ECO Design: Green Roofs. Bioclimatic Design http://socratesarchitects.com

1. Nicholas Socrates 2011
TU Delft 4123875
SMART: Bioclimatic Design
Green Roof Study & Research
ECO DESIGN
Over the last several years, the green-building movement has really taken off.
The movement has touched every aspect of commercial-building construction from
heating, ventilating and air-conditioning systems, to lighting, roofing and even carpet
and paint.
Green Roofs: What are they?
As the name implies, green roofs are
roofs made of plants. They're
comprised of a waterproof membrane
followed by a root barrier, a drainage
layer and finally the growing medium
and a variety of plants, grasses,
sedums, cactus or shrubs -- hence, the
green. The technology, of course, isn't
entirely new. For millennia, the natives
of Scandinavia and Iceland,
particularly barren environments with
limited building materials, used sod on
their roofs as insulation; in Tanzania,
mud huts with grass roofs are
common; and closer to home, many
early settlers used sod to insulate their
walls and prairie grass to cover their roofs.

2. Introduction
Establishing vegetation on rooftops, commonly referred to as green roofs, is an
emerging strategy for retaining storm-water runoff. In addition, green roofs offer
numerous other benefits beyond storm-water mitigation. They provide insulation for
buildings, thus saving on energy consumption, increase the life span of a typical roof
by protecting the roof components from damaging ultraviolet rays, extreme
temperatures, and rapid temperature fluctuations, filter harmful air pollutants, provide
a more aesthetically pleasing environment to live and work, provide habitat for a
range of organisms from microbes to birds and have the potential to reduce the Urban
Heat Island Effect.
Container gardens on roofs, where plants are maintained in pots, are not generally
considered to be true green roofs, although this is an area of debate. Rooftop ponds
are another form of green roofs, which are used to treat grey-water.
Also known as “living roofs,” green roofs serve several purposes for a building, such
as absorbing rainwater, providing insulation, creating a habitat for wildlife, and
helping to lower urban air temperatures and combat the heat island effect. There are
two types of "green" roofs: intensive roofs, which are thicker and can support a wider
variety of plants but are heavier and require more maintenance, and extensive roofs,
which are covered in a light layer of vegetation and are lighter than an intensive green
roof.
The term green roof may also be used to indicate roofs that use some form of "green"
technology, such as solar panels or a photovoltaic module; for example what may
appear as a typical, low-slope commercial roof. What distinguishes it from a typical
roof is the cap sheet material and the amount of insulation. There may be a significant
amount of insulation (up to 12 inches in some locations). Building owners are
investing in the additional insulation to lower utility costs.
Green roofs are also referred to as eco-roofs, vegetated roofs and living roofs

3. Benefits of these vegetated Green Roofs consist of;
1. 70-90% of rain-water retained, easing pressure on drains and prevents river
pollution
2. Reduced energy and maintenance costs
3. Long roof life: Protects against UV and weather damage
4. Provides a habitat for fauna and flora species
5. No reflected heat and prevents sealed surface heat build-up
6. Cools buildings in summer and insulates in winter
7. A useful, recreational space for roof gardens or terraces
8. Higher property value & quality of life
9. Increased efficiency of solar panels
10. LEED accredited
Absorb Storm-water
Green roofs are a best practice for onsite water management. They slow the velocity of
runoff volume to sewer systems by 60 to 90%.
During heavy rainfalls excess water and the water contaminants associated can lead to
combined sewer overflows into our watersheds. Green roofs present an opportunity to
mitigate this all-too-common problem by absorbing much of the water in the root systems
and releasing the rest back into the atmosphere through evapotranspiration. If there is
runoff, green roofs slow it down so that the sewer system isn't overburdened during peak

