Valer daniel rudics green roofs dissertation_project

How can green roofs
influence the urban
environment?
Dissertation for 7th semester Bachelor
in Architectural Technology and
Construction Management
Student: Valer Daniel Rudics
Consultant: Mihoko Goto Brethvad
VIA University College, Aarhus, Denmark
Hand-in date: October 2013

Valer Daniel Rudics Green Roofs - 7th
sem.
October 2013 Dissertation project
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TITLE SHEET
TITLE OF THE REPORT: How can green roofs influence the
urban environment?
SUPERVISOR: Mihoko Goto Brethvad
AUTHOR: ____Valer Daniel Rudics____
DATE/SIGNATURE: ____25/10/ 2013______
STUDENT IDENTITY NUMBER: 178744
NUMBER OF COPIES: 1 (one in pdf format)
NUMBER OF PAGES (2400 characters per page): 27 pages
GENERAL INFORMATION:
All rights reserved – no part of this publication may be reproduced without the prior
permission of the author.
NOTE: This report was compiled as part of the
Constructing Architect education – every responsibility
concerning guidance, instructions or conclusions is
hereby renounced.

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1. Preface / Acknowledgements
This report is the last of its kind in the Architectural Technology and Construction
Management education. The dissertation report consists of 1/3 of the ECTS points accredited
for this semester from a total of 30 ECTS and it should convey to which degree I can
complete a problem based dissertation of my own choice and it should give a further
familiarity to a restricted topic within the education. Furthermore, the dissertation should
document my ability to communicate in writing.
The purpose of this report is to write about green roofs, but since this theme has
become more and more familiar nowadays, I have decided to focus on a certain area and
analyze how the urban environment can be influenced by this technology.
The research of the report is based on written literature related to green roofs as well as
websites, on-line videos and internet articles, and interviews with several professionals from
the green roof industry.
I would like to thank the people who supported me in the realization of this report.
Many thanks to my guiding teacher, Mihoko Goto Brethvad who accepted the problem
statement and the role to supervise my working process, as well many thanks to Ulrich Reeh
and Gregers S. Gregersen from VegTech A/S, Lise Mansfeldt Faurbjerg from Henning
Larsen Architects A/S, Anja Pelle and Torben Hoffmann from BygGros A/S, Søren Nielsen
from DanJord A/S, my guiding teacher for the bachelor project Henrik Windbirk, and all my
colleagues and friends who supported me in writing this report.

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2. Abstract
The problem statement for the dissertation is ‘how can green roofs influence the
urban environment’. The theory is based on analyses related to the green roof technology
and how could green roofs make the urban life a more sustainable, a more habitable and a
more pleasant environment to live in. The analyses focus on several points that bring out the
impacts urban life is combating with at the moment and the aim is to find out how the
problems can be remediated.
There are many analyses that argument about green roofs having a positive impact upon the
urban environment. And even though the technology is rather new, green roofs projects are
increasingly implemented nowadays. In order to find more about those impacts and their
solutions you are invited to read about them in the following pages.
After the introduction where the basic information about green roofs is presented, the report
will continue with analyses and conclusions covering subjects such as: storm water
management, heat island effect, urban environment, green architecture and solutions, nature
reintegration, urban sustainability, storm water runoff, energy saving, and some more facts
related to green roof implementation in urban environments.

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Table of contents
1. Preface / Acknowledgements.................................................................................................2
2. Abstract..................................................................................................................................3
3. Introduction with problem statement.....................................................................................5
3.1. Background information and presentation......................................................................5
3.2. Rationalization of choice of subject and profession relevance.......................................5
3.3. Problem formulation questions.......................................................................................5
3.4. What is a green roof? ......................................................................................................6
3.5. How are green roofs made? ............................................................................................7
4. Main section.........................................................................................................................10
5. Conclusion ...........................................................................................................................29
6. List of illustrations...............................................................................................................32
7. List of references: ................................................................................................................34
8. List of enclosures .................................................................................................................38

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3. Introduction with problem statement
3.1. Background information and presentation.
The dissertation is part of the 7th
semester Bachelor in Architectural Technology and
Construction Management programme at VIA UC Aarhus. In this report I will analyze and
research information about green roofs and try to explain ‘how can green roofs influence the
urban environment’ and how to improve the living conditions in this area.
3.2. Rationalization of choice of subject and profession relevance.
Nowadays 'sustainability' has become a big-time trending in the design world, it is a
word that anoints all it touches with an air of innovation and freshness. Yet, what
sustainability truly aspires for is independence from such trends, aiming rather for longevity
and the promise of a healthy and dependable environment well into the future.
In the era of modern architecture the urban environment is becoming more and more
artificial in terms of living space. The green spaces are replaced with boxes made of concrete
and steel and as a result the environment is engaged in the famous duel of ‘David and
Goliath’ where only the strongest survives.
There are many environmental problems the urban environment encounters with because of
the modern architecture, and as a result city dwellers have started to take initiatives in order
to face this great challenge. Some of the problems urban environment is facing are heavy rain
falls and storm water management, the heat island effect, surplus of CO2, lack of green areas
and animal habitat, lack of biodiversity, etc.
Green roof technology is one of the most common methods of reintroducing nature back into
the living urban space. During this report I will search for information and data regarding the
problems the urban environment faces and I will analyze and debate how can green roofs
influence this situation.
3.3. Problem formulation questions.
In order to answer the problem statement ‘How can green roof influence the urban
environment?’ I have formulated several research questions:
What is a green roof?
How are green roofs made?

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What are the advantages and disadvantages of building a green roof?
What are the problems the urban environment faces nowadays?
3.4. What is a green roof?
A green roof, also called eco-roof is an engineered vegetative roof cover with plants
and growing medium or engineered soil, taking the place of regular concrete, tile, or shingle
roof. The most important aspect is that they are living breathing roofs planted with many
types of vegetation that use the foliage of plants in order to protect the building.
Green roofs have been around in various
forms since the ‘Hanging gardens of Babylon’
thorough Scandinavian homes, thorough the
elaborate Rockefeller Center roof gardens built in
the 1930’s (Figure 2). But since 1960’s Germany
has been the birthplace for modern day green roof
technology, where the engineered systems have
been tested and developed.
Green roofs are a form of low impact development that help reduce the negative
effects of a building’s footprint by recreating the lost green area at the roof level.
Because of their thermal behavior under the solar radiation, green roofs are used in
warm climates but they are also used in northern climates to improve the insulation
performance of the building environment. They have several positive effects in the urban
environment with the most significant being their ability to retain and detain storm water,
mitigate the urban heat island effect, improving of outdoor air quality, noise reduction,
reduce the building energy consumption by cooling the roof in the hot season and also create
habitat for animals and plants thus improving urban biodiversity.
In terms of design there are two main classifications of green roofs: extensive and
intensive. Extensive green roofs have a thin substrate layer with low level planting, usually
sedum or lawn, and can have a lightweight structure. Sedum is suitable and very common for
using on extensive green roofs. They are succulents and they store water in their leaves,
allowing them to be drought resistant, simply turning red/brown when they dry out. Extensive
green roofs are very popular in Europe (“In Germany more than eighty percent of green roofs
Figure 2

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are extensive” – Snodgrass 2010, p.22). They are simpler and thinner in profile as well as
less expensive compared to the other category. The medium depth of an extensive green roof
can vary from 2,5-15cm and they can be installed on slopes up to 30o
.
Intensive green roofs generally assimilated to conventional roof gardens, have a deeper
substrate layer to allow deeper rooting and more organic growing medium capable of
supporting a large variety of plants, sometimes also trees and shrubs. Intensive roofs are
generally open for regular use and sometimes serve as amenities for the inhabitants of the
building. Medium depth on an intensive roof can go up to 1m or even deeper for more
intensively managed roof gardens.
Research into the field of environmental psychology has shown that people have a
more positive response to areas with vegetation and natural elements than those without.
People tend to prefer urban green environments and they find them more beautiful, but
having plants on a roof requires water to live and prosper. And because the function of any
roof, green or conventional, is to keep water out of the building, some people find it tough to
get their minds around.
Re-designing the rooftop as a space for plants opens up attractive possibilities. If you
have the possibility to grow plants up there, why settle for modest succulents when you can
restore some native flora, offer wildlife habitat, harvest fruits and vegetables, or walk
barefoot through the grass?
3.5. How are green roofs made?
Depending on the type and/or weather conditions, green roofs are built with different
layers and variable thicknesses. The standard layers of a green roof system, from bottom to
top generally consists of a root barrier, drainage, filter, growing medium, and vegetation
layer. In roofing language, the whole roof construction above the waterproofing membrane is
known as the overburden. The most basic green parts of a green roof are the growing medium
and plants. The roof deck and the waterproof membrane together, ensure the structural
integrity of the building. Any roofing system should have some kind of drainage layer in
addition to the primary and secondary overflow drains, and other layers can vary.
The root barrier is the first layer above the buildings’ roof and its purpose is to provide a
waterproof membrane to the assembly. One of the most important objectives of any green
roof system design is leak prevention and in case it occurs, then all the layers need to be

