The world's largest rooftop greenhouse is about to open in Chicago, and it's the size of an entire city block

GreenhouseMethodA rendering of the completed greenhouse.

In April, the eco-friendly soap manufacturer Method opened up its newest factory on Chicago’s South Side. This is no ordinary factory — the $US30 million space is equipped with three solar “trees” that move with the sun and a 230-foot-tall wind turbine. Combined, the on-site renewable energy sources generate a third of all energy for the building.

But the most innovative element of the factory is on the roof, where a a 75,000 square foot greenhouse is set to be fully planted this fall. When complete, the space will be the largest rooftop greenhouse in the world, growing up to one million pounds of greens each year.

For some perspective on the size of the greenhouse: the average size of a city block in many parts of the U.S. — including Portland, Oregon and Houston, Texas — is 67,600 square feet. An NFL football field is 57,600 square feet. The Method greenhouse is larger than all of these things.

MethodMethodInside Method’s factory.

When designing the factory, Method looked to Ecover, its green cleaning partner brand, for inspiration. In 1992, Ecover built the first of what it calls “ecological factories,” outfitted with sustainable building materials and a green roof.

“We wanted to meet the highest standards of green building,” says Saskia Van Gendt, Method’s Chief Greenskeeper.

The rooftop greenhouse, which was built by a company called Gotham Greens, is much more efficient than a conventional agriculture operation, using 20 times less land and 10 times less water.

Instead of going in the ground, the plants are grown with a hydroponic system that requires water but no soil. Computer systems control irrigation, heating, cooling, and other variables.

MethodfactoryMethodA rendering of the factory with the completed greenhouse.

The greenhouse, combined with its accompanying growing system, weighs a lot — so much so that Method had to re-engineer the factory roof for structural integrity. It also insulates the factory below, helping to keep energy costs down.

Once it’s up and running, the greenhouse will produce a number of different kinds of pesticide-free greens, including kale, arugula, bok choy, and butterhead lettuce. Gotham Greens will distribute the produce to local stores, restaurants, and farmer’s markets.

“We need to use our urban spaces more efficiently,” says Van Gendt. “Rooftop greenhouses are a representation of a model of doing that.”

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