4. usage in times of extreme rainfall.
Most commercial spaces are required to retain storm-water on site. A green roof eliminates
or greatly decreases the space needed and costs associated with dealing with the storm-
water.
Reduce Energy Costs
Green roofs greatly reduce the temperature of the roof in the summer time. It works best in
buffering against daily temperature extremes. Roofs can reach temperatures of 70º C. With
a green roof the temperatures stay closer to 26º C. This means in the summer when energy
demands and their associated utilities costs are the highest, you are reducing the amount of
energy the building requires. The same is true in the winter, that the green roof acts as
extra insulation keeping the heat in the building, but to a lesser degree.
In today's world of rising energy costs, green roofs provide a tremendous benefit.
Extend Service Life of the Roof
The application of a green roof protects the waterproofing membrane from UV
radiation, therefore the life of the waterproofing membrane is extended three to four
times its average life, meaning that, in the long run, money is saved and fewer
materials go into the landfill because it does not need to be replaced as frequently.
Green roofs also protect the roof surface from human traffic, dust and other debris.
Create Wildlife Habitats
Green roofs create new wildlife habitats for pollinators and insects.
Improve Air Quality
Like all plants, green roof plants sequester carbon dioxide from the air and release oxygen.
Additionally, they remove smaller amounts of other contaminants in the air.
Reduce Heat Island Effect
A natural function of plants is to cool the air through evapotranspiration (or release of
water through plants into the atmosphere). With an increase of green roofs in the
urban fabric we will start to see a reduction of the overall heat trapped in our cities.

5. Higher Property Value & Quality of Life
Although difficult to quantify, green roofs provide many auxiliary benefits;
• Introduce an attractive and a dramatic amenity and transform rooftop eyesores into
assets.
• Reclaim space for relaxation and passive recreation for employees and residents.
• Increase productivity for employees and recovery time for patients in health care
facilities.
• Reduce noise heard by occupants, particularly near highways and airports.
• Create green space in neighborhoods that have little ground level space, increasing
livability and helping to meet municipal mandates for green space.
• Create marketing value for your building and organization, resulting in higher
rents and increased resale value.
Increase the Efficiency of Solar Panels
Solar panels operate most efficiently at 80° F. In general, a standard roof surface can
reach temperatures of 70°C-80°C during the summer season. A green roof will lower
the ambient temperature to 26°C even on the hottest days, therefore making the solar
panels work more efficiently. This is why green roof systems and solar energy panels
make for a great energy saving solution when used in combination.

6. LEED Credits
Green roofs can earn LEED credits in the following categories of the USGBC's green
building rating system:
PART 1: SUSTAINABLE SITES
• Reduced Site Disturbance, Protect or Restore Open Space
• Reduced Site Disturbance, Development Footprint Credit
• Landscape Design That Reduces Urban Heat Islands
PART 2: WATER EFFICIENCY
• Storm Water Management
• Water Efficient Landscaping
• Water Use Reduction
• Innovative Wastewater Technologies
PART 3: ENERGY & ATMOSPHERE
• Optimize Energy Performance
• Renewable Energy
• CFC and Ozone Depleting Substance Reduction
PART 4: MATERIALS & RESOURCES
• Storage and Collection of Recyclables
• Recycled content materials
PART 5: INDOOR ENVIRONMENTAL QUALITY
PART 6: INNOVATION IN DESIGN

7. Green Roof Summary
Green roofs are used to:
• Grow fruits, vegetables, and flowers
• Reduce heating (by adding mass and thermal resistance value) and cooling (by
evaporative cooling) loads on a building — especially if it is glassed in so as to act
as a terrarium and passive solar heat reservoir — a concentration of green roofs in
an urban area can even reduce the city's average temperatures during the summer
• Increase roof life span
• Reduce storm-water run off
• Filter pollutants and carbon dioxide out of the air
• The soil and plants on green roofs help to insulate a building for sound; the soil
helps to block lower frequencies and the plants block higher frequencies.
• Filter pollutants and heavy metals out of rainwater
• Increase wildlife habitat in built-up areas
Types of Green Roofs
Green roofs can be categorized as "semi-intensive", intensive, or extensive, depending
on the depth of planting medium and the amount of maintenance they need.
Traditional roof gardens, which require a reasonable depth of soil to grow large plants
or conventional lawns, are considered "intensive" because they are labour-intensive,
requiring irrigation, feeding and other maintenance. Intensive roofs are more park-like
with easy access and may include anything from kitchen herbs to shrubs and small
trees. "Extensive" green roofs, by contrast, are designed to be virtually self-sustaining

