![20080708 Chicago City Hall Green Roof](https://upload.wikimedia.org/wikipedia/commons/d/de/20080708_Chicago_City_Hall_Green_Roof.JPG)
A green roof or living roof is a
roof
A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temper ...
of a
building
A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and fun ...
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
A root barrier is an underground wall placed to block plant roots. This is often for the purpose of protecting structures or other plants, but root barriers are also used to preserve soil moisture.
Development
Root barriers were developed to stop ...
and
drainage
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic conditio ...
and
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
systems.
Container garden
Container gardening or pot gardening/farming is the practice of growing plants, including edible plants, exclusively in containers instead of planting them in the ground. A container in gardening is a small, enclosed and usually portable object ...
s on roofs, where plants are maintained in pots, are not generally considered to be true green roofs, although this is debated. Rooftop ponds are another form of green roofs which are used to treat
greywater
Greywater (or grey water, sullage, also spelled gray water in the United States) refers to domestic wastewater generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater from ...
. Vegetation, soil, drainage layer, roof barrier and irrigation system constitute green roof.
Green roofs serve several purposes for a building, such as
absorbing rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
water, providing
insulation
Insulation may refer to:
Thermal
* Thermal insulation, use of materials to reduce rates of heat transfer
** List of insulation materials
** Building insulation, thermal insulation added to buildings for comfort and energy efficiency
*** Insulated ...
, creating a habitat for wildlife, increasing benevolence and decreasing stress of the people around the roof by providing a more aesthetically pleasing landscape, and helping to lower urban air temperatures and mitigate the
heat island effect
An urban heat island (UHI) is an urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent w ...
. Green roofs are suitable for retrofit or redevelopment projects as well as new buildings and can be installed on small garages or larger industrial, commercial and municipal buildings.
They effectively use the natural functions of plants to filter water and treat air in urban and suburban landscapes. There are two types of green roof: intensive roofs, which are thicker, with a minimum depth of , and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are shallow, ranging in depth from to , lighter than intensive green roofs, and require minimal maintenance.
The term ''green roof'' may also be used to indicate roofs that use some form of green technology, such as a
cool roof
Reflective surfaces or ground-based albedo modification (GBAM) is a solar radiation management method of enhancing the Earth's albedo (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to t ...
, a roof with
solar thermal collector
A solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and sola ...
s or
photovoltaic panels
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
. Green roofs are also referred to as ''eco-roofs'', ''oikosteges'', ''vegetated roofs'', ''living roofs'', ''greenroofs'' and ''VCP
H (Horizontal Vegetated Complex Partitions)''
Environmental benefits
Thermal reduction and energy conservation
Green roofs improve and reduce energy consumption. They can reduce
heating
A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning (short: HVAC) systems, which can both cool and warm interior spaces.
...
by adding
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
and thermal resistance value, also can reduce the heat island by increasing evapotranspiration. A 2005 study by Brad Bass of the
University of Toronto
The University of Toronto (UToronto or U of T) is a public research university in Toronto, Ontario, Canada, located on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution ...
showed that green roofs can also reduce heat loss and energy consumption in winter conditions. A modeling study found that adding green roofs to 50 percent of the available surfaces in downtown Toronto would cool the entire city by .
A green roof reduces cooling (by
evaporative cooling
An evaporative cooler (also known as evaporative air conditioner, swamp cooler, swamp box, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning sy ...
) loads on a building by fifty to ninety percent, especially if it is glassed-in so as to act as a
terrarium
A terrarium (plural: terraria or terrariums) is usually a sealable glass container containing soil and plants that can be opened for maintenance to access the plants inside; however, terraria can also be open to the atmosphere. Terraria are ofte ...
and
passive solar
In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...
heat reservoir.
A concentration of green roofs in an urban area can even reduce the city's average temperatures during the summer, combating the
urban heat island effect
An urban heat island (UHI) is an urban area, urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human impact on the environment, human activities. The temperature difference is usually larger at nigh ...
. Traditional building materials soak up the sun's
radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
and re-emit it as heat, making cities at least hotter than surrounding areas. On Chicago's City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically 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. Green roofs are a type of
low impact development. 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 .
Water management
![Green roof bike rack](https://upload.wikimedia.org/wikipedia/commons/b/b2/Green_roof_bike_rack.jpg)
Green roofs can reduce
stormwater
Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed la ...
runoff via
water-wise gardening
Xeriscaping is the process of landscaping, or gardening, that reduces or eliminates the need for irrigation. It is promoted in regions that do not have accessible, plentiful, or reliable supplies of fresh water and has gained acceptance in other ...
techniques. Green roofs play a significant role in retrofitting the
Low Impact Development (LID) practices in urban areas. A study presented at the Green Roofs for Healthy Cities Conference in June 2004, cited by the EPA, found water runoff was reduced by over 75% during rainstorms.