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removed to locate it. As the name suggest, another purpose of the root barrier is to protect the
roofing system from plant roots that seek for water and nutrients for the plant. Roots grow
and move through soil and they could penetrate the assembly from the upper layers.
The drainage layer which in most cases has a water retention capacity; is important to provide
an empty cavity between the layers in order to allow the excess water to move freely out of
the roof. This role reduces the risk of water leaking in the assembly. To be considered that
water adds an extra weight to the roofing system and therefore to maintain the structural
capacity of the assembly it is important to ensure a good drainage. An efficient drainage also
prevents plants from growing and damaging the root barrier and the roofing assembly from
excess water that can be accumulated in the membrane. The main objective of the water
retention layer is to control water runoff and keep the medium layer moist. Since the
extensive green roofs have a small thickness of growing medium and vegetation they require
less water holding capacity compared to intensive green roofs which have a bigger growing
medium and vegetation with stronger roots that require more water and nutrients in order to
survive and bloom.
No matter the type of the green roof system, the purpose of the filter is to prevent water
runoff together with the particles from the upper layers and block the drainage layer. The
filter prevents fine materials from infiltrating into the lower layers during the drainage
process as well as maintains the integrity of the growing medium and the vegetation.
The growing medium layer supplies nutrients and water for the plants’ biological functions
and it also contributes to thermal performance and water retention. Moreover, the growing
medium is a space provider for plant roots to settle and strengthen, to be able to withstand
rough weather conditions and wind forces on the roof tops. The age and the content of the
medium are important to be considered because they directly affect the performance of the
layer. The content of the growing medium is kept confidential by manufactures and may vary
depending on the type of chosen vegetation. All plants need organic matter to grow and
prosper, but some need more than others. For example, larger plants such as small trees and
shrubs require more nutrients present in the growing medium compared to smaller plants, like
sedum. Sedum is a very reliable genre of plant that has great endurance for drought. Many
species can tolerate up to 1 month without precipitation and some species can endure up to 4
months.

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The aesthetic layer of a green roof, and possibly the symbol that categorizes a green roof as
an environmental friendly product is the vegetation layer.
As mentioned previously, the thickness of the growth
medium can vary depending on the layer structure. Figure
3 represents an example of extensive green roof with
minimum dimensions. This type of medium is most
common used; it is called sedum and it can be placed on
roofs with a slope up to 10o
and roofs that can take low
dead loads. For this example the used layers are: 30mm of
sedum mat, 150g of filter cloth, 25mm of drain plate,
waterproof and root-resistant membrane, and root barrier foil.1
Some of the advantages are: lightweight construction, easy installation, uniform expression,
minimal annual maintenance (1-2 times/year), and a 25 year product warranty.
By using this type of green roof with a thickness of approximately 55mm, there is an
estimated 50% rain water retention per annum, with ca. 15 ltr./m2. When saturated the
assembly weights approximately 50kg/m2.
Since the vegetation consists of extreme drought tolerant herbs which can also thrive under
harsh conditions in their natural environment, they have a high capacity of regeneration and
require minimal care. The selected sedum typically takes 2-3 seasons before it covers the roof
surface completely. The main flowering system is from
April to July, but having also other flowers the
blooming season can be extended. In the flowering
season the sedum grows 7-9 different species of herbs
and grasses with varying colors like white, yellow,
pink, red to blue, but also outside the season the roof
offers a great sight, such as the one on the roof of ‘8
Tallet’ in Copenhagen, Denmark (Figure 4).
Depending on the layer structure, in Denmark are also used other types of extensive green
roof that can vary from 50 to 150mm in thickness and what is above it is considered an
intensive roof.
1
Byg-gros A/S - http://www.byggros.com/da/produkter/gronne-tage/gronne-tage-systemer/sedumtag-50
Figure 3
Figure 4

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One of the thickest intensive green roofs can be up
to 1200mm (Figure 5), which are considered like
rooftop gardens. In most cases they are located at
ground level because of the high load capacity they
have (750-1200kg per m2). This type of roof can
be implemented on top of underground parkings.
Some of the advantages are: retention of water
approximately 90%, drainage and water reservoir
plate can hold up to 29 liter of water per m2,
covers and protects the building, fast and easy installation, ability to bring gardening to the
buildings below ground, etc. Having a deeper medium, there are more possibilities for plants
to be grown, varying from grasses, herbs to shrubs and threes.2
Nowadays a lot of literature babbles about how delightful and environmentally
friendly green roofs are. But the fact that sustainable design can save the planet as well as the
troubled economy is not enough. It will actually need much more to bring about the
implementation of green roof technology and other correlative sustainable building methods.
It will require a straightforward debate of the challenges, commitment, and also costs
involved as well as the paybacks. Research will be necessary to be made in the constructions
and the sometimes difficult maintenance work in order to evaluate what works and what does
not.
4. Main section
In Europe, green roof systems have been shown to provide many ecosystem services
for more than three decades. Much of green roof research and product development took
place in Germany, Switzerland, and Scandinavia, and articles were written in in languages
other than English. One of the most well-known set of guidelines for green roofs throughout
Europe is the FLL Guidelines (Forschungsgesellschaft Landschaftsentwicklung
Landschaftsbau [the German Landscape Research, Development and Construction Society]).
They are formally known as the Guidelines for the Planning, Execution and Upkeep of Green
Roof Sites, and are used for green roof design, specification, maintenance, and testing. The
2
Byg-gross A/S - http://www.byggros.com/da/produkter/gronne-tage/gronne-tage-systemer/diadem-1200
Figure 5

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FLL guidelines correspond to findings from empirical green roof research and application
throughout Germany (Dvorak 2010, p.198).
In Denmark for example, some professionals say that they do not follow the FLL Guidelines.
Anja Pelle from BygGross A/S says “we do not use FLL Guidelines because their German
empirical research does not fit to ours”3
. It is most likely that each country should have its
own guidelines because of the different climate conditions, and other approaches towards
green roof industry.
It is easier said than done to make generalizations about green roofs because the
benefits provided on a particular case depend on many variables and can be different from
one another. For example the climate conditions in North America are much more diverse
and there are few standards for design details and materials compared to Western Europe.
Most projects are not monitored, as a result data are insufficient and expectations for
performance are problematic. On the other hand green roofs are well documented in Europe.
Most often they are built for other reasons than aesthetics, after all even the most basic
extensive green roof offers a better look than its asphalt- or clad- conventional counterparts.
Research is in early stages, but studies advocate that the most significant energy
impact is the reduction of heat flow into buildings during the summer season, and also the
need for air conditioning, thus resulting in lower annual energy costs. Some studies also
present lower winter heating costs during the coldest months.
Weather conditions and the way the building is functioning, as well as specifics of the roof
construction are some of the factors that will directly impact the actual savings of a green
roof. But building characteristics together with roof –to – wall ratio is another significant
factor. To be considered that the bigger the ratio the bigger the impact of the green roof is
likely to be, although the impact of the roof in taller buildings is most significant on the top
floor.
Due to their environmental benefits, green roofs became more and more popular over time
and nevertheless, their biggest disadvantage remains the cost. In most cases, green roofs
experts agree that some of the reasons for high green roof costs are because of the materials
that need to be lifted with cranes to the roof tops, high insurance premiums, and also the
3
External lecture from BygGros A/S with Anja Pelle at VIAUC Aarhus – September 2013

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expensive labor cost. Besides that, green roofs add more weight to the roof, which leads to
changes in the structural system, increasing the structural costs.
While a green roof can be designed to maximize some benefits of the building, that
improved performance might come with the cost of another or make the project more
miscellaneous and overpriced. Some individual projects will provide the building owners
and its users benefits such as energy savings, but in order to reduce the impact of the urban
heat island effect, if will require a large scale implementation of green roofs. However, in
some cases the energy savings alone perhaps will not justify the implementation of a green
roof, but they are on the list of benefits that makes green roofs alluring as sustainable design
tools. Keeping that in mind, it is becoming clearer that green roofs can be good tools to
achieve many sustainable purposes. Green roofs built on a large scale in urban areas, show
some potential for meaningful energy saving and other environmental retributions as well as
a less perceptible development in the quality of urban life.
During the hot season, urban environments have higher temperatures compared to
suburban and rural areas because of their congregated buildings and paved surfaces that
retain heat during the day and slowly release solar radiation during the night. This
phenomenon is not only a matter of comfort but also of public health and in the past ten years
it has become more and more difficult to combat with it.
Statistics have shown that one of the
main causes of natural hazard
mortality, mainly among elderly and ill
people is extreme heat, in the urban
environment also known as the urban
heat island effect (Figure 6). This
phenomenon is the reason why urban
areas have higher temperatures than
suburban and rural, and it is caused mainly because of the dark colors of building’s roof tops
that absorb energy from the sun. In 2003 over 70.000 people have died because of the heat
wave that stuck Europe and only in Paris alone over 19.000 people4
. Because the lack of
vegetation to cool down the surrounding environment, urban areas deal with the heat waves
by using air conditioning. This method not only contributes to energy use increases in
4
Insolation (heat wave) - http://www.youtube.com/watch?v=xRD8maZuXr4
Figure 6