8. and should require only a minimum of maintenance, perhaps a once-yearly weeding
or an application of slow-release fertilizer to boost growth. Extensive roofs are
usually only accessed for maintenance. They can be established on a very thin layer of
"soil" (most use specially formulated composts): even a thin layer of Rockwool laid
directly onto a watertight roof can support a planting of Sedum species and mosses.
Extensive or Intensive Green Roofs?
There are two general types of green roofs: extensive and intensive. Intensive green
roofs, commonly thought of as “garden roofs,” are the more complex of the two,
exhibiting much greater plant diversity, and a greater need for design expertise, says
Peck. Planting media for intensive green roofs are a 30cm deep at minimum, and are
heavy.
They are almost always used for new construction, intensive green roofs can be
anything from a public garden to an entire park — as is the case with the world’s
largest green roof, Millennium Park in Chicago, which is 24.5 acres of landscaping on
top of two subterranean parking garages.
Extensive green roofs, with a much lighter saturated weight are most common. With
planting media (soil) of 1 to 5 inches thick, most extensive green roofs are not
designed for public access or to be walked on any more than a typical membrane roof
would. Several modular extensive green roof products have emerged in the last few
years that allow plants to be grown at the factory prior to actually being installed on a
roof, so it is possible to get an instant green roof.
Flat & Pitched Green Roofs
Another important distinction is between pitched green roofs and flat green roofs.
Pitched sod roofs, a traditional feature of many Scandinavian buildings, tend to be of
a simpler design than flat green roofs. This is because the pitch of the roof reduces the
risk of water penetrating through the roof structure, allowing the use of fewer
waterproofing and drainage layers.
Usage
Many green roofs are installed to comply with local regulations and government fees,
often regarding storm-water runoff management. In areas with combined sewer-
storm-water systems, heavy storms can overload the wastewater system and cause it
to flood, dumping raw sewage into the local waterways. Green roofs decrease the total
amount of runoff and slow the rate of runoff from the roof. It has been found that they
can retain up to 75% of rainwater gradually releasing it back into the atmosphere via
condensation and transpiration, while retaining pollutants in their soil.
Rainwater Harvesting Systems
The new code for sustainable homes requires a vast reduction in water consumption.
Rainwater harvesting can provide this, very cost effectively.

9. Recently, water demand has started to exceed supply, and localized flooding has
become an issue. Industry experts are now recognizing the important role that
rainwater harvesting has to play in alleviating both these problems.
Rain-water is part of a never ending cycle. It is the perfect sustainable solution.
Watermetric Rain Water System. (Domestic Rainwater Harvesting System).
What are the Benefits in Rainwater Harvesting?
As well as being environmentally friendly, collecting and using your own water can
significantly reduce your water bills.
Delivering precious clean tap water requires more and more effort, energy and
expense, and for irrigation we simply don't need to use purified drinking mains water.
Harvesting rain-water is another free resource to use and is perfect for automated
watering irrigation systems, landscape irrigation, lawn irrigation domestic and
commercial irrigation.
Domestic rainwater harvesting systems are designed to collect roof and/or ground rain

10. water via pipes filtering out leaves and particles, and store collected water above or
below ground tanks.
Green Roofs History
Germany spearheaded the modern movement back to grassy rooftops, but this time
with an urban twist. During the 1970s, the densely populated country began installing
green roofs to prevent storm water from surging into its ageing sewer systems, and the
industry has since boomed, experiencing rapid and sustained growth. Today, roughly
14 percent of the country's total roofs are greened, the industry continues to grow 10
percent per year and some German cities actually levy a "rain tax" on non-greened
asphalt rooftops.
Germany's pioneering work has encouraged other countries such as Australia, Japan,
Mexico, the Netherlands, the United Kingdom and Switzerland to actively embrace
the concept. But there's more to the mounting buzz than sheer novelty. In an era when
global warming, catastrophic weather patterns, flooding, sustainability issues, and
man's very tangible impact on the planet's health grab daily headlines, green roofing
offers positive solutions.
Energy Budgets of Individual Buildings
Green roofs have been investigated for their effects on building energy costs. The
insulating effects of added materials seem likely to reduce the penetration of summer
heat and the escape of interior heat in winter and there is some scientific evidence to
support these notions. There is possibly an even greater benefit in the summer due to
the cooling created by the evapotranspiration effect from plants and the evaporation
of retained moisture from the soil.
Green roofs prevent temperature extremes and the insulation value of the soil on the
structure lowered the cooling energy costs.
Green Amenity Space
Some researchers believe that the need for meaningful contact with nature may be as
important as people’s need for interpersonal relationships (Kaplan, 1993). Moreover,
impediments to meaningful contact with nature can be seen “as a contributing factor
to rising levels of stress and general dissatisfaction within our modern society”
(Zubevich, 2004).
Many urban buildings are positioned along busy streets and transportation routes
where access to green space is negligible. Green roofs provide a measurable
psychological benefit to urbanites by adding tangible, accessible natural viewing
space for social interaction, recreation, and relaxation. A green roof offers building
occupants proximity to common spaces where they can relax, dine, meditate, do yoga,
interact with friends or business colleagues, and enjoy proximity to green plants.
Research on human behavior suggests that a view of gardens and green plants serves
to restore calm and reduce stress in humans - particularly those that drive a vehicle

11. (Cackowski & Nasar, 2003).
Other studies suggest that humans generally prefer a view of natural settings rather
than congested or cluttered built environments and that accessibility to nature,
specifically by way of a window or a walk, which improves worker concentration and
job satisfaction, and buffers negative job stress (Hertzog, Maguire & Nebel, 2003,
Laumann, Garling & Morten Stormark (2003) and Leather, Pygras, Beale, &
Lawrence (1998).
A study by Tayor et al. (2001) determined that children with Attention Deficit
Disorder (ADD) were noticeably more relaxed and better behaved after playtime in
green settings compared with children who did not have access to green space.
There is significant evidence springing from multiple research projects to support the
theory that people’s exposure to natural elements increases their ability to focus, cope
with stress, generate creative ideas, reduce volatility and promote the perception of
self as part of a meaningful greater whole.
Exposure to natural elements enhances an individual’s mental well-being.
Habitat Preservation
Many authors report that adding green space in the form of green roofs to densely
populated urban environments provides eco-restorative habitats for displaced
creatures. Green roofs provide food, habitat, shelter, nesting opportunities and a safe
resting place for spiders, beetles, butterflies, birds and other invertebrates
(Brenneisen, 2003; Gedge, 2003).
Green roofs are being studied for their unique ability to provide undisturbed, viable
sanctuaries for rare and nearly extinct species. Studies report that this elevated urban
ecosystem affords unique protection from grade level predators, traffic noise and
human intervention.
Studies reveal that butterflies can access green space on the 20th floor of a building
(Johnston & Newton, 1992).
Air Quality Impacts
Declining air quality is an ongoing problem in cities globally, and solutions are being
proposed. Some have been acted upon, ranging from local initiatives to global
accords. Among these are both restriction of point-source emissions and restoration of
biological systems that reduce airborne contaminants.
In cities there is strong interest in measuring and dealing with air pollution levels
since air contaminants are intensified due to the density of human activity, including
the increased use of fossil fuels, the presence of the urban heat island and the absence
of natural biological controls.
Inter-regional transport and global warming concerns serve only to heighten the issue,

