Green roof - AbsoluteAstronomy.com

A green roof is a roof

Roof

A roof is the covering on the uppermost part of a building. A roof protects the building and its contents from the effects of weather. Structures that require roofs range from a letter box to a cathedral or stadium, dwellings being the most numerous....

of a building

Building

In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...

that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. (The use of “green” refers to the growing trend of environmentalism and does not refer to roofs which are merely colored green, as with green roof tiles or roof shingle

Roof shingle

Roof shingles are a roof covering consisting of individual overlapping elements. These elements are typically flat rectangular shapes laid in rows from the bottom edge of the roof up, with each successive higher row overlapping the joints in the row below...

s.)

Container garden

Container garden

Container gardening is the practice of growing plants exclusively in containers instead of planting them in the ground. Pots, traditionally made of terracotta but now more commonly plastic, and windowboxes have been the most commonly seen. Small pots are commonly called flowerpots. In some cases,...

s 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 greywater

Greywater

Greywater is wastewater generated from domestic activities such as laundry, dishwashing, and bathing, which can be recycled on-site for uses such as landscape irrigation and constructed wetlands...

.

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

Roof

.

The term green roof may also be used to indicate roofs that use some form of green technology, such as a cool roof

Cool roof

Cool roofs are the roofs that can deliver high solar reflectance and high thermal emittance...

, a roof with solar thermal collector

Solar thermal collector

A solar thermal collector is a solar collector designed to collect heat by absorbing sunlight. The term is applied to solar hot water panels, but may also be used to denote more complex installations such as solar parabolic, solar trough and solar towers or simpler installations such as solar air...

s or photovoltaic panels. Green roofs are also referred to as eco-roofs, oikosteges, vegetated roofs, living roofs, greenroofs and VCW_H (Horizontal Vegetated Complex Walls).

Environmental benefits

Green roofs are used to:

Reduce heating
HVAC
HVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...

(by adding mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

and thermal resistance value)

A 2005 study by Brad Bass of the University of Toronto

University of Toronto

The University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...

showed that green roofs can also reduce heat loss and energy consumption in winter conditions.

Reduce cooling (by evaporative cooling) loads on a building by fifty to ninety percent, especially if it is glassed in so as to act as a terrarium and passive solar
Passive solar building design
In passive solar building design, windows, walls, and floors are made to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer...

heat reservoir — a concentration of green roofs in an urban area can even reduce the city's average temperatures during the summer
Reduce stormwater
Stormwater
Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...

run off — see water-wise gardening
Natural Habitat Creation — see urban wilderness
Urban wilderness
Where appreciation for the importance of biodiversity meets the New Urbanism movement, one can find the pursuit of the creation of urban wilderness...
Filter pollutant
Pollutant
A pollutant is a waste material that pollutes air, water or soil, and is the cause of pollution.Three factors determine the severity of a pollutant: its chemical nature, its concentration and its persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the...

s and carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

out of the air which helps lower disease rates such as asthma— see living wall
Living wall
A green wall is a wall, either free-standing or part of a building, that is partially or completely covered with vegetation and, in some cases, soil or an inorganic growing medium. The concept of the green wall dates back to 600 BC with the Hanging Gardens of Babylon...
Filter pollutants and heavy metals out of rainwater
Help to insulate a building for sound; the soil helps to block lower frequencies and the plants block higher frequencies
If installed correctly many living roofs can contribute to LEED
Leadership in Energy and Environmental Design
Leadership in Energy and Environmental Design consists of a suite of rating systems for the design, construction and operation of high performance green buildings, homes and neighborhoods....

points
Increase agricultural space

Financial benefits

Increase roof life span dramatically
Increase real estate value

A green roof is often a key component of an autonomous building

Autonomous building

An autonomous building is a building designed to be operated independently from infrastructural support services such as the electric power grid, gas grid, municipal water systems, sewage treatment systems, storm drains, communication services, and in some cases, public roads.Advocates of...

.

Several studies have been carried out in Germany since the 1970s. Berlin is one of the most important centers of green roof research in Germany. Particularly in the last 10 years, much more research has begun. About ten green roof research centers exist in the US and activities exist in about 40 countries. In a recent study on the impacts of green infrastructure, in particular green roofs in the Greater Manchester area, researchers found that adding green roofs can help keep temperatures down, particularly in urban areas: “adding green roofs to all buildings can have a dramatic effect on maximum surface temperatures, keeping temperatures below the 1961-1990 current form case for all time periods and emissions scenarios. Roof greening makes the biggest difference…where the building proportion is high and the evaporative fraction is low. Thus, the largest difference was made in the town centers.”