[ Water is stored by the roof's substrate and then taken up by the plants, from which it is returned to the atmosphere through transpiration and evaporation.
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 is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...
and transpiration
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...
, while retaining pollutants in their soil. Many green roofs are installed to comply with local regulations and government fees, often regarding stormwater
Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed la ...
runoff management. In areas with combined sewer-stormwater systems, heavy storms can overload the wastewater system and cause it to flood, dumping raw sewage into the local waterways. Often, phosphorus and nitrogen are in this category of environmentally harmful substances even though they are stimulating to the growth of plant life and agriculture. When these substances are added to a system, it can create mass biological activity since they are considered limiting factors of plant growth and by adding more of them to a system, it allows for more plant growth.
Ecological benefits
Green roofs create natural habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
as part of an urban wilderness
Urban wilderness is vacant property in urban areas that is reverted to its original biome and repurposed for recreation. This is part of the New Urbanism movement that seeks to combine greenery in urban planning. Urban wilderness is also seen as a ...
. 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. A recent list of the bee species recorded from green roofs (worldwide) highlights both the diversity of species, but also the (expected) bias towards small ground-nesting species (Hofmann and Renner, 2017). Rooftop greenery complements wild areas by providing stepping stones for songbirds, migratory birds and other wildlife facing shortages of natural habitat.
Green roofs also serve as a green wall, filtering pollutant
A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oi ...
s and carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
out of the air, helping to lower rates of diseases such as asthma. They can also filter pollutants and heavy metals out of rainwater.
Carbon sequestration
An additional environmental benefit of a green roof is the ability to sequester carbon. Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
is the main component of plant matter and is naturally absorbed by plant tissue. The carbon is stored in the plant tissue and the soil substrate through plant litter and root exudates. A study on green roofs in Michigan and Maryland found the above ground biomass and below ground substrate stored on average between 168 g C m−2 and 107 g C m−2 . Variations occurred among the different species of plant used. Substrate carbon content averaged 913 g C m−2 and after the subtraction of the original carbon content the total sequestration was 378 g C m−2. The sequestration can be improved by changing plant species, increasing substrate depth, substrate composition, and management practices. In a study done in Michigan above ground sequestration ranged from 64 g C m−2 to 239 g C m−2 for S. acre and S album. Also, by increasing the substrate depth would allow for more area of carbon storage and diversify the types of plants with greater potential of carbon storage. The direct carbon sequestration
Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land ...
techniques and methods can be measured and accounted for. Green roofs also indirectly reduce CO2 given off by power plants through their ability to insulate buildings. Buildings in the US account for 38% of the total carbon dioxide emissions. A model supported by the U.S. Department of Energy found a 2 percent reduction in electricity consumption and 9-11% reduction in natural gas when implementing green roofs.
Other
*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 (LEED) is a
green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council (USGBC), it includes a set of rating systems for the design, construction ...
points
*Increase agricultural space
*Green roofs not only retain rainwater, but also moderate the temperature of the water and act as natural filters for any of the water that happens to run off.
Costs and financial benefits
A properly designed and installed extensive green-roof system can cost while an intensive green roof costs However, since most of the materials used to build the green roof can be salvaged, it is estimated that the cost of replacing a green roof is generally one third of the initial installation costs.
With the initial cost of installing a green roof in mind, there are many financial benefits that accompany green roofing.
*Green roofing can extend the lifespan of a roof by over 200% by covering the waterproofing membrane with growing medium and vegetation, this shields the membrane from ultra-violet radiation and physical damage. Further, Penn State University's Green Roof Research Center expects the lifespan of a roof to increase by as much as three times after greening
Greening is the process of transforming living environments, and also artifacts such as a space, a lifestyle or a brand image, into a more environmentally friendly version (i.e. 'greening your home' or 'greening your office'). The act of greenin ...
the roof.
*It is estimated that the installation of a green roof could increase the real estate value of an average house by about 7%.
