115
Compiled by Lisa Hammershaimb OPEN SPACE The Urban Living Roof Movement
| Date post: | 22-Mar-2016 |
| Category: |
Documents |
| Upload: | lisa-hammershaimb |
| View: | 221 times |
| Download: | 1 times |
Com
pile
d b
y Li
sa H
amm
ersh
aim
b
op
en s
pa
ceT
he
Urb
an L
ivin
g R
oof
Mov
emen
t
ed
ito
r’s
no
te
Op
en s
pac
e, i
n t
his
boo
k, r
efer
s ex
clu
sive
ly t
o th
e op
en p
lace
s on
th
e to
ps
of
bu
ildin
gs f
oun
d w
ith
in u
rban
sp
aces
.
op
en s
pa
ceCo
mp
iled
by
Lisa
Ham
mer
shai
mb
Th
e U
rban
Liv
ing
Roo
f M
ovem
ent
open space
book design © 2009 Lisa Hammershaimb
Published by Lisa Hammershaimb as part of the greater MFA thesis project, Urban Acres. Advised by:
Carolina de bartolo, Marc english, brian Majeski, Jeremy stout, and Aran baker. Fall 2009, Academy of
Art University, san Francisco, California. All rights reserved.
con
te
nt
s12 Preface
Lisa HammersHaimb
wHy Living roofs?
rooftop resources
Living roof stories
Buildings Like Trees, Cities Like Forests biLL mcdonougH
Living Roofs Explained city of portLand environmentaL services
Living Roofs Performance Studybas baskaran and karen Liu
16
24
48
View From the Bridge Lisa cunningHam
The Residential Front patrick carey
A Rooftop Farm for the Future catHy erway
60
68
84
Living Roof Quick Facts
Plant Resources
Regional Resources
About the Contributors
Bibliography
92
98
108
112
114
—f
re
idr
icH
Hu
nd
er
tw
as
se
r, a
rc
Hit
ec
t
Wh
en o
ne
crea
tes
livi
ng
roo
fs o
ne
doe
s n
ot
nee
d t
o fe
ar t
he
so-c
alle
d p
avin
g o
f th
e la
nds
cap
e: t
he
bu
ilt
stru
ctu
res
them
selv
es b
ecom
e p
art
of
the
lan
dsca
pe.
—w
ins
to
n c
Hu
rc
HiL
L, f
or
me
r p
rim
e m
inis
te
r
We
shap
e ou
r bu
ildin
gs in
itia
lly
; an
d f
rom
th
en o
n o
ur
bu
ildin
gs s
hap
e u
s.
14 /
op
en
sp
ac
ePrefaceLisa HammersHaimb
My initial interest in living roofs and sustainable urban design had rather strange
beginnings. About to begin a cross-country drive from Colorado to Chicago and feel-
ing ill-prepared with reading material, my mom grabbed a stack of free magazines on
my way out the door at a favorite local breakfast spot. The magazines contained the
usual glossy images of beautiful mountains, remote f ields of wildf lowers, and constant
reminders that life in Colorado is much better than anywhere else in the world, imme-
diately followed by slick realtor ads and enticing custom home-building information.
When not driving, I browsed through them uttering the appropriate superlatives at
the soaring mountain vistas and brilliant f lowers and wondering yet again why I was
heading out of the mountains and into an urban area for an extended period of time,
when suddenly I stumbled across an article addressing how to make your home more
“friendly and green.” The easy tips gave way to larger design and lifestyle changes in
an effort to reconcile the ever shaky relationship between man, nature, and the built
environment. Futuristic solar panels clad one home while sexy sculptural wind tubines
towered over another. Both homes looked bold and powerful, proudly showcasing the
triumph of cutting edge green technology.
And then in the next article I saw something that was a bit less f lashy. It was something
that was not space age or sexy but rather was just a home covered with a meadow of
grass, visually quiet and beautiful. It was a home that, in an effort to improve insula-
tion, absorb runoff, and create personal greenspace and a garden for the inhabitants
sheltered below, had traded shingles for sedum and native plants and transformed an
overhead barren wasteland into something lush and serene.
As I read more about living roofs and the myriad of benefits, I was amazed and in-
trigued that something so simple, indeed so elementary as sowing seed and growing
plants, could have such positive long-reaching results. In a world increasingly detached
from nature yet obsessed with extolling its preservation, living roofs not only provide
the results that make them a major player in the emerging world of sustainable design,
but also provide the aesthetic connection to nature that we all crave. Needless to say I
was a quick convert to the living roof movement.
When, during grad school, the opportunity arose for me to use my developing graphic
design skills as “a way to promote positive change and reframe challenges and issues
facing culture” through my graduate thesis project, a project promoting living roofs for
urban spaces immediately made sense. Blending my skills in design with my passion for
nature, Urban Acres: The Urban Living Roof Project was born.
This book is not intended as a living roof how-to guide or an exhaustive technical
manual for creating and installing your own living roof. For those questions I recom-
mend you contact one of the licensed living roof installers listed in the resources sec-
tion at the back of the book or connect with one of the grassroots community education
organizations that have been created across the country. Instead this book shares a
broad overview of living roofs, a bird’s eye view if you will, and shares stories of a few
buildings that have begun to open the way for a new urban landscape where structures
do not isolate people from nature but rather remind us of the beauty that comes from
living as a creature in part of an amazing natural world. Living roof also go by other
names such as “green roofs” or “ecoroofs.” Though there is no one right name, I have
chosen to call them living roofs because to me this name ref lects what they do with
the most accuracy. Plants, when applied to the surface of a roof bring life to an unex-
pected place, thus making it living. The ultimate goal of Urban Acres is to transform
our rooftops from barren to lush and in so doing transform what it means both to have
a roof and to connect with nature in the context of an urban environment in a way that
is deeply meaningful.
wH
y L
ivin
g r
oo
fs?
18 /
op
en
sp
ac
e
we
mu
st
le
ar
n t
o a
sk
mo
re
of
ou
r c
re
at
ed
en
vir
om
en
t. s
us
ta
ina
bl
e d
es
ign
m
us
t b
ec
om
e t
he
no
rm
al
bu
ild
ing
sc
he
me
fo
r h
ar
mo
ny
wit
h n
at
ur
e.
When the architect and theorist Le Corbusier imagined the future of cities from the
vantage of the early 20th century, he foresaw a new industrial aesthetic that would free
design from the constraints of the natural world. For Le Corbusier, the city was “a human
operation directed against nature” and the house was “a machine for living in.” He
imagined architecture worldwide shaped by a “mass production spirit.” The ideal: “One
single building for all nations and climates.” Le Corbusier’s friends dismissed his futuristic
ideas. “All this is for the year 2000,” they said.
It seems they were right. In many ways, our world is LeCorbusier’s world: From Rangoon
to Reykjavik one-size-fits-all buildings employ the “engineer’s aesthetic” to overcome the
rules of the natural world. As uplifting as that might be for the spirit of LeCorbusier, it is
becoming more apparent all the time that buildings conceived as mass-produced machines
impoverish cultural diversity and leave their inhabitants cut-off from the wonders and
delights of nature.
Imagine a building, enmeshed in the landscape, that harvests the energy of the sun,
sequesters carbon and makes oxygen. Imagine on-site wetlands and botanical gardens
recovering nutrients from circulating water. Fresh air, flowering plants, and daylight
everywhere. Beauty and comfort for every inhabitant. A roof covered in soil and sedum to
absorb the falling rain. Birds nesting and feeding in the building’s verdant footprint. In
short, a life-support system in harmony with energy flows, human souls, and other living
things. Hardly a machine at all.
This is not science fiction. Buildings like trees, though few in number, already exist. So
when we survey the future-the prospects for buildings and cities, settled and unsettled
lands-we see a new sensibility emerging, one in which inhabiting a place becomes a
mindful, delightful participation in landscape. This perspective is both rigorous and
poetic. It is built on design principles inspired by nature’s laws. It is enacted by immersing
Buildings Like Trees, Cities Like ForestsbiLL mcdonougH
But what if buildings were alive? What if our homes and workplaces were
like trees, living organisms participating productively in their surroundings?
Bringing value to the spaces they inhabit?
20 /
op
en
sp
ac
e
einstein’s principLe iLLustrated
b b
Buildings like trees, though few in number, already exist. So when we survey the
future—the prospects for buildings and cities, settled and unsettled lands—we see a
new sensibility emerging, one in which inhabiting a place becomes a mindful, delightful
participation in landscape. This perspective is both rigorous and poetic. It is built on
design principles inspired by nature’s laws. It is enacted by immersing oneself in the life
of a place to discover the most fitting and beautiful materials and forms. It is a design
aesthetic that draws equally on the poetics of science and the poetics of space. We truly
hope it is the design strategy of the future.
tHe Human Leaf
If one unpacks the compressed verse of Einstein—e=mc2—one finds poetry, beauty, the
dynamic structure of the universe. Following Einstein’s inimitable lead, we see in e=mc2
a kind of design koan. e is the energy of the sun-physics and planetary motion. m is
the mass of the earth-chemistry. When the two interact at the speed of light, biology
flourishes and we celebrate its increase-the growth of trees, plants, food, biodiversity
and all the cycles of nature that run on the sun. Good growth. And when human systems
support ecological health, that’s good growth too.
Applied to design, the laws of nature give architects, designers and planners a set of
principles that allow them to articulate in form a building’s or a town’s connection to a
particular place. They allow us to create buildings that make the energy of the sun a part
of our metabolism and apply it to positive human purpose—the building as “human leaf.”
The principles, illustrated by the life of a tree, are basic.
sun energizes eartH eartH grows pLans pLants renew Life
use current solar income Living things thrive on the energy of the sun. Simply put, a tree
manufactures food from sunlight, an elegant, effective system that uses the earth’s only
perpetual source of energy income. Buildings that tap into solar income—using direct solar
energy collection; passive solar processes such as daylighting; and wind power, which is created
by thermal flows fueled by sunlight-make productive and profitable use of local energy flows.
celebrate diversity “The tree” provides not just one design model but many. Around the
world, photosynthesis and nutrient cycling, adapted to locale, yield an astonishing diversity
of forms. Bald cypress, desert palm, and Douglas fir suggest a range of niches. The hundreds
of tree species within a single acre of Southern Appalachian forest suggest the diversity of
a single region. Architects and planners, applying a diversity of design solutions, can create
buildings and cities that fit elegantly and effectively into their own niches.
waste=food The processes of each organism in a living system contribute to the health of
the whole. A fruit tree’s blossoms fall to the ground and decompose into food for other living
things. Bacteria and fungi feed on the organic waste of both the tree and the animals that eat
its fruit, depositing nutrients in the soil in a form ready for the tree to take up and convert
into growth. One organism’s waste becomes food for another. Applied to architecture, these
cradle-to-cradle nutrient cycles can serve as models for the design of materials and building
systems eliminating the concept of waste. Materials designed can be either safely returned to
the soil or re-utilized as high-quality materials for new products.
kinsHip witH aLL Life
As architects and planners explore these principles—what amounts to a new conception of
design—they will become more adept at creating fit and fitting spaces for human habitation.
New benchmarks will emerge. Rather than overpowering nature or limiting human impact,
good design will affirm the possibility of developing healthy and creatively interactive
relationships between human settlements and the natural world.
With new benchmarks will come new practices, and a design process that is now rare will,
we hope, become the norm. Design teams in many regions would begin with an assessment
of the natural systems of a place—its landforms, hydrology, vegetation, and climate. They
would tap into natural and cultural history; investigate local energy sources; explore the
cycles of sunlight, shade and water; study the vernacular architecture of the region and the
lives of local fauna, flowers and grasses.
22
/ o
pe
n s
pa
ce
a l
ivin
g r
oo
f i
nt
eg
ra
te
d i
nt
o a
to
ro
nt
o o
ff
ice
bu
ild
ing
pr
ov
iid
es
hu
ge
be
ne
fit
s f
or
it
s
inh
ab
ita
nt
s a
nd
en
ha
nc
es
th
e v
iew
s f
ro
m s
ur
ro
un
din
g b
uil
din
gs
.