Types

Green roofs can be categorized as intensive, semi-intensive, or extensive, depending on the depth of planting medium and the amount of maintenance they need. Traditional roof garden

Roof garden

A roof garden is any garden on the roof of a building. Besides the decorative benefit, roof plantings may provide food, temperature control, hydrological benefits, architectural enhancement, habitats or corridors for wildlife, and recreational opportunities....

s, 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 and should require only a minimum of maintenance, perhaps a once-yearly weeding or an application of slow-release fertiliser 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

Sedum

Sedum is a large genus of flowering plants in the family Crassulaceae, members of which are commonly known as stonecrops. It contains around 400 species of leaf succulents that are found throughout the Northern Hemisphere, varying from annual and creeping herbs to shrubs. The plants have...

species and moss

Moss

Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

es.

Another important distinction is between pitched green roofs and flat green roofs. Pitched sod roof

Sod roof

A sod roof or turf roof is a traditional Scandinavian type of green roof covered with sod on top of several layers of birch bark on gently sloping wooden roof boards. Until the late 19th century it was the most common roof on rural log houses in large parts of Scandinavia...

s, 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.

History

Green Roofs have a centuries-long history.

Modern green roofs, which are made of a system of manufactured layers deliberately placed over roofs to support growing medium and vegetation, are a relatively new phenomenon. However, green roofs or sod roof

Sod roof

s in Northern Scandinavia

Scandinavia

Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

have been around for centuries. The modern trend started when green roofs were developed in Germany in the 1960s, and has since spread to many countries. Today, it is estimated that about 10% of all German roofs have been “greened”. Green roofs are also becoming increasingly popular in the United States, although they are not as common as in Europe.

A number of European Countries have very active associations promoting green roofs, including Germany, Switzerland, the Netherlands, Norway, Italy, Austria, Hungary, Sweden, the UK, and Greece. The City of Linz in Austria has been paying developers to install green roofs since 1983, and in Switzerland it has been a federal law since the late 1990s. In the UK, their uptake has been slow, but a number of cities have developed policies to encourage their use, notably London and Sheffield.

Many green roofs are installed to comply with local regulations and government fees, often regarding stormwater

Stormwater

Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...

runoff management. In areas with combined sewer-stormwater systems, heavy storms can overload

Sanitary sewer overflow

Sanitary sewer overflow is a condition whereby untreated sewage is discharged into the environment prior to reaching treatment facilities thereby escaping wastewater treatment. When caused by rainfall it is also known as wet weather overflow. It is primarily meaningful in developed countries,...

the wastewater system

Water treatment

Water treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the...

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

Condensation

Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

and transpiration

Transpiration

Transpiration is a process similar to evaporation. It is a part of the water cycle, and it is the loss of water vapor from parts of plants , especially in leaves but also in stems, flowers and roots. Leaf surfaces are dotted with openings which are collectively called stomata, and in most plants...

, while retaining pollutants in their soil.
Elevation 314, a new development in Washington, D.C. uses green roofs to filter and store some of its storm water on site, avoiding the need for expensive underground sand filters to meet D.C. Department of Health storm-water regulations.

Combating the urban heat island effect is another reason for creating a green roof. Traditional building materials soak up the sun's radiation and re-emit it as heat, making cities at least 4 degrees Celsius (7 °F) hotter than surrounding areas. On Chicago's City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically 1.4–4.4 degrees Celsius (2.5–8.0 °F) cooler than they are on traditionally roofed buildings nearby.

Green roofs are becoming common in Chicago, as well as in Atlanta, Portland, and other United States cities, where their use is encouraged by regulations to combat the urban heat-island effect. In the case of Chicago, the city has passed codes offering incentives to builders who put green roofs on their buildings. The Chicago City Hall green roof is one of the earliest and most well-known examples of green roofs in the United States; it was planted as an experiment to determine the effects a green roof would have on the microclimate of the roof. Following this and other studies, it has now been estimated that if all the roofs in a major city were greened, urban temperatures could be reduced by as much as 7 degrees Celsius.

Green roofs have also been found to dramatically improve a roof’s insulation

Building insulation

building insulation refers broadly to any object in a building used as insulation for any purpose. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation...

value. A study conducted by Environment Canada found a 26% reduction in summer cooling needs and a 26% reduction in winter heat losses when a green roof is used. In addition, greening a roof is expected to lengthen a roof’s lifespan by two or three times, according to Penn State University’s Green Roof Research Center.

