This Dutch tower makes elite green design affordable. But is it actually green?

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It's one of the world's most iconic examples of green design. To start, it's literally green — encased in hundreds of trees and thousands of shrubs that ascend on ladder-like balconies 26 storeys into the sky.

Milan's Bosco Verticale — "vertical forest" in Italian — opened in 2014 to wide acclaim from the design world. Its attractive vision of skyscrapers with leafy-green canopies has spawned dozens of imitations from France to Shanghai, including one underway in Toronto's Annex neighbourhood.

But critics say these buildings typically share some not-so-green traits: their construction relies on vast quantities of carbon-intensive concrete, and they are very expensive to own. 

"I think it's completely missing the point of green design," said Lloyd Alter, a professor of sustainable design at the University of Toronto and author of Living the 1.5 Degree Lifestyle.

For Alter and other critics, Bosco Verticale represents an exclusive, and expensive, vision of a green future, where the benefits of living closer to nature are accrued to an enriched few, at an enormous carbon cost.

All of which helps explain why Stefano Boeri, the Bosco Verticale's celebrated architect, turned his attention to a different project: duplicating his iconic design as public housing in the Dutch city of Eindhoven.

"This is really the goal we had from the beginning of the vertical forest," Boeri told CBC News, "to show … that it's possible … to realize [a vertical forest] that is affordable for everybody, smart and sustainable."

That project, dubbed the Trudo Vertical Forest, officially opened last month. The pared-back recreation of the Bosco Verticale features some 125 trees and 5,000 shrubs over 19 storeys, filled with 540-square-foot starter apartments for young couples and emerging professionals.

It's Boeri's hope that this tower answers critics that vertical forests are greenwashing for an elite few. But even though he's succeeded in making his innovative design more affordable, there are reasons critics of the model like Alter remain unconvinced of its merits.

Boeri's vision for Bosco Verticale, developed in the early 2010s, was a version of architecture that did not centre around sheltering human beings from the environment. In his words, "living nature is not an ornamental presence" but a "basic component" of the building.

The pair of Milan towers — standing at 18 and 26 storeys, respectively — house a staggering total of 800 trees and 20,000 smaller plants, equivalent to three hectares of forest.

The trees eliminate the heat-magnifying effect of glass-fronted skyscrapers, absorb carbon dioxide from the air, and act as an urban oasis for dozens of species of birds and insects — and they're pretty nice to look at, too.

But all of that splendour comes at a cost. Carrying the weight of growing trees required enormous amounts of concrete, one of the most carbon-intensive building materials available.