Sustainable Rooftop Greenhouses: The Future of Urban Agriculture

Inside the Ville Saint Laurent location, one of the rooftop greenhouses © Courtesy of Lufa Farms

Sustainable Rooftop Greenhouses: The Future of Urban Agriculture

ALLAN BRITNELL

When we think of Canadian agriculture, we tend to imagine picturesque farms or sweeping pastures in the country's rural areas. But there’s a growing trend to eat foods grown closer to home—maybe even as close as an urban rooftop greenhouse.

Montréal-based Lufa Farms, for example, operates five rooftop greenhouses across the city, with a combined total of more than 500,000 square feet of growing space. Their Ville Saint Laurent location, reportedly the largest rooftop greenhouse in the world, boasts 163,800 square feet of hydroponic crops growing on vines. That’s about the size of two CFL football fields.

Inside this and its other locations, it grows more than 50 types of vegetables, including eggplant, cucumbers, lettuce, and several varieties of tomato. It harvests more than 200,000 vegetables every week.

Each greenhouse has been built with the latest sustainable practices in mind. They use high-intensity LED grow lights and even capture rainwater and snow melt to irrigate the plants.

“We follow the tenets of responsible agriculture. So that’s everything from recirculating the irrigation water to saving energy to composting all of our green waste,” said company co-founder and co-CEO Lauren Rathmell on Agriculture and Agri-food Canada's Taste the Commitment video series.

As with any type of agriculture, there are challenges. “We thought we would be relatively immune from pests being in the city, but that’s not the case,” said Rathmell. Her team does not use any synthetic pesticides. Instead, they regularly monitor the plants and employ biological controls and predatory insects, such as wasps that eat crop-damaging aphids. “The most important thing is vigilance. We remove affected plants if need be.”

In addition to the more than 600 employees working at their greenhouses and distribution centres, they also employ a team of pollinators—bumblebees that live inside the greenhouses.

The company sells directly to consumers through weekly subscriptions. The produce is harvested and then packed into durable “baskets.” Within 24 hours of being harvested, the baskets are delivered to one of 350 pickup points around the city or, for a small fee, right to customers’ doors.

They’ve also partnered with other local companies so customers can customize their deliveries to include everything from meat, eggs and dairy products to baked goods and complete meal kits.

With nearly 70,000 current subscribers, they estimate that they grow enough produce to feed two per cent of the families living in Montréal.

Rooftop greenhouses have many other benefits. Commercial rooftops, for example, are typically “heat islands” that get hot in the summer sun and release that warmth into the air after the sun has gone down.

Instead, the greenhouses act as insulation for the building. “We’re this insulation bubble of plants and warmth that helps cool in the summertime and keep things warm in the winter,” said Rathmell. The greenhouses also capture heat rising from the building below. “We save about half the energy needed by building our greenhouses on rooftops, as opposed to the ground,” she added. Growing right in the city also reduces the delivery distance for food to get from farm to table. —NC