Rooftop water purification is also being implemented in green roofs. These forms of green roofs are actually treatment ponds built into the rooftops. They are built either from a simple substrate (as being done in Dongtan

Dongtan

Dongtan is a plan for a new eco-city on the island of Chongming in Shanghai, China. The name of the city literally translates as "East Beach".-Population:...

) or with plant-based ponds (as being done by WaterWorks UK Grow System and Waterzuiveren.be Plants used include calamus, Menyanthes trifoliata, Mentha aquatica, etc.)

Green roofs also provide habitat

Habitat

* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

s for plants, insects, and animals that otherwise have limited natural space in cities. Even in high-rise urban settings as tall as 19 stories, it has been found that green roofs can attract beneficial insects, birds, bees and butterflies. Rooftop greenery complements wild areas by providing stepping stones for songbirds, migratory birds and other wildlife facing shortages of natural habitat

Habitat destruction

Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...

Brown roofs

Industrial brownfield sites can be valuable ecosystems, supporting rare species of plants, animals and invertebrates. Increasingly in demand for redevelopment, these habitats are under threat. "Brown roofs", also known as "biodiverse roofs", can partly mitigate this loss of habitat by covering the flat roofs of new developments with a layer of locally sourced material. Construction techniques for brown roofs are typically similar to those used to create flat green roofs, the main difference being the choice of growing medium (usually locally sourced rubble, gravel, spoil, etc...) to meet a specific biodiversity objective. In Switzerland, it is common to use alluvial gravels from the foundations; in London, a mix of brick rubble and some concrete has been used. Although the original idea was to allow the roofs to self-colonise with plants, they are sometimes seeded to increase their biodiversity potential in the short term, although such practices are derided by purists. The roofs are colonised by spiders and insects (many of which are becoming extremely rare in the UK as such sites are developed) and provide a feeding site for insectivorous birds. Laban

Laban Dance Centre

Laban in Deptford, south-east London, is a conservatoire and centre for contemporary dance, and includes 13 dance studios, a 300-seat theatre, dance health suite, Pilates studio, library and café...

, a centre for contemporary dance in London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

, has a brown roof specifically designed to encourage the nationally rare black redstart

Black Redstart

The Black Redstart Phoenicurus ochruros is a small passerine bird in the redstart genus Phoenicurus. Like its relatives, it was formerly classed as a member of the Thrush family , but is now known to be an Old World flycatcher .-Description:The Black Redstart is 13–14.5 cm in length and 12–20...

. (In 2003, Laban won the RIBA

Riba

Riba means one of the senses of "usury" . Riba is forbidden in Islamic economic jurisprudence fiqh and considered as a major sin...

Stirling Prize

The Royal Institute of British Architects Stirling Prize is a British prize for excellence in architecture. It is named after the architect James Stirling, organised and awarded annually by the Royal Institute of British Architects...

.) A green roof, 160m above ground level, and claimed to be the highest in the UK and Europe "and probably in the world" to act as nature reserve, is on the Barclays Bank HQ in Canary Wharf

Canary Wharf

Canary Wharf is a major business district located in London, United Kingdom. It is one of London's two main financial centres, alongside the traditional City of London, and contains many of the UK's tallest buildings, including the second-tallest , One Canada Square...

. Designed combining the principles of green and brown roofs, it is already home to a range of rare invertebrates.

Australia

Green roofs have been increasing in popularity in Australia over the past 10 years. Some of the early examples include the Freshwater Place residential tower in Melbourne

Melbourne

Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...

(2002) with its Level 10 rooftop Half Acre Garden, CH2 building housing the Melbourne City Council (2006) - Australia’s first 6-star Green Star Design commercial office building as certified by the Green Building Council of Australia, and Condor Tower (2005) with a 75-square-metre lawn on the 4th floor.

In 2010, the largest Australian green roof project was announced. The Victorian Desalination Project http://www.aquasure.com.au will have a “living tapestry” of 98,000 Australian indigenous plants over a roof area spanning more than 26,000 square metres. The roof will form part of the desalination plant’s sophisticated roof system, designed to blend the building into the landscape, and provide acoustic protection, corrosion resistance, thermal control, and reduced maintenance. The green roof will be installed by Fytogreen Australia http://www.fytogreen.com.au

Since 2008, City Councils and influential business groups in Australia have become active promoting the benefits of green roofs. “The Blueprint to Green Roof Melbourne” is one program being run by the Committee for Melbourne.http://www.growingup.org.au/

Canada

The city of Toronto

Toronto

Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

approved a by-law in May 2009, mandating green roofs on residential and industrial buildings. There is criticism from Green Roofs for Healthy Cities

Steven W. Peck

Steven Peck is founder and president of Green Roofs for Healthy Cities, a non-profit industry association promoting the planning, designing and building of green roof, green walls and other architecture projects. Green Roofs was established in 1999....

that the new laws are not stringent enough, since they will only apply to residential building that are a minimum of six storeys high. By 31 January 2011, industrial buildings will be required to render 10% or 2,000m² of their roofs green.
In 2008, the Vancouver Convention Centre installed a six-acre living roof of indigenous plants and grasses on its West building, making it the largest green roof in Canada.