24
/ o
pe
n s
pa
ce
use soLar income
ceLebrate diversit y
waste=food
Learning from a tree
Combining an understanding of building and energy systems with this emerging “essay of
clues,” designers would discover appropriate patterns for the development of the landscape.
Building materials would be selected with the same care, chosen only after a careful
assessment of a variety of characteristics, ranging from their chemistry to the impacts of their
use, harvesting and manufacture. We might also expect to see the industry-wide pooling of
architectural products as builders begin to create closed-loop recycling systems to effectively
manage the flow of materials.
With this emphasis on sustaining and enhancing the qualities of the landscape, architectural
and community designs would begin to create beneficial ecological footprints-more habitat,
wetlands and clean water, not fewer negative emissions.
Vital threads of landscape would provide connectivity between communities, linking urban
forests to downtown neighborhoods to riparian corridors to distant wilds. Cities and towns
would be shaped and cultivated by an understanding of their singular evolutionary matrix, a
new sense of natural and cultural identity that would grow health, diversity and delight, and
set the stage for long-term prosperity.
Changes such as these, many already afoot, signal a hopeful new era. Ultimately, they will
lead to ever more places that honor not just human ingenuity but harmony with the exquisite
intelligence of nature. And when that becomes the hallmark of good design, we will have left
behind the century of the machine and begun to celebrate our kinship with all of life.
In this new landscape, we would see buildings like trees, alive to their
surroundings and inhabitants, and cities like forests, in which nature and
design create a living, breathing habitat.
26 /
op
en
sp
ac
e
(up
pe
r)
a l
ivin
g r
oo
f t
ra
ns
fo
rm
s u
nu
se
d s
pa
ce
in
to
a g
re
en
an
d b
re
at
hin
g s
ur
fa
ce
th
at
bo
th
p
ro
te
ct
s t
he
bu
ild
ing
be
low
an
d g
ro
ws
pr
od
uc
e f
or
ne
igh
bo
rh
oo
d i
nh
ab
ita
nt
s.
(lo
we
r)
sw
iss
ch
ar
d a
nd
ve
ge
ta
ble
s b
rin
g v
eg
et
ab
le g
ar
de
ns
up
to
th
e r
oo
f.
a l
ivin
g r
oo
f i
nt
eg
ra
te
d i
nt
o a
to
ro
nt
o o
ff
ice
bu
ild
ing
pr
ov
iid
es
hu
ge
be
ne
fit
s f
or
it
s
inh
ab
ita
nt
s a
nd
en
ha
nc
es
th
e v
iew
s f
ro
m s
ur
ro
un
din
g b
uil
din
gs
.
28
/ o
pe
n s
pa
ce
synergistic reLationsHip
acted out on a Living roof
pLants sHeLter animaLs b
wa
st
e f
ee
ds
mic
ro
or
ga
nis
msb
microorganisms enricH tHe soiLb
so
iL a
nc
Ho
rs
pL
an
ts
pL
an
ts
pr
ot
ec
t s
oiL
b
b
Living roofs are living, breathing, vegetated roof systems that provide a sustainable
alternative to conventional roofing. They are part of a growing world-wide effort to promote
sustainable development and reduce negative impacts on air, water, energy, and the earth.
Cities encourage the use of living roofs as part of their efforts to promote sustainable
development and protect their sewer infrastructure.
A living roof is a lightweight system of soil (growing media or substrate) and vegetation
designed to be as self-sustaining as possible. A successful living roof is synergetic. The soil
anchors the plant roots and supports plant growth. The plants protect the soil from erosion
and heat gain. Roots and soil foster microorganisms that make the soil and plants healthier.
Water and sun feed the soil and plants. Plants photosynthesize and produce food for other
species. The other species in turn produce waste matter that helps improve the soil. Living
roofs are also known as ecoroofs, extensive greenroofs, or vegetated roofs.
Buildings are predominately made of wood, steel, brick, some form of concrete, or
a combination of two or more of these materials. When properly designed, all of these
materials are appropriate for living roof installations. Living roofs often enhance the
structure and durability of the buildings upon which they are placed. Based on documented
experience and studies, living roofs offer a number of important benfits that conventional
roofs do not. In fact, conventional roofs cause many of the urban infrastructure problems
that living roofs solve.
Living Roofs Explainedcity of portLand environmentaL services
Living roofs can be used on most types of commercial, multifamily, and
industrial structures, as well as single-family homes, garages, and other
facilities. Living roofs are suitable for both new construction and re-roofing of
existing buildings, and can be located on both flat and pitched roofs.
30 /
op
en
sp
ac
e
intensive and extensive Living roof exampLes and cHaracteristics
intensive roof extensive roof
b sHaLLower soiL
b cHeaper to buiLd
b LigHter weigHt
b can Have HigHer sLope
b may Have Limited access
b require Less maintenance
b retain Less stormwater
b Have Less diversit y
b deeper soiL
b more expensive to buiLd
b Heavier weigHt
b Lower sLope
b can support Human activit y
b require more maintenance
b retain more stormwater
b Have more diversit y
extensive and intensive Living roofs
There are two types of living roof systems—“extensive” and “intensive.” An extensive living
roof weighs less than an intensive green roof. It generally has shallower growing material
and heartier plants that require little maintenance. It also can be at a steeper slope. Intensive
living roofs are the like gardens on the ground—with deeper growing material, more intricate
or delicate plantings, and more maintenance needs such as irrigation and pruning. They have
greater variety and because of the intensive nature of their plants, a less steep slope.
The type of rooftop you design depends partly on your interest in gardening and maintenance,
and on the environmental benefits you may wish to achieve. Most importantly, you must
evaluate the structural capacity of the building in order to assess your options.
rooftop container gardens
A simple rooftop garden can also be created with planting containers, potted plants, and grow
boxes. Whether on one-story structures or on skyscrapers, container rooftop gardens are havens
with a charm of their own. For their owners, they provide private worlds in which to grow plants
and escape the bustle of city life. All this, of course, is made possible with soil brought in and
carried to the top of the building for the pots and boxes that comprise the rooftop garden. If
you have ever seen a penthouse garden, you know what a feeling of space it gives, especially if
the building is high. It is like being on a mountain top, with a panoramic view that on clear days
seems limitless. It is not a permanent structure, as a living roof is, and as such can be created in
a rental unit or when financial or structural issues make a rooted living roof impossible.
This kind of garden is the most common for homeowners to construct because they are relatively
low in cost and easy to maintain. It can be an extremely effective way to grow fruits and vegetables
in densely populated urban areas. Uncommon Ground, a restaurant in Chicago has the first
certified organic rooftop farm that is created exclusively from built containers. Uncommon
Ground is able to grow a significant portion of its required restaurant produce, providing diners
with a more flavorful experience as well as food with very little transportation from plant to
plate. A container garden provides the benefits of reflectivity, shade, and evapotranspiration.
On the negative side, when compared to a living roof system, it is not as effective at insulating,
reducing stormwater runoff, or supporting bird and insect diversity.
32 /
op
en
sp
ac
e
For a new building project, the best time to consider a living roof is during the initial
concept/schematic design phases. Even though the living roof is on top of the building,
many building design elements need to be considered.
Many living roofs have also been installed on existing buildings throughout cities. The
best time to consider a living roof for an existing building is when the roof needs repair
or replacement, when considering seismic upgrades, or when considering building
remodeling. Some building owners have installed living roofs on their existing roof
membrane to extend the life span or have installed modified living roofs or even
intensive rooftop gardens after taking into account the nature of their pre-existing roof.
Again, while rooted rooftops provide the most benefits, intensive rooftop container
gardens also aid in stormwater management and rooftop membrane protection.
un
co
mm
on
gr
ou
nd
, a r
es
ta
ur
an
t i
n c
hic
ag
o, h
as
ta
ke
n f
ul
l a
dv
an
ta
ge
of
th
eir
un
us
ed
ro
of
to
p s
pa
ce
an
d g
ro
ws
a l
ar
ge
po
rt
ion
of
th
eir
v
eg
et
ab
le
s s
ho
win
g o
nc
e a
ga
in t
ha
t o
pe
n r
oo
fs
me
an
op
en
op
po
rt
un
itie
s.
a l
ivin
g r
oo
f i
s b
es
t i
ns
ta
ll
ed
wh
ile
th
e s
tr
uc
tu
re
is
be
ing
bu
ilt.
it
is
alw
ay
s i
mp
or
ta
nt
to
w
or
k w
ith
ce
rt
ifie
d l
ivin
g r
oo
f p
ro
fe
ss
ion
al
s t
o e
ns
ur
e t
ha
t y
ou
r r
oo
f p
er
fo
rm
s t
he
be
st
it c
an
an
d p
ro
vid
es
yo
u m
ax
imu
m b
en
ef
its
.
34
/ o
pe
n s
pa
ce
liv
ing
ro
of
s c
an
tu
rn
an
y s
pa
ce
in
to
a g
ar
de
n. H
er
e a
sm
all
su
n r
oo
m a
tt
ac
He
d t
o
a l
on
do
n H
om
e b
len
ds
se
am
les
sly
in
to
tH
e g
ar
de
n. t
He
ro
of
ab
so
rb
s w
at
er
an
d
als
o H
as
a r
ain
ba
rr
el
at
ta
cH
ed
to
co
lle
ct
ex
ce
ss
ru
no
ff
.
roof trays
fascia
rafters
waLL
base
foundation
fascia
waLL
foundation
roof trays
Living roof eLevation and section
36 /
op
en
sp
ac
e
It is important to determine the basic design concept, including analysis of the building
structure and anticipated level of operations and maintenance (O&M) required for the
ecoroof before starting the design process. Living roofs afford many options depending
on the purpose of the roof. Building owners and designers may want a relatively
utilitarian living roof that provides stormwater management and building insulation,
while others may want their living roof to provide habitat for greater biodiversity,
aesthetics, access for human use, or some combination of any of these.
Most buildings require roof access for operations and maintenance of mechanical units,
window washing, and other activities. Access requirements should be identif ied during
the design phase, and access paths of gravel or other inert materials provided. Where
access is needed only occasionally, paths may not be required because the vegetation
can tolerate some foot traff ic. The living roof design should include provisions for
storage of maintenance equipment and materials, especially for large buildings.
it i
s v
ita
l t
o p
la
n a
nd
cr
ea
te
sa
fe
po
int
s o
f a
cc
es
s o
n a
liv
ing
ro
of
so
yo
u c
an
ea
sil
y t
en
d t
o p
la
nt
s a
nd
pe
rf
or
m m
ain
te
na
nc
e.
A successful living roof requires that all elements are well executed and work well
together. These include design, construction, establishment, o&m plan, and o&m
implementation. If any of these elements is poor, the project and certainly the roof
may fail.
Living roofs weigh from 15 to 30 pounds per square foot (psf) saturated, depending on
the vegetation and growth medium used. The building being considered for an living
roof must be able to support this additional weight.
For new construction, the additional weight of the living roof may or may not require
a more substantial structure. Design issues include the building’s foundations, rafters,
posts, beams, decking, and other structural elements.
For existing buildings, needed structural upgrades may include additional decking,
roof trusses, joists, columns, or foundations. Many buildings already have a 15 psf
gravel ballast roof and are usually structurally sufficient to hold a living roof. One
caution, if they are used in mixes, they will be subject to scour and blow-off. If a
significant amount of these materials is used, gravel ballast (mulch) on top or vegetated
mats should be considered in order to limit the scouring.
structuraL Loads for materiaLs per cubic foot
Water 62.4
Pumice 40
Silty Loam (dry) 70–75
Silty Loam (moist) 90–100
Silty Loam (saturated) 100–120
Perilite (expanded) 11
Concrete 150
Peat (dry) 24
Peat (saturated) 70
Gravel (dry) 105
Gravel (wet) 125
material weight(lbs/cubic foot)
38 /
op
en
sp
ac
e
liv
ing
ro
of
s a
re
no
t l
imit
ed
to
fl
at
ro
of
s. w
ith
pr
op
er
ma
te
ria
ls
an
d
inf
ra
st
ru
ct
ur
e, l
ivin
g r
oo
fs
ca
n h
av
e u
p t
o a
40
de
gr
ee
sl
op
e. l
ivin
g r
oo
fs
m
os
t c
om
mo
nly
ha
ve
a 2
to
15
pe
rc
en
t s
lo
pe
wh
ich
al
lo
ws
fo
r g
oo
d d
ra
ina
ge
wit
ho
ut
pu
tt
ing
to
o m
uc
h v
er
tic
al
st
re
ss
on
th
e p
la
nt
s.
Slope is the angle of pitch of the roof plane. Slope affects the irrigation, plant material, and
materials needed (e.g., lattice to prevent soil sloughing). Most living roofs are relatively
flat, with slopes around 2 percent, although some are as steep as 40 percent. Because flat
slopes have less sun exposure and less need for irrigation they work well for southern and
eastern exposure.
b Find True North
An ideal living roof in North America would have a north aspect (face north.) North is
best to help reduce evaporation and solar exposure, which helps support vegetation.
A north-facing living roof may not require irrigation.
ideal roof slope: 2 to 15 percent
b Learn from the East
An eastern exposure is second best. Receiving morning sun, it still has longer periods of
time away from direct rays slowing evaporation and helping keep the roof moist.
ideal roof slope: 2 to 15 percent
b Southwest is Not Best
Avoid any south and west exposures. Both receive the most intense and drying solar
exposure and will require greater soil depth and irrigation to keep plants alive.
ideal roof slope: less than 2 percent
choosing the right living roof site and roof slope
40
/ o
pe
n s
pa
ce
cHoosing a membrane
modified asphalt membranes Modified asphalt, or bitumen, is generally asphalt
material that has been improved with petroleum-based additives. It is a multi-layer
system that comes in sheets, rolls, and liquid. Modified asphalt can be applied hot,
cold, torched, or self-adhered. It can be laid loose or adhered to the roof deck.
thermoplastic membranes Thermoplastic membranes include pvc (polyvinyl chloride),
tpo (thermoplastic olefin or polyolefin), and epdm (ethylene propylene diene terpoly-
mer). These membranes are all single-ply systems that come in rolls or large sheets.
They can be laid loose or adhered to the roof deck. Many companies already manufac-
ture waterproof membranes appropriate for living roofs.
insuLation
Building insulation is often associated with the ecoroof ’s waterproof membrane and is
therefore important to consider at the early stage of design. Insulation can be placed
in one of two placed either above the ceiling inside the building which keeps the
insulation out of the way of the ecoroof or above the roof deck, under the waterproof
membrane. The downside of the latter is that the insulation is often damaged during
the re-roofing process.
root barriers
Root barriers prevent vegetation roots from penetrating the membrane and causing
leaks. The need for a root barrier depends on the waterproof membrane selected.
Consult the membrane manufacturer to determine if a root barrier is required for a
particular product. Physical root barriers are made of dense plastic. The material is
overlaid on the membrane and overlapped at the seams by f iveh feet or more. pvc,
epdm, and tpo membranes act as the physical root barrier themselves.
a l
ivin
g r
oo
f i
ns
ta
ll
at
ion
is
a m
ult
i-s
te
p p
ro
ce
ss
. t
he
ma
ny
la
ye
rs
co
me
to
ge
th
er
to
cr
ea
te
a l
ivin
g h
ab
ita
t. t
his
ro
of,
on
th
e p
en
n c
ha
rt
er
sc
ho
ol
in p
hil
ad
el
ph
ia p
ro
vid
es
a h
ug
e a
mo
un
t o
f a
dd
itio
na
l g
re
en
sp
ac
e t
o t
he
co
mm
un
ity
an
d v
al
ua
bl
e h
ab
ita
t f
or
lo
ca
l b
ird
s.
42
/ o
pe
n s
pa
ce
rooftop drainage methods
slope gravel
porous soil drainage channel
bb b
bb b
bb b
bb b
drainage metHods
slope The steeper the slope, the faster water drains. A slope of two percent or more will
facilitate drainage off the roof and will minimize standing water, even with surface
irregularities. At slopes greater than twenty percent, some sort of soil stabilization
method is needed.
gravel or sub-rock Layer This is perhaps the oldest drainage method for roof gardens
and vegetative roofs. Since the advent of many plastic drainage products, gravel has
been used on ecoroofs less often. Some living roof designers, however, are f inding that
gravel is sometimes still a preferred option.
porous soil Porous soil allows horizontal f low through the soil during storm events,
and no other drainage material is used. When the soil is saturated, the stormwater
f lows across the surface to the vertical drain. This approach has been used primarliy
on small and medium size projects. The negative side of these soils is that stormwater
management may not be optimum and summer irrigation needs may be higher
drainage channels This approach uses a narrow gravel channel that runs along a
contour of the slope and facilitates the f low of water to the drain. It is not a sub-layer;
it can stand alone or be used in conjunction with a gravel sub-layer. Since most living
roof soils are porous, the channel helps relieve water buildup during heavy rains.
It should be noted that some living roofs with river gravel support sedums without any
irrigation. It is anticipated that stormwater management would be less.
ad
eq
ua
te
dr
ain
aig
e i
s e
ss
en
tia
l t
o
liv
ing
ro
of
via
tl
ity
.
44
/ o
pe
n s
pa
ce
growing pLants
growth medium (soil) The growth medium is one of the most important components
affecting the success of an ecoroof, but there is no clear answer about the best soils
to use. Living roof plants can grow in many soils and conditions and different soils
provide different levels of stormwater management. Most soils are prone to wind
erosion when exposed. It is important to ensure good plant coverage or mulch to keep
soil on the roof.
soil mixes Soil mixes used for living roofs vary. The average is a mixture of 75 percent
mineral and 25 percent compost/organic with most of the mineral being pumice or
expanded shale. Soil formulated specif ically for living roofs is available, and hopefully
soil companies will continue to research and develop the most sustainable blends.
Studies will continue to monitor performance and at some point will determine a
minimum specif ication to ensure living roofs are performing adequately.
soil depth Deeper soils allow for greater moisture retention, building insulation, and
vegetation support. For living roofs on new buildings, a depth of 4 to 6 inches appears
to work well though deeper, if possible, is always better. For living roofs on existing
buildings, soil depth can be from 3 to 6 inches depending on the structural capacity
of the building.
mulch A rock covering over living roof soil can retard evaporation caused by solar
exposure and dry air from building vents. Sedums appear to prefer gravelly soils. Bark
or wood mulch has the potential to blow off, burn, or decompose over time. Rock
mulch has proven to be most effective in protecting soil and plants. River rock and
large aggregate red cinder are great options.
a l
ivin
g r
oo
f i
s a
sy
ne
rg
ist
ic
co
mb
ina
tio
n o
f m
an
y f
or
ce
s.
instaLLation metHods
seeds Seeds can be used for many species considered to be appropriate for a living roof.
Wildf lower seeds are most often planted after the sedum plants. Careful attention to
irrigation is required to ensure the seeds germinate and grow to their full capacity.
cuttings/sprigs These are small pieces of sedum and other succulents thrown evenly
across the top of the soil. Cuttings usually require frequent light irrigation for 3 to 6
months to accelerate establishment.
bulbs Bulbous plants have been installed successfully on many roofs. They include
daffodils, onions, bluebells, muscari, and tulips. Bulbs are simply pushed 2 to 3 inches
into the soil.
plugs Plugs are small plants in 2-inch or smaller pots or sometimes in large trays. The
plants are individually removed and planted with 12-inch spacing.
pots These plants are grown in 4-inch or larger pots. When they have grown largers,
they are removed from the pot and planted with 12-inch or greater spacing.
Hydro-seed/mulch Hydro-seeding has been done on a couple of projects, with some
successes and some problems. Effective hydro-seeding has been done with marigolds
and clover.
vegetated mats Vegetated mats are a sod-like approach to vegetation on living roofs.
Plants are grown in relatively thin soils that have been spread over a fabric-type of
material. Some mats are grown similarly to turf sod and have only soil, not fabric. They
produce a quick and easy living roof.
trays A tray is a shallow container that contains soil and plants. It is rectangular or
square, from 2 to 6 inches deep and 12 to 48 inches wide or long. Most trays are made
of plastic; some are aluminum and some are bio-trays of coir fabric.
Heat that ref lects off building surfaces can damage vegetation. Living roof placement
should be carefully considered before installation. Solar exposure that is related to
aspect and slope is also very important to consider when designing an living roof.
46
/ o
pe
n s
pa
ce
pl
ug
s p
ro
vid
e a
n e
as
y l
ivin
g r
oo
f s
ol
ut
ion
.
48
/ o
pe
n s
pa
ce
water sources
Water is vital to a living roof and all water sources should be considered early in the
design stage.
precipitation The ideal choice would be an ecoroof without need of water other than
the precipitation that lands on it.
shade (natural and applied) Many native and non-native plants can survive without
irrigation if some shade is present. Shade can be provided by taller buildings that
shade a lower roof, roofs with a north aspect, trees that cast shadows, parapets, and
photovoltaics and other mechanical equipment. Rock mulch may also help to retard
evaporation on the roof.
non-potable water (condensate) Many buildings have air conditioning equipment
that discharges water condensate. Some living roof projects are designed to capture
condensate and rainwater, with potable water as a potential backup plan.
potable water Although potable water is readily available, it is desirable to limit use.
Many types of irrigation systems, both manual and automatic, are being used on living
roofs. These include hand watering, back-yard sprinklers, commercial spray or stream
heads on risers and pop-ups, large rotary heads, and various drip systems. Irrigation
systems may not last for the life of an living roof and may require replacement or major
repair over time. This is another reason to keep them simple and minimize their use.
To minimize water needs, early autumn is the best planting season. Contractors have
often over-watered living roofs, especially during the plant establishment period. This
can damage succulents and other plants.
weeding
Depending on the planting method, weeding and mulching may be needed during the
establishment period and periodically thereafter over the life of the living roof.
The best approach is to be patient, watch the plants f irst, and then decide what to do.
Checking for undesirable weeds and trees should be done in late May or early June.
Most summers will be dry enough to inhibit weeds, unless the living roof is over-
watered. In wet summers, weeds may come back after removal, requiring a second or
even third weeding.
Pulling causes more disturbance to the ecoroof, and soil is often removed. It also
removes the diversity of weed roots and microorganisms. Cutting disturbs the soil less
and may allow many weeds to return from the base. If not watered, the base of many
weeds die and can break down in soil. Herbicides or pesticides should be avoided at
all costs as they can runoff and contaminate water systems and hurt other plants and
insects that they come in contact with.
b Large Roots
Small trees or plants with aggressive root structures will penetrate the membrane creating
holes and leaks in the living roof. Tree saplings should be immediately weeded out.
rooftop preditary plants
b Dry Growth
Plants, such as certain tall grasses and herbaceous species that grow in abundance
can dry out, and become a fire hazard. Dry growth should be immediately removed and
rooftops should be constantly monitored for dry growth.
50 /
op
en
sp
ac
e
ev
en
in
fa
ll a
nd
win
te
r w
he
n t
he
ro
of
is
no
t a
s g
re
en
, liv
ing
ro
of
s r
et
ain
th
eir
ab
ilit
y t
o a
bs
or
b
st
or
mw
at
er
, in
su
lat
e b
uil
din
gs
, an
d p
ro
vid
e b
ird
an
d i
ns
ec
t h
ab
ita
t.
liv
ing
ro
of
s c
an
so
ft
en
th
e h
ar
sh
lin
es
of
ur
ba
n b
uil
din
g a
nd
br
ing
co
lor
an
d l
ife
to
un
ex
pe
ct
ed
p
lac
es
, en
ha
nc
ing
vie
ws
fr
om
ot
he
r b
uil
din
gs
.
52 /
op
en
sp
ac
e
liv
ing
ro
of
s h
el
p d
ive
rt
ur
ba
n h
ea
t i
sl
an
ds
th
at
ca
n f
or
m i
n l
ar
ge
cit
ies
.
