Rooftop farming turns underused urban roof space into growing areas, but its scale varies widely between open-air farms, greenhouses, and citywide scenarios. Available evidence ranges from historical measurements and company-reported operating figures to modeled estimates, with geography and measurement period important to every comparison.
Contents
- Rooftop footprint and available space
- Production and crop yields
- Water use and stormwater
- Food supply and community reach
- Construction, climate, and ecosystems
- Commercial greenhouse scale
Rooftop footprint and available space
New York City illustrates the difference between total roof area and realistically suitable farm area. A 2020 review, citing a 2013 estimate, put the city’s total rooftop surface at 15,482 hectares. That was 445 times the area of the city’s existing community gardens. A 2020 city-scale scenario then identified 1,246 hectares of suitable rooftops. These figures describe potential space, not a completed farming network. (Urban Rooftop Agriculture: Challenges to Science and Practice)
Operating farms occupy a much smaller footprint. Brooklyn Grange farms three New York City rooftops and reports 5.6 total acres, including greenhouses, patios, and walkways. Its Long Island City farm has 43,000 square feet of cultivated growing beds; its Navy Yard farm occupies a 65,000-square-foot building roof; and its Sunset Park farm totals 140,000 square feet, including its greenhouse. These are current site descriptions accessed in 2026, although the individual farms opened in 2010, 2012, and 2019 respectively. (Brooklyn Grange FAQ)
Montreal-based Lufa Farms reports four active rooftop farms and 300,000 square feet of rooftop growing space in its current company profile, accessed in 2026. The company’s figure is a corporate-reported operating total, not an independently audited measurement. (Lufa Farms press room)
Production and crop yields
The modeled production potential of suitable roofs is substantial, but it should not be confused with current annual harvests. The 2020 review describes a New York City scenario in which all suitable rooftops produced 27,344 metric tons of fresh vegetables per year. The scenario equated that output with fresh-vegetable consumption for about 380,000 people. A separate scenario for Bologna, Italy, estimated 16,169 metric tons of vegetables per year from 82 hectares of flat roofs, enough for an estimated 77% of the city’s fresh-vegetable demand. Both are scenario outputs summarized by the review, not measured citywide production. (Urban Rooftop Agriculture: Challenges to Science and Practice)
Published yield figures also differ by system. A rooftop greenhouse near Barcelona produced 19.6 kilograms of tomatoes per square meter per year in a 2018 study summarized by the review. Reported open-air rooftop-farm yields in the reviewed studies ranged from 5.1 to 14.3 kilograms per square meter per year. The range covers studies with differing crops, conditions, and methods, so it is not a universal benchmark for every roof. (Urban Rooftop Agriculture: Challenges to Science and Practice)
Brooklyn Grange’s current FAQ says its three farms harvest about 100,000 pounds of produce annually. Historical and project-specific estimates are lower or narrower: Sunset Park was reported to produce approximately 30,000 pounds of vegetables per year in 2019, while the Navy Yard farm was expected to yield 20,000 pounds annually in a 2013 expectation cited by the 2020 review. The Javits Center rooftop farm was expected to produce up to 40,000 pounds of fruit, vegetables, and greens per year in 2022. “Expected” and “approximately” identify estimates rather than audited harvest totals. (Brooklyn Grange FAQ; Brooklyn Grange Opens Largest Rooftop Farm)
Water use and stormwater
The New York City all-suitable-rooftops scenario estimated that rooftop farming would supply 4% of the city’s fresh-vegetable consumption. In the same scenario, potable-water consumption would increase by 0.3%, while nitrogen discharge from wastewater treatment plants to surface water would increase by 0.6%. Those percentages are model outputs tied to the scenario’s assumptions, not citywide measurements after implementation. (Urban Rooftop Agriculture: Challenges to Science and Practice)
Crop selection changes the modeled result. If all cropped rooftop area in that scenario were dedicated to mixed greens, estimated output could meet 38% of city demand for that crop mix. The same review estimated rooftop-farming evapotranspiration could provide 2.3 times the stormwater-retention potential of New York City’s urban forest. These figures compare modeled potential and should not be read as a measured performance ratio for every farm. (Urban Rooftop Agriculture: Challenges to Science and Practice)
Site-level estimates show how storage capacity can vary with roof design and rainfall. Brooklyn Grange reports that Long Island City can absorb 60,000 gallons in a single 2.5-inch rainfall, while Navy Yard can absorb 100,000 gallons in a single rainfall. Sunset Park’s farm beds can absorb 164,000 gallons in a single rainfall, and its paved patios and paths can store another 10,000 gallons per rain event. These are farm-specific estimates from current or 2019 site descriptions, not a standard capacity per square foot. (Brooklyn Grange FAQ; Brooklyn Grange Opens Largest Rooftop Farm)