Egypt

In Egypt

Egypt

Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

, soil-less agriculture is used to grow plants on the roofs of buildings. No soil is placed directly on the roof itself, thus eliminating the need for an insulating layer; instead, plants are grown on wooden tables. Vegetables and fruit are the most popular candidates, providing a fresh, healthy source of food that is free from pesticides.

A more advanced method, (aquaponics

Aquaponics

Aquaponics is a sustainable food production system that combines a traditional aquaculture with hydroponics in a symbiotic environment. In the aquaculture, effluents accumulate in the water, increasing toxicity for the fish...

), being used experimentally in Egypt, is farming fish next to plants in a closed cycle. This allows the plants to benefit from the ammonia excreted by the fish, helping the plants to grow better and at the same time eliminating the need for changing the water for the fish, because the plants help to keep it clean by absorbing the ammonia. The fish also get some nutrients from the roots of the plants.

France

In France, an 8000 square metres (86,111.3 sq ft) extensive, cable-supported green roof has been created on the International School in Lyon. Another huge green roof of roughly 8000 square metres (86,111.3 sq ft) has been incorporated into the new museum L'Historial de la Vendée which opened in June 2006 at Les Lucs-sur-Boulogne

Les Lucs-sur-Boulogne

Les Lucs-sur-Boulogne is a commune in the Vendée department in the Pays de la Loire region in western France.-References:*...

Germany

Long-held green roof traditions since the early industrialization more 100 years ago exist in Germany. In the 70s, green roof technology was elevated to the next level. Serious storm-water issues made cities to think about innovative solutions, preferable with living plants. Modern green roof technology with high performance and lightweight materials were utilized to grow hardy vegetation even on roofs that hardly support additional load. In the 80s modern Green Roof Technology was common knowledge in Germany where it was practically unknown in any other country in the world. Stuttgart - with one of the most innovative Department of Parks and Recreation and with the worlds oldest horticultural Universities - modern green roof technology was perfected and implemented on large scale.

With the first boom in the German green roof industry and since it was never done in this scale there were quality issues recorded. The FLL formed a committee that is only focused on modern green roof technology. FLL stands for Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V. (FLL)or in English: The German Landscape Research, Development and Construction Society. The FLL is an independent non-profit organization. It was founded in 1975 by eight professional organizations for “the improvement of environmental conditions through the advancement and dissemination of plant research and its planned applications”. The FLL green roof working group is only one of 40 committees which have published a long list of guidelines and labor instructions. Some of these guidelines also available in English including THE GERMAN FLL-GUIDELINE FOR THE PLANNING, EXECUTION AND UPKEEP OF GREEN-ROOF SITES. The results of the research and synthesis done by FLL members are constantly updated and promulgated utilizing the same principles which govern the compilation of DIN standards and are published as either guiding principles or labor instructions.

The current Green Roof Guideline was published in 2008. There is also an introduction to FLL to download at a FLL member and promoter. http://www.greenrooftechnology.com/case-studies.
Today most elements of the German FLL are part of standards and guidelines around the world (FM Global, ASTM, NRCA, SPRI etc..

Fachvereinigung Bauwerksbegrünung (FBB) was founded in 1990 as the first green roof association in the world.
FBB was founded as an open forum for manufacturers and planners, merchants and operators in 1990. The organization was born from the then-visionary idea of understanding the relationship between nature and constructions not as oppositional, but as an opportunity. Both the green roofing and conventional roofing industries are equally represented.
The FBB has developed to become an innovative lobbying group with a strong market presence, internationally known through its cooperation with other European associations. Today, approximately 100 member companies use the multifaceted services offered by FBB, which offers a greater degree of market expertise and competitiveness. "Kompetenz im Markt".

Today, about 10,000,000m² (or 100.000.000 square feet) of new green roofs are being constructed each year. According latest studies about 3/4 of these are extensive; the last 1/4 are roof gardens. The two cities with the most green roofs in Germany are Berlin and Stuttgart

Stuttgart

Stuttgart is the capital of the state of Baden-Württemberg in southern Germany. The sixth-largest city in Germany, Stuttgart has a population of 600,038 while the metropolitan area has a population of 5.3 million ....