Living roofs not only add aesthetic appeal to the unused roof space that is available
in most urban areas; they also provide many benefits. Living roofs can protect the
roofing membrane from exposure to ultra violet radiation and hail damage. They can
reduce energy demand on space conditioning, and hence greenhouse gas emissions.
If widely adopted, living roofs could reduce the urban heat island (an elevation of
temperature relative to the surrounding rural areas due to the concentration of heat
absorbing rooftops and pavements.)
Reducing the heat island effect would further lower energy consumption in urban
areas. Living roofs can also be used as part of the stormwater management strategy in
the urban area. Part of the rain is stored in the growing medium temporarily, and to
be taken up by the plants and returned to the atmosphere through evapotranspiration.
Living roofs delay runoff into the sewage system, thus help to reduce the frequency of
combined sewage overf low (cso) events, which is a significant environmental problem
for many of the major cities in North America. Living roofs helps sewer systems cope.
Living Roofs Performance Study bas baskaran
te
mp
er
at
ur
e in
fa
re
nh
eit
82
84
86
88
90
92
su
bu
rb
an
ur
ba
n
ru
ra
l
su
bu
rb
an
ru
ra
l
summer urban heat island temperature effect
54
/ o
pe
n s
pa
ce
tHe test site
The National Research Council of Canada (ncr) has constructed the Field Roofing
Facility in Ottowa. It provides an experimental roof area of about 800 ft2 representing
a low slope roof with a high roof-to-wall ratio. The roof is divided into two equal areas
separated by a median divider: a generic extensive living roof was installed on one
side and a modified bituminous roofing assembly was installed as a reference on the
other. The surface of the roof membrane (on both) is covered with light grey coloured
granules, to avoid extremes in ref lection.
While the Green Roof have the same basic components up to the membrane level, it
incorporates additional elements to support plant growth. In the f irst year of the study
(2001), a wild f lower meadow was established in the garden and in the second year
(2002), common lawn grass (Kentucky blue grass) was planted.
Both the Living Roof and the Reference Roof have been instrumented. The local
meteorological data such as temperature, relative humidity, rainfall and solar radiation
are monitored continuously by a weather station located at the median divider on the
rooftop and an additional weather station situated approximately 160 ft from the site.
The plants and the growing medium can also remove airborne pollutants picked up by
the rain, thus improving the quality of the runoff. In addition, green roofs can improve
air quality, provide additional green space in urban areas, and increase property values.
Living roofs are found throughout many European countries such as France, Germany
and Switzerland. They are rapidly gaining popularity across different parts of the world
as well. In North America, Portland, Oregon has pioneered a cutting-edge incentive
program many cities are copying.
The Clean Air Incentive and Discount Program encourages the installation of green
roofs on commercial, industrial, institutional and residential properties, with the aim
of reducing the stormwater runoff problem and relieving the loading on the sewage
infrastructure. Many businesses as well as homeowers are taking advantage of the
generous f inancial incentive. In Asia, Tokyo, Japan has initiated a new ordinance to
install green roofs on new buildings with f loor space more than 10800 ft2 to mitigate
the urban heat island effects.
56 /
op
en
sp
ac
e
reference roof and Living roof comparison
Living roofreference roof
b covered in drainage Layer,
extensive growing medium
and native vegetation
b 18 days over 86ºf
b 0 days over 122ºf
b HigH temperature of 91ºf
b covered in LigHt gray
waterproof membrane
and wHite graveL
b 342 days over 86ºf
b 219 days over 122ºf
b HigH temperature of 158ºf
temperature overview
An exposed roof membrane absorbs solar radiation during the day and its temperature
rises. Light colour membranes are cooler because they ref lect solar radiation but
dark colour membranes are hotter because they absorb much of the solar radiation.
Results show that the roof membrane on the Reference Roof experienced much higher
temperatures than that on the Living Roof. The membrane on the Reference Roof
absorbed the solar radiation and reached close to 158°f in the afternoon. However, the
membrane on the Green Roof only remained around 77°f.
Heat exposure can accelerate aging in bituminous material, thus reducing its
durability. Ultra violet radiation can change the chemical composition and degrade
the mechanical properties of the bituminous materials. Although long-term durability
data is not available from the study yet, the growing medium and the vegetation of the
green roof can prevent the UV radiation from attacking the roofing membrane and
minimize aging of the membrane from heat exposure, which might extend the life of
the membrane.
temperature variance
An exposed membrane absorbs solar radiation during the day and its surface temperature
rises. It re-radiates the absorbed heat at night and its surface temperature drops.
Diurnal (daily) temperature f luctuations create thermal stresses in the membrane,
affecting its long-term performance and its ability to protect a building from water
infiltration. The membrane temperature f luctuation (daily maximum temperature–
daily minimum temperature) of the Reference Roof and the Living Roof and the daily
ambient temperature f luctuations have huge variance from cold to hot.
The Living Roof moderated the daily temperature f luctuations that the membrane
experienced during early winter (November and December), while the membrane
temperature of the Reference Roof followed the daily ambient temperature f luctuations.
This protection was somewhat dissipated during the accumulation of snow, and once
heavy snow coverage was established both roofing membranes were protected from
temperature f luctuations. The Living Roof significantly moderated daily f luctuations
experienced in spring and summer.
58 /
op
en
sp
ac
e
Liv
ing
ro
of
s a
bs
or
b a
nd
re
fLe
ct
su
nLi
gh
t h
eLp
ing
th
em
co
oL
th
e b
uiL
din
gs
be
ne
at
h t
he
m.
The daily membrane temperature f luctuations of the Living Roof were consistently
lower than the diurnal ambient temperature f luctuations. The exposed membrane in
the Reference Roof experienced high daily temperature f luctuation, with a median of
about 81°f. However, the Living Roof reduced the temperature f luctuation in the roof
membrane throughout the year, keeping a median f luctuation of about 11°f only.
The energy eff iciency of the Living Roof was slightly better than that of the Reference
Roof in the fall and early winter as the green roof system acted as an insulation layer.
However, as the growing medium froze, its insulation value was greatly diminished.
Snow coverage provided excellent insulation to the roofing system and stabilized the
heat exchange between the building and its surrounding. The snow coverage on the
roof was not uniform in early winter due to the wind and the inf luence of the high
parapet. Once snow coverage was established on the roof, heat f low through both roofs
was almost the same.
The Living Roof significantly outperformed the Reference Roof in spring and summer
(April to September). Solar radiation has a strong inf luence on the heat f low through
the roof. The membrane on the Reference Roof, being exposed to the elements,
absorbed solar radiation during the day and re-radiated the absorbed heat at night,
creating high daily energy demand for space conditioning. On the other hand, the
growing medium and the plants enhanced the thermal performance of the Living Roof
by providing shading, insulation and evaporative cooling. It also effectively damped
thermal f luctuations.
The average daily energy demand for space conditioning due to the heat f low through
the Reference Roof was 6.0–7.5 kwh/day. However, the growing medium and the
plants of the living roof modified the heat f low and reduced the average daily energy
demand to less than 1.5 kwh/day—a reduction of over 75%. Note that these values
were due to the heat f low through the roof only (400 ft2) and did not include heat f low
through other parts of the building.
60
/ o
pe
n s
pa
ce
The plants and the growing medium in the Living Roof kept the roofing membrane
cool by direct shading, evaporative cooling from the plants and the growing medium,
additional insulation values from both the plants and the growing medium, and the
thermal mass effects of the growing medium.
The membrane on the Reference Roof, being exposed to the elements, absorbed solar
radiation during the day and re-radiated the absorbed heat at night, creating positive
heat f low in the afternoon and negative heat f low in the early morning and evening.
The Living Roof significantly moderated the heat f low between the building and its
surrounding through the roofing system. In the winter, data showed that once the snow
coverage was established, the heat f low through both the Reference Roof and the Living
Roof became the same as snow coverage provided good insulation and stabilized heat
f low through the roof.
During the 22-month observation period, the Living Roof reduced 95% of the heat gain
and 26% of the heat loss as compared to the Reference Roof, with an overall heat f low
reduction of 47%. Since an extensive green roof was more effective in reducing heat
gain than heat loss, and Ottawa is in a predominantly heating region, it is expected that
its effectiveness will be even more significant in warmer regions.
Observation from the Field Roofing Facility showed that a generic extensive green roof
with 150 mm of growing medium could reduce the temperature of the roof membrane
significantly in the summer. The exposed roof membrane on the Reference Roof was
recorded to reach over 158°f in the summer but that under the Living Roof rarely
reached over 86°f. Also the Living Roof modified the temperature f luctuations the
roof membrane experienced, especially in the warmer months. The median daily
temperature f luctuation of the membrane on the Reference Roof in spring and summer
ranged from 81°f, however, the Living Roof reduced the temperature f luctuation to
11°f. The Living Roof also significantly moderated the heat f low through the roofing
system in the warmer months. This corresponded to a reduction in energy needs of
over 75%. Living Roofs can moderate heat f low through the roof through shading,
insulation, evapotranspiration and thermal mass effects. This reduces the energy
demand for space conditioning, most significantly in spring and summer.
The Living Roof was found to be very effective in helping to keep the building
significantly cooler in the summer when compared to the Reference roof.
All elements on a living roof working together have the potential to produce
dramatically positive change in our urban spaces.
liv
ing
ro
of
s t
ru
ly h
av
e t
he
po
we
r t
o t
ra
ns
fo
rm
un
us
ed
op
en
sp
ac
e i
nt
o s
om
et
hin
g b
ea
ut
ifu
l.
62
/ o
pe
n s
pa
ce
Liv
ing
ro
of
st
or
ies
64
/ o
pe
n s
pa
ce
liv
ing
ro
of
s a
re
br
ing
ing
he
alt
h b
ac
k t
o p
la
ce
s o
nc
e c
on
sid
er
ed
to
xic
.
Long Island City, just across the East River from Manhattan, has been one of those
up-and-coming neighborhoods for more than a quarter-century. Despite its proximity
to midtown, the once heavily industrial area has been slow to transform itself. Due to
air pollution, a lack of green space, and heavy traff ic over the Queensboro Bridge, it
took nearly two decades to see an uptick in residential and nonindustrial work spaces.
But a tipping point has f inally been reached, and environmental advocates believe the
neighborhood could—over the next 20 years—become a model for urban living roof
development and neighborhood transformation.
Silvercup Studios is most famously home to Tony Soprano; since last July the former
bakery, located next to the Queensboro Bridge, also became the site of New York’s
largest largest roof. In 2002 landscape architect Diana Balmori conducted a study
of the city’s rooftops to identify the best area where living roof construction could
have an impact not just on an individual building but an entire neighborhood. The
study revealed that Long Island City would be the most promising neighborhood
for clustering these environmentally friendly roofs, which help clean the air, reduce
storm-water runoff, lower energy consumption, and ultimately reduce the heat caused
by urban congestion.
View From the BridgeLisa cunningHam
th
e q
ue
en
sb
or
o b
rid
ge
fo
rm
s a
div
ide
be
tw
ee
n t
he
gl
am
ou
r o
f m
an
ha
tt
an
an
d
th
e i
nd
us
tr
y o
f l
on
g i
sl
an
d c
ity.
66
/ o
pe
n s
pa
ce
There is enough suitable f lat roof space in Long Island City to cover more than 26 million
square feet with living roof technology—or 667 acres, nearly the size of Central Park.
Known as pancake roofs, the countless f lat-topped warehouses were mostly built before
1955, when structures were generally overengineered; therefore they can withstand
rooftop vegetation without additional support. Long Island City is in serious need of
greening: it has one of the lowest percentages of parkland per acre of any neighborhood
in New York, and the area around the bridge is referred to by locals as “asthma alley.”
“If you aggregate lots of buildings with living roofs, you can lower the heat-island
effect,” says Balmori, referring to the heat-trapping properties of asphalt, concrete, and
black tar, which raise the temperature of dense urban areas. “I really think that is where
the ecological contribution is going to be—creating microclimates. How you shape a
building, how you place it on a street, what kind of shadows it casts, what types of
vegetation you put where: it all contributes to the microclimate.”