12. as the magnitude and frequency of smog alerts and summer heat waves increase.
Smog forms when nitrogen oxides (NOx) reacts with volatile organic compounds, a
process that is accelerated by higher ambient temperatures.
Evidence suggests that green roofs provide one opportunity to reduce local air
pollution levels by lowering extreme summer temperatures, trapping particulates and
capturing gases.
Johnson and Newton (1996) estimate in urban forestry studies that 2,000 m2 of un-
mowed grass on a roof could remove as much as 4,000 kg of particulates from the
surrounding air by trapping it on its foliage.
Several researchers report that vegetation benefits air quality by trapping particulates
and dissolving or sequestering gaseous pollutants, particularly carbon dioxide,
through the stomata of their leaves.
Urban Heat Island
The air in urban areas is typically warmer than that in surrounding undeveloped areas.
This concept has been recognized in publications since early in the Industrial
Revolution. Over the years, concern for the catastrophic effects on human health has
prompted the development of strategies for reducing the urban heat island effect.
These strategies have included reducing heat radiation and other emissions, expanding
vegetated spaces, and most recently the implementation of cool roofs and green roofs.
The most frequently observed and documented climatic effect of urbanization is the
increase in surface and air temperatures over the urban area, as compared to the rural
surroundings. Oke (1995) simply defines an urban heat island (UHI) as the
‘characteristic warmth’ of a town or city. This warmth is a consequence of human
modification of the surface and atmospheric properties that accompany urban
development. This phenomenon is given its ‘island’ designation due to the isotherm
patterns of near-surface air temperature which resemble the contours of an island
rising above the cooler conditions that surround it.
The maximum difference in the urban peak temperature and the background rural
temperature defines the urban heat island intensity. Over large metropolitan areas,
there may be several plateaus and peaks in the surface temperature. Cooler patches
coincide with open areas where vegetation or water are found.
The intensity of an urban heat island depends on many factors, such as the size of city
and its energy consumption, geographical location, absence of green space, month or
season, time of day, and synoptic weather conditions.
Oke (1987) recognized that the urban heat island is especially related to the high
urban densities and configurations of buildings in downtown areas. He demonstrated
that buildings can create ‘canyons,’ which substantially reduce the amount of sky
view available for long wave radiation heat loss at night.
Other factors contributing to the intensity of the heat island effect include:
containment of heat by pollutants in the urban atmosphere, daytime heat storage due

13. to the thermal properties of urban surface materials, emission of heat (from buildings,
transportation, and industrial operations), decreased evaporation due to the removal of
vegetation and the hard surface cover in the city which prevent rainwater percolation
into the soil.
The absence of vegetation and the nature of this hard surface cover can be addressed
by green roof treatments. It is impermeable urban surfaces (buildings, roadways,
sidewalks, patios, parking lots etc.), and an absence of soil and vegetation that results
in rapid shedding of water from rainfall and snowmelt.
In the presence of stored moisture, energy is naturally used to evaporate water (as in
rural and open areas). This sensible heat used to evaporate water creates a cooling
effect, thereby reducing the temperature of the surroundings. In cities, the absence of
such stored moisture, due to the increase of impervious surfaces, results in an
elevation of surface temperature, which in turn increases the air temperature due to
radiative heat transfer.
Through better understanding of the general causes and associated problems of the
urban heat island, specific strategies for reversing the effect have been gaining
acceptance by municipalities. These include designs to exploit natural sources of
cooler air from the surrounding countryside and adjacent water bodies, parks within
the city, air circulation created by urban structures themselves, and evaporative
cooling from vegetation or other sources of water in the city.
Designs to reduce the heating of surfaces are also seen as especially useful in
overcoming the urban heat island effect. The benefits of tree planting programs in
metropolitan areas have been significant in cooling the air, as well as adding to the
aesthetics, and reducing greenhouse gas (CO2) contributions.
However, the demand for space in cities inhibits expansion of forested areas.
Green roofs present the opportunity to expand the presence of vegetated surfaces by
replacing impermeable surfaces in urban areas, providing for a reduction in peak
summer urban heat island temperatures.
The urban environment, the lack of vegetation, which controls evapotranspiration, is
the most significant factor contributing to the urban heat island. Therefore green roof
technology offers the possibility of a great impact on the urban heat island effect.
It should be noted that UHI is of major concern in summer months. It is not deemed
to be of much concern in the winter months in northern climates.
Storm-water Management Implications
Many consider storm-water runoff mitigation to be the primary benefit of green roofs
due to the prevalence of impervious surfaces in urban and commercial areas and a
failing storm-water management infrastructure. Rapid runoff from roofs and other
impervious surfaces can exacerbate flooding, increase erosion, and result in combined
sewer overflows that could potentially discharge raw sewage directly into our
waterways.