. Surveys about the status of regulation are done by the FBB (Fachvereinigung Bauwerksbegrünung = German organization for green building technologies). Nearly one third of all cities have regulations to support green-roof and rain-water technology. Green-roof research institutions in Germany are located in several cities as including Hannover, Berlin, Geisenheim

Geisenheim

Geisenheim is a town in the Rheingau-Taunus-Kreis in the Regierungsbezirk of Darmstadt in Hessen, Germany, and is known as Weinstadt , Schulstadt , Domstadt and Lindenstadt ....

and Neubrandenburg

Neubrandenburg

Neubrandenburg is a city in Mecklenburg-Vorpommern, Germany. It is located in the southeastern part of the state, on the shore of a lake called the Tollensesee ....

.

Germany is the country with the most green roofs in the world and it is the country with the most advanced knowledge in modern green roof technology. Green Roofs in Germany are part of the 2 -3 years apprentice educations system of landscaping professionals. Since green roof are common knowledge and common sense it is interesting to take a look at the German Wikipedia page for green roofs - there is no need to describe projects, case studies or related research. The green roof technology was implemented before the internet age.

Greece

The Greek Ministry of Finance has now installed a green roof on the Treasury in Constitution Square in Athens. The so called "oikostegi" (Greek - oiko, pronounced eeko, meaning building-ecological, and stegi, pronounced staygee, meaning roof-abode-shelter) was inaugurated in September, 2008. Studies of the thermodynamics of the roof in September 2008 concluded that the thermal performance of the building was significantly affected by the installation. In further studies, in August 2009, energy savings of 50% were observed for air conditioning in the floor directly below the installation. The ten-floor building has a total floor space of 1.4 hectares. The oikostegi covers 650m², equalling 52% of the roof space and 8% of the total floor space. Despite this, energy savings totalling €5,630 per annum were recorded, which translates to a 9% saving in air conditioning and a 4% saving in heating bills for the whole building. An additional observation and conclusion of the study was that the thermodynamic performance of the oikostegi had improved as biomass was added over the 12 months between the first and second study. This suggests that further improvements will be observed as the biomass increases still further. The study also stated that while measurements were being made by thermal cameras, a plethora of beneficial insects were observed on the roof, such as butterflies, honey bees and ladybirds. Obviously this was not the case before installation. Finally, the study suggested that both the micro-climate and biodiversity of Constitution Square, in Athens, Greece had been improved by the oikostegi.

Iceland

Sod roof

s are frequently found on traditional farmhouses and farm buildings in Iceland

Iceland

Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

Switzerland

Switzerland has one of Europe's oldest green roofs, created in 1914 at the Moos lake water-treatment plant, Wollishofen

Wollishofen

Wollishofen is a suburb in Zurich's 2nd district.It was formerly a municipality of its own, having been incorporated into Zurich in 1893.The suburb has a population of 15,592 distributed on an area of 5.75 km².-Transport:...

, Zürich

Zürich

Zurich is the largest city in Switzerland and the capital of the canton of Zurich. It is located in central Switzerland at the northwestern tip of Lake Zurich...

. Its filter tanks have 30000 square metres (322,917.3 sq ft) of flat concrete roofs. To keep the interior cool and prevent bacterial growth in the filtration beds, a drainage layer of gravel and a 15-cm (6-in) layer of soil was spread over the roofs, which had been waterproofed with asphalt

Asphalt

Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

. A meadow developed from seeds already present in the soil; it is now a haven for many plant species, some of which are now otherwise extinct in the district, most notably 6,000 Orchis morio (green-winged orchid

Green-winged Orchid

The Green-winged Orchid or Green-veined Orchid is a flowering plant of the orchid family, Orchidaceae....

). More recent Swiss examples can be found at Klinikum 1 and Klinikum 2, the Cantonal

Cantons of Switzerland

The 26 cantons of Switzerland are the member states of the federal state of Switzerland. Each canton was a fully sovereign state with its own borders, army and currency from the Treaty of Westphalia until the establishment of the Swiss federal state in 1848...

Hospitals of Basel

Basel

Basel or Basle In the national languages of Switzerland the city is also known as Bâle , Basilea and Basilea is Switzerland's third most populous city with about 166,000 inhabitants. Located where the Swiss, French and German borders meet, Basel also has suburbs in France and Germany...

, and the Sihlpost platform at Zürich's main railway station.

Sweden

What is claimed to be the world's first green roof botanical garden

Botanical garden

A botanical garden The terms botanic and botanical, and garden or gardens are used more-or-less interchangeably, although the word botanic is generally reserved for the earlier, more traditional gardens. is a well-tended area displaying a wide range of plants labelled with their botanical names...

was set up in Augustenborg

Augustenborg

Augustenborg is a town with a population of 3,279 on Als Island in Sønderborg Municipality, Region of Southern Denmark in Denmark. The town lies at the head of Als Fjord. To the east is the Little Belt...

, a suburb of Malmö

Malmö

Malmö , in the southernmost province of Scania, is the third most populous city in Sweden, after Stockholm and Gothenburg.Malmö is the seat of Malmö Municipality and the capital of Skåne County...

, in May 1999. The International Green Roof Institute (IGRI) opened to the public in April 2001 as a research station and educational facility. (It has since been renamed the Scandinavian Green Roof Institute (SGRI), in view of the increasing number of similar organisations around the world.) Green roofs are well-established in Malmö: the Augustenborg housing development near the SGRI botanical garden incorporates green roofs and extensive landscaping of streams, ponds, and soak-ways between the buildings to deal with storm water run-off.

The new Bo01 urban residential development (in the Västra Hamnen

Västra hamnen

Västra hamnen is a neighbourhood of Malmö, situated in the Borough of Centrum, Malmö Municipality, Skåne County, Sweden....

(Western Harbour) close to the foot of the Turning Torso

Turning Torso

HSB Turning Torso is the tallest skyscraper in Sweden and the Nordic countries, situated in Malmö, Sweden, located on the Swedish side of the Öresund strait. Upon completion, it was the tallest building in Scandinavia, the tallest residential building in the EU and the second tallest residential...

office and apartment block, designed by Santiago Calatrava

Santiago Calatrava

Santiago Calatrava Valls is a Spanish architect, sculptor and structural engineer whose principal office is in Zürich, Switzerland. Classed now among the elite designers of the world, he has offices in Zürich, Paris, Valencia, and New York City....

) is built on the site of old shipyards and industrial areas, and incorporates many green roofs.

United Kingdom

In 2003 English Nature concluded that 'in the UK policy makers have largely ignored green roofs'. However, British examples can be found with increasing frequency. A notable early roof garden was built above the Derry & Toms Department Store in Kensington, London in 1938. More recent examples can be found at the University of Nottingham

University of Nottingham

The University of Nottingham is a public research university based in Nottingham, United Kingdom, with further campuses in Ningbo, China and Kuala Lumpur, Malaysia...

Jubilee Campus, and in London at Sainsbury's Millennium Store in Greenwich, the Horniman Museum

Horniman Museum

The Horniman Museum is a museum in Forest Hill, South London, England. Commissioned in 1898, it opened in 1901 and was designed by Charles Harrison Townsend in the Arts and Crafts style....

and at Canary Wharf

Canary Wharf

. The Ethelred Estate, close to the River Thames in central London, is the British capital's largest roof-greening project to date. Toxteth

Toxteth

Toxteth is an inner city area of Liverpool, England. Located to the south of the city, Toxteth is bordered by Liverpool City Centre, Dingle, Edge Hill, Wavertree and Aigburth.-Description:...

in Liverpool

Liverpool

Liverpool is a city and metropolitan borough of Merseyside, England, along the eastern side of the Mersey Estuary. It was founded as a borough in 1207 and was granted city status in 1880...

is also a candidate for a major roof-greening project.

In the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, intensive green roofs are sometimes used in built-up city areas where residents and workers often do not have access to gardens or local parks. Extensive green roofs are sometimes used to blend buildings into rural surroundings, for example by Rolls-Royce Motor Cars

Rolls-Royce Motor Cars

Rolls-Royce Motor Cars is a British manufacturer of luxury automobiles based at the Goodwood plant in West Sussex, England. It is the current producer of Rolls-Royce branded automobiles, whose historical production dates back to 1904. The factory is located across from the historic Goodwood Circuit...

, who has one of the biggest green roofs in Europe (covering more than 32,000m² on their factory at Goodwood, West Sussex.

The University of Sheffield has created a Green Roof Centre of Excellence and conducted research, particularly in a UK context, into green roofs. Dr Nigel Dunnett of Sheffield University published a UK-centric book about green roofing in 2004 (updated 2008).

United States of America

One of the largest expanses of extensive green roof is to be found in the US

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, at Ford Motor Company

Ford Motor Company

Ford Motor Company is an American multinational automaker based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford and Lincoln brands, Ford also owns a small stake in Mazda in Japan and Aston Martin in the UK...

