Wise viewers, welcome
to Planet Earth:
Our Loving Home
for the first
in our two-part series on
green roofs or rooftops
covered with vegetation
to reduce the
Urban Heat Island effect,
promote energy savings,
improve air quality,
grow fresh produce,
minimize
storm water runoff and
lessen climate change.
There are two main types
of green roofs –
intensive and extensive.
The former requires
a large flat surface area,
features many kinds of
plants including
trees and shrubs,
has greater than
10 centimeters
of soil substrate
and is high-maintenance.
The latter has
less than 10 centimeters
of soil substrate,
is generally made up of
herbs, grasses, mosses
and other types
of groundcover
and is low-maintenance.
Today we will focus on
the greening
of building rooftops
in metropolitan areas.
In large cities, skyscrapers,
concrete buildings,
infrastructure
and pavement trap heat
from the Sun, as well as
waste heat from cars,
air conditioning units,
factories and
other sources, creating
“Urban Heat Islands”
or UHIs.
This effect can raise
the temperature in a city
two to 10 degrees Celsius
higher than if it was a
vegetation-filled rural area.
The United Nations
Intergovernmental Panel
on Climate Change
states in its
Third Assessment Report,
“It is well-known
that compared to
non-urban areas
urban heat islands
raise [both] night-time
temperatures [and]
daytime temperatures.”
UHIs cause
energy imbalances,
degrade living conditions
and can also affect
local weather by altering
wind patterns, producing
clouds, fog and
humidity and changing
the frequency and
intensity of precipitation.
The extra heat generated
by UHIs can induce
thunderstorm activity.
The resulting
rapid, heavy rainfall
heated by hot pavements
and rooftops flows into
streams, rivers, ponds,
lakes, and seas
producing stress
in aquatic ecosystems.
In recent years,
global warming
has intensified
and those living in
large metros have been
especially affected by
rising temperatures
exacerbated by
the UHI phenomenon.
In 2003 a devastating
heat wave in Europe
killed 35,000 people,
many of whom were
living in urban areas.
Many structures
standing today
are energy inefficient.
For example,
a 2007 analysis of
China’s largest buildings,
comprising
46 billion square meters
of floor space
found only four percent
could be classified as
energy efficient.
Green roofs serve as
extra layers of insulation,
reducing the amount of
heating needed in winter
and air conditioning
in summer, thus decreasing
power consumption.
On a hot summer day,
the rooftop
of the City Hall building
in Chicago, USA,
a model intensive
green roof,
will be the same as
that of the surrounding
air temperature,
say 32 degrees Celsius.
By contrast, the rooftop
of a neighboring building
without any greenery
may reach almost
71 degrees Celsius.
For many years
Western European nations,
particularly Germany,
have been promoting the
installation of green roofs
to mitigate UHIs,
improve local ecosystems
and enhance the quality
of city life.
The green roof trend
is now taking off in
large Asian metros as well.
For example in Japan,
the government
at the national
and local levels
has enacted laws
to encourage
urban roof greening.
We recently visited Tokyo
and interviewed
Mr. Taro Hitokoto,
chief official
of the Green Spaces
Environment Office,
a part of Japan’s Ministry
of Land, Infrastructure,
Transport and Tourism.
Mr. Hitokoto will now
discuss one of the
Ministry’s demonstration
rooftop garden projects.
This roof garden
with an area of
500 square meters was
installed on the building
by the Ministry of Land,
Infrastructure
and Transport in 2002,
seeking to verify rooftop
gardening technology,
measure the garden’s effects
and provide information
(on rooftop gardening)
to the public.
Does it involve
experimenting with
weights of soil or
which plants are suitable
for rooftop greening?
Yes, when installing
we seek weight-saving
materials for greening
and verify which of
the various soils,
pavements and containers
are suitable.
Also, we use
environmentally-friendly
materials such as
scrap tires and paper for
the pavement material.
Ten years ago
when rooftop greening
was not yet widespread
in Japan, you started
rooftop greening
on the Ministry of Land,
Infrastructure
and Transport building.
Could you tell us about
the results of this project?
Yes. Actually,
we have data showing
that the inter-building
temperature fell when
the rooftop was greened.
How is it structured
under this turf?
First of all, there’s
a layer of light soil about
15 centimeters deep.
Beneath this layer
is a permeable filter,
through which water
can pass but plant roots
cannot pass easily.
Beneath it is
a five centimeter-wide
path for water to flow.
At the bottom is a layer
to protect the building
from intrusion by both
water and plant roots.
How many degrees did
the surface temperature
of the roof go down
through the impact
of rooftop gardening?
This graph shows
the surface temperature
during a day in summer,
and here it is when
the tiles become the hottest.
Here is the surface
temperature of the lawn.
The temperature fell
about 20 degrees Celsius.
I wonder how many
beings have increased
their presence due to
this rooftop garden.
Up to now,
180 kinds of insects
have been identified.
The Imperial Palace
is nearby and
various insects fly in
and live here
since we’ve made
a green space a little way
from the Palace.
In Japan,
local governments
offer subsidies to
popularize wall greening,
or covering exterior walls
of buildings with plants,
and rooftop greening.
We’ll next speak with
Mr. Munetaka Takahashi
about the operation
of this subsidy system
in Tokyo’s Minato Ward,
as well as the current
status of the program.
Mr. Takahashi is the chief
of the Greenery
Promotion Subsection of
the Environmental Section,
a part of
Minato’s Environment
and Recycling Support
Department.
Would you explain
the subsidy system
for rooftop
and wall greening?
Minato Ward has been
subsidizing those who
install green rooftops
since 2008;
¥25,000 (US$300)
per square meter
is the upper limit.
The total subsidy amount
is up to ¥5 million
(US$60,000)
and rooftop greening
up to 200 square meters
per building is subsidized.
The actual result last year
was 15 projects, which
means an area of about
980 square meters of
new green rooftop space
was created.
Does the subsidy
encompass all buildings
including
private residences
and office buildings?
Those that have lot areas
of less than
250 square meters
are eligible.
When a building of
over 250 square meters
is newly constructed,
rooftop greening
is required.
Thus, we limit subsidies
to buildings
over five years old
with lot areas of
over 250 square meters.
Our concept is to enable
as many people
to install green rooftops
as possible.
I understand
that in Minato Ward, the
upper limit of the subsidy
for rooftop greening
was raised from
¥300,000 (US$3,500) to
¥5 million (US$60,000)
in May 2008.
What was the reason
for this move?
Yes.
Roads and buildings
exceed 70%
of the ward’s total area.
As a way
to increase green areas
in this ward in the future,
the rooftop space
of a building
becomes very important.
In Minato Ward there is
a lot of rooftop space
on both private houses
and office buildings.
We want to increase
rooftop greening
as much as possible,
and in the case of
private housing,
it doesn’t cost much.
However, promoting the
greening of big buildings
requires a lot of money.
So, we think that
large areas should also
be eligible for subsidies.
In Minato Ward, we are
seeking a green ratio
of 25% or covering 25%
of the ward’s total area
with plants.
We are also about
to promote
rooftop gardening as
part of a focused policy.
How effective was it
to raise the upper limit
of the subsidy?
Has it contributed
to increasing the area
and the number of
rooftop gardens?
After the upper limit
was raised, we could
secure five times
the greened area of before.
How are you going to
promote rooftop gardening
in the future in order to
reduce global warming?
We would like people
to install green rooftops
as much as possible,
because it also becomes
a measure to
counter global warming.
Also, we would like to
continue with creating
pleasant surroundings for
living things and humans.
I think it’s really wonderful
for the government
of Japan to implement
such a subsidy system
for this highly necessary
and effective approach
to counteracting
global warming.
I sincerely hope
other urban areas will be
covered by green areas
in the future.
Thank you very much.
Thank you very much.
Finally we visit
Meguro Ward Office’s
green roof,
which is very elegant.
Our guide is
Mr. Yojiro Shigeno
of the Parks and
Greenery Section of
Meguro’s Urban Planning
and Development
Department.
What was the concept
behind this roof garden,
which is beautifully
designed like
a Japanese garden?
Yes, it’s a garden
designed with a modern
Japanese-style theme.
It was designed
by Dr. Kondo
of the Tokyo University
of Agriculture.
I saw a little while ago
that the trees are watered
by an automatic
sprinkling system.
Yes, this automatic
sprinkling system
depends partly
on wind power
and solar-electric power
generation.
Will you talk about
future plans
for rooftop gardening at
the Meguro Ward Office?
Yes, the Meguro Ward
is planning to build
a rooftop park at the
Ohashi junction in 2012.
We will build a rooftop
park on artificial ground
about a hectare in size,
where people
will be able to enter.
One building has already
been built, but we’ll
construct another one
in the future
to be connected
by a bridge so that people
can come and go freely.
The rooftop garden will
slope and lead to the
new nine-story building,
and the park will
slowly descend from
the building’s ninth story
towards the other
building’s fifth story.
Moreover, further ahead
the park will be
connected with
Route 246 by a bridge,
so that people can
go down to a part
which is as high as a
two- or three-story building.
This will be completed
in 2012.
Thank you very much for
speaking with us today.
Thank you for coming here.
We would like to
sincerely thank
Taro Hitokoto,
Munetaka Takahashi,
and Yojiro Shigeno
for providing us
with the opportunity
to explore some of
the cool and inviting
green rooftops in Japan.
May many more buildings
in this great nation and
elsewhere in the world
soon feature their own
gardens in the sky.
Friendly viewers,
thank you
for your company today
on our program
and please join us
next Wednesday on
Planet Earth:
Our Loving Home
for the conclusion of
our series on green roofs.
Enlightening Entertainment
is up next,
after Noteworthy News.
May your days be filled
with joy and love.