ECO DESIGN, Green Roofs, Nicholas Socrates

7/31/2019 ECO DESIGN, Green Roofs, Nicholas Socrates

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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 carpetand paint.

Green Roofs: What are they?

As the name implies, green roofs are

roofs made of plants. They're

comprised of a waterproof membranefollowed 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.


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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 UrbanHeat 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 mayappear 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


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Benefits of these vegetatedGreen Roofs consist of;

1. 70-90% of rain-water retained, easing pressure on drains and prevents riverpollution

2. Reduced energy and maintenance costs

3. Long roof life: Protects against UV and weather damage

4. Provides a habitat for fauna and flora species5. 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 life9. Increased efficiency of solar panels

10. LEED accredited

bsorb Storm-water

reen roofs are a best practice for onsite water management. They slow the velocity of

unoff volume to sewer systems by 60 to 90%.

uring heavy rainfalls excess water and the water contaminants associated can lead to

ombined sewer overflows into our watersheds. Green roofs present an opportunity to

itigate this all-too-common problem by absorbing much of the water in the root systems

nd releasing the rest back into the atmosphere through evapotranspiration. If there isunoff, green roofs slow it down so that the sewer system isn't overburdened during peak


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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 70 C. With

a green roof the temperatures stay closer to 26 C. This means in the summer when energydemands 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 UVradiation, 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.

sage in times of extreme rainfall.

ost commercial spaces are required to retain storm-water on site. A green roof eliminatesr greatly decreases the space needed and costs associated with dealing with the storm-

ater.


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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 intoassets.

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 higherrents 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 70C-80C during the summer season. A green roof will lower

the ambient temperature to 26C even on the hottest days, therefore making the solarpanels work more efficiently. This is why green roof systems and solar energy panels

make for a great energy saving solution when used in combination.


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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 IslandsPART 2: WATER EFFICIENCY

Storm Water Management Water Efficient Landscaping Water Use Reduction Innovative Wastewater TechnologiesPART 3: ENERGY & ATMOSPHERE

Optimize Energy Performance Renewable Energy CFC and Ozone Depleting Substance ReductionPART 4: MATERIALS & RESOURCES

Storage and Collection of Recyclables Recycled content materialsPART 5: INDOOR ENVIRONMENTAL QUALITY

PART 6: INNOVATION IN DESIGN


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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 smalltrees. "Extensive" green roofs, by contrast, are designed to be virtually self-sustaining


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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 areusually 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 worlds

largest green roof, Millennium Park in Chicago, which is 24.5 acres of landscaping ontop 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 roofwould. 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.


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Recently, water demand has started to exceed supply, and localized flooding hasbecome 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


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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, roughly14 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 evaporationof 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 peoples need for interpersonal relationships (Kaplan, 1993). Moreover,

impediments to meaningful contact with nature can be seen as a contributing factorto 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


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(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 ingreen 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 peoples exposure to natural elements increases their ability to focus, copewith 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 individuals 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, viablesanctuaries for rare and nearly extinct species. Studies report that this elevated urban

ecosystem affords unique protection from grade level predators, traffic noise andhuman 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 beingproposed. Some have been acted upon, ranging from local initiatives to global

accords. Among these are both restriction of point-source emissions and restoration ofbiological 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,


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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 theincrease 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 thecharacteristic warmth of a town or city. This warmth is a consequence of human

modification of the surface and atmospheric properties that accompany urbandevelopment. 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 highurban densities and configurations of buildings in downtown areas. He demonstrated

that buildings can create canyons, which substantially reduce the amount of skyview 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


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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 inrural 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 ofsuch stored moisture, due to the increase of impervious surfaces, results in an

elevation of surface temperature, which in turn increases the air temperature due toradiative heat transfer.

Through better understanding of the general causes and associated problems of theurban 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 peaksummer urban heat island temperatures.

The urban environment, the lack of vegetation, which controls evapotranspiration, is

the most significant factor contributing tothe urban heat island. Therefore green rooftechnology 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 deemedto 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 ourwaterways.


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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 naturalhydrologic 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 heavymetals 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 stormgutters, sewers and engineered channels (collectively called the urban drainagesystem). Urban runoff eventually reaches receiving waters as sudden uncontrolled

surges. Many surface contaminants are picked up in the passage of this runoff and arecarried with this surge of storm-water. Common contaminants include suspended

solids, heavy metals, chlorides, oils and grease, and other pollutants that arise fromthe 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.


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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 changeadversely impacts health. While scientists debate what exact influence cities have onclimate 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 theextreme 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 alsooffer 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.


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References

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the 2nd North American Green Roof Conf.: Greening Rooftops for Sustainable

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walls and pavements. The London Ecol. Unit, London.

Liptan, T. 2003. Planning, zoning and financial incentives for ecoroofs in Portland,

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Documents

ECO DESIGN, Green Roofs, Nicholas Socrates