Community-gardening advocates have sold urban farming as a sustainable local alternative to industrial-scale farming and as an educational platform for healthier living. And municipalities are buying in, adopting urban ag to transform vacant lots into productive civic assets. In the last two or three years, however, entrepreneurial urban farmers have opened a new frontier with a different look and operating model than most community gardens. Their terrain is above the ground, not in it. Working with help from engineers, architects, and city halls, they have sown rooftops and the interiors of buildings worldwide. “There’s a lot of activity right now, and there is huge potential to do more of it,” says Gregory Kiss, principal at Brooklyn-based architecture firm Kiss + Cathcart.

Exploiting the wide-open technology and design potential of these vertical farms—as building-based agriculture is increasingly known—should make them “more energy- and water-efficient and better integrated with their host buildings,” says Kiss.

The simplest vertical farms are soil-based agricultural extensions of the green-roof concept. Rather than covering rooftops with drought-resistant sedums to help control stormwater runoff and combat the urban-heat-island effect, they grow edible herbs and vegetables that deliver additional benefits. These roofs create jobs, provide fresh produce, and raise consciousness to combat the rising incidence of obesity, diabetes, heart disease, and other diet-related illnesses.

Adding a greenhouse, meanwhile, can add another level of verticality, in which the well-protected crops are stacked to multiply the growing area. Further enhancing output are high-tech additions such as automated conveyance systems, supplemental lighting, and hydroponics, which substitutes nutrient-enriched water for soil. Eliminating soil—which can weigh 50 pounds or more per square foot—slashes structural costs. And all these enhancements boost the output of fruit, vegetables, and herbs, creating additional revenue to finance the capital-intensive installations.

The most innovative vertical-farm designs are expanding urban ag’s potential by moving high-tech growing systems below the rooftop. Some current and future schemes include exploiting space deep in the belly of buildings, substituting grow lamps for sunlight, and encasing buildings in hydroponic greenhouses. Such projects would feed people more sustainably than current industrial practices, in the view of vertical-farming advocates. If they are right, these farms could feed the world’s growing population while shutting down many of today’s mega-farms.

As Kiss explains this most utopian view of vertical farming’s potential: “You eliminate the enormous pollution from agricultural runoff and pesticides, monoculturing of ecosystems, and water-usage problems, and allow land to return to nature, which restores habitats and sequesters carbon. It is a radical view of how the food system ought to be.”

Excerpted from the July 2013 edition of Architectural Record magazine. Get the full scoop via ArchRecord…