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residences but in fact air conditioning consumes more electricity than any other household
appliance.
Some of the causes of urban heat island effect are absorption of short-wave radiation from the
sun in low reflective materials and trapping them by multiple reflections between buildings
and street surface, air pollution that absorbs and re-emits long-wave radiation to the urban
environment, increased heat storage by building materials with large thermal admittance,
turbulence heat transport from within streets that is decreased by reduction of wind speed,
etc.
In the last 30 years the land development has rapidly increased in suburban and urban
areas, as well as the water runoff, among other. The explanation is that, before land is
developed, the runoff and stormwater are accommodated by natural systems. Some examples
are leaves and undisturbed soil that absorb rain, recharge groundwater levels and sustain plant
life; and rough and uneven topography that slow the flow of water running over its surface
into rivers and bigger water collecting bodies. But because of increases in pavement,
buildings and other water-resistant surfaces, runoff volumes have increased dramatically, and
managing it has become a state of urgency.
Most water treatment systems were not built to withstand the high volumes of water
cities face nowadays and most traditional control measures do not work very well. In some
cases stormwater runoff can overload the water treating systems. Because some systems treat
sanitary sewage from showers and toilets together with stormwater in the same facility,
during a rainstorm the water coming in can exceed the system’s capacity, thus resulting in
discharges of mixed sewage and stormwater directly into rivers, lakes, and streams. In the
United States, these combined sewer overflows (also called CSO) discharge 3.2 trillion liters
of untreated sewage and stormwater every year (U.S. Environmental Protection Agency
[EPA] 2004a)5
. CSO’s can contaminate drinking water supplies, waterfront parks and
beaches, seafood stocks, threatening public health and environmental quality.
Unfortunately, separate sanitary and stormwater sewers will not magically solve water
pollution problems; there are also other factors that influence it. When it rains, water running
off from conventional roofs and paved areas collect and carry pollutants to rivers, lakes, and
other water bodies. Those pollutants can include fertilizers, herbicides, and insecticides from
5
U.S. Environemental Protection Agency - http://water.epa.gov/aboutow/owm/upload/Water-Reuse-Guidelines-
625r04108.pdf

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farms and residential developments; oil and grease from roads and energy production
facilities; sediment from construction sites; etc. In the United States alone, more than 38
trillion liters of this untreated runoff flow in the receiving waters every year (EPA 2004a).
The result of this contamination is a danger to aquatic life by reducing the diversity of insect
and fish population; it can also make water unsafe for humans, because of unsafe levels of
bacteria from stormwater runoff. In addition, stormwater runoff during the hot season months
contributes to higher temperatures in rivers and streams (from 3 to 7o
C) potentially
compromising the health of temperature-sensitive aquatic species [EPA 2004b].
Green roofs can be part of a more effective approach in terms of stormwater
management. In Europe and North America it is the benefit that has been most amply
documented and validated by research.
Stormwater runoff can be minimized in the case of green roofs during storms, and even
during the worst storm, there will almost always be less runoff compared to a conventional
roof. The advantage of a green roof is that not only the assembly can retain water but it also
allows water to run off more slowly and over a longer time frame, thus reducing the intense
peak flows during storms. In addition, the water used by green roof plants never runs off, but
evaporates back into the atmosphere. This process is called evapotranspiration and it is
explained as evaporation of water from the green roof assembly and release of moisture from
the plants. Vegetation in open areas use sun energy to control the ambient temperature by
releasing vapor intro the air and also contributing to the water cycle, however in urban areas
there is not enough vegetation to cool down the environment thus leading to temperature
increases.
In Scandinavian countries where there are a lot of precipitations, such as Denmark, specialists
say that green roofs are seen as a benefit due to their water retaining properties to combat
frequent rain falls and heavy storms. In a publication from a Danish tabloid magazine
‘Licitationen’, ARK BYG declared that for all new flat roofs with a slope of less than 30
percent, it is strongly encouraged to implement a green roof construction. If old roof have to
be retrofitted, the building owners may be able to receive public financial support for a green
roof. In Switzerland, the cities of Baser, Zürich, and Lucerne mandate that every new flat
roof be planted per building code (Dakin 2013, p.140).

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Due to the filtering effect of the plants and the growing medium, stormwater that
drains off a green roof is cleaner to some extents. Not only that it filters the water of some
pollutants such as potassium, phosphorus, calcium, magnesium, etc; but green roofs also
neutralize acid rain by filtration.
Another example of benefits of vegetation in the urban environment is the air purification
capability of plants that can improve air quality by removing air pollutants and trapping them
into their leaves. Because of the rapid deterioration of the urban environment, air purification
capability of vegetation has been receiving increasing attention. Even though trees seem to
have a low impact on the temperature within the city because they are distributed, since there
are so many they can actually have a big impact. On a sunny day the evapotranspiration of a
tree alone is able to cool with a power of 20-30 kW, a power comparable to more than 10 air-
conditioning units (Kleerekoper 2012, p.32).
There have been many discussions about how green a green roof is, and from my
research in literature and empirical data I have found different opinions about it. The reason
of this question is the fact that manufacturers use similar layers and materials for green roofs;
however each manufacturer has developed its own system. General data about green roof
systems are available on the market and virtual media but information about production and
installation process, specific content of substances and engineering technical information is
kept away from public as trade secrets in most cases in order to achieve competitive
advantage on the market.
In general, green roof materials usually use low density polyethylene and polypropylene
(polymers) materials in order to reduce the weight on the roof. Even though green roofs are
seen as a sustainable solution, the production process of polymers is highly polluting; and
because of the long time it needs to biodegrade in landfills, rather than producing new ones it
is preferable to recycle and reintroduce them into the market. It is important to keep in mind
that the manufacturing process of low density polyethylene and polypropylene has high
negative impact towards the environment; however the pollution released into the air due to
their production process can be balanced in the long run, in about 13-32 years depending on
the green roof type.

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‘Some producers are using systems which are 100% degradable, but then the whole system is
not functioning any longer than 3-5 years, and that is not sustainable. A green roof should
live forever, just like a biotope does in nature.’ – says Torben Hoffmann from BygGros A/S 6
Nevertheless, it is still beneficial to install polymers on green roofs, but it is recommended to
explore materials that could replace the current use of polymers to increase the sustainability
impact.
Some studies revealed that extensive green roofs require less materials compared to intensive
green roofs due to their layer thickness. However, intensive roofs usually have bigger plants
and vegetation and they have a higher air dilution rate compared to extensive green roofs. As
a conclusion, despite the fact that they require more materials, intensive green roofs have a
better performance in the life cycle analysis compared to extensive green roofs.
In practice, in Denmark, some professionals use
environmental materials as much as possible in
order to lower the CO2 emission into the
environment. At Moesgård Museum (Figure 7),
in Aarhus the growing medium used on the semi-
intensive green roof is made of recycled
materials such as crushed bricks and tiles, leca
nuts and organic materials (compost)7
. Taking
into consideration that the growing medium is
20cm thick and covers almost 10.000m2
proves that Danish professionals think not only
about minimizing the construction costs but also about the environment by using sustainable
materials as much as possible.
‘If a green roof system should be really ‘green’ it is necessary to have a sustainable and local
production. – says Anja Pelle from BygGros A/S 8
The layers that go below the substrate, usually fabricated out of polymers are a technology
burrowed from civil engineering and the agriculture industry. But some designers such as
Andy Creath continue to look for ways to simplify the layers and reduce the amount of
polymers used. Creath explored the replacement of drainage boards in the drainage layer with
6
Interview with Torben Hoffman from BygGros A/S
7
Interview with Søren Nielsen form DanJord A/S
8
Interview with Anja Pelle from BygGros A/S
Figure 7

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gravel where the roof can withstand more weight. By using a moisture mat and 50mm of
gravel topped with a fiber fabric, he gained an extra 50mm of space for the plants. This extra
50mm will allow plants to thrive in a more oxygenated space and will give roots more space
to grow. As a result, the system increases the potential substrate depth with 50mm and
because most of the time aggregate is less expensive, this solution proves to be a financial
benefit (Dakin 2013, p.221).
In Spain, a research team conducted an experiment on the use of rubber crumb in green roofs
focusing on the energy and environmental benefits. Instead of using porous stone materials
they investigated the possible use of rubber crumb as drainage layer and compared the two in
terms of optimum balance rate between air and water.
They found out that the use of rubber crumbs saves a big amount of energy in comparison to
the use of current commercial materials considering the energy need for transformation
process. Besides that, using rubber crumbs will solve the problem of disposing waste tires,
and they are also a good substitute for stone materials used in the drainage layer in terms of
insulation.
If you have ever been on a roof deck in a hot summer day, you can distinguish the
temperature difference of the sun on the top of the building and at the ground. Not only that
plants and components of the assembly mitigate9
the temperature of a green roof making it a
more pleasant place to be but they also protect the roof’s waterproofing membrane from
ultraviolet lights and the degrading effects of extreme temperatures.
In general, green roofs are regarded as
mediums that can reduce the
temperature of a roof. For example, in a
hot summer day, a green roof can
reduce the temperature of a black roof
from 80o
to 27o
C (Sadaatian 2012,
p.161). This efficiency has been
considered as equal to the brightest
possible white roofs. The graphic in (Figure 8) illustrates the temperature fluctuations on a
black conventional roof, a white roof, and a green roof between 5 and 14 June 2008. I have
9
Mitigate – reduce, lessen - http://thesaurus.com/browse/mitigate
Figure 8