*Reduction in energy use is an important property of green roofing. By improving the thermal performance of a roof, green roofing allows buildings to better retain their heat during the cooler winter months while reflecting and absorbing solar radiation during the hotter summer months, allowing buildings to remain cooler. 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. With respect to hotter summer weather, green roofing is able to reduce the solar heating of a building by reflecting 27% of solar radiation, absorbing 60% by the vegetation through photosynthesis and evapotranspiration, and absorbing the remaining 13% into the growing medium. Such mitigation of solar radiation has been found to reduce building temperatures by up to and reduce energy needs for air-conditioning by 25% to 80%. This reduction in energy required to cool a building in the summer is accompanied by a reduction in energy required to heat a building in the winter, thus reducing the energy requirements of the building year-round which allows the building temperature to be controlled at a lower cost.
*Depending on the region in which a green roof is installed, incentives may be available in the form of stormwater tax reduction, grants, or rebates. The regions where these incentives will most likely be found are areas where failing storm water management infrastructure is in place, urban heat island effect has significantly increased the local air temperature, or areas where environmental contaminants in the storm water runoff is of great concern. An example of such an incentive is a one-year property tax credit is available in New York City
New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...
, since 2009, for property owners who green at least 50% of their roof area.['Tax Credits For Green Rooftops In NYC'](_blank)
Environmental Leader, 29 June 2008. Retrieved 10 July 2012.
Disadvantages
The main disadvantage of green roofs is that the initial cost of installing a green roof can be double that of a normal roof. 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 is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...
system of the structure, both because water is retained on the roof and due to the possibility of roots penetrating the waterproof membrane. Another disadvantage is that the wildlife they attract may include pest insects which could easily infiltrate a residential building through open windows.
The additional mass of the soil substrate and retained water places a large strain on the structural support of a building. This makes it unlikely for intensive green roofs to become widely implemented due to a lack of buildings that are able to support such a large amount of added weight as well as the added cost of reinforcing buildings to be able to support such weight. 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 roofs because of the weight load of the substrate and vegetation exceeds permitted static load
A structural load or structural action is a force, deformation, or acceleration applied to structural elements. A load causes stress, deformation, and displacement in a structure. Structural analysis, a discipline in engineering, analyzes the effe ...
ing. The weight of a green roof caused the collapse of a large sports hall roof in Hong Kong in 2016. In the wake of the disaster numerous other green roofs around the territory were removed.
Green roofs require significantly more maintenance and maintenance energy compared to a standard roof. Standard maintenance include removing debris, controlling weeds, deadhead trimming, checking moisture levels, and fertilizing. The maintenance energy use for green roofs has many variables including: climate, intensity of rainfall, type of building, type of vegetation, and external coatings. The most significant effect comes from scarce rainfall which will increase the maintenance energy due to the watering required. During a 10-year roof maintenance cycle a house with a green roof requires more retrofit embodied energy than a house with a white roof. The individual components of a green roof have implications during the manufacturing process have additional implications compared to a conventional roof. The embodied energy for green roof components are of green roof. This value is equivalent to 6448 g C m−2 which is significantly greater than 378 g C m−2.
Both sod roofs and LWA-based (Lightweight Aggregates) roofs have been found to have a negative impact on the quality of their resulting runoff.
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. Extensive green roofs traditionally support of vegetation while intensive roofs support of vegetation. Traditional roof garden
A roof garden is a 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, recreational oppo ...
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
Mineral wool is any fibrous material formed by spinning or drawing molten mineral or rock materials such as slag and ceramics.
Applications of mineral wool include thermal insulation (as both structural insulation and pipe insulation), f ...
laid directly onto a watertight roof can support a planting of ''Sedum
''Sedum'' is a large genus of flowering plants in the family Crassulaceae, members of which are commonly known as stonecrops. The genus has been described as containing up to 600 species, subsequently reduced to 400–500. They are leaf succulen ...
'' species and moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
es. Some green roof designs incorporate both intensive and extensive elements. To protect the roof, a waterproofing membrane is often used, which is manufactured to remain watertight in extreme conditions including constant dampness, ponding water, high and low alkaline conditions and exposure to plant roots, fungi and bacterial organisms.
Advances in green roof technology have led to the development of new systems that do not fit into the traditional classification of green roof types. Comprehensive green roofs bring the most advantageous qualities of extensive and intensive green roofs together. Comprehensive green roofs support plant varieties typically seen in intensive green roofs at the depth and weight of an extensive green roof system.
Another important distinction is between pitched green roofs and flat green roofs. Pitched 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 ...
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
In ancient times green roofs consisted of cave-like structures or 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 ...
s covered with earth and plants commonly used for agriculture, dwelling, and ceremonial purposes. These early shelters provided protection from the elements, good insulation during the winter months, and a cool location in the summer. Unfortunately for modern conveniences, these were neither waterproