The Greenroof Project – Making the Environment Friendly and Safe
(Read the articles below. They
will provide you with all the necessary information to do the tasks of the
What is a green roof? Surely the term does not
refer to roofs which are just coloured green or covered with green tile or
green shingles. A green roof, as an environmentally friendly
construction, is a roof that is partially or completely covered with vegetation
and a growing medium, planted over a
waterproof membrane. It may also
include additional layers such as a root
barrier and drainage and irrigation
Container gardens with plants grown in pots are
not generally considered to be true green roofs, although this is an area of
debate. A rooftop pond is another form of green roofs which are used to treat
The term green roof may also be used to
indicate roofs that use some form of "green" technology, such as a roof
with solar thermal collectors and a cool roof. Green roofs are also
referred to as greenroofs, living roofs, eco-roofs,
oikosteges, and vegetated roofs.
green roofs, which are made of a system of manufactured layers deliberately
placed over roofs to support growing medium and vegetation, are a relatively
new phenomenon, green roofs have a long history starting back centuries ago.
In NorthernScandinavia green roofs or sod roofs Picture 3) have been around
for centuries. A sod roof or turf roof consists of several layers
of birch bark, which ensures that the roof will be waterproof, on gently
sloping wooden roof boards with a layer of sod set on top. Sod is also a
reasonably efficient insulator in a cold climate. So until the 19th century it
was the most common roof on rural log houses in large parts of Scandinavia.
The modern "trend" started in the
1960s when green roofs were developed first in Germany and then spread to many
countries. Today, it is estimated that about 10% of all roofs in Germany have been "greened.”
Green roofs are also becoming more and more popular in the United States, although they are not
as common as in Europe.
As for European Countries, many of them, including Germany, Switzerland, the Netherlands, Italy, Austria, Hungary, Sweden, the UK and Greece, have very active
associations promoting green roofs, The City of Linz in Austria has been paying
developers to install green roofs since 1983 and in Switzerland it has been a federal
law since the late 1990s. In the UK their up-take has been
slow but a number of cities have developed policies to encourage their use,
notably in London and Sheffield.
Many green roofs
are installed to comply with local regulations and government fees, often
regarding stormwater runoff management. In rainy areas heavy storms can
overload the wastewater system and cause it to flood. Green roofs decrease the
total amount of runoff and slow the rate of runoff from the roof. It has been
found that they can retain up to 75% of rainwater, gradually releasing it back
into the atmosphere via condensation and transpiration, while retaining
pollutants in their soil.
urban heat island effect is another reason for creating a green roof.
Traditional building materials soak up the sun's radiation and re-emit it as
heat, making cities at least 4 degrees Celsius (7
°F) hotter than surrounding areas.
The ChicagoCity Hall green roof (Picture 4),
which is one of the earliest and most well-known examples of green roofs in the
United States, was planted as an
experiment to determine the effects a green roof would have on the microclimate
of the roof. Following this and other studies, it has now been estimated that
if all the roofs in a major city were "greened," urban temperatures
could be reduced by as much as 7 degrees Celsius.
Green roofs are
becoming common in Chicago, as well as New York (Picture 5) Atlanta, Portland, and other United States cities, where their use
is encouraged by regulations to combat the urban heat island effect. In the
case of Chicago, the city has passed codes
offering incentives to builders who put green roofs on their buildings..
Green roofs have
also been found to dramatically improve a roof’s insulation value. A study
conducted by Environment Canada found a 26% reduction in summer cooling needs
and a 26% reduction in winter heat losses when a green roof is used. In
addition, greening a roof is expected to lengthen a roof’s lifespan by two or
three times, according to PennStateUniversity’s GreenRoofResearchCenter.
purification is also being implemented in green roofs. These forms of green
roofs are actually treatment ponds built onto the rooftops.
Green roofs can also provide habitats for
different species of insects, birds and animals that otherwise have limited
natural space in cities. Even in high-rise urban constructions as tall as 19 floors,
it has been found that green roofs can attract insects, birds, bees and
butterflies. Rooftop greenery complements wild areas by providing "stepping
stones" for songbirds, migratory birds and other wildlife facing shortages
of natural habitat.
