Green Roofs - Living Architecture Monitor - Spring 2020 - 6

A study by the Council of Tall Buildings
and Urban Habitat, found that the overall
energy consumption reduction rate was
7.5 per cent annually, making the Bosco
Verticale more energy efficient than the
majority of buildings in Milan.
Vertical forests promote biodiversity. The
hosting over 100 species of plants at Bosco
Verticale has attracted over 1600 specimens
of birds and butterflies to the tower oasis.
The irrigation system, fed by groundwater,
is controlled by a central monitoring system
which pumps water through all of the building's floors and into the plant containers,
which each have two sensors to register the
substrate moisture levels.
All of these positive features sound great
but what about the embodied emissions
and additional costs associated with such a
special building? For instance, the installation and maintenance of vegetation would
assumedly require extra building materials
and resources to maintain. What makes
the Bosco Verticale a true flagship project
is that the building design helps reduce
the embodied emissions and costs. The
energy consumption from the geothermal
irrigation system is offset by solar powered
pump systems. The additional weight of
the soil in the planters is reduced by using
a light aggregate mixture comprised of
agricultural soil, organic matter and volcanic material. The insulation provided by
the external greenery reduces heating and
cooling costs/unit.
The average construction cost for the
building was US$200/sf and the average
selling price US$1028/sf in 2015. With
an additional average maintenance cost
of $6.47/sf per year the Bosco Verticale
is a financially sustainable condominium.
The plants are maintained using a roofmounted crane and a basket that facilitates
bi-annual pruning. Maintenance is
performed by the buildings management
team and the plants are not included in the
ownership of the condominium unit. The
individual tenants are not permitted to interfere with the maintenance of the plants,
without prior authorization. COIMA,
the condominium developer, pays for the
maintenance of the building. In 2011,
prices (in US dollars) of units ranged from
LIVING ARCHITECTURE MONITOR / SPRING 2020 / 6

$845,000 for an 861/sqft apartment to
$2.6 million for a 2163/sf penthouse suite.
Today not a single unit is for sale but you
can rent a 1723/sf unit for $2760 a month.
It is clear that the aesthetically pleasing
design and the embodied environmental
benefits increase the value of the units, but
can the same be expected for other vertical
forests being developed around the world?
Over 15 vertical forest projects are
under development. Many of these are
projects by Stefano Boeri Architetti.
Perhaps the most ambitious of these is in
Liuzhou, China. "Liuzhou Forest City"
is a project, which plans to blanket an
entire city with greenery totalling over
40,000 trees and 1 million plants. This
level of greenery is estimated to annually
sequester 10,000 tons of Co2 and 57 tons
of micro-particles. Other similar projects
include one by UNstudio and Cox Architecture, a two billion dollar mixed-use
project dubbed "The Green Spine" in
Melbourne. In Toulouse, Studio Libeskind
is building a vertical forest project, called
"Occitanie"; a mixed-use building including both residential units and a Hilton
Hotel, slated for completion in 2022.
There are a lot of factors involved in
designing a vertical forest. The plants for
each building have to be chosen to include
considerations such as the local climate,
wind patterns, and available light. There is
no one-size-fits-all design. The computergenerated images of various proposed
vertical forests differ vastly in shape,
size, amount of foliage, and presumably
cost. Each new design has to be uniquely
catered to local climate demands, making
vertical forest projects unlike regular steel,
glass, and concrete buildings that can be
constructed anywhere. This complexity is
why on any given vertical forest project,
there needs to be a wide array of specialists
involved in the process.
In Toronto, architect Brian Brisbane
of Brisbane Brook Beynon has brought
together a team of specialists including
leading horticulturists, irrigation experts,
academics, and forestry experts to ensure
the 400-500 tree vertical forest building
on Yorkville's Designers Walk will be able
to survive over the long-term. According

to Brisbane, "A vertical forest is really
like a hillside. It's not potted plants on a
decorated building. The building is really
a host." Brisbane expects that his first
"hillside" development will add a premium
of $15,054,200 (Cdn) to the value of the
27-storey building.
It's no secret that building vertical forests involves significant development costs;
however the payout for the developers
lies in their ability to market them at rates
higher than a regular condominium. They
are a luxury. Will the public be intrigued
enough to pay a premium? The answer
thus far seems to be yes. The residents
of the 6-year-old Bosco Verticale report
they enjoy being surrounded by greenery
and some have even stopped using their
air conditioners because they no longer
need to regulate their unit's internal
temperature. These resident reports speak
to the biophilia hypothesis, which posits
that people have an innate tendency to
seek connections with nature and other
forms of life. Vertical forests represent the
ultimate embodiment of urban biophilic
design, because they function much like
an oasis in a desert, providing people with
natural green environments to escape to
from the surrounding concrete jungle.
Unlike public parks, vertical forests
provide both a full immersion in nature,
combined with prospect - the ability to
see into the distance - and a place to call
home.
The appeal of vertical forests is undeniable. While the number of proposed projects has sprouted up at a relatively fast pace
over the past decade, there is still a long
road ahead to widespread adoption. One
thing is for certain; vertical forests are here
to stay and for both industry professionals
and buyers, they are worth a closer look.
Oliver Gillings-Peck is a researcher and
freelance writer.
For More Information
Vertical Greenery: Evaluating the High-rise
Vegetation of the Bosco Verticale, Milan.
CTBUH research report, 2015 (Council of Tall
buildings and Urban habitat)
https://www.stefanoboeriarchitetti.net/en/
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Green Roofs - Living Architecture Monitor - Spring 2020

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