Upon completion of the study, Balmori made a presentation to the Long Island
City Business Development Corporation, a nonprofit neighborhood improvement
organization. Her idea was to develop a demonstration project with high visibility, but
she needed committed partners to make it come to fruition. As a longtime contributor
to the Environmental Action Coalition, Stuart Match Suna—cofounder of Silvercup
Studios along with his brother Alan (both are trained architects)—was immediately
interested in Balmori’s proposal. Having built a duplex on the Silvercup site, where he
lived for ten years and tended to a roof garden, Suna was well aware of how polluted
the air could get, especially on hot summer days, and the extent to which greenery can
mitigate extreme temperatures. He made Silvercup available as the demonstration site
and offered to pay for the necessary architectural and engineering studies to achieve
optimal roof performance.
The green-roof partners then secured a $500,000 grant from Clean Air Communities—a
local organization devoted to reducing air pollution in New York’s low-income
neighborhoods—to fund the design, construction, and plantation of the roof, which was
undertaken last summer at an auspicious time. Donning wide-brimmed hats, landscapers
with Greener by Design planted the Silvercup roof just as the city was experiencing
stif ling temperature spikes and breaking records for electricity consumption. “The need
for green-roof technologies couldn’t have been more striking,” Suna says.
If Long island City could convert all flat roofs to living roofs, they would
acquire an area of green space almost as large as Central Park. Climate and
quality of life would improve dramarically. With city incentives and public
education this lofty goal is very attainable.
The living roof system on Silvercup is a modular one built by GreenTech, a company
based in Roswell, Georgia, which donated a third of the modules for the project.
Unlike plantings directly on the roof—a more common type of green-roof system—the
interlocking modules can be moved and replaced. Covering 35,000 square feet required
1,500 modules f illed with a lightweight soil and then planted with 20 different varieties
of sedum. Sedum is heat and drought resistant because it retains a high percentage
of water in its shallow root system. Therefore it absorbs and holds more rainwater,
reducing storm-water runoff and minimizing landscaping maintenance. Irrigation is
needed to get the plants established, but they eventually become self-sustaining.
A living roof is clearly an ecological workhorse rather than an aesthetic amenity
like a garden, but that’s not to say it can’t be attractive. The plants were chosen and
arranged by Balmori, and then the modules were interspersed with panels of brightly
colored fabric to accentuate the yellow, red, and blue foliage. Along with the giant
Silvercup sign visible from the Queensboro Bridge, the colored panels attract the eyes
of motorists to the living roof.
While energy savings as a result of the insulating properties of green roofs are not
likely to be significant in tall buildings with small footprints in Long Island City—
where buildings are low and f lat—conservation is expected to be significant. A similar
control study conducted in Chicago in 2003 showed that green-roof temperatures
were 19 to 31 percent cooler during peak daytime hours in July compared with those
on a conventional roof. What is expected to be even more significant, however, is
the difference in storm-water runoff. The same study demonstrated that a green roof
absorbed nearly half the water from a downpour.
Since the benefits are realized by the community at large, green-roof proponents
strongly favor government incentives to stimulate property owners to both retrofit
green roofs on existing buildings and install new ones. Stress on the city’s sewer system
is reduced when rainwater is absorbed by greenery rather than being discharged into
the system. Because so much of Long Island City is paved over, the sewage system gets
overwhelmed, resulting in back-ups that cause raw sewage to be discharged directly
into the East River after heavy rain.
“We call the green roof the fifth facade of the building,” Balmori says,
“because it can be very pleasant to look at from the surrounding buildins and
the Queensboro Bridge. The roof can make all the difference in a building.”
68
/ o
pe
n s
pa
ce
Government incentives might include a tax credit, density bonuses, and an expedited
building-permit process. But one question remains: Would that be enough to entice
developers and property owners to undertake what is—in the most narrow view—
expensive insulation? Chicago has more green roofs by far than any other American
city. Like an urban canopy, more than two million square feet of greenery is or soon
will be planted on rooftops. That is roughly 49 acres, or equivalent to the entire historic
Greenwich Village neighborhood of New York City.
But the vast majority of Chicago’s green roofs are being installed because the city
requires them. Any developer that receives f inancial help from the city must have
a green roof, as determined by a complex formula. Mayor Richard M. Daley—in his
f ifth term in office and known for his autocratic style—can push through whatever
regulation he wants. No New York mayor will ever have that much power, let alone
use it on behalf of the environment, because developers won’t tolerate it. “I would be
reluctant to require them,” Suna says when asked about applying Chicago’s regulations
here. “That would make New York City that much more expensive, which isn’t good for
the economy or the environment.” And that is perhaps where even the most enlightened
property owners and environmentalists part company.
“In some cases it might be appropriate to have them partially required by building
owners,” Hoffman continues. “But if the savings in storm-water treatment is
significant enough, the city’s department of environmental protection should provide
major incentives; because when you have a whole community of green roofs, everyone
will benefit. That requires a little more than just enlightened self-interest.”
“Our overarching goal is to quantify the benefits of green roofs,” says Leslie
Hoffman, executive director of Earth Pledge, “so that building owners,
developers, and ultimately city, state, and other government officials can
understand where to implement them, what the return on investment is,
and ultimately depending on where the benefits are, who should pay for
green-roof implementation.”
siLvercup Living roof instaLLation
planting
The rooftop was
planted with 20
different varieties
of sedum.
creating the grid
The 35,000 square-
foot green roof was
created with 1,500
interlocking GreenTech
roof modules.
filling the grid
A soil mixture
of lightweight
expanded shale and
organic material was
prefilled into each
module.
planting
A piece of small
biodegradable fabric
was laid on top to
protect the plants
from being uprooted
by wind.
installation
The roof offers
great views of the
Queensboro Bridge
and Manhattan.
70 /
op
en
sp
ac
e
th
e s
ilv
er
cu
p s
tu
dio
liv
ing
ro
of
is
ju
st
th
e b
eg
inn
ing
ot
a n
ew
s
ea
so
n u
r u
ra
n r
en
ew
al
th
at
wil
l r
ev
iat
liz
e m
an
y o
f n
ew
yo
rk
c
ity
’s m
os
t p
ol
lu
te
d a
re
as
.
72 /
op
en
sp
ac
e
re
sid
en
tia
l lv
ing
ro
of
s h
av
e t
he
po
te
nt
ial
to
in
cr
ea
se
bo
th
b
ea
ut
y a
nd
pe
rf
or
ma
nc
e.
Residential roof surface represents an area that is approximately eight times greater
than commercial roof surface. Residential development square foot per square foot
is responsible for more deforestation and reduction of aerable land than commercial
development. Residential development is generally closer to riparian waterways and
has a more dramatic effect on them than commercial development.
What follows is a discussion of the factors that impede the inclusion of this residential
market and strategies to break down these barriers. Living roofs, to bring change that is
lasting and effective, must transform the residential roofing sector. In one form or other
green roofs have been in existence for thousands of years. However, it is their latest
reincarnation in Europe dating from the 1960’s that has transformed a practice into an
industry. Relatively recent accelerations of urban density, global warming, shrinking
government budgets, and increased legislation to abate environmental damage and
conserve resources have all shed a brighter light on the benefits of green roofs.
European companies like ZinCo, Optigrun, Optima, Famos, Soprema, and Erisco-
Bauder led the way in terms of developing green roof systems. American waterproof
membrane specialists like American Hydrotech, Garland, and Sarnafil allied themselves
with these Europeans in order to provide a green roof product to the American market.
It was a market that was getting increased attention because of the ecological promise
and the novel image of green roofs.
Architects have traditionally used plants to soften the hard lines of their projects.
Now landscape architects f ind a new province to assert expertise. Civil engineers
f ind new ways to address issues like storm water abatement, energy conservation,
waste reduction, urban heat island phenomena, as well as air and water treatment.
Environmentalists are enthusiastic about urban reforestation and wildlife habitat. But,
each step along this path of growing enthusiasm is made with blinders on. It appears
as if all the members of the chorus read from only one text, commercial development.
The Residential Frontpatrick carey
Every benefit claimed for green roofs can be multiplied by at least eight
times if applied to the residential market. Yet available green roof systems
are targeted strictly for the commercial market, thus pricing them out of
the reach of over 80% of the potential greenable roof area. This should
definitely not be so.
74 /
op
en
sp
ac
e
This is the current state of affairs. However, the vast majority of roof surface is being
ignored. Look at any zoning map of any city in North America and compare the area
taken up by single family residential construction with that of commercial construction.
You will find that single family residential roof surface dwarfs commercial roof surface by
a factor of at least five to one.
In addition to its much larger roof production, residential development is more
responsible for far more deforestation, conversion of untilled or tillable soil into building
developments, and is generally in closer proximity to riparian waterways than commercial
development. So, square foot for square foot, residential roof area has more developmental
impact than that of commercial development. Every promoted benefit of green roofs
could be multiplies by a factor of six if the residential market were seriously addressed.
Public expense for stormwater infrastructure, public expense for solid waste, and the
resources devoted to residential cooling and heating, the livability of neighborhoods,
interior acoustics, air f iltration, and wildlife habitat could all be radically more affected
with the greening of this vast resource. Currently there is no market for residential
green roofs. Therefore, there is no list of tried and true strategies and tactics to produce
one. Producing a significant change in this market is a very complex endeavor. It
involves a strategy that is as broad as the full range of inf luences on this market and
tactics that are as varied as each element of it.
The residential market is a polyglot of frequently conf licting codes and regulations.
Contractors in this market are for the most part non-union and are held to less stringent
training and installation standards than those of the commercial sector. Green
standards in the residential market are less stringent and have no teeth. Incentives
offered to home owners or residential builders are usually less compelling than those
in the commercial market.
The fundamental element of the residential market is the individual home
owner. To change the perspective and the market circumstances of the
living roof movement can make the difference between green roofs being
an experimental curiosity to a significant force to heal our planet.
b Individual Stormwater Management
Roofs can absorb most of the rain that falls on them, thus reducing loads on residential
sewer and stormwater systems.
b Neighborhood Livability
Many studies have shown that green space has a positive impact on mental health. Living
roofs bring green space to overlooked areas and improve the view from upper floors.
home sweet home: residential living roof benefits
b Interior Acoustics
Living roofs help muffle outside noise that might be intrusive, makeing a home more
soundproof and quiet.
b Wildlife Habitat
Birds, bees, and butterflies that are often diplaced during urban building projects flock to
living roofs.
b Air Filtration
Living roofs cleanse the air surrounding them through photosynthesis. This means the air
that flow in windows or through HVAC system is less polluted and more healthy.
Though this is the case, paradoxically there is eveidence to prove that homeowners are
very interested in the sustainable design movement. Denver, after spending $500,000
on an education campaign to encourage sustainable housing construction found that
sustainably constructed housing was outselling comparable unsustainably constructed
housing by 50%. The Denver project used every opportunity to piggy back on to every
event, every program, and every publication it could to get its idea across. Green roofs
are rarely mentioned as a residential roofing option, and home owners are at the mercy
of their construction market ignorance. There is enough information out there for any
home owner to become well informed. But this information is not coordinated and the
home owner lives in a world that screams: junk mail, junk email, screaming headlines,
truck loads of pamphlets, reams of f liers, a galaxy of web sites all conspire to distract
more than inform. A simpler message with a simpler approach is a more eff icient
strategy and these messages must be coordinated instead of competing for attention.
76 /
op
en
sp
ac
e
pl
ug
s p
ro
vid
e a
n e
as
y l
ivin
g r
oo
f s
ol
ut
ion
.
78 /
op
en
sp
ac
eb Allow controlled expansion into residential market.
Commercial vendors can open their doors to certain residential contractors for traning in the
use of their products to beomce approved contrators.
b Develop specific residential roofing product.
Conscisouly place reseach and funding toward the creation of a resonably priced,
effective, residential living roof.
b Free up components of existing roofing system for residential use.
Create materials in smaller sizes and quantities. Keep quality consistent with
commercial standards but accessible to the residential market.
residential market development
b Create a fund that all commercial vendors pay into to shrink the gap between commercial
and residential living roof sectors.