Green roofs are
Reduce heating (by adding
mass and thermal resistance value);
Reduce heat loss and energy
consumption in winter conditions;
Reduce cooling (by
evaporative cooling) by fifty to ninety percent;
Reduce stormwater run off;
To create Natural Habitat;
Filter pollutants and carbon
dioxide out of the air which helps lower disease rates such as asthma;
Filter pollutants and heavy
metals out of rainwater;
Help to insulate a building
for sound; the soil helps to block lower frequencies and the plants block
Increase roof life span
Increase Real Estate Value;
beneficial green roofs can be, certain disadvantages should also be taken into
consideration. The main weak point of green roofs is the higher initial cost.
Some types of green roofs do have more demanding structural standards especially
in seismic regions of the world. As the weight load of the substrate and
vegetation may exceed permitted static loading, the retrofit of some existing
buildings can hardly be realised. Depending on what kind of green roof it is,
the maintenance costs could be higher, but some types of green roof have little
or no ongoing cost. Some kinds of green roofs also place higher demands on the waterproofing
system of the structure both because water is retained on the roof and due to
the possibility of roots penetrating the waterproof membrane.
However,properly designed and installed systems
include root barriers. It is true that installing adequate waterproofing
systems and root barriers can increase the initial cost of the roof, but due to
the fact that a green roof protects the waterproofing membrane from bad weather,
UV light in particular, the life expectancy of the membranes is doubled or even
tripled, and it leads to recovered initial cost differentials.
green shingle roofsrooftop pondscool roofssod roofs
oikostegesgreen colouredroofscontainer gardens
3. Match the words with their definitions. Mind, one of thedefinitions is extra.
2. heat island
3. growing medium
8. treatment ponds
9. root barrier
a) long energy electron diffraction;
b) any kind of solid protection
from excessive growth of roots;
c) loss of water from plants;
d) a reservoir to purify water
fouled by anaerobic bacteria;
e) a substance that pollutes
f) wastewater generated from
domestic activities and whichcan be
g) built-up areas that are
hotter than nearby rural areas;
h) water originating from
i) anything that a plant can grow in;
j) prevention or reduction of
the transmission of heat, sound, etc. by using a nonconductive material;
4.The following layers make up a green roof. What are they used for and
what is their correct order, do you think? (See Picture 2)
a) drainage layer
b) thermal insulation
d) filter membrane
e) growing medium
f) waterproof layer
g) structural support
5. Some facts are wrong in this article. Correct the mistakes.
1)The idea of green roofs is not new, it is centuries
old. 2)Sod roofs first appeared in Northern
Ireland. 3)But it was only
in the 1990s that green roofs re-appeared in Europe. 4)First
they spread in Austria, then
in Germany. 5)Gradually
they were installed in cities and towns in the United
States and became even more popular than in Europe.
6)However, in most countries the up-take, i.e. the
installation of green roofs was not warmly received and the governments had to
encourage the developers by granting immunity from taxation to them.
7)Why are the governments so concerned with green
6. Look through the list of major benefits and choose the new ones not
mentioned in the text. Then put all the benefits in order of importance for you.
1) creating oases of beauty
4) cleaning the air
5) space saving
6) sound absorption
7) food production
8) providing a wildlife
9) storm water retention
10) a place for urbanites
to grow flowers and vegetables
11) saving energy
7. What are the disadvantages ofgreen roofs?
8. Think of constructing green roofs in your place. Give arguments for
and against the project.
A: you represent the government
funding committee. Your task is to assess project proposals and to choose the
best to provide its funding. You also have the right to decline both if neither
of them meets the requirements.
You may find the following guidelines useful when assessing the
Good projects should …
1. improve the local
2. solve a
3. need no, or little,
annual financial support;
4. offer ideas for future
B: You represent the company "COOL ROOF” You install decorative intensive
green roofs. Work out your project.
C: You represent the company "ROOF GARDENS”. You construct container
gardens. Work out your project.
Each project should contain the following information:
Benefits of the Project ……………………….
D: You represent the local community. You wish your area could be
beautiful, safe and green zone. You are aware of all the benefits of green
roofs, but the majority of houses in your area not new and you are worried
about the problemsthe projects might
1. – students’ own answers.
2. Green tile roofs, green
shingle roofs, green coloured roofs should be excluded. Container gardens are
not proper green roofs either.
5. 2) Northern Scandinavia3)in the 196s 4) first in Germany5)more common
installment of green roofs is encouraged but greenroof companies are not free