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observed that on the black conventional roof the temperature has the highest values while on
a white and green roof are lower, with a more constant value for the latter.
From the category of cool roofs, white roofs are also considered to reduce energy costs, but
they have the disadvantage of having to be cleaned regularly in order to stay highly reflective
and work at best performance. Moreover, compared to green roofs, they do not offer as many
benefits as the former. White reflective roofs are generally made of a single-ply membrane,
that is less durable than a conventional roof or a green roof and it would require a more
frequent replacement and maintenance that not only makes white roof more expensive but
also less sustainable. ‘The argument’ says green roof engineer and designer Charlie Miller,
“is that the white roof is going to go gray, while the green roof will only get better”.
On a conventional flat roof, if the waterproofing membrane is not protected by insulation or
other material it will require to be replaced more frequently, after fifteen or twenty years. For
example, in Germany the membranes under a green roof built some decades ago are intact
even now. Designers there usually plan for a life span of at least thirty to forty years long. In
Portland, Oregon, and intensive roof planted on the top of a parking garage of a federal
building has been working excellently without any leaks in its membrane since 1975 (U.S.
General Services Administration [GSA] 2008b). In the present, there are about 6 to 9 million
tons of roofing material waste added to landfills every year in the United States. Maybe it is
too early to make conclusive judgments about green roofs in North America, but the
experiences are promising. Having less frequent roof replacements is better not only for the
environment in terms of production and waste but as well as for the property owners in terms
of investment. The longer life span is another justification why green roofs are more
expensive than simple conventional roofs.
Even though Germany is a world leader in green roof technology, they are not amongst the
first that used this environmental solution. More than twelve centuries after the gardens of
Semiramis, Vikings were using as well green roofs and green houses. This population located
in northern Europe were using between eight and eleventh century, green roofs as an energy
solution in order to protect the building envelope against thermal dispersions, wind and rain.
In the first half of the twentieth century Le Corbusier, Frank Lloyd Wright, and Walter
Gropius started to implement green roofs and green gardens in their projects. After the
reinforced concrete appeared around 1960’s new structural possibilities allowed green roofs
to be widely implemented in new buildings in several Central and Northern European

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nations. Even today, the Færøer Islands, situated between Norway and Iceland, reveal many
examples of dwellings equipped with old-style green roofs.
An economic opportunity of green roofs is achieved in the Northern Europe, where they
contribute in reducing the winter heating need and costs. The evaporating cooling effect and
the low maintenance cost because of the abundance of rainfall imply satisfactory
performances by all types of vegetation. Green roofs use the vegetation layer to protect the
building environment by reducing the thermal loads from solar radiation and air temperature
before entering the building. The protection from extreme temperatures can also reduce
energy costs. Moreover, the growing medium gives added insulation properties to the roof
and the water content increases thermal inertia of the structure. Because a green roof is a
dynamic system, with varying air and moisture content and biomass, in some conditions it
can act as an insulator, while in others a thermal mass effect will act to reduce the
temperature values above and beneath the roof as the system absorbs and slowly releases
heat.
Despite its high initial costs, over the long run green roofs are an economical option
considering their energy saving. To be considered that the total amount of energy savings of
green roofs is most significant for single story buildings and less for other types. In fact, in
multistory buildings, the effect is almost insignificant for the third story below the green roof
and lower.
Studies revealed that temperature fluctuations can be significantly decreased in
summer periods with a green roof substrate layer of 100mm thickness. As example, a
research team from the National Research Council of Canada compared in their study two
different green roof systems, each with 75-100mm of light weight growing medium and a
steel decked reference roof. The result pointed out that green roofs (in Canada) could reduce
the heat gain by an average of 70-90% during summer periods and could prevent heat loss by
10-30% during winter periods (Saadatian 2012, p.161).
In warm climates, green roofs are appropriate for decreasing the energy demand for space
cooling, with an annual reduction of energy between 1-11% in Tenerife and Sevilla (Spain),
and 2-8% for Rome (Italy).
Green roofs are poorly appropriate in hot and also cold climates if water costs are considered,
thus making them moderately suitable only when rainfall is very significant. As a solution,

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installing a watering smart controller could improve the maintenance quality and keep the
irrigation costs low. For safety reasons, it is vital to know that the stored water on a green
roof should not be accumulated for periods longer than three weeks because the stagnant
water could induce risks of bacteria and fungi, dangerous for people and pumping devices.
In order to show that green roofs offer benefits in winter heating as well as summer cooling
reduction costs, in the past decade there have been many studies conducted to prove these
arguments. In Europe, recent directives strongly promote the energy savings for the summer
air-conditioning (Ascione 2013, p.845). The most important principle of a functioning green
roof is the evapotranspiration of water, which induces the evaporative cooling that dissipates
the sensible load connected to the solar radiation by means of a latent heat transfer. This
phenomenon implies cooling energy savings. In order to achieve clear benefits, the design
and construction of a green roof should be precise, also eliminating the thermal bridges, water
losses and infiltration.
Because in the United Kingdom more than half of the building stock was built before
any roof insulation was required, it is older buildings that could benefit most if green roofs
are implemented. The case of retrofitting existing buildings is therefore reviewed and found
that there is a strong potential for green roof retrofit in the UK. Green roofs can significantly
reduce energy use in buildings with poor insulation values, both in summer cooling and
winter heating, but modern buildings, built to the 2006 UK building regulations will have
better U-values because of the insulation quality and green roof will have little impact on
reducing the energy consumption.
Intensive green roofs are real hanging gardens that necessitate substantial costs in terms of
installation, maintenance and irrigation. The substrate layers are complex and have high loads
and because of that the building structure must be carefully evaluated. In most cases an
intensive green roof assembly will not allow the installation on existing buildings, but on the
other hand extensive green roofs are better suited for retrofitting. They require low initial
costs and low maintenance requirements, and they are lightweight and have low layer
thickness. Extensive green roofs are the preferred option for retrofitting onto existing
buildings because of their structural capacity that can take extra loads to some extents due to
the improved structural efficiency of modern analysis, design, and construction methods.
UK’s medium-rise buildings with concrete roofs could probably be retrofitted with a green
roof without any additional structural modifications, but before designing the retrofitting a

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structural survey is recommended in most cases in order to determine a building’s roof load
capacity.
Buildings justify for almost half of the primary energy consumption in developed countries,
hence also the CO2 emissions. A large amount of this energy is used to maintain internal
building temperatures by heating and cooling systems. Older buildings can greatly benefit
from the additional green roof layer because it reduces the proportion of solar radiation that
reaches the roofing beneath and also offers additional insulation values, hence reducing
annual energy consumption. Even though many studies assess the potential energy savings of
green roofs, it should be noted that these are predominantly for climates warmer than UK. As
a conclusion green roofs are seen more as a passive cooling technique rather than as a thermal
insulator in the winter. In the summer the exposed area of a black roof can reach 80o
C when
the equivalent area beneath a green roof is only 27o
C. The reasons why green roofs cool
down is because of latent heat loss and improved reflectivity or incident solar radiation.
There are suggestions that green roofs cool as effectively as the brightest possible white
roofs, with an equivalent albedo10
(the fraction of incident electromagnetic radiation reflected
by a surface) of 0.7 – 0.8, compared with the typical 0.1 – 0.2 of a bitumen roof. Some filed
studies shown that in hot conditions the heat accumulated by a conventional roof during the
day continued to enter the building also during the night. Another study has shown that by
measuring the air temperature at various heights above the vegetation on a green roof, the
values were reduced significantly and also continued to cool the ambient air throughout the
night (Castleton 2010, p. 1583). Air conditioners cool interior spaces by discharging heat to
the outside, as a result the surrounding temperature increases. And because HVAC (heating,
ventilation, and air conditioning) efficiencies depend on input temperature, the costs of
neighboring air conditioning will use more energy to cool the air coming in the building, thus
increasing the energy costs. But if a green roof is implemented, then the lack of heat around
the building could increase the efficiency of air-cooling and ventilation systems and also
lower the energy costs.
Unless there is a change in use, commercial and institutional buildings do not require a
planning permission and usually they are repaired / refurbished every 15-20 years. This could
be a great opportunity for building owners to implement a green roof which could offer
10
Definition taken from dictionary - http://www.thefreedictionary.com/albedo

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substantial energy saving throughout the year and also reduce the CO2 emitted into the
atmosphere.
Data from Lambeth Council, which is based on real green roof retrofit experience, suggests
costs between £120 - £180/m2
.
The Ethelred estate (Figure 9), in Kennington, Bauder constructed an extensive system of
4000m2
in 2005 with a total cost of £716,000 equating to £179/m2
.
In terms of whole-life cost analysis, the calculated Net Present Value (NPV) of a green roof
is estimated around 10 – 14% more expensive than a conventional roof over a period of 60
year lifetime. If energy costs will increase or stormwater prevention will become a higher
public priority, then green roofs will become more economically attractive and there will be
more opportunities for the technology to be implemented on a large scale.
Green roofs are engineered ecosystems and in order to achieve sustainable benefits it
is important that all their parts and acting agents be understood. Amongst the basic things one
should know what questions to ask and what data to research and collect. For example, to be
able to investigate biodiversity on green roofs it is important to understand the context of the
roof to its environment. Is it located in the urban environment or is it in suburban or rural? –
The importance of this question is reflected in the opportunities for food and cover available
in each of those environments so that biodiversity can thrive. In general, rural environments
can offer more opportunities compared to suburban and urban thus the implementation of a
green roof in that rural environment would not have such a big impact while in the latter ones
there is lack of vegetation and the living conditions are scarcer.
In general, biodiversity is defined as the amount of variation within an ecosystem, biome,
continent, or planet. But when we define biodiversity in the urban environment we often pick
only the pretty inhabitants or the ones we believe to be beneficial such as bees, butterflies or
Figure 9