Water sourcing can also differ by system. Rainwater supplied 80% to 90% of the total water used by the cited Barcelona rooftop greenhouse in the 2018 study summarized by the 2020 review. The percentage belongs to that greenhouse and study period; it does not establish a universal rooftop-farm water ratio. (Urban Rooftop Agriculture: Challenges to Science and Practice)
Food supply and community reach
Rooftop farms can serve nearby markets as well as produce food. Brooklyn Grange reported that nearly 60% of its annual rooftop-farm yields were distributed to New Yorkers at no or low cost. It estimated 44,985 pounds of vegetables for community members at no or low cost in 2025. The company also reports more than 12,000 visitors to its farms each year. These are company-reported figures and should not be treated as independently audited. (Brooklyn Grange About)
The farm-to-market distance can be short. In its first year of operation in 2011, Brooklyn Grange’s Long Island City farm grew and distributed more than 7 tons of fresh food, and its first-year produce rarely traveled more than 5 miles from farm to plate. The figures describe that historical first-year operation, not the current distribution pattern. (Greening the Industry with Brooklyn Grange)
Lufa Farms reports a larger delivery operation. Its current press profile says the company assembles and ships 25,000 customized baskets each week and grows more than 50 varieties of rooftop-grown vegetables. The company reported more than 100,000 customers in its community in 2021. In 2020, Lufa said its largest greenhouse doubled capacity from feeding 1% to 2% of Montreal families. Earlier, in 2011, it grew 15 vegetable varieties and delivered roughly 200 baskets per week. These dated figures show changing operating scale rather than one simultaneous measurement. (Lufa Farms press room)
Construction, climate, and ecosystems
Rooftop agriculture depends on structural capacity before it depends on crop choice. Brooklyn Grange says its roofs were approved for loads exceeding 65 to 85 pounds per square foot of saturated green-roof soil. The Long Island City farm uses roughly 8 to 10 inches of rooftop growing media; Navy Yard uses 10 to 12 inches; and Sunset Park uses a 12-inch layer of its rooftop soil blend. These specifications belong to the named farms and should not be generalized to every building. (Brooklyn Grange FAQ)
Sunset Park also includes a 4,800-square-foot hydroponic greenhouse. Its Skypaver pathways are made from 95% post-consumer recycled rubber tires and milk-jug plastic. These details show how a rooftop project can combine soil-based beds, protected growing space, and specialized circulation surfaces within one site. (Brooklyn Grange Opens Largest Rooftop Farm)
The Javits Center adds ecosystem measurements to the production picture. Its rooftop food forest occupies a 10,000-square-foot orchard and is designed with seven distinct vertical layers. From 2014 through 2022, the green roof recorded 35 bird species, five bat species, and more than 1,000 observed insects. The rooftop ecosystem also included five active bee hives in the 2022 site description. These are observations and site features for the Javits Center, not a citywide biodiversity count. (Governor Hochul Announces New Rooftop Farm)
Weather remains an operating constraint. Brooklyn Grange farmers reported that 30-mile-per-hour winds can kill vulnerable early-spring plants and damage yields. During Hurricane Ida in 2021, more than 8 inches of rain fell in 24 hours on the Brooklyn Grange area. The case study presents these as climate-exposure examples rather than a predicted frequency of future losses. (Growing on Rooftops: How One Urban Farm Is Adapting to Climate Change)
Commercial greenhouse scale
Commercial rooftop greenhouses can be much larger than open-air demonstration plots. Lufa Farms’ largest greenhouse, completed in 2020, covers 163,800 square feet. Gotham Greens reports that its Brooklyn Whole Foods rooftop greenhouse measures more than 20,000 square feet, while its Queens rooftop greenhouse spans 60,000 square feet. Its first Chicago rooftop greenhouse measures more than 75,000 square feet, its second Chicago greenhouse covers 150,000 square feet, and its Providence greenhouse covers 112,500 square feet.
| Rooftop greenhouse | Reported area | Period or facility context |
|---|---|---|
| Lufa Farms largest greenhouse | 163,800 sq. ft. | Completed 2020 |
| Gotham Greens, Brooklyn Whole Foods | More than 20,000 sq. ft. | Built 2013; current company page |
| Gotham Greens, Queens | 60,000 sq. ft. | Completed 2015 |
| Gotham Greens, first Chicago | More than 75,000 sq. ft. | Opened 2015 |
| Gotham Greens, second Chicago | 150,000 sq. ft. | Opened 2019 |
| Gotham Greens, Providence | 112,500 sq. ft. | Opened fall 2019 |
The Gotham Greens figures come from the company’s current farm portfolio, while the facility dates identify when each greenhouse opened. They indicate reported physical scale, not comparable production because crop mix, growing methods, operating schedules, and market channels are not provided for every facility. (Lufa Farms press room; Gotham Greens farms)