“Man, it’s hot,” says Jim Hole, co-owner of the Enjoy Centre.
He’s dressed in a black T-shirt and dark pants, and standing thigh-deep in the year’s experimental tomato crop. Around him, plants bearing deep crimson fruit tumble out of a dozen or so big black tubs. On this late August (2013) morning, it’s already 20 C, but roughly one storey up on this St. Albert rooftop it feels even hotter.
That’s because it actually is. Unsheltered and covered in light grey shingles, the roof captures and amplifies heat – making this an excellent site for another installment of NAIT’s ongoing research into the benefits and challenges of living roofs in the Edmonton area.
Since 2010, Biological Sciences Technology instructor Dave Critchley has monitored the roof using four high-tech, data-tracking planters the size of Smart cars. “We have harsh conditions on roofs” on the prairies, says Critchley, who notes that surface temperatures on a 25 C day can reach, even pass, 70 C.
But, as his studies have shown, that can be turned into an advantage for builders, and for urban agriculture.
Critchley’s data-trackers represent a long-term study with two primary focal points. One: do living roofs lead to energy savings? Two: can they help municipalities manage storm water runoff, an issue that hit Alberta hard this summer, particularly Calgary and points south. Overall, he asks, “What is the benefit of putting a living roof into this space?”
Over time, he’ll record and analyze changes in soil temperature and moisture, as well as the speed and volume of water flow through the planters. They’ll also help him – and participating NAIT students and staff and Queen Elizabeth high school students – find plants hardy enough to withstand heat and drought, as well as exposure to winter winds.
His early results already shown that a living roof can cut those extreme rooftop surface temperatures by roughly a third.
More tangible outcomes, however, are obvious in the produce. Last year’s crop consisted of nearly 30 varieties of heirloom tomatoes – those oddball, flavourful varieties seen in farmers’ rather than supermarkets.
“They taste so much better. They have such a nice smell, texture, everything,” says Critchley. “Absolutely delicious.”
And, with the right soil composition – another matter of research for Critchley and Hole – they’re bountiful. This year’s crop was smaller by design (and included peppers and cucumbers), but more than a tonne of tomatoes were harvested in 2012 and used in the Enjoy Centre’s restaurant, the Glasshouse Bistro and Café.
In terms of production capacity, Hole ranks rooftops second to greenhouses, thanks mostly to the increased heat on plant roots, and puts them ahead of conventional garden plots.
They’re also surprisingly simple to keep (if your roof is reinforced for such a project). Pests are less prevalent, pollinators plentiful, and in this case maintenance involved a couple of watering sessions a week, which Hole did himself. “A five-year-old could have done what I did," says Hole.
“The plants know what to do. You just have to support them.”
Set to run at least five years, Critchley’s experiment will continue to collect data that may inspire and encourage Edmonton-area builders and building owners to include living roofs in their structures. His hunch is that they will save on cooling costs and increase the lifespan of roofs themselves.
“The only way to know is to have projects like this set up over the long term,” says Critchley.
Piggybacking on the continued strength of the “buy local” movement, his project, in partnership with Hole, will yield more information on what and how much these gardens can produce. Given the short central-Alberta summers, the results could be transformative.
On the Enjoy Centre roof, “We're adding 20, 25 days of growing season, which equates to jumping down to Medicine Hat,” says Critchley. "It's tremendous production. When you look at the 100-mile diet concept, why don't we go up onto the roof and produce all we need?”
That logic would certainly appeal to Hole, who grew up on a farm on what was once the edge of St. Albert. Today it's surrounded by subdivisions. “When you look at a city, originally that was farmland,” he says. “But in some respects, the farm is still there.”
It’s tucked away in people’s yards, he points out, and in whatever other green spaces they carve out of the concrete and asphalt of the urban environment. Perhaps, in time, this project will show the potential to carve out even more.