14. Green roofs help mitigate the impact of high-density commercial and residential
development by restoring displaced vegetation.
Studies have shown that green roofs can absorb water and release it slowly over a
period of time as opposed to a conventional roof where storm-water is immediately
discharged. Research has indicated that an extensive green roof, depending on
substrate depth, can retain 60 to 100% of incoming rainfall.
This reduction in quantity of runoff from a green roof leads to improved storm-water
runoff and surface water quality. Results from a Vancouver, BC, modeling study
suggest that if all of Vancouver's existing buildings were retrofitted with green roofs
over the next 50 years, the health of the area watershed could be restored to natural
hydrologic conditions in terms of flood risk, aquatic habitat, and water quality
(Graham and Kim, 2003).
This would occur because green roofs have the ability to filter numerous
contaminants from rainwater that has flowed across the roof surface.
Other studies showed roof runoff contained higher amounts of numerous heavy
metals and nutrients when compared with rainfall, probably due to the runoff picking
up particulate pollutants when flowing across the roof. For green roofs, these
pollutants can be taken up and degraded by the plants or bound in the growing
substrate of green roofs.
Rainfall and snowmelt in urban areas are typically more problematic than in rural
environments. Under natural conditions, precipitation is impeded from runoff by
vegetation, ground-surface retention and subsurface storage. The retained rainwater
will contribute to the soil moisture and ground water replenishment. Urban landscapes
are dominated by impervious surfaces, such as concrete sidewalks, building walls and
roofs, and paved parking lots and roads. These collect the flow and direct it into storm
gutters, sewers and engineered channels (collectively called the urban drainage
system). Urban runoff eventually reaches receiving waters as sudden uncontrolled
surges. Many surface contaminants are picked up in the passage of this runoff and are
carried with this surge of storm-water. Common contaminants include suspended
solids, heavy metals, chlorides, oils and grease, and other pollutants that arise from
the use of roadways and from other surfaces the water has passed over.
There are two basic categories of interrelated problems concerning urban runoff and
wastewater from areas served by drainage systems: quantity management and quality
management. Quantity management problems arise from upstream and downstream
flooding, associated with overloaded sewer systems, and from erosion of conveyance
channels downstream in the drainage basin.
Untreated overflows to receiving waters from combined storm and sanitary sewer
systems result in water quality management problems. Sanitary overflows usually
contain high concentrations of organic compounds, bacteria and nutrients, which
cause short and long-term quality problems to receiving waters. On the other hand,
storm overflows often contain a considerable amount of trace metals and a high
concentration of suspended solids, which may have long-term impacts on receiving
waters as pollutants slowly release from deposited sediments. The following sections
describe quantity and quality problems associated with each type of drainage system.

15. Conclusion
Modern architecture is essentially closed blocks of concrete and glass. Heating and
cooling these structures is done with high-energy output and considering limited oil
reserves and rising energy costs, this is a highly negative effect.
Because city surfaces absorb, rather than reflect the sun's heat, surface temperatures
quickly rise. Green roofs, however, make a noticeable impact on a building's heat and
gain loss. During the summer, for example, the temperature of a gravel roof can
increase by as much as 25 degrees Celsius, fluctuating between 60 and 80 degrees
Celsius. But covered with grass, the roof temperature doesn't rise above 25 degrees
Celsius. Not only do they absorb less heat, green roofs also help cool their
surroundings, suck up airborne toxins and put oxygen back into the air.
As cities continue to expand, there's increasing concern whether their additional
warmth will further impact global temperatures. The disastrous 2003 summer heat
wave that lead to 35,000 deaths in Europe showed how global climate change
adversely impacts health. While scientists debate what exact influence cities have on
climate change, one thing is for certain, urban heat islands effects city dwellers --
nearly half of the word's population.
In addition to mitigating water runoff and heat, green roofs boast a variety of gains,
the first being economic. Because they are protected from ultraviolet radiation and the
extreme fluctuations in temperature that cause roof membranes to deteriorate, green
roofs offer longer roof life -- they can last up to 40 years -- and lower roof
maintenance. They beautify bare concrete stretches, are able to grow food, attract
wildlife and provide habitat in areas with fewer resources; they provide business
opportunities for nurseries, landscape contractors and irrigation specialists, and also
offer substantial noise insulation, which is why Amsterdam and Zurich use it at their
airports.
Green roofs offer so many benefits -- they reduce energy consumption, create greater
biodiversity and help mitigate the effect of urban land use. For a few additional costs,
they bring greater long-term economic benefits, as well as a hugely better
environment in the city center.

16. References
Dramstad, W.E., J.D. Olson, and R.T.T. Forman. 1996. Landscape ecology. Principles
in landscape architecture and land-use planning. Harvard Univ. Graduate School of
Design, Island Press, and Am. Soc. of Landscape Architects, Washington, DC.
Durhman, A., N.D. VanWoert, D.B. Rowe, C.L. Rugh, and D. Ebert-May. 2004.
Evaluation of Crassulacean species on extensive green roofs. p. 504–517. In Proc. of
the 2nd North American Green Roof Conf.: Greening Rooftops for Sustainable
Communities, Portland, OR. 2–4 June 2004. The Cardinal Group, Toronto.
Gedge, D. 2003. From rubble to redstarts. p. 233–241. In Proc. of 1st North American
Green Roof Conf.: Greening Rooftops for Sustainable Communities, Chicago. 29–30
May 2003. The Cardinal Group, Toronto
Graham, P., and M. Kim. 2003. Evaluating the stormwater management benefits of
green roofs through water balance modeling. p. 390–398. In Proc. of 1st North
American Green Roof Conf.: Greening Rooftops for Sustainable Communities,
Chicago. 29–30 May 2003. The Cardinal Group, Toronto.
Herman, R. 2003. Green roofs in Germany: Yesterday, today and tomorrow. p. 41–45.
In Proc. of 1st North American Green Roof Conf.: Greening Rooftops for Sustainable
Communities, Chicago. 29–30 May 2003. The Cardinal Group, Toronto.
Johnston, J., and J. Newton. 1996. Building green. A guide for using plants on roofs,
walls and pavements. The London Ecol. Unit, London.
Liptan, T. 2003. Planning, zoning and financial incentives for ecoroofs in Portland,
Oregon. p. 113–120. In Proc. of 1st North American Green Roof Conf.: Greening
Rooftops for Sustainable Communities, Chicago. 29–30 May 2003. The Cardinal
Group, Toronto.
Monterusso, M.A. 2004. Runoff water quantity and quality from green roof systems.
Moran, A., B. Hunt, and G. Jennings. 2003. A North Carolina field study to evaluate
greenroof runoff quality, runoff quantity, and plant growth. ASAE Paper 032303.
Am. Soc. of Agric. Eng., St. Joseph, MI.
Wong, N.H. 2003. Investigation of thermal benefits of rooftop garden in the tropical
environment. Build. Environ. 38:261–270.