The United States has lost more than 11 million acres of farmland to development over the last 20 years. A recent report by American Farmland Trust shows that agricultural land is increasingly being converted, fragmented or paved over, challenging local and regional food systems.
In that same amount of time, the global population has increased from 6.19 billion in 2001 to 7.9 billion in 2021. This rapid population growth and lack of agricultural land create an urgent need for more food production in underutilized spaces.
IT HAS BEEN ESTIMATED THAT ALMOST
1.4 MILLION HECTARES OF ROOFTOP SPACES ARE AVAILABLE FOR FARMING IN CITIES GLOBALLY.
The 2018 study, A Global Geospatial Ecosystem Services Estimate of Urban Agriculture, estimated almost 1.4 million hectares of available rooftop spaces for farming in cities globally. With street-level space at an ever- increasing premium in urban built-up cities, rooftops are an unused area ripe with potential for food production.
Although selecting the correct cultivation and production methods for these rooftops will be a challenge—some methods require at least 1 acre of space to be commercially successful—rooftops are the single greatest opportunity to grow food in cities.
So why should you consider a rooftop farm for your next building project?
As an architect, developer, building owner or tenant, there are numerous reasons that you would benefit from an urban rooftop farm. Consider the following 10 benefits of this conversion:
1. Food Production
The most obvious benefit of a rooftop farm is food production. In the Bronx, N.Y., an approximate 8,000-square-foot rooftop hydroponic greenhouse was erected on top of a new affordable housing building. This farm, Sky Vegetables, introduced fresh and delicious produce to a community with limited access to healthy foods. The farm employs local residents and sells varieties of herbs and leafy greens to local and national supermarkets, as well as reserves a portion of each harvest for the immediate local community, free of charge.
2. Green Building Amenity
In Toronto, Avling Brewery built a rooftop farm on top of its existing restaurant and brewery. With an enclosed green- house, the team is able to utilize the excess heat generated from the brewing process to extend the growing season. Plus, the brewery uses the green space for events, education and as a local food hub. By converting its generic concrete rooftop and redirecting wastewater and kitchen waste, Avling Brewery can produce food hyper-locally and create a more circular business.
3. Mitigation of Urban Heat Island Effect
The heat island effect is the result of a city’s highly dense infrastructure that absorbs and re-emits the sun’s heat. The concentration of buildings, roads and other structures result in higher temperatures compared to natural green spaces. According to the U.S. Environmental Protection Agency, the heat island effect can increase daytime temperatures in an urban area by 1 to 7 degrees F compared to outlying areas.
Green roof temperatures can be 30 to 40 degrees F lower than those of conventional roofs and can reduce citywide ambient temperatures by up to 5 degrees F. (Learn more from “The Benefits and Challenges of Green Roofs on Public and Commercial Buildings” and “Cooling the cities—A review of reflective and green roof mitigation technologies to fight heat island and improve comfort in urban environments”.) These interventions can help cities avoid extreme temperatures in the face of climate change.
4. Energy Efficiency and Reduced Operational Costs
One of the major downsides to building a green roof or rooftop farm is the upfront costs. According to a study by the University of Michigan, a 21,000-square-foot green roof costs about $100,000 more to install than a conventional roof. But, throughout its lifetime, it would save more than $200,000, thanks mostly to reduced energy needs. The reduced operating costs and lower carbon footprint of this cost-effective design solution are a great benefit of the insulating effect of plants.
For example, in New York, the Jacob K. Javits Convention Center’s rooftop glass pavilion, 1-acre farm and 7-acre green roof have been said to reduce the building’s energy consumption by 26 percent.