Require all companies to contribute to a research and development fund so that residntial
needs may be adequately met.
wit
h p
ro
pe
r i
nc
en
tiv
es
an
d a
cc
ou
nt
ab
ilit
y t
he
re
sid
en
tia
l l
ivin
g r
oo
f m
ar
ke
t c
an
fl
ou
ris
h.
One model that is useful is that of the news media. Newspapers, radio, and television
all have nationally syndicated news sources as well as local news sources. A green
roof information network could provide the same kind of vehicle with large sources of
concentrated information, leaving regional specialization up to regional information
sources. The eff iciencies of this kind of system are proven. Redundant information
will be minimized and resources from this can be devoted to improvements in quality
versus mere quantity. This kind of information strategy will perform one very crucial
task, to make information more understandable and thorough for the consumer.
Everyone else along the line will be paid in some way for the risk the consumer is about
to make and this risk must be recognized and applauded. Every element of the picture
is using the consumer as the market development tool. And to the extent the consumer
helps to create a market from which all will benefit, that gesture must be supported.
This is the single most important part of this puzzle, the point of sale. For that sale to
be possible on a large scale the individual consumer must be informed and the message
must be organized and accessible.
commerciaL green roof industry and business community
There is a litmus test that can be given to any green roof system vendor, designer,
assembly part provider, or advocate. This is simply to ask the question “Of the roofs
that are built, how many can your system or company supply a green roof for?” Keep
in mind that residential roof surface comprises approximately 80% of all roof surface
produced. If you can only provide for the wealthy, you fail. If you can only provide for
commercial roofs, you fail. If you are making no attempt to support the residential
green roof industry beyond pursuing profits for your own company, you fail. Those
who fail have no legitimate right to claim they are environmentally progressive. Their
activity in selling a product or service has no more merit than anyone else trying to sell
their wares, whether they be green roof systems, or steak knives. The environmental
benefit of their product is incidental to their activity, not the focus of it. There is a
deeper meaning to ecology than profit motive and growing market share.
A residential green roof industry cannot survive on subsidies, grants, and volunteerism.
Until skilled and knowledgeable people can make a living from designing residential
green roofs, no such industry will develop. Any progress in the market of residential
green roofs ultimately benefits the commercial companies in that it will provide yet
another market for their products and a source of installation expertise for its business.
80
/ o
pe
n s
pa
ce
government sector and incentives
Governmental organizations are given the role of serving the public good. The
resources they can bring to bear are tremendous, in terms of technical expertise,
funding, public education, and establishment of regulations and incentives. However,
each culture perceives the public good with different perspectives. Policies that have
worked well in promoting progressive goals in one culture may appear to be draconian
when applied to a culture that prizes individual freedom over collective responsibility.
Government organizations are not monolithic and frequently compete for turf. Their
power to regulate, promote , and educate is a critical element in this over all strategy.
When I go to the City of Seattle and ask for a green home remodel guide, I get several
brochures covering different aspects of home renovation. One of these brochures
covers roofs. In it there is a two page explanation of residential green roofs. This is one
small example of the legitimizing power of governmental recognition on the local level.
In the past there have been a number of governmental programs to address
weatherization issues from the standpoint of energy savings. Let’s say that an
innovative settlement from a Supplemental Environmental Project negotiation is used
as seed money for a Habitat for Humanity housing development. Supplemental funds
come in from the Endangered Species Act, for wild life habitat. More comes in from the
Clean Water Act. The local solid waste authority allows for some funds for materials
that will stay out of the waste stream longer. Some green roof vendors donate parts
of their assemblies, and local tradesmen donate their skills at installation. The result
is an example that can be demonstrated. The second project will be easier. Does this
sound like a long shot?
The truth is that each of these elements has been used to either achieve or promote a
residential green roof project. But the door is open. Programs exist within hud, the
epa and both the national and state levels and at the city levels to make demonstration
projects work.
The availability of government funding is less an issue than the ability of
green roof advocates to focus their attention on a few specific projects that
can then produce evidence for more leverage. Green roofs for residential
spaces must be legitimized in the eyes of the public.
living roof incentives
b Density Bonus
A program that allows developers to increase the floor area of a structure beyond existing
zoning limitations when they implement green roofs.
b Fast-Track Permitting
Permits are reviews in a matter of weeks rather than the months as it usually takes.
b Green Space Allocation
Green space allocation is a regulatory measure used by governments that sets a minimum
green space requirement depending on the lot size or occupancy of a new building. The
municipality may allow the builder to meet the green space requirement by adding a green
roof or by contributing to a fund that will be used to support green roof development.
b Grants/Direct Investment
Direct investments are monetary incentives used to encourage implementation of green
roof infrastructure. Direct investments are usually grants given by a funding agency (e.g.,
governments, non-profit foundations) with the condition that certain specifications or
requirements are met and maintained. There is a growing number of government and non-
profit funds for which green roofs can now qualify.
b Low-Interest Loan
The purpose of a low- interest (or interest-free) loan is to encourage investment in green
roofs by lending the building money to help cover the extra costs involved in installing one.
Such loans are usually made by the municipality, utility, or a non-profit foundation and the
principal is repayable over a specified period, such as ten years.
b Tax Credit
Tax credits are financial incentives that reduce the amount of tax owed if a building owner
contributes privately toward certain public goals. New or renovated buildings that conform
to a specific standard, such as installing a green roof or other green building technologies,
may receive a credit for a portion of their property tax.
Policies to facilitate green roofs take a variety of forms, from density bonusings and fast-
track permits to tax credits and low-interest loans. All incentives help make living roofs more
accessible and ultimately benefit communities.
82
/ o
pe
n s
pa
ce
84
/ o
pe
n s
pa
ce
ov
er
lo
ok
ing
ma
nh
at
ta
n t
he
6,0
00
sq
ua
re
fo
ot
gr
ee
np
oin
t, b
ro
ok
lyn
fa
rm
br
ing
s f
re
sh
p
ro
du
ce
in
to
th
e n
eig
hb
or
ho
od
fo
r t
ho
us
an
ds
of
ne
w y
or
ke
rs
.
A rustic scarecrow looms before the skyline of Manhattan’s midtown skyscrapers.
Under its watch lie more than 30 varieties of vegetables, fruits, f lowers and herbs on a
rooftop in Greenpoint, Brooklyn. But its real scarecrows, the overseers of this rooftop
farming project, are Ben Flanner and Annie Novak. I asked if they’d had any problems
with pest.
“Lately, we’ve just begun getting some bugs. Both good and bad bugs. But even if
they’re the bad ones, bugs are a good thing, because it means that they’re beginning to
recognize that there’s an ecosystem here,” Novak replied.
The bugs are taking notice, and hopefully the general public soon will, too. Similar
in mission to the New York Sunworks Science Barge project, in which the nonprofit
forged a viable ecosystem on a raft on the Hudson, Eagle Street Rooftop Farm is
further proof that agriculture can thrive in the unlikeliest of places.
On top of an industrial building overlooking the East River, just a stone’s throw from
the Pulaski Bridge, sits the 6,000 square foot urban farm. The farmers hired a crane
to pour 150,000 pounds of soil onto the roof and created an irrigation system to
distribute the wealth of water. A cache of seedlings ready to be transferred to the soil
on the roof sits just adjacent to the rooftop, grown from seeds purchased from organic
seed savers like Seed Savers Exchange. A beehive has been set on another neighboring
rooftop, and on the day I visited the farm, so did a local beekeeper who was excited
about lending her expertise to the project. There was talk of building a coop to hold
ten or so chickens on the roof. All told, however, the directors cite a modest budget
for starting their project.
A Rooftop Farm for the FuturecatHy erway
86
/ o
pe
n s
pa
ce
86
/ o
pe
n s
pa
ce
Last November, Ben Flanner read an article about Chris Goode in New York Magazine,
and how he’d built several green rooftops in New York City, including his own in
Soho. Then working in an office for eTrade, Flanner had been devouring books about
farming all winter, and knew he’d wanted to do “something with it” that summer.
The two mens’ dreams came together after Flanner contacted Goode about starting
a rooftop gardening project. They eventually found an industrial warehouse on Eagle
Street willing to host the rooftop farm. Owned by Broadway Stages, its cavernous
interior is frequently rented by the f ilm industry for movie sets. For a partner, Flanner
was constantly referred to Annie Novak, a farmer at Evolutionary Organics.
Both originally from the Midwest—Annie, from Chicago, and Ben from Milwaukee—
the two were inspired by the urban farming activity there. “Chicago is a great place for
apiaries,” said Novak, who estimates there are over 3,000 are present in the windy city.
While Novak has had rigorous experience in farming and farm education (she is also a
Children’s Gardening Program Coordinator at the New York Botanical Garden in the
Bronx, school gardening programmer with Slow Food USA, and runs the workshop
Growing Chefs), Ben cites no farming experience, “ just passion.” He’d debated
splitting his time between his office job and running the rooftop farm before quickly
realizing the demands of the farm.
ch
ar
d t
hr
ive
s o
n a
ro
of
to
p f
ar
m a
nd
re
qu
ire
s o
nly
s
imp
le
dr
ip i
rr
iga
tio
n.
on the house: the urban rooftop farming movement
They’re not likely to replace the large-scale farming anytime soon, but rooftop agriculture
projects are sprouting all over the world these days. The basic idea is brilliant: there’s a huge
demand in urban areas for fresh produce, particularly organic goods—but land costs in urban
areas make urban farming completely nonsensical from an economic point of view. There’s one
patch of land that’s usually not being used, however—the rooftop.
Three ways of doing rooftop gardening:
b Container Gardening
The rooftop is used as a handy place to have lots of containers for growing smaller crops.
ideal crops: assorted herbs, tomatoes, assorted small lettuce varieites,
b Agricultural Living Roof
The living roof is planted in crop rows, just as a farmer’s field would be on ground-level.
ideal crops: chard, kale, zucchini, eggplant, tomatoes, peppers, mushroom, onion,
potatoes, wheat, amaranth
b Hydroponic System
Hydroponic systems dispense with the need for soil, which is tremendously heavy, making
them more practical for rooftops that cannot bear a significant load. Though not as
aesthetically pleasing as the other two systems, they provide huge yields in produce.
It was a sunny Memorial Day when I f irst stepped atop the rooftop farm. On it were
two women who were volunteering that day, and throughout the next hour or so,
several more volunteers would pop up. The rooftop’s crops were divided into two neat
sets of rows about 100 feet long and 60 feet wide, with a wood chip-strewn walking
path along the midsection and in between each row. The volunteers had just direct-
sown radishes that morning. The directors estimate that close to 100 people have come
through the farm to help out, going through one whole crop in a day, like radishes or
scallions—many of which, according to popsicle stick-sized markers planted before
each row, were only transplanted to the soil about one week ago. They looked almost
ready to eat.
88
/ o
pe
n s
pa
ce
Taking a languid break, the farmers discussed inter-cropping the lettuces with
tomatoes, so that the tall tomato plants would provide shade for its neighboring crops.
Or at least, that’s what I thought I heard. Novak answered my hapless question to
clarify this point with a breathless explanation on the plants just at my feet: because
lettuces are one of those plants that go to f lower when it gets too hot, and going to
f lower early will spoil the harvest, the tomatoes are inter-cropped for shade, but
that’s not the case with the pepper plants that are inter-cropped with the radishes
over in the next row, they’ve been put in the same bed because radishes take 35 days
to harvest while the peppers take much longer, so once they’re done new crops can be
put in its place, maximizing the rooftop space.
Without all the enormous response they’d received from various friends and
volunteers, none of it could have been possible. In their call for volunteers last
week, twenty people responded, out of the forty people on the email list. Both of
the volunteers I chatted with had heard about the project at the Brooklyn Food
Conference, too—Bruni Torras, who’d worked at Added Value farm in Red Hook last
year, and Betsey McCall, who manages Murray Hill Greenmarket and teaches yoga.
Learning how to grow plants can be intimidating for a lot of people, Annie observed,
“because it’s a living thing and you can kill it. But just with experience you’ll get to
watch how things grow,” she explained.