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birds, but true diversity in the urban context means all living creatures, ants, beetles, rats,
cockroaches, pigeons, spiders, and so on. Each one of these serve a purpose, and urban
rooftops, especially the ones with low- or no human interaction are the perfect places to
facilitate wildlife habitats.
There are strong unreliable evidences that green roofs attract insects and birds, but the extent
to which green roofs can have a significant impact on wildlife habitat is unclear because of
the lack of available data. Even though research on this subject is in early stages, European
studies on mature green roofs suggest that when properly designed to accommodate wildlife
and offer food and shelter, they can have an important role in sustaining urban biodiversity.
There are examples on European green roofs that have been found to be ecologically rich
with abundance of insects, birds, wildlife and plants.
In the United Kingdom, extensive green roofs are a key
part of the London Biodiversity Partnership plan to
restore the black redstart population11
(figure 10). This
protected bird species prefers urban habitat but because
of lack of appropriate insect life to support, the flying
population is in danger. Recently, many sustainability
activists and noticeable results have convinced the U.K.
Green Building Council that green roofs are among the
most effective ways to restore biodiversity in urban
environments.
In Zürich, Switzerland, one of the world’s oldest green
roofs built in 1914, (Orchid Meadow on the Moos
Water Filtration Plant12
) provides habitat for 175
species of plants including 9 native species of rare or
endangered orchids (figure 11). The most interesting
part of the story is that this roof was not planned to be
a green roof and plants have naturally colonized there.
The Moss filtration plant processes water from Lake Zürich with sand filters to produce
drinking water. The water is pumped from the lake into the building and as it slowly filters
11
The black redstart bird - http://www.rspb.org.uk/wildlife/birdguide/name/b/blackredstart/index.aspx
12
The Moos filtration plant - http://www.greenroofs.com/projects/pview.php?id=680
Figure 11
Figure 10

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through a layer of sand, clean drinking water comes out. The building was one of the first
reinforced concrete buildings to be constructed in Zürich, with a ceiling of 8cm thick slab
beams finished with a layer of 2cm mastic asphalt. After more than 90 years the two layers
have finally combined but without any negative impacts on the impermeability of the
membrane or the vegetation. The only reconstructions carried out after all these years were at
the edges of the roof, besides that the membrane is fully functional.
In the United States, some green roofs are being designed specifically to attract endangered
butterflies and other species; moreover some research has surprisingly found high levels of
biodiversity even on the simplest extensive green roofs.
The Chicago City Hall reporting on bird diversity demonstrates that if a varied habitat
structure is provided, wildlife will find it (Dvorak 2010, p.210).
Some people think that all green roofs can perform as an excellent wildlife habitat and some
believe that using native plants on a green roof makes that roof a substitute for habitat but the
reality is different. While on a green roof will usually offer possibilities for biodiversity, it is
impossible to recreate at-grade habitat on the roof of a building. Even though a green roof can
offer a better environment compared to a traditional black roof or a parking lot in a densely
built city, it is not a replacement for the open green space destroyed by urban development.
While projects in Europe show that green roof design for wildlife habitat can be successful in
urban environments, also demonstrate how complicated it is to achieve that success. Habitat
can be replicated, but it cannot be recreated.
Traditionally, the history of landscape design has been more about conquering or taming
nature than about embracing it; however we need more animals and green spaces in our cities
for us to be healthy and happy. In order to make this happen, green roof designers have the
unique opportunity to lead the way by learning methods that allow nature to feed itself and
thrive in urban environments. This new age of coexistence could be framed as an age of
integration, where the relation between human and nature is strongly encouraged.
There are many possibilities for growing plants when rethinking the rooftop of a
building. If you are going to plant up there, why settle for modest succulents when there are
so many possibilities to restore some native flora, provide wildlife habitat, or serve as
amenity spaces. Besides offering possibilities for biodiversity, green roof can serve as farms
for growing vegetables and food crops. Even though it is much easier and more economical

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to grow vegetables and other food crops on ground, on a small scale and with attention to
irrigation, maintenance, and fertility requirements, food can be grown on roof tops as well. In
general, this can be done only on intensive green roofs because of the medium depth plants
need to grow their roots and prosper; however there have been successful cases where an
extensive system was used. In an urban environment, such food growing spaces can function
as community gardens and places for educational programs for children who have little, or no
access to country-side farms and growing gardens.
Food production on rooftops is becoming more
and more popular nowadays. In the United
States, in Greenpoint, Brooklyn, there is a 560
m2
rooftop farm (figure 12) that sells
vegetables grown on the building’s own roof.
Some people might find it unessential to grow
food on roof tops, but having the opportunity
to do this in an urban environment where there
is lack of vegetation allows you to go out of
the concrete jungle for a while and experience the wonderful work of nature. Just imagine
how it feels to walk around mounded beds flushed with greenery while you can look over the
East River towards the skyline of Manhattan.
In Vancouver, growing food seems to be a shared passion among local people. The Fairmont
Waterfront Hotel herb garden is one of the city’s first green roofs with a garden of 195 m2
planted with over sixty varieties of herbs, fruits, vegetables, and edible blossoms which are
used in the hotel kitchen. Hidden behind the diving board of the swimming pool adjacent to
the garden, blackberries prosper. The hotel management is also proud of the eight bee hives,
safely nested below the roof main deck13
. Not only that honey bees are one of the most
important pollinators, but pollination is considered to be the single most important reason for
biodiversity when it comes to think about survival of human species. Without pollination,
there will be not enough food to sustain life and diversity on our planet would diminish
significantly.
13
Fairmont Waterfront Hotel harvest -
http://www.youtube.com/watch?feature=player_embedded&v=hZcR8x0OgFk
Figure 12

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Another green roof initiative situated on the
other side of Vancouver, in Richmond, is the
BMW car dealership14
where the owners have
invested into an extensive green roof and planted
a large variety of plants such as alpine and
regular strawberries, blueberries, red currants,
banks of lavender, roses, and other herbs. The
dealership is in an agreement with the food bank
and supplies them with vegetables grown on the
green roof’s community garden. As mentioned in
the previous case of Fairmont Waterfront Hotel,
here as well the owners are combating the
worldwide phenomenon CCD (Colony Collapse
Disorder) and have given special attention to
their honeybees and ensured a special location
out of the coastal winds, behind the espaliered
apple trees( figure 13), that grow in just 30cm of soil. The apiary (figure 14) consists of 3
colonies that host approximately 150,000 bees which pollinate the green roof gardens and the
surrounding environment15
.
These urban roof tops serve as perfect places to facilitate not only wild life diversity but also
plant and harvest a large variety of food crops. Having these opportunities proves once more
that green roofs can be beneficial to the urban environment.
Including green roofs and green gardens into building design in some cities and
communities incentives and policies are offered that guide green roof implementation. One
type of indirect subsidy is allowing developers to use green roofs as mitigation for the
provision of open space. In Chicago, for example, all projects with residential units to
provide open space require paying an impact fee; moreover if a green roof is implemented in
the project then the developer can receive a credit on the impact fee if the green roof is
accessible to the residents of the building or the public.
14
Richmond BMW dealership – http://www.youtube.com/watch?v=P6G8DQ6UVJM
15
Richmond BMW dealership (honey bees) - http://www.youtube.com/watch?v=ixspasu_kmM
Figure 13
Figure 14

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In Germany, the world leader of green roof implementation, taxes are collected for
anticipated stormwater control or usage fees, and owners of waterproof roof covers are
perceived a 100% utility surcharge. Among that, thirteen German cities benefit a reduction of
between 50 and 80% of the utility fee when installing a green roof.
In other parts of the world, such as Singapore, the NParks program founds up to 50% of the
installation costs on green roofs to increase the level of sky rise greenery and enrich the city’s
image in high activity open spaces.
In Tokyo, in 2011, in an effort to combat the urban heat island effect, the “Tokyo Plan 2000”
was established, requiring new buildings greater than 1000 m2
or over 0.1ha to green at least
20% of their usable roof space (Dakin 2013, p.140).
Other incentives are offered for using green roofs to filter storm water before it reaches the
ground. Green roof approach on infrastructures are one method of decimating the pollution
on navigable waterways by capturing and filtering storm water in order to maintain and
restore natural hydrologies. Green roofs are part of the solution of the Clean Water Act,
because they slow stormwater down and filter it of pollutants.
In general, green roofs are an integral part of a social or cultural context that examines what
is happening in and around the potential site regarding humans and social interaction. But
when it comes down to observation, there is no substitute for an on-site visit. Being there in
person allows you not only to feel the wind, or foresee limitations and opportunities, but also
think about what type of garden is most suitable.
Even a simple green roof and a plant
palette can provide an attractive and comfortable
amenity space if the building’s loading capacity is
able to accommodate people, furniture and other
accessories. An amenity roof is an aesthetic
upgrade from a basic extensive green roof to a
space that might include gatherings, or serve to
beautify a view out a window or from a
neighboring building (figure 15).
Amenity green roofs compared to basic extensive green roofs have several advantages, such
as a more dynamic, textural, and colorful appearance and their better looks and accessible
Figure 15

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space, if available, might increase the value of marketability of the building. Some of the
disadvantages to amenity green roofs include higher constructions and maintenance costs and
the possible need of a more complex assembly compared to the basic green roof.
As a medical recommendation, being outside
and doing physical activities is far better than
being stuck in a gym looking at the screen.
Forward thinking managers often convert
rooftops to play areas that are available for
their employees. Some of them include
swimming pools, basketball- or tennis courts.
For example, in the heart of Aarhus, Denmark
the roof top of the Bruuns Galleri serves as an
amenity for golf players with a track of 18
holes under the blue sky, six levels above the
ground (figure 16).
Another green roof implementation in Denmark
can be seen in Horsens at the Vitus Bering
Innovation Park (figure 17). The building was
constructed in 2009 and since then a sedum
green roof with blooming plants and grass
beautifies the place which offers a great
panoramic view around the city.
Other institutions, such as hospitals and schools
create roof gardens with the needs for children in
mind (figure 18). One way to see it is the
opportunity for designing vegetable gardens on
the top floors of educational high-rise buildings
to provide experiences to children who rarely or
never see countryside farms. These kinds of
solutions are increasingly happening on
building’s roof tops in urban environments.
Figure 16
Figure 18
Figure 17