's River Rouge Plant

River Rouge Plant

The Ford River Rouge Complex is a Ford Motor Company automobile factory complex located in Dearborn, Michigan, along the Rouge River, upstream from its confluence with the Detroit River at Zug Island...

, Dearborn

Dearborn, Michigan

-Economy:Ford Motor Company has its world headquarters in Dearborn. In addition its Dearborn campus contains many research, testing, finance and some production facilities. Ford Land controls the numerous properties owned by Ford including sales and leasing to unrelated businesses such as the...

, Michigan

Michigan

Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....

, where 42000 square metres (452,084.2 sq ft) of assembly plant roofs are covered with sedum

Sedum

and other plants, designed by William McDonough

William McDonough

William Andrews McDonough is an American architect, founding principal of , co-founder of with German chemist Michael Braungart as well as co-author of also with Braungart...

. Built over Millennium Park Garage, Chicago's 24.5 acres (99,148.1 m²) Millennium Park

Millennium Park

Millennium Park is a public park located in the Loop community area of Chicago in Illinois, USA and originally intended to celebrate the millennium. It is a prominent civic center near the city's Lake Michigan shoreline that covers a section of northwestern Grant Park. The area was previously...

is considered one of the largest intensive green roofs.http://www.msnbc.msn.com/id/24056306/greenroofspoppingupinbigcities Other well-known American examples include Chicago’s City Hall and the Gap headquarters in San Bruno, CA. Recently, the American Society of Landscape Architects

American Society of Landscape Architects

The American Society of Landscape Architects is the national professional association representing landscape architects, with more than 17,000 members in 48 chapters, representing all 50 states, U.S. territories, and 42 countries around the world, plus 68 student chapters...

retrofitted their existing headquarters building in Washington, D.C. with a green roof designed by landscape architect Michael Van Valkenburgh

Michael Van Valkenburgh

Michael R. Van Valkenburgh is an American landscape architect and educator. He has worked on a wide variety of projects in the United States, Canada, Korea, and France including public parks, college campuses, sculpture gardens, city courtyards, corporate landscapes, and private gardens-Early...

.

Another example of a green roof in the United States is the Ballard Library in Seattle. The landscape architect was Swift & Co., and the building architect was Bohlin Cywinski Jackson. This green roof has over 18,000 plants to help with insulation and reduce runoff. The plants used on the roof include Achillea tomentosa (woolly yarrow), Armeria maritima

Armeria maritima

Armeria maritima is the botanical name for a species of flowering plant.It is a popular garden flower, known by several common names, including thrift, sea thrift, and sea pink. The plant has been distributed worldwide as a garden and cut flower...

(sea pink, sea thrift), Carex inops pensylvanica (long-stoloned sedge), Eriophyllum lanatum (Oregon sunshine), Festuca rubra

Festuca rubra

Festuca rubra is a species of grass known by the common name red fescue. It is found worldwide and can tolerate many habitats and climates; it generally needs full sun to thrive...

(red creeping fescue), Festuca idahoensis

Festuca idahoensis

Festuca idahoensis is a species of grass known by the common names Idaho fescue and blue bunchgrass. It is native to western North America, where it is widespread and common...

(Idaho fescue), Phlox subulata

Phlox subulata

Phlox subulata is a perennial creeper growing to a height of 6 inches and covering a area. The small, five-petaled flowers bloom in rose, mauve, blue, white, or pink in late spring to early summer...

(creeping phlox), Saxifraga caespitosa (tufted saxifrage), Sedum oreganum

Sedum oreganum

Sedum oreganum is a species of succulent plant of the genus Sedum. It grows along the Pacific Coast of North America from Alaska to far northern California. The plant, known by the common name Oregon stonecrop, grows in many types of rocky habitat, including coastal bluffs and cliffs and the talus...

(Oregon stonecrop), Sedum album

Sedum album

Sedum album or White stonecrop, is a flowering plant of the genus Sedum in the family Crassulaceae. Sedum album is able to acclimate according to the environment...

(white stonecrop), Sedum spurium

Sedum spurium

Sedum spurium is a plant in the orpine family, Crassulaceae.-Description:Sedum spurium is a herbaceous plant with alternate, simple leaves, on creeping stems. The flowers are pink, borne in spring through fall....

(two-row stonecrop), Sisyrinchium idahoense

Sisyrinchium idahoense

Sisyrinchium idahoense, or Idaho blue-eyed grass, is a perennial that is native to the Western United States and Canada. It It is not a true grass, but is related to the Iris in the Iridaceae family.-Characteristics:...