Once they’re ready to harvest, the group plans to provide local restaurants and other
community organizations with their crops. But only very local ones—they plan to
transport everything they grow by bike. Nearby Greenpoint restaurants might be in
luck, like Anella, where the group often picks up compost scraps from. The Eagle
Street Rooftop Farm might also set up a stand for passer-by customers later in the
summer. Ben plans on growing some hops for Sixpoint Brewery soon.
At f irst, Novak admitted, she’d hoped the rooftop had been smaller. Now, she wishes
it were 100 times bigger: “We could be growing so much more.” It’s all a learning
experience, though. A diverse ecosystem is the f irst goal. Hopefully the lessons
learned will become useful for later rooftop farmers.
“We want to teach as many people as possible,” said Novak, taking a seat
along a bench of volunteers. “We believe so strongly that rooftop farms can
bring so many positive benefits to the city and we want everyone to learn
about their potential.”
That is the ultimate goal of its founders, setting the mold for future rooftop farms to
come. While we can all use more freshly grown produce in the city, the projects stands
a testament that it can simply be done.
“I just want it to be possible, and something that’s done all over,” said Novak. “It’s
amazing how nature can be squeezed into New York City.”
pe
rh
ap
s r
oo
ft
op
fa
rm
s w
ill
be
co
me
th
e n
or
m a
nd
al
l p
eo
pl
e i
n
ur
ba
n a
re
as
wil
l h
av
e a
cc
es
s t
o f
re
sh
an
d a
ff
or
da
bl
e p
ro
du
ce
.
ro
of
to
p r
eso
ur
ces
92
/ o
pe
n s
pa
ce
b
b
b1 square meter of extensive living roof removes up to 0.2 kg
of airbourne particulates per year.
four square meters of extensive living roof on a home will
supply enough oxygen to fully support a family of four
Living Roof Quick Factsbarrett roofing company
converting a traditional roof to a living roof on a home
will allow it to absorb up to 95% of the rain that falls on it
compared to less than 1% on a conventional, non-living roof.
living roofs provide homes for many birds that would be
otherwise displaced in dense urban areas.
living roofs are naturally fire resistant. the plants and
growing medium help quench flames.
b
b
b
94
/ o
pe
n s
pa
ce
zone 3: -40 to -30˚ F
zone 4: -30 to -20˚ F
zone 5: -20 to -10˚ F
zone 6: -10 to 0˚ F
zone 7: 0 to 10˚ F
zone 8: 10 to 20˚ F
zone 9: 20 to 30˚ F
zone 10: 20 to 30˚ F
hardiness zones for the continenetal united states
Successful regional living roofs hinge on knowing what plants are suited for your zip
code’s climate. What flourishes in Boston may wither in Fresno, California, or Cheyenne,
Wyoming, since the cities don’t share identical growing conditions. Or the same plant
could require different levels of care in different locations. To help us know what plants
will thrive in our areas, the U.S. Department of Agriculture (usda) devised a cheat sheet,
called the Hardiness Zone Map. Most plants you buy come with a reference tag that details
optimal sunlight, season and watering schedule. Plants may also have a number listed
beside a color-coded map of the United States. That number and map refer to hardiness
zones.hardiness zone map
The usda’s map divides the United States into 11 hardiness zones. Hardiness zones,
numbered one through 11, denote the lowest temperature ranges typical for that region
and are ranked from coldest to warmest. Neighboring zones are 10 degrees higher or lower
than each other. All zones, except for 1 and 11, also are split into “a” and “b” subregions,
which are separated by 5 degrees. Why do hardiness zones only measure cold extremes?
Plants are more sensitive to cold than heat.
For example, peonies grow in hardiness zones 3 through 8, which means the flowers can
withstand cold temperatures from 20 to minus 40 degrees Fahrenheit. You can feasibly
plant them if you live in Austin, Texas, since your plant hardiness zone would be 8b. In
normal weather, the mercury should drop no more than to 15 or 20 degrees Fahrenheit.
But you’d have to leave them behind if you moved to chilly Pinecreek, Minn. There, the
hardiness zone is a 2b, and it could reach minus 45 to minus 40 degrees Fahrenheit.
When using the hardiness zones as your gardening guides, remember that it applies only
to perennials. Annual plants die at the conclusion of their growing seasons, rendering the
zone distinctions irrelevant. The usda hardiness zone map also isn’t flawless. Its accuracy
varies depending on your location. If you live in the flatter geography of the Eastern and
Plains states, the zones are fairly reliable. But as you travel west, the map skews somewhat
because of the mountainous geography. Higher elevations and weather moving eastward
from the Pacific Ocean interacts to produce isolated temperature in certain areas.
Regional Plant SelectionnationaL gardening association
96
/ o
pe
n s
pa
ce
Common Living Roof Plants
Suggested Living Roof Plants by Zone Plants are perhaps the most important part of a living roof. They provide both the aesthetic
appeal and, through evapotransperation, help cool the roof and the air surrounding it.
They also provide habitat for local birds and insect. To get the most benefit from a living
roof, it is vital to use plants that are native to your region and fit into your geographic
climate zone. Though many plants are able to adapt to a rooftop climate, some are better
suited than others. Some also have a longer growing period, resulting in longer green time.
This is just an overview of some of the most common rooftop plants that thrive in zones
4–6, the zones that cover the most area in the States. To learn more or learn about a specific
plant, connect with your local living roof community or visit Emory Knoll Farms, one of
North America’s most well-established living roof nurseries. www.greenroofplants.com.
Chives are a very versatile plant. They can be used as both an ornamental and as a kitchen
herb. The purple flower adds a bright pop of color. Chives are also self-sowing and easily
spread over empty spaces.
common name: chives
Botanical: allium schoenoprasum
Flower color: pink
winter interest: no
height/spread: 15"/2"
Contraray to common thought, cactus can grow in many climate zones and is particularly well
suited to the dry environment of a living roof. While the prickly pear will not grow to very
large sizes on a living roof or flower as frequently, it will still retain a vibrant green color and
thrive in the bright and hot sun that is a mainstay on many living roofs.
common name: Prickly Pear cactus
Botanical: oPuntia humifusa
flower color: yellow
winter interest: no
height/sPread: 5”/8”
Black Eyed Susan is hardy, drought resistant, and able to grow in almost every geographic
region. When blooming in the summer, Black Eyed Susan brings bright yellow flowers to liv-
ing roofs, attracting butterflies and birds.
common name: Black eyed SuSan
Botanical: RudBekia HiRta
FloweR coloR: yellow
winteR inteReSt: no
HeigHt/SpRead: 18”/9”
98
/ o
pe
n s
pa
ce
Sedum Album is a top choice for roof garden projects and living roofs. This bright green
sedum sports panicles of white flowers. It spreads easily making it ideal for ground or roof
cover. One caveat, Sedum Album doesn;t like being wet and requires excellent drainage.
common name: common stonecrop
Botanical: sedum alBum
Flower color: white
winter interest: no
height/spread: 4”/12”
Sedum Acre is a plant that loves the cooler weather. The foliage tends to stay bright green
throughout the winter and most growth will occur in the cool early spring and late autumn
months. This low growing ground cover will flower in light yellow in early summer.
common name: golden stonecrop
Botanical: sedum acre ‘aureum’
Flower color: yellow
winter interest: yes
HeigHt/spread: 3”/10”
An American native widely distributed through the mid-west, Rock Pink self sows freely, but
doesn’t displace other ground covers but rather grows inbetween existing plants. The flowers
are delicate and open every afternoon from May to September.
common name: rock pink
Botanical: talinum calycinum
Flower color: rose-pink
winter interest: no
HeigHt/spread: 12”/7”
A selection of Sedum Album, or Common Stonecrop, African Sunset has red foliage during
periods of cold or stress. It adds valuable color during bleak winter months or during hot
summer droughts. It is also very hardy, easliy tolerating both cold and hot temperatures.
common name: african sunset
Botanical: sedum alBum ‘murale’
flower color: white
winter interest: yes
height/spread: 4”/12”
100
/ o
pe
n s
pa
ce
Roseum Stonecrop has rounded, flattened, leaves, to 1 inch long, and star-shaped, rosy-red
flowers, borne in mid summer. This is a vigorous, evergreen perennial with a mat-forming
growth habit. Roseum Stonecrop is very hardy and drought tolerant.
common name: roseum two-row stonecrop
Botanical: sedum spurium ‘roseum’
Flower color: pink
winter interest: no
HeigHt/spread: 6”/8”
John Creech has rounded, flattened, medium green leaves, to 1 inch long, and star-shaped,
pink flowers, to 3/4 inch wide, held in round corymbs, and borne in early summer. Sedums
are excellent grown in rocky conditions on well-drained roofs.
common name: john creech two-row stonecrop
Botanical: sedum spurium ‘john creech’
Flower color: pink
winter interest: no
height/spread: 4”/10”
This tough sedge, or grass, can grow in very diverse habitats. It is often found in full sun with
prairie grasses but will do well in the shade of large trees or buildings. It retains its green
color year round, making it great for roofs in winter.
common name: blue sedge
botanical: carex flacca
flower color: blue-gray
winter interest: yes
HeigHt/spread: 16”/12”
One of the most popular native grasses of all time, Prairie Dropseed creates height and a
new form on a rooftop garden. The long and delicate leaved and the pink fragrant flowers
brighten rooftop spaces. The flowers are also excellent for creating dried arrangements.
common name: prairie dropseed
Botanical: sporoBolus heterolepsus
Flower color: pale pink
winter interest: no
height/spread: 24”/12”
102
/ o
pe
n s
pa
ce
Two-Row Stonecrop is one of the red foliage Sedum Spuriums. It is very easy to grow, covers
the ground quickly, and requires very little water to thrive. Forming a dense mat of leaves, it
produces red flowers in late July or August and keeps its color through winter.
common name: two-row stonecrop
Botanical: sedum spurium ‘Fuldaglut‘
Flower color: pink
winter interest: yes
HeigHt/spread: 6”/8”
This cool-season grass begins the season with bright green blades. In late summer and early
fall, it produces silvery inflorescences which complement its golden-hued autumn foliage
and persist throughout the winter. It is a great option for rooftops in winter.
common name: autumn moor grass
Botanical: sesleria autumnalis
Flower color: light green
winter interest: yes
height/spread: 8”/14”
A favorite among the groundcover sedums, Bailey’s Gold is covered in canary yellow star-
shaped flowers in late spring. Tough and easy to grow, it survives in just about any sunny
location and spreads slowly to form a lustrous green groundcover.
common name: bailey’s gold stonecrop
botanical: sedum floriferum ‘Weihenstephaner gold’
floWer color: yelloW
Winter interest: yes
height/spread: 4”/10”
Spruced Leaved Sedum looks like a bit like a Blue Spruce tree, only it is much softer in
texture. It gives a nice touch of blue/grey on the roof and when planted around more vibrant
sedums, prvices a nice contrast. It blooms in early summer and attracts butterflies.
common name: spruced leaved sedum
Botanical: sedum reflexum
flower color: yellow
winter interest: no
HeigHt/spread: 4”/8”
104
/ o
pe
n s
pa
ce
A white flowering form of Sedum spurium also known as Sedum spurium alba superbum.
Dragon Blood Sedum works well in cooler climates and it can shrug off heavy snow cover,
heavy rains, cold winters, and hot summers. It is very versatile.
common name: dragon’s blood
botanical: sedum spurium ‘White Form’
FloWer color: White
Winter interest: no
height/spread: 6”/8”
A quick-spreading groundcover with jellybean foliage that turns shades of rose and copper
in the sun creating a tapestry of color that bursts in to brilliant yellow bloom in mid summer.
