Kriston Capps is a staff writer for CityLab covering housing, architecture, and politics. He previously worked as a senior editor for Architect magazine.
A vertical garden tower just won a significant award for architecture. Is it time to start taking these designs seriously?
Passive House designers are the Fremen of the architectural world. They look at buildings the same way that Dune’s noble desert tribe thinks about water. For the Fremen, the stillsuit is an essential tool for capturing moisture on a harsh desert world at all costs. For the Passive House designer, designing a building involves sealing it to retain energy and heat at all costs—or rather at low costs.
So when I asked a Passive House designer for his thoughts about a relatively new and unconventional type of building design, he replied with the kind of concern a water-conscious Fremen might feel looking at a leaky faucet on Arrakis.
Call it the treescraper: It’s a building type that is every bit as fantastical as the giant Shai-Hulud sandworms of Dune. Treescrapers have emerged as a popular typology in speculative architecture, a building scheme that pledges environmental gains and density—but exists mostly on paper. The porosity of these designs upends conventional standards for construction. They look futuristic, maybe so much so that they don’t look like the future of architecture.
One treenscraper project, however—Bosco Verticale, designed for Milan by Stefano Boeri—has just been named the Best Tall Building Worldwide for 2015 by the Council on Tall Buildings and Urban Habitat. That could be a significant step away from architectural fiction and toward built reality. But it only makes the questions about these projects more urgent: Can they work? Are they green?
Boeri recently revealed plans for Tour des Cèdres, a different treescraper project meant for Switzerland. Arup, the architecture and engineering firm, didn’t respond right away about its work for the award-winning Bosco Verticale project. And Boeri didn’t get back with a comment about how these projects are supposed to work.
Mike Eliason, a Passive House designer for Bjarko|Serra Architects in Seattle, spoke generally about the broad sustainability concerns that treescraper projects raise. “There are two things that stand out for me, mostly on the energy side,” he writes in an email.
One is the additional force that it takes to shore up a balcony to support the weight of a tree. (Trees on balconies are the definitive features of the designs I’m lumping together under the treescraper label.) Increasing the steel reinforcement or concrete slab of a balcony increases the embodied carbon emissions for the project.
The other broad issue is the operational: the loss of heat where the balcony meets the exterior wall. Thermal bridges, essentially areas where heat loss happens at an intersection with the building’s envelope, can potentially lead to problems, namely an increased heating requirement to keep the building comfortable. There are ways to thermally break the juncture using insulation to protect against heat loss, but the question gets a bit technical for a broad look at a range of buildings.
“The net result of carbon emissions (embodied and operational) could be way more than the [kilograms] of carbon sequestered in smaller diameter trees,” Eliason writes. “So the amount of work undertaken to make that effect look cool and function could actually be less sustainable.”
Put aside, for a moment, whether these buildings are on net sustainable. That question will only be resolved when a few more of them are built—if a few more of them are built. (And if they are built to the design when they are built and not value-engineered into something cheaper.) Even as a purely speculatively form of design, though, treescrapers represent an idea about sustainability that’s worth weighing. The buildings don’t need to be built for that idea to matter.
These designs do not shy away from the lessons of Mies van der Rohe and Le Corbusier. The notion that harmony rises out of order—that the house is a machine for living in—is preserved in most of these designs. Some of them are curvier than others, but the fundamental unit, and the relationship between the unit and the whole, the individual and the collective, carries through across the set.
Yet these buildings are inflected with nature. They are defined by their allegiance to nature, even though the buildings are not natural. They do not derive from nature, like the work of Frank Lloyd Wright, the other architect in the Big Three. Instead these buildings assimilate nature, incorporating it into the machine.
Those trees don’t push back against the International Style, which is sometimes criticized as cold. Treescrapers are more like an apology for Mies and Le Corb, correcting an oversight. As if they had neglected to include a crucial gear—a tree—without which a home cannot thrive.
Bringing nature into urban living at the atomic unit level is a radical approach to the urban habitat. Think of Central Park, where New Yorkers come together from dense living configurations to take in nature. Treescrapers disaggregate the park asset and divy it up between homes. These designs indulge in the individual, building access to nature into self-contained housing units.
It’s a strategy that bows to a certain reality, perhaps. As land costs rise in dense cities, it becomes harder and harder to set aside land for parks and maintain them for people. Maybe an in-apartment option could be construed as a planning work-around.
But a balcony tree is not a public park—especially not a tree growing on the north face of a building in the northern hemisphere (where trees would be cast in shadow). Reorienting nature from a collective experience to an individual one is true science-fiction design. And it forgets the value in bringing people together in parks, where they do more than commune with nature. It might be too obvious to say, but treescrapers miss the forest for the trees.