There are multitudes of projects all unique to their setting, I particularly like those that incorporate flowering plants, and water-catchment systems.
Another popular greenroof sprouting up over the past 4 years in hipster cities like Brooklyn, Philadelphia, Boston, and Chicago are high maintenance rooftop farms. For these endeavors, there is a constant work load involved, and a lot more planning than simply putting up a sedum bed. Some farms introduce many raised beds, other farm directly into the soil laid on top of the roof. An interesting website, FarmingUp, posts research that compares rooftop farm produced vegetables and those produced at ground level, paying close attention to contaminants, production, and nutrient levels. A lot of these trendy rooftop farms used Kickstarter.com to get the funding necessary to start their revolutionizing space.
Lastly there is another group of sophisticated farmers who chose to erect greenhouses on the top of buildings, Lufa Farms in Montreal harvests the rain off their greenhouse roofs to water the plants. Gotham Greens in Brooklyn is a hydroponic greenhouse that re-circulates its water. The plants at Gotham aren’t the only ones using sunlight for energy, the roof is covered in many solar panels. Both companies are striving to produce local produce throughout the year with a low impact on the environment.
Many individuals, and restaurants are beginning to grow on their roofs in raised beds and greenhouses to supplement their menus with local grown vegetables and fruit. The best way to learn more about growing on your rooftop is to look into local groups offering affordable instructional classes. The Brooklyn Brainery offered a class that taught anyone with $20 how to grow fruit on their rooftop. Keep garden organizations on your radar,they offer informative monthly meetings and one could be about gardening in the sky.
What do you think, what is the best system for urban gardening? Are rooftop farms the most energy-efficient way to produce food, while using a vacant lot in the sky? Tell me what you think, I would love more ideas.
DIANE COOK AND LEN JENSHEL/National Geographic Stock
Thanks for writing on this “growing” topic! My 2 cents:
I think the usefulness and feasibility of green roofs is really dependent on two issues: the amount of space available on the ground in the city, and the intended purpose of the green roof. If the goal is urban agriculture and food production beyond an individual restaurant’s menu, 95% percent of cities have sufficient vacant space at ground level that whole neighborhoods would benefit from retrofitting old lots and public spaces with gardens. Raised beds along sidewalks, plots along old rail road tracks or bike paths, margins of underutilized parks, etc… This is cheaper and more accessible to the population that would ultimately benefit from growing food. A rooftop, on the other hand, is not always publicly accessible, nor is the start up cost of a mid-large scale green roof cheap.
However, if the building owner/business/public entity has the financial means to implement a green roof, and that system has been thought through in a way that it enhances multiple other building functions (water/temperature/ventilation/etc…), there is no good argument against them (especially in highly dense urban areas).
Green roofs are trendy at the moment, and the danger with a trend is that investments can be made for the wrong reasons, and resources can be accrued without reasonable justification (e.g. $200,000 for a green roof that does not enhance building functions or partially sustain a businesses fresh food supply). That being said, green roofs also offer a completely logical (and if we were more attentive to the benefits of emulating natural processes, obvious) solution to a massive amount of horizontal space that goes to waste. Why not have multi-functional green roofs? Stick some solar panels, raised beds, hoop houses, youth garden, bee hives (excellent way to pollinate the city above the public), and a gathering area for potlucks on a roof, and you have more than a building; you have a dynamic community asset in the sky! We should always think through our alternatives first though. It’s more efficient and accessible to convert a vacant residential lot than a roof top.
Thanks for the 2 cents. This subject, as you said is growing, therefore there is plenty I left out. I completely agree with your statement that it is more accessible to convert a vacant residential lot. In a perfect world it seems that utilizing a rooftop space to house solar panels, and collect rain water in conjunction with using a vacant lot below would be ideal. As well as a multi-functional green-roof, I love that idea.