Often used on green roofs, it thrives in any sunny location. Tough and easy to grow.
common name: tasteless stonecrop
Botanical: sedum sexangulare
Flower color: yellow
winter interest: yes
HeigHt/spread: 4”/8”
Stonecrop is also known as a sedum. The Orange Stonecrop is a somewhat taller sedum. It
is remarkably tough and drought tolerant plant for its size and is well-suited to a rooftop
environment. The bright colors attract bees, butterflies, and birds.
common name: orange stonecrop
Botanical: sedum kamtschaticum
Flower color: yellow
winter interest: no
height/spread: 6”/10”
Delospermas are low-growing plants with thick leaves. The hardiest of the Delospermas, this
plant is notable for its ability to absorb a rainwater after a dry period. Hardy Ice Plant has
fleshy leaves and brilliant yellow flowers in early summer.
common name: hardy ice plant
Botanical: delosperma nuBigenum ‘Basutoland’
Flower color: yellow
winter interest: no
height/spread: 3”/10”
106
/ o
pe
n s
pa
ce
nortHeast dc greenworks DC Greenworks, is the national capital region’s preeminent green roof advocate and
educator, as well as a one stop shop for green roof consultation, design, and installation. Serving
the Washington, D.C. community by providing training, tools, and techniques that utilize, protect
and advance the environment, DC Greenworks sees a vital connection between economy and ecology,
employment potential and environmental sustainability. DC Greenworks actively seek to discover,
promote, and deliver cutting edge solutions that are cost effective.
web: www.dcgreenworks.org
capital green roofs Capitol Greenroofs has been founded to provide design and construction
administration services to ensure that home owners, developers, public planners, facility managers
and architects understand how these systems are installed and maintained. The living roof and
landscape architecture group based in Washington, d.c. Includes a networking blog of over 1,000
living roof professionals from across the country who are open to answering questions, offering
advice, and sharing stories and pictures of their living roof experience.
web: www.capitolgreenroofs.com
emory knoll farms Located in Maryland, Emory Knoll Farms is a leading supplier of plants and
plant expertise for extensive green roof systems. They offer a high level of service in selecting the
optimal plants for each installation. They currently stock over 100 varieties of green roof plants and
are always acquiring and testing new plants. In addition they have r&d plots on site to test plants, and
work with universities, supporting various green roof research projects. Their plant database covers
all geographic zones and owners Ed and Lucie Snodgrass have written Green Roof Plants, the go-to
book for living roof plants.
web: www.capitolgreenroofs.com
Regional Living Roof Organizations This is by no means an exhaustive list. Rather these are people and organizations that I have been in
contact with and found to be very helpful and passionate in passing along their living roof knowledge,
plant information, and striking visual imagery.
soutHeast
earth to sky roofing Earth to Sky Roofing is dedicated to quality installation of each living
roof. Owner Janie Turnamian is an Accredited Green Roof ProfessionalSpecialist that oversees all
installations. She is also a green roof consultant dedicated to educating people about living roofs
and can help plan, design, organize, install, maintain and guarantee living roofs will stay healthy.
web: www.earthtoskyroofing.com
midwest
minnesota green roofs council The Minnesota Green Roofs Council promotes green rooftop
technology as a sustainable building strategy in Minnesota and the Midwest. They work to educate
developers, architects, landscape architects, engineers, roofers, building owners, policy makers and
others about green rooftops as a cost-effective strategy to improve building performance, reduce
environmental impacts and improve urban livability. The steering committee meets monthly and
hosts workshops, social events, tours of local green rooftops. They have developed resources like the
RoofBloom guide and Minnesota Green Roofs Directory.
web: www.mngreenroofs.org
urban Habitat chicago Urban Habitat Chicago (uhc) formed in 2004 to demonstrate the viability
of sustainable concepts and practices in urban environments through research, education, and hands-
on projects. Working at the intersections of urban agriculture, the built environment, materials
recovery and reuse, and emerging local industries—focusing on creating seamless transitions in the
cycles of resources at all scales, uhc has pioneered methods of rooftop urban agriculture that yield an
abundant harvest of food in a very small amount of rooftop growing medium.
web: www.urbanhabitatchicago.org
intrinsic perennials Intrinsic Perennial Gardens Inc. started in 1992. Currently they list over
900 varieties of plants and have a special focus on living roof plants. They are a wholesale nursery,
propagate about 80% of the plants grown, and have a robust educational initiative, focusing on
plants native to the Midwest.
web: www.intrinsicperennialgardens.com
108
/ o
pe
n s
pa
ce
soutHwest
Ladybird Johnson wildflower center The mission of the Lady Bird Johnson Wildflower Center is
to increase the sustainable use and conservation of native wildflowers, plants, and landscapes. Now
an organized Research Unit of the University of Texas at Austin, the extensive living roof at the center
is a valuable research tool to study living roof performance in hot and arid landscape. They also offer
many public education classes promoting the preservation of native plants.
web: www. wildflower.org
nortHwest
Hadj design Hadj Design, a living roof design studio in northern Washington, is dedicated to both
living roof installation and education. Founded by Patrick Carey, an offical instructor for Green Roofs
for Healthy Cities, an organization dedicated to the advancement of green roofing awareness and
infrastructure in North America, Hadj Design offers a variety of workshops to help increase green
roofing awareness and disseminate practical knowledge. The workshop strategy is an integral part of
the business plan. Workshops provide some of the best public information available on living roofs.
Workshops also provide technical expertise priced for even the smallest of green roof projects.
web: www.hadj.net
portland bureau of environmental services The Portland Bureau of Envrionmental Services
(pbes) includes the Portland Ecoroof Program, a public outreach education program promoting living
roof incentives, how-to workshops, and sustainable building events. A clearinghouse for all living roof
information, the pbes’s mission is to empower all Portlanders to embrace sustainable design for their
own benefit and the benefit of the greater city of Portland.
web: www.portlandonline.com
canada
green roofs for Healthy cities Green Roofs for Healthy Cities’ stated mission is to increase the
awareness of the economic, social, and environmental benefits of green roof infrastructure across
North America and rapidly advance the development of the market for green roof products and
services. Although the current roof market does not value many of the tangible public and private
benefits of green roofs to their full potential, Green Roofs for Healthy Cities are striving to facilitate
changes that will bring green roof technologies to the forefront of high performance green building
design. They offer professional education, sponsor several international conferences, and keep a
database of living roofs worldwide.
web: www.greenroofs.org
austraLia
green roofs australia Green Roofs Australia (gra) is a not-for-profit public membership
organisation with an elected committee that draws together the various governmental,
organisational and business groups and individuals interested in being kept informed about green
roof science, technology, practice, regulations and specifications. An active part of the world-wide
living roof movement, gra promotes green roofs as an effective response to climate change and city
heat island effects, and to reduce buildings’ carbon footprints. They offer public education as well as
sponsor living roof tours to help demystify the living roof movement.
web: greenroofs.wordpress.com
united kingdom
Livingroofs.org Livingroofs.org is an independent organization that promotes living roofs in the
UK and is the representing UK member of the European Federation of Green Roof Associations.
Livingroofs.org has been actively promoting living roofs to such an extent that London now has a
distinct living roof policy and other cities and areas in the UK are developing similar approaches to
encourage the uptake of living roofs. The website highlights the latest research information on the
benefits of living roofs and provides case studies of seminal living roof projects throughout the UK.
The site also provides details of contractors, manufacturers, suppliers and designers who are active
in the European living roof industry.
web: www.livingroofs.org
110
/ o
pe
n s
pa
ce
Cathy Erway is a freelance writer based in Brooklyn. She is the author of the book,
The Art of Eating In: How I Learned to Stop Spending and Love the Stove, based on a two-
year mission to forgo restaurant or take-out food and writes the blog, Not Eating Out
in New York. She writes about small farms for Saveur.com, green living tips for The
Huffington Post, and her work has appeared in Edible Brooklyn and The L Magazine.
She also hosts the weekly talk radio show, Cheap Date, on Heritage Radio Network,
tackling all topics food and love-related.
About the Contributors
catHy erway
William McDonough is a world-renowned architect and designer, and winner of three
U.S. presidential awards. He is founder and principal of William McDonough+Partners,
Architecture and Community Design; and McDonough Braungart Design Chemistry;
and a venture partner at VantagePoint Venture Partners. McDonough co-authored
with Dr. Michael Braungart, The Hannover Principles: Design for Sustainability (City
of Hannover, 2000), and Cradle to Cradle: Remaking the Way We Make Things (North
Point Press, 2002).
wiLLiam mcdonougH
Dr. Baskaran is a Group Leader and Senior Research Officer at the nrcc, Institute for
Research in Construction (nrc/irc). He has spent 25 years researching wind effects on
building envelopes through wind tunnel experiments and computer modeling.Baskaran
acts as adjunct professor at the University of Ottawa. His work in has received national
and international recognition.He has an extensive research record with more than 150
publications in refereed journals and conference proceedings. He has received several
honors and awards. A professional engineer, Baskaran received his master’s degree
in engineering and a doctorate from Concordia University, Montreal, Canada. His
research topics focused on the wind effects on buildings and earned best dissertation
awards from the Canadian Society of Civil engineers.
dr. bas baskaran
This project would not be possible without a lot of help from the sustainable design
community. Many thanks to the sustainable design and living roof community both in
the States and worldwide for education, information, and never discouraging my many
silly questions. Your passion for living roofs and hope for the future of urban America
has inspired me and I feel truly blessed to be a part of the living roof movement.
Thanks also to the professors at the Academy of Art University especially Carolina
DeBartolo, Marc English, Jeremy Stout, and Anitra Notthingham, and Aran Baker for
helping me on my thesis journey and being committed to the next season of work. And
last a huge thanks to my family and the people of Steamboat Springs, Colorado who
first showed me how dazzling nature can be and got this whole idea started.
Thanks
Carey’s academic background is in architecture and philosophy. While directed the
Northwest EcoBuilding Guild’s Green Roof project from 2000–2004, Carey designed
and installed 20 residential green roofs. In 2003, he was asked to help develop the
training content for Green Roofs for Healthy Cities’ training program for architects,
landscape architects, and building professionals. Carey then became one of their f irst
trainers for North America. Carey’s f irm, Hadj Design, has completed another 65
commercial and residential green roofs. He remains dedicated to promoting residential
green roofs and educating green roof professionals. Carey also is the architecture
editor for Greenroofs.com.
patrick carey
112
/ o
pe
n s
pa
ce
Image Credits
patrick boury 75
sage brown 64
casey cunningHam 44 / 53 / 54 / 61
grant davis 68 / 84
sHeryL daye 90 / 93
marcus de La fLeur 72
Lisa HammersHaimb 16 / 18 / 26 / 31 / 32 / 33 / 36 / 43 / 47 / 50 / 58 / 65 / 79 /
80 / 87 / 94
bruce Hemstock 38
susanne Jespersen 27
London permacuLture society 34
david pLecHner 41
regeneration group 12 / 52
dustin sacks 20
ed snodgrass 102 / 103 / 104 / 105
Janie turnamian 62
mitcH waxman 70
edgar zuniga, Jr 64
biLL mcdonougH, “buiLdings Like trees, cities Like forests.”
the catalogue of the future. new Jersey: pearson, 2002.
matt burLin, et aL. ecoroof handbook 2009. oregon: city of portLand, 2009.
bas baskaran, living roof Performance Study: thermal Performance of green roofS through field evaluation. nationaL researcH counciL of
cananda, 2003.
Lisa cunningHam, “view from tHe bridge.” metroPoliS magazine.
september 2005.
patrick carey, (2004) the reSidential front: reSidential green roof Policy, Strategy, and tacticS. unpubLisHed paper presented at green
roofs for sustainabLe communities, seattLe, wa.
catHy erway. “a rooftop farm for tHe future.” no eating out in nyc. may 27 2009. web. november 12 2009.
barret roofing, “roofscape facts and ecoLogicaL benefits.” barrett roofS. november 9 2009. web. november 24 2009.
Bibliography
This book was designed by Lisa Hammershaimb using the two typefaces, Klavika and
Maxime. All headings, tables, and captions are set in Klavika. Klavika was designed
in 2004 by Eric Olson, a type designer and teacher based in Minneapolis, Minnesota.
All body text is set in Maxime. Maxime was designed in 1999 by Éric de Berranger, a
type designer based just outside of Paris, France. When working together Klavika and
Maxime produce a dynamic reading experience that embraces both the clean modern
lines of a sans serif face with the classic elegance of a serif.
coLopHon