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In Switzerland, city of Basel, a water park created on top of a parking garage by artist Jean
Tinguely attracts thousands of visitors each year. The place is filled with moving sculptures
that spout water.
Just about everybody has experienced flying above a city on a clear day and just before
landing, from those tiny airplane windows, are able to preview the urban landscape. For a few
magical moments you have that unique bird’s eye view from which you can observe all the
building rooftops that come out from small forests or parks. In those moments designers have
realized that urban rooftops are blank canvasses of black, grey, or white nuances that are just
waiting to be greened.
5. Conclusion
Assuming that the best landscape architect is nature and the whole purpose of a green
roof is to create an ecosystem where biodiversity can live and prosper then we also have to
accept that bringing nature into the urban space will solve many of our problems and needs.
In the last three decades green roofs have been implemented into urban environments in order
to improve the ecology situation which humans have neglected while focusing more on
modern architecture.
From a first point of view green roofs have existed since centuries ago in the gardens
of Semiramis which implemented them on top of their buildings in the middle of the desert.
Then the idea was developed in Scandinavian countries where green roofs have been used to
insulate the building envelope against thermal dispersions. Later on after the Second World
War, when reinforced concrete was broadly used green roofs were implemented on a large
scale in Europe, thus giving Germany the opportunity to become the world leader in this
technology with more than three decades of experience.
Nowadays green roofs are implemented worldwide, some countries using the German FLL
guidelines, others using their own ‘know-how’ and they observe and reflect upon the
opportunities green roofs can offer.
During this report I have been analyzing examples of green roof implementation from
around the world, from Europe to North America, and Asia. Together with the written
literature research and empirical data collected from interviews with professionals in the

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green roof industry and online publications and articles I have formed this document that
presents how green roofs can influence the urban environment.
I have been through many study cases of green roof projects worldwide that present some of
the advantages and disadvantages of implementing this technology on building’s roof tops
and despite their high costs, the results seem promising. Of course, there are still many
improvements to be done but as green roofs continue to be a growing and integral part of our
urban environments, ten, twenty, or thirty years from now we will have more examples to
reflect upon as well as more experience in the field.
Even though green roofs investors expect fast responses and pay-backs, the reality isn’t by
their side and they will have to have patience and let the professionals do their job. Great
results take time, and the famous quote says it best “Rome wasn’t built in a day”.
Energy saving during hot and cold season, mitigation of urban heat island effect and
CO2 emissions, habitat and biodiversity opportunities, cultivation of food and crops, roof
membrane protection and life span improvement, stormwater retention, filtering and runoff
control, cooling of urban environment, and job opportunities are just some of the advantages
compared to the high costs for maintenance and construction of green roof implementation
we face nowadays.
Considering all those benefits I believe that green roof technology will be more
affordable in the near future and their implementation on a large scale in the urban
environments will be an important step to a cleaner and more sustainable habitat for humans
and nature to co-exist in the same place.
As a future perspective, I believe that this dissertation report has had a great influence upon
my learning activity due to the variety of activities and research I made in order to create it,
as well as great asset for my portfolio in the future job search. The complexity of gathering
the information from written literature, internet articles, on-line publications and videos, as
well as interviews with professionals from the green roof industry, proved to be a challenge
that I managed to overcome with great passion and interest.

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To end-up this report I would like to share the vision of the Swiss architect Le
Corbusier who almost a century ago wrote his sentiments in his book Le Petite Maison16
(the
little house):
“We climb up to the roof – a pleasure known to some civilizations in former centuries.
The reinforced concrete forms the terrace roof and, with 20 or 30 centimeters of earth, the
“roof garden.” Here we are on top! We are in the middle of the dog-days; the grass is
parched. What does it matter, for each tiny leaf gives shade and the compact roots insulate
from heat and cold…Pay attention! It is towards the end of September. The autumn flowers
are blossoming and the roof is green once more, for a thick carpet of wild geraniums has
over grown everything. It is a wonderful sight. In spring, the young grass sprouts up with its
wild flowers; it is high and luxuriant. The roof garden lives independently, tended by the sun,
the rain, the winds, and the birds which bring the seeds.”
16
Fragment taken from The professional design guide to green roofs – Dakin 2010, p.277( see list of references)

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6. List of illustrations
Figure 1 (front cover) - Green roofs 2010/2030
Link<https://www.facebook.com/photo.php?fbid=483709078365793&set=a.2467596020607
43.58106.246755835394453&type=1&theater>
Figure 2 – Rockefeller Center, New York, USA
Link < http://weirdcreative.com/astounding-nature-in-the-middle-of-big-cities-around-the-
world-18-beautiful-rooftop-gardens-461/>
Figure 3 – Sedum green roof (Diadem 50)
Link < http://www.byggros.com/da/produkter/gronne-tage/gronne-tage-systemer/sedumtag-
50>
Figure 4 – 8 Tallet, Copenhagen, Denmark
Link < http://designkbh.blogspot.dk/>
Figure 5 – Intensive roof (Diadem 1200)
Link < http://www.byggros.com/da/produkter/gronne-tage/gronne-tage-systemer/diadem-
1200>
Figure 6 – Urban heat island effect illustration
Link < http://www.urbanreleaf.org/get-educated/benefits-of-trees>
Figure 7 – Moesgård Museum (on-site picture)
Figure 8 – Scan from Green roof manual p.31 (see list of references for information about
the book)
Figure 9 – Ethelred estate, Kennington, UK
Link < http://www.homeprotect.co.uk/Media/278340/ethelred_roof.jpg>
Figure 10 – Black redstart bird, UK
Link < http://www.rspb.org.uk/wildlife/birdguide/name/b/blackredstart/index.aspx>

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Figure 11 – Orchid plantation on Moos Water Filtration Plant, Zürich, Switzerland
Link < http://www.greenroofs.com/projects/pview.php?id=680>
Figure 12 – Eagle Street farm, Brooklyn, NY, USA
Link<http://thescoutmag.com/assets/0000/2575/article_eaglestfarm_benefit_01_grid_4.jpg?1
313973662>
Figure 13 – Honey bee apiary, Auto West BMW Vancouver, Canada
Link < http://www.richmond-news.com/news/richmond-businesses-vying-to-be-greenest-
1.495737>
Figure 14 – Honey bee apiary, Auto West BMW Vancouver, Canada
Link < http://green.autowestgroup.ca/portfolio/autowestbmw/>
Figure 15 - Green roof at Mountain Equipment Coop, Toronto, Canada
Link < http://www.inspirationgreen.com/urban-institutional-green-roofs.html>
Figure 16 – Overview of minigolf course, Aarhus, Denmark
Link < http://www.panoramio.com/photo/28478635>
Figure 17 – Green roof over Vitus Bering Innovation Park, Horsens, Denmark (on-site visit)
Figure 18 – Green roof garden on top of educational building
Link < http://www.playground-landscape.com/en/article/view/349.html>
!Note: more illustrations of green roofs are attached to the enclosures.

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7. List of references:
7.1. Books:
 ‘The green roof manual’
Author(s): Edmund C. Snodgrass and Linda McIntyre
Published by: Timber Press
Release date: 2010
Place of publishing: Portland | London
 ‘The Professional Design Guide to Green Roofs’
Author(s): Lisa Lee Benjamin, Karla Dakin, Mindy Pantiel
Published by: Timber press
Release date: 2013
Place of publishing: Portland | London
 ‘Sustainable Urban Environments – an ecosystem approach’
Author(s): Ellen van Bueren, Hein van Bohemen, Laure Itard, Henk Visscher
Published by: Springer
Release date: 2012
Place of publishing: London | New York
 ‘City Design’
Author(s): Jonathan Barnett
Published by: Routledge
Release date: 2011
Place of publishing: USA and Canada

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7.2. Articles:
 ELSEVIER, 2013. A review of energy aspects of green roofs [pdf].
Available at: <http://www.sciencedirect.com.ez-
aaa.statsbiblioteket.dk:2048/science/article/pii/S136403211300124X>
[Accessed September 10th
2013]
 ELSEVIER, 2012. Acoustic effects of green roof systems on a low-profiled structure
at street level [pdf].
aaa.statsbiblioteket.dk:2048/science/article/pii/S0360132311003532#>
2013]
 ELSEVIER, 2012. Cool and green roofs. An energy and comfort comparison between
passive cooling and mitigation urban heat island techniques for residential buildings
in the Mediterranean region [pdf].
Available at:
<http://www.sciencedirect.com/science/article/pii/S0378778811004129>
2013]
 ELSEVIER, 2012. A field study to evaluate runoff quality from green roofs [pdf].
Available at:
<http://www.sciencedirect.com/science/article/pii/S004313541100844X>
2013]
 ELSEVIER, 2010. Effect of green roof on ambient CO2 concentration [pdf].
Available at:
2013]
 ELSEVIER, 2010. Green roof vegetation for North American ecoregions: A literature
review [pdf].
aaa.statsbiblioteket.dk:2048/science/article/pii/S0169204610000782>
2013]
 ELSEVIER, 2013. Green roofs in European climates. Are effective solutions for the
energy savings in air-conditioning? [pdf].
Available at:

