of the product: one that purges the reservoir on demand via the cloud and another that uses only a flow regulating mechanism developed by the parent company, which allows water to empty from the blue roof at a constant rate, Garthwait said.
The cloud-based system will not be available commercially right away, but the company will begin selling the stock-and-flow product without the cloud technology in March in Europe and the U.S., Garthwait said.
Vegetal has submitted a proposal to Milwaukee Metropolitan Sewerage District to potentially back the Milwaukee pilot project. It is also exploring grants from the National Oceanic and Atmospheric Administration and the Fund for Lake Michigan, Garthwait said.
MMSD executive director Kevin Shafer said he is intrigued by the potential for Vegetal’s product to purge the roof reservoirs at strategic times or store the rainwater until the sewer system can handle the additional volume.
“It would allow us to integrate this roof storage with our control mechanisms for the tunnel and the water reclamation facilities so we can maximize the capture of water, reducing basement backups and reducing sewer overflows,” Shafer said. “From what I’ve seen so far, [Vegetal and its parent have] a good scientific background on what they’ve done so far that indicates this will work really well for us.”
Vegetal officials envision a network of roofs throughout the city equipped with the product. The cloud-based control program would run autonomously, monitoring local weather reports on the Internet and purging all the reservoirs in advance of a rainstorm, Garthwait said. During periods of heavy rainfall, storm water officials could manually override the system and purge the reservoirs as needed.
If the product could help avoid a flood, it could save millions of dollars in repairs and new infrastructure. For example, a particularly devastating storm in summer 2010 led MMSD and Milwaukee’s Department of Public Works to spend $8 million on infrastructure projects to help prevent sewage backups. Milwaukee County has experienced more than $200 million in flood damage since 1997, Shafer said.
For building owners, the benefits of Vegetal’s stock-and-flow system include better insulation than the current green roof standard since the water reservoir provides more nourishment to the plants, and potentially the ability for property owners to remotely monitor the green roof’s condition, Garthwait said.
Outfitting a building with such a system isn’t cheap though: An installation of the stock-and-flow system will cost between $20 and $25 per square foot, compared with about $15 per square foot for a more conventional green roof, Berges said. (That estimate doesn’t include the cloud application, since Vegetal is still testing it and has yet to calculate the full cost.)
Vegetal officials are hopeful that the higher cost of their system compared with other green roofs would be offset by additional government incentives. Milwaukee has rebate programs for green roofs and cisterns, and perhaps both could apply to the stock-and-flow system, Garthwait said. And if the product demonstrates enough value to entities like MMSD, that could lead to more municipal rebate programs.
But Garthwait admitted it’s a challenge for green roof companies because incentives vary across municipalities.
“We’re trying to find additional benefits that would go with it to make it more advantageous for the building owner,” Garthwait said. “We’re trying to figure out how to incentivize that additional jump [to this product].”
Most of the stock-and-flow product’s R&D was done by the parent company over the past four years, but Berges and Garthwait last year came up with the idea of incorporating cloud technology to remotely monitor and control the release of water from the reservoir, they said.
Garthwait said their idea was validated in conversations with Veolia Water North America, a subsidiary of France-based Veolia Environnement (NYSE: [[ticker:VE]]) that has a presence in the Global Water Center near downtown Milwaukee. The center, launched last year by The Water Council, a Milwaukee-based fresh water industry organization, houses the seed accelerator, R&D teams from more established water-related companies, academic researchers, and more.
“[Veolia] invented a sensor to see the level of water in a rain barrel, connect to the cloud, and you can purge it,” Berges said. “We thought, ‘Well we can do this with our product.’”
Whether that inspiration will translate into a viable commercial product remains to be seen, of course. Demonstrating a quantifiable return on investment has been a challenge for the green roof industry, and moving beyond early adopters and making green roofs a more pervasive product will require more evidence of their benefits, Berges said. She thinks the Milwaukee pilot will be a step in that direction.
“In our industry, [this new product] is huge because we’re really creating a storm water [management] machine on the roof, directly at the source of the rain,” Berges said.
