The Inside Details on the Award-Winning IGA Organic Rooftop Farm

Published by Roxanne Miller

Project Description

Name of the project: IGA Duchemin Urban Rooftop Farm
Location: Saint-Laurent Borough, Montréal, QC
Type of solution: SOPRANATURE Vegetative Solutions
Total area: 31,000 ft²

Project Group

Owner: IGA Marché Duchemin et Frères, Inc.
Green Roof Designer, Installer and Farmer: La Ligne Verte – Toit vert
Initial Extensive Green Roof and Building Architect: NEUF Architects
Green Roof System: SOPRANATURE by SOPREMA

When you see the IGA’s rooftop farm, it’s hard to imagine that it came very close to never happening at all. If it hadn’t been for the visionary output of La Ligne Verte’s cofounders Antoine Trottier and Patrice Godin, this project would have been a four-inch sedum mat extensive green roof. Not that this would have been a bad thing in itself, but we all agree that it would have been very far from the iconic grocery store rooftop farm it has now become in Saint-Laurent, on the Island of Montréal. This neighbourhood’s regulations stipulate new roofs must be either green or reflective (white), and this specific project was required to have 50% of the building roof area covered with a green roof system. To meet this obligation, a simple extensive sedum roof was designed, and the bidding process went out as such. The project was awarded to La Ligne Verte, who was able to convince the IGA’s owner of the added value of investing in a large-scale urban rooftop farm. The roof was also redesigned to highlight the IGA logo, which is represented in the shape of the green roof.

When the Duchemin family partnered with La Ligne Verte, they didn’t think the project would have such a big impact. The rooftop farm gained a lot of attention in the media across North America and even further, being published in many countries throughout the world.

The project won the Green Roofs for Healthy Cities Award of Excellence, and involved many professionals, including SOPREMA, NEUF Architects, Groupe Mach and Sobeys.

The entire concept was brought forth and came together as a result of the involvement and persistence of La Ligne Verte, the local Montréal company that incorporated a very creative solution-based approach.

IGA Duchemin is now the first grocery store in Canada to sell fresh organic produce harvested directly from its roof. Here are a few interesting facts about the project:

More than 30 kinds of vegetables are grown on the roof: kale, lettuce, carrots, green beans, eggplant, garlic, tomatoes, spinach, and more.
On the roof, there is a very productive flower cutting activity going on.
Eight newly installed beehives on the roof produced 500 jars of honey in 2021.
Vegetables and flower bouquets are sold in the IGA below.
From 35,000 to 40,000 units of vegetables and flowers are sold annually (one unit represents a carrot bunch, a leafy green bin, an eggplant, etc.). That is approximately 7.2 tons of harvested produce, out of which more than 1.3 tons are leafy greens.
The farm requires three full-time farmers (one full-time year-round, and two full-time seasonal), six interns, and over ten volunteer workers every summer.

“Over the years, we conducted trials with nearly all kinds of vegetables. We were able to successfully grow crops that you wouldn’t expect on a roof, such as broccoli, cauliflowers, parsnips, carrots, cabbages, melons, and artichokes. Although these crops have mostly been experimental, we now focus on lower maintenance crops with high economic value such as greens, small roots (turnips and radishes), and cherry tomatoes, because who doesn’t love garden-fresh cherry tomatoes?”

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The only means of transportation required to get the produce from the roof to the market are the 44 steps in the staircase that connects the farm to the back of the store. All of the fresh produce sold in the IGA store gives nearby residents a local source of extremely fresh, organic food. Being able to integrate urban greening strategies and green infrastructure solutions to an otherwise common building can also contribute to preventing the risks related to certain physical and mental diseases. These projects can also improve lifestyle and increase the well-being of individuals, because rooftop farms provide the food that we consume daily.

Harvesting locally grown produce reduces the ecological and economic impacts of long-distance freight. This rooftop allows us to cultivate fruits and vegetables that are not usually cultivated in the urban environment of Montréal. One of the biggest advantages of a rooftop farm is the very good drainage of the soil and the fact that the “field” is workable very early in the spring. That gives the farmers a much-needed head start, letting them seed a lot of crops very early in the season. These specific conditions provide a growing environment that allows the team to harvest garlic nearly a month before most other farms in Québec. The team is always amazed at being able to harvest huge cloves at the end of June.

The building is owned by IGA and the farm is rented by La Ligne Vert, which generates revenues from the sale of produce. In order to gain more revenue and promote the farm, rooftop dinners and brunches are also organized on the roof’s amenity spaces, and the dishes are cooked with fresh food from the roof.

The waterproofing system was initially designed and installed as an inverted single-ply assembly, with the membrane protection needed for a green roof installation. As this project evolved into a rooftop farm, it had to sustain a lot of foot traffic and farming activities, so the inverted roofing assembly became even more crucial to protect underlying waterproofing. This assembly and the SOPRANATURE green roof system together, apart from protecting the waterproofing from any physical harm, add an extra layer of insulation, which reduces the store’s power consumption. The XPS insulation laid on top of the waterproofing system also adds a very strong physical barrier against shock from farming tools.

SOPRANATURE’s semi-intensive systems are mid-light green roofs ranging from 150 mm to 300 mm in depth of SOPRAFLOR growing media. Plant types typically include sedums, grasses, perennials, shrubs and edibles. These are the systems that are preferred for urban rooftop agriculture. Typically, green roof media has a very low organic content to ensure minimal maintenance and adequate drainage, as well as minimize compaction. These types of growing media are not adequate for food production and need to be adapted to support vegetable growth. Active monitoring and adjustments over the course of four years supported the development of new organic green roof soils specifically designed for vegetable production on green roofs. The growing media at IGA, after a few years of farming, now contains approximately 35% organic matter by volume. This specific growing media blend is Ecocert certified and allows for food produced to be qualified as organic.

Drainage was also key in the project’s success, and IGA Duchemin is the very first Canadian store to use an irrigation system partially based on the recovery of water from its air-conditioning system. Even though SOPRANATURE systems have a capacity of absorption, retention and filtration of water, a rooftop farm still requires frequent irrigation to ensure maximum yields. As with any green roof, the rooftop farm improves stormwater management while helping to reduce the risks associated with overflows and floods. The irrigation system takes into account rain episodes and is triggered as needed in order to use as little potable water as possible. The store itself is LEED Gold certified, one of the highest standards for green buildings.

SOPRANATURE systems create conditions promoting the development of microhabitats to support life, and the roof is home to different pollinators and nesting birds. The flowering plants look as beautiful as they are useful! The rooftop farm has been such a great addition to the store’s image and revenues, so much so that the owners expanded it by an additional 5,000 square feet to the existing 25,000 square feet in the fall of 2021.

With the increasing awareness that food supply must not be taken for granted anymore, let’s hope that this successful project inspires others to invest in their community’s future and well-being.

“As an organic vegetable farmer coming from a rural background, I was skeptical that a rooftop farm could be productive given the very shallow depth of soil. It turns out that there are many advantages to a rooftop farm. Amongst others, perfect light exposure, the absence of deer and other small mammals, and near-perfect “field” conditions very early in the season. Combined with beneficial farming practices such as cover crops, green manure, minimum soil disturbance and regular additions of compost, we created an urban farm with a true living soil where insects, worms and bacteria are thriving and make our system truly productive.”

“You would expect a rooftop farm to be free of most pests typically encountered in the countryside. However, despite our urban location, we do struggle with the same weeds, insects and fungal diseases from time to time, as would any other farm. Fortunately, we are able to keep most of these problems under control, even under organic management, by implementing preventive strategies. If it was too easy, it would be boring, right?”