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2013]
 ELSEVIER, 2009. Green roofs in sustainable landscape design [pdf].
2013]
 ELSEVIER, 2009. Green roofs in sustainable landscape design [pdf].
2013]
 ELSEVIER, 2010. Green roofs; building energy savings and the potential for retrofit
[pdf].
Available at:
2013]
 ELSEVIER, 2011. Greenery on residential buildings: Does it affect preferences and
perceptions of beauty? [pdf].
Available at:
<http://www.sciencedirect.com/science/article/pii/S027249441000099X>
2013]
 ELSEVIER, 2012. How to make a city climate-proof, addressing the urban heat
island effect [pdf].
[Accessed September 23rd
2013]
 U.S. Environmental Protection Agency, 2004. Guidelines for Water Reuse [pdf].
< http://water.epa.gov/aboutow/owm/upload/Water-Reuse-Guidelines-625r04108.pdf
2013]
 Skælskør Anlægsgarnere A/S, 2010. Grøn tage[pdf].
<http://www.skag.dk/files/Groenne_tage/PPT_SKAG_Grnne_tage_samlet_3.pdf>
[Accessed October 8th 2013]

sem.
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7.3. Internet links:
 Link address: http://www.greenroofs.com/
Page accessed: 27/08/2013
 Link address: http://www.youtube.com/watch?v=pp79mGpomf4
 Link address: http://www.greenroofs.com/projects/pview.php?id=680
Page accessed 18/09/2013
 Link address:
http://www.rspb.org.uk/wildlife/birdguide/name/b/blackredstart/index.aspx

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8. List of enclosures
8.1. Auto-family house – Poland, 2012
8.2. Villa Topoject - Gyeonggido, Korea 2010
8.3. Mountain Dwellings – Copenhagen, Denmark, 2008
8.4. Kastrup Power Plant at Copenhagen International Airport – Kastrup, Denmark, 2005
8.5. Green roofs in Stuttgart, Germany
8.6. Logistics Center - Bondorf, Germany, 1996
8.7. Ford Rouge Plant – Michigan, United States, 1999
8.8. Vancouver Convention Center – Vancouver, Canada, 2009
8.9. Penn State Hershey Children’s Hospital - Hershey, Pennsylvania, United States, 2012
8.10. Green roofs Iceland
8.11. Interview with Anja Pelle from Byg Gros A/S (Sweden)
8.12. Interview with Ulrich Reeh from VegTech A/S (Denmark)
8.13. Interview with Lise Mansfeldt Faurbjerg from Henning Larsen Architects (Denmark)
8.14. Interview with Henrik Windbirk, VIAUC Aarhus lecturer (Denmark)
8.15. Interview with Torben Hoffmann from Byg Gros A/S (Denmark)
8.16. Interview with Søren Nielsen from Dan Jord A/S (Denmark)

sem.
39 of 49
8.1. Auto Family House – Poland, 2012 –
http://www.archello.com/en/project/auto-family-house

sem.
40 of 49
8.2. Villa Topoject - Gyeonggido, Korea 2010 - http://www.archdaily.com/161360/villa-
topoject-and/

sem.
41 of 49
8.3. Mountain Dwellings – Copenhagen, Denmark, 2008 -
http://www.archdaily.com/15022/mountain-dwellings-big/

sem.
42 of 49
8.4. Kastrup Power Plant at Copenhagen International Airport – Kastrup, Denmark, 2005
http://www.greenroofs.com/projects/pview.php?id=1257

sem.
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8.5. Green roofs in Stuttgart, Germany.
Steven W. Peck, founder of the Canada-based industry association Green Roofs for Healthy
Cities, says “all you have to do is climb a tall building in Germany, and you’re going to see
green roofs all over the place."
http://urbangreens.tumblr.com/image/914031202

sem.
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8.6. Logistics Center - Bondorf, Germany, 1996 -
http://www.greenroofs.com/projects/pview.php?id=536

sem.
45 of 49
8.7. Ford Rouge Plant – Michigan, United States, 1999
Ford's Rouge Plant, at over 450,000 square feet, is the largest green roof in the United States
and saved over $10 million on the installation of a storm water runoff treatment system.
http://www.apexgreenroofs.com/green-roof-benefits.html

sem.
46 of 49
8.8. Vancouver Convention Center – Vancouver, Canada, 2009
http://www.alternativeconsumer.com/2010/09/13/green-roof-of-the-day-vancouver-
convention-center/

sem.
47 of 49
8.9. Penn State Hershey Children’s Hospital - Hershey, Pennsylvania, United States, 2012
http://www.liveroof.com/blog/2012/green-roofs-offer-natural-views-and-access-to-green-
space-for-patients-and-families-at-penn-state-hershey-childrens-hospital/

sem.
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http://www.prweb.com/releases/Hershey_Childrens/Hospital_LiveRoof/prweb10192342.htm
 http://ww1.prweb.com/prfiles/2012/11/30/10192342/LiveRoof_Hershey_8b.jpg

sem.
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8.10. Green roofs Iceland
http://www.greenfab-media.com/landscape-and-habitat/456/iceland-and-green-roofs

1
Valer Daniel Rudics (178744)
From: Anja Pelle <ape@Byggros.com>
Sent: Wednesday, September 18, 2013 12:04 PM
To: Valer Daniel Rudics (178744)
Subject: SV: Interview about green roofs.
Attachments: image001.png
Categories: Important
Hello Valer
Thank you for your email.
Please see my answer below.
I hope the answer can help you further with your report
Med venlig hilsen/Best regards
Anja Pelle
Teknisk Salgskonsulent
Mobile: +45 22 94 51 23
Email: ape@Byggros.com
Byggros A/S • Egegårdsvej 5 • DK-5260 Odense S • Tel: +45 5948 9000 • Fax: +45 5948 9005
info@byggros.com • www.byggros.com
Company of Byggros Holding A/S
Fra: Valer Daniel Rudics (178744) [mailto:178744@VIAUC.DK]
Sendt: 12. september 2013 18:24
Til: Anja Pelle
Emne: Interview about green roofs.
Greetings,
My name is Valer Daniel Rudics, I am a constructing architect student at VIA University College in Århus, Denmark. At
the moment I am writing my dissertation report which is part of the syllabus for the last semester of my education, and I
am writing to ask you several questions. The main subject of my dissertation is green roofs, but my focus is on 'how can
green roofs influence the urban environment?'
I would really appreciate if you could take some time and answer the following questions which are part of my research
for the empirical data.
1. How 'green' is a green roof? Is the construction sustainable from a material point of view?
That is a very good question and an important one also. First of all the vegetation is making the green roof
‘green’, but what about the system below. I can only comment on our system.
Enclosure 8.11.

2
If a green roof system should be really ‘green’ it is necessary to have a sustainable and local production.
Our products is mostly made of recycled material, which is a good way to start, but the products are
produced in Hungary, which we can’t call local.
The substrate is produced in Denmark. We have a depot in Lisbjerg and Næstved, so we don’t have to fare
to our clients.
I don’t thing we that we can call it a cradle to cradle product, but we are working to get it more green.
2. Do you think that there are more financial benefits to retrofit an old building with green roof or to
implement the green roof in a new building? (Could you explain your decision?)
That’s a difficult one! I will say it depends of the benefits you want from the green roof, so I think that you
can get financial benefits in both cases.
I think it depends of the project and which type of green roof, we are talking about.
An intensive green roof will always give a financial benefit because it is possible to make a roof to a place
where people can stay, play or relax. That will give the building an extra value.
An extensive roof can be “just” an extra cost on old and new buildings, but it is also possible to withhold
water on the roof, and thereby min. the costs for a new drain system.
3. What is the clients' opinion when suggesting the implementation of a green roof in your projects?
I think the general opinion is very positive. The most critical point is the financial aspect.
4. It is known that Germany is the world leader in green roof technology. Do you think Denmark is following
the path?
I don’t think Denmark will be comparable with Germany, but we are doing a great job to get there. The
municipalities are making a lots of rules to make sure that the amount of green roofs will grow.
5. Do local authorities encourage the Danish building industry include green roof technology in urban design?
The short answer is yes, a good example is Københavns Kommune.
Looking forward to hearing from you!
Kind regards / Med venlig hilsen
Valer Daniel Rudics
Constructing Architect Student
VIA University College Aarhus
Halmstadgade 2, 8200, Aarhus Nord
School e-mail: 178744@viauc.dk
Privat e-mail: dani.rudics@gmail.com
Tlf: 27 89 73 45
Please save a tree and do not print this e-mail! ☺☺☺☺

1
From: Ulrik Reeh <Ulrik.Reeh@vegtech.dk>
Sent: Friday, September 13, 2013 5:33 PM
Subject: SV: Interview about green roofs.
Hi
I´m not shure what this Guldhornet is. Do you mean Snozelhuset??
Short answers to difficult questions will follow below.
I hope you will send your final thesis – thank you and good lcuk
Med venlig hilsen
Ulrik Reeh
Veg Tech A/S
Annasvej 2
2900 Hellerup
Tlf.: 3962 6869
Mobil: 2835 6869
ur@vegtech.dk
www.vegtech.dk
Fra: Valer Daniel Rudics (178744) [mailto:178744@VIAUC.DK]
Sendt: den 13 september 2013 10:15
Til: Ulrik Reeh
Emne: Interview about green roofs.
Greetings,
My name is Valer Daniel Rudics, I am a constructing architect student at VIA University College in Århus, Denmark. At
the moment I am writing my dissertation report which is part of the syllabus for the last semester of my education, and I
am writing to ask you several questions. The main subject of my dissertation is green roofs, but my focus is on 'how can
I am writing to you because you have been recommended by my consulting teacher Henrik Windbirk, and he shortly
introduced me to the project that you have worked together at “Guldhornet” in Skanderborg.
I would really appreciate if you could take some time and answer the following questions which are part of my research
for the empirical data.
Depends on which construction you think of and what are your criteria!
Must be the same, but always depending on the actual case!
Enclosure 8.12.