(blue-eyed grass), Thymus serpyllum (wild thyme), Triteleia hyacinthina

Triteleia hyacinthina

Triteleia hyacinthina is a species of flowering plant known by the common names white brodiaea and fool's onion. It is native to western North America from British Columbia to Idaho to central California. Its habitat includes grassland and vernally moist areas such as meadows and vernal pools. It...

(fool's onion).

The new California Academy of Sciences

California Academy of Sciences

The California Academy of Sciences is among the largest museums of natural history in the world. The academy began in 1853 as a learned society and still carries out a large amount of original research, with exhibits and education becoming significant endeavors of the museum during the twentieth...

building in San Francisco's Golden Gate Park

Golden Gate Park

Golden Gate Park, located in San Francisco, California, is a large urban park consisting of of public grounds. Configured as a rectangle, it is similar in shape but 20% larger than Central Park in New York, to which it is often compared. It is over three miles long east to west, and about half a...

has a green roof that provides 2.5 acres (10,117.2 m²) of native vegetation designed as a habitat for indigenous species, including the threatened Bay checkerspot butterfly. According to the Academy's fact sheet on the building, the building consumes 30-35% less energy than required by code.

An early green-roofed building (completed in 1971) is the 358000 sq ft (33,259.3 m²) Weyerhaeuser Corporate Headquarters building in Federal Way, Washington. Its 5-story office roof system comprises a series of stepped terraces covered in greenery. From the air, the building blends into the landscape.

The first green roof in New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

was installed in midtown Manhattan

Manhattan

Manhattan is the oldest and the most densely populated of the five boroughs of New York City. Located primarily on the island of Manhattan at the mouth of the Hudson River, the boundaries of the borough are identical to those of New York County, an original county of the state of New York...

atop the United States Postal Service

United States Postal Service

The United States Postal Service is an independent agency of the United States government responsible for providing postal service in the United States...

's Morgan Processing and Distribution Center. Construction on the 109000 sq ft (10,126.4 m²) project began in September 2008, and was finished and dedicated in July 2009. Covered in native vegetation and having an expected lifetime of fifty years, this green roof will not only save the USPS approximately $30,000 a year in heating and cooling costs, but will also significantly reduce the amount of storm water contaminants entering the municipal water system.

Costs

A properly designed and installed green-roof system can cost 15 to 20 dollars per square foot as a total cost, not including the roof's waterproof layers.
In Europe, a well-designed and professionally installed fully integrated green roof can cost anywhere between 100 to 200 euros per square meter, depending on the kind of roof, the building structure, and which plants are used.

Some cost can also be attributed to maintenance. Extensive green roofs have low maintenance requirements but they are generally not maintenance free. German research has quantified the need to remove unwanted seedlings to approximately 0,1 min/m²/year. Maintenance of green roofs often includes fertilization to increase flowering and succulent plant cover. If aesthetics are not an issue, fertilization and maintenance are generally not needed. Extensive green roofs should only be fertilized with controlled-release fertilizers in order to avoid pollution of the storm water. Conventional fertilizers should never be used on extensive vegetated roofs. German studies have approximated the nutrient requirement of vegetated roofs to 5gN/m². It is also important to use a substrate that does not contain too many available nutrients. The FLL guidelines specify maximum-allowable nutrient content of substrates.

Disadvantages

The main disadvantage of green roofs is the higher initial cost. Some types of green roofs do have more demanding structural standards especially in seismic regions of the world. Some existing buildings cannot be retrofitted with certain kinds of green roof because of the weight load of the substrate and vegetation exceeds permitted static loading. Depending on what kind of green roof it is, the maintenance costs could be higher, but some types of green roof have little or no ongoing cost. Some kinds of green roofs also place higher demands on the waterproofing

Waterproofing

Waterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths...

system of the structure both because water is retained on the roof and due to the possibility of roots penetrating the waterproof membrane. "However, a sedum covering doesn't need water to be retained on the roof as these plants can tolerate long periods without rainfall, so a drainage layer will combat this particular problem" (Chris Sorrell). Moreover, properly designed and -installed systems include root barriers. It is true that installing adequate waterproofing systems and root barriers can increase the initial cost of the roof; however, due to the fact that a green roof protects the waterproofing membrane from the elements, particularly UV light, the life expectancy of the membranes is doubled or even tripled, leading to recovered initial cost differentials.

Environmental benefits

Financial benefits

Types

History

Brown roofs

Australia

Canada

Egypt

France

Germany

Greece

Iceland

Switzerland

Sweden

United Kingdom

United States of America

Costs

Disadvantages

See also

Further reading