2
Differs from nice design, green profile, storm water retention, etc.
the path?
Yes
5. Do local authorities encourage the Danish building industry include green roof technology in urban design?
Yes more and more, but different from municipality to municipality!
Looking forward to hearing from you!
Valer Daniel Rudics
Tlf: 27 89 73 45

10/19/13 Gmail - SV: Interview regarding green roofs.
https://mail.google.com/mail/u/0/?ui=2&ik=94655e90c8&view=pt&search=starred&msg=1414a3a63c6d42a7 1/3
Valer Daniel Rudics <dani.rudics@gmail.com>
SV: Interview regarding green roofs.
Lise Mansfeldt Faurbjerg <LFAU@henninglarsen.com> Mon, Sep 23, 2013 at 11:50 AM
To: "dani.rudics@gmail.com" <dani.rudics@gmail.com>
Hi Valer,
I’m sorry for the late answer. See answers below marked with blue. In case you quote any answers in your report
with the mentioning of Henning Larsen Architects, please run the quotes by me before you print it.
Good luck on your thesis!
Best regards,
Lise Mansfeldt Faurbjerg
____________________________________________
Lise Mansfeldt Faurbjerg
B. eng. Architectural Engineering
BA Aesthetics & Culture
Direct tel +45 8231 3179
Henning Larsen Architects A/S
Vesterbrogade 76
1620 Copenhagen V
Denmark
Tel +45 8233 3000
www.henninglarsen.com
____________________________________________
From: Valer Daniel Rudics (178744) [mailto:178744@VIAUC.DK]
Sent: 11. september 2013 10:17
To: Henning Larsen Architects - Mail
Subject: Interview regarding green roofs.
Enclosure 8.13.

Greetings,
My name is Valer Daniel Rudics, I ama constructing architect student at VIA University College in Århus, Denmark. At the
moment I amwriting my dissertation report which is part of the syllabus for the last semester of my education, and I am
writing to ask you several questions. The main subject of my dissertation is green roofs, but my focus is on 'how can
I would really appreciate if you could take some time and answer the following questions which are part of my research for
the empirical data.
1. How'green' is a green roof? Is the construction sustainable from a material point of view? Depending on the context
andthe local climate a green roof can be more or less green. As a rule of thumbwe regardgreen roofs as highly green
feature – but a decision about a green roof shouldbe accompaniedby clear reasons for the functionality of the green roof.
Is it a feature for the local water management? Is it part of an Urban Cool Islandstrategy? Is it for leisure purposes? Or
bio-diversity? Or, or, or…? These questions shouldbe explicitly answered.
2. Do you think that there are more financial benefits to retrofit an oldbuilding with green roof or to implement the
green roof in a newbuilding? (Couldyou explain your decision?) This question cannot be answeredwith a general
statement. Every case is unique: Howis the structure of the existing/newbuilding, what kindof green roof is anticipated,
what is the purpose of the green roof? Existing roofs – especially in dense urban areas – is a resource that is not fully
unlocked. The roof areas can be usedwisely to enhancedthe quality of the city, andif green roofs is the right solution
can only be answeredindividually for each case. Translating quality into financiel benefits – or the other way round– is a
very complex procedure.
3. What is the clients' opinion when suggesting the implementation of a green roof in your projects? We mainly get
very positive feedback. So far Ihaven’t heardof a client refusing to have a green roof, if we argue that this is the optimum
solution for the specific project.
4. It is known that Germany is the worldleader in green roof technology. Do you think Denmark is following the path?
Absolutely. But again: Both clients, architects andengineers are realizing that the roof is a resource for the building
andthe city – andthat it shouldbe developedto obtain the best purpose. According to context andclimate the use of the
roof shouldbe established– not on the basis of a green or non-green question.
5. Do local authorities encourage the Danish building industry include green roof technology in urban design? Yes.
Briefs are becoming more andmore aware of sustainability matters, andespecially green roofs are explicitly mentioned
as a possible strategy. Denmark currently has a great challenge on managing water due to climate changes, andgreen
roofs are often mentionedas a feature to counterbalance the changes.

Looking forward to hearing fromyou!
Valer Daniel Rudics
Tlf: 27 89 73 45
Please save a tree and do not print this e-mail! J

1
From: Henrik Windbirk (HENW)
Sent: Friday, September 13, 2013 9:30 AM
Subject: SV: green roof
Hello Daniel,
of course you are wellcome to mention my name in Skanderborg, but I am not sure that Hanne knows me.
(I do not remember her!)
I will look forrward to see some pictures from the Biennale.
And now to your questions:
Well, the herbs and grass is sustainable it self, if it is not "fed" with toxic liquids. There are some materials
comming with the system, that might not be sustainable.
As we briefly talked about, the green roof will give a longer life to the membranes underneath it. That is benefit.
Another, an more important benefit is, that is it not necessary to enlarge til sewer-pipes in the terrain, because the
green roof delays the rainwater by heavy rain. If a city have mays squaremeters of green roof, it will help the city
to breath.
My former clients were all very positive, where they were explained the benefits of the green roof. An important
thing here, is that they can use is as marketing.
the path?
Yes, here in Denmark we know theat the germans are very good at this, and there are ahead of us. I hope
Denmark will follow that path. We are not there yet...
5. Do local authorities encourage the Danish building industry include green roof technology in urban
design?
I think Copenhagen encourage to "think green" using green roofs. It is not my experience with the local
authorities, I have been working with, but they like the idea.
My experience is, that the most good ideas, concerning this, comes from architects and scientists.
Money rules, you know!
Maybe, you can use my answers, otherwise, we can talk about it next time, I am in your class.
Best regards and have a nice weekend
Henrik WindbirkHenrik WindbirkHenrik WindbirkHenrik Windbirk
Arkitekt MAA|Architect MAA
Enclosure 8.14.

2
Underviser|Lecturer
VIA University College
Halmstadsgade 2
DK - 8200 Aarhus N
Mail: henw@viauc.dk
Fra: Valer Daniel Rudics (178744)
Til: Henrik Windbirk (HENW)
Emne: RE: green roof
Hello Henrik,
First of all, thank you so much for the information supplied! I will try to contact the company to ask them several
questions and I will also try to write to Hanne if it is possible to visit the place one day. (Is it okay to mention you as
reference when contacting the people from the company?)
Then I want to congratulate you for the award!!!!! I am sure you are very proud to have a prize for one of your
projects!!!!! I also had a little prize back in 2010 at ‘Bucharest Architectural Biennale’ before coming to study in
Denmark. I can show some pictures next time you are coming to class. ☺
And last but not least, would you like to dedicate some time to answer few questions regarding the green roof
approach? I will put them here in the e-mail and if any of them fit to your knowledge and curiosity to answer, I would be
very grateful.
the path?
5. Do local authorities encourage the Danish building industry include green roof technology in urban
design?
Again thank you so much for everything! Speak soon!
Valer Daniel Rudics

3
Tlf: 27 89 73 45
From: Henrik Windbirk (HENW)
Sent: Thursday, September 12, 2013 8:50 AM
Subject: SV: green roof
Hello Daniel,
I think, I can help you!
The building is situated in Skanderborg and it is an activity-house for disabled people, and is it part of the
buildings, that belong to "Landsbyen Sølund" in Skanderborg.
Here is a link to the website: http://www.solund.dk/Guldhornet.aspx. Unfortunately the website is in
danish...
I designed the building in 2008/2009, an it got an architectual prize in 2010, so it is quite new!
The company, that supplied the building with the green roof is called VegTech; www.vegtech.dk. It think it
is a swedish company, but also situated in Denmark.
The guys from the company, I was working with were Ulrik Reeh and Gregers S. Gregersen.
It should be no problem to visit the building, because it is situated in an public area. If you want to see it
from the inside, you need to make an appointment.
I think you can contact Hanne Jørgensen tlf. 8794 8190 or e-mail: hanne.joergensen@skanderborg.dk
Good luck!
Bedste hilsner/Best regards
Henrik WindbirkHenrik WindbirkHenrik WindbirkHenrik Windbirk
Arkitekt MAA|Architect MAA
Underviser|Lecturer
VIA University College
Halmstadsgade 2
DK - 8200 Aarhus N
Mail: henw@viauc.dk
Fra: Valer Daniel Rudics (178744)
Til: Henrik Windbirk (HENW)
Emne: green roof
Hello Henrik,

4
Regarding that project you mentioned the other day in class, that building that comes out of the ground the one with
the green roof. Could you possibly share a link to more information about it or maybe who was responsible for the
green roof design and implementation? I think it would be very helpful for the dissertation if I could to ask that person
several questions for empirical data, and hopefully also visit the building if that is possible. Unfortunately in Aarhus
seems like there is a lack of green roof buildings in the present, except ‘Moesgård Museum’ which is not completed yet.
Looking forward to hear from you!
Valer Daniel Rudics
Tlf: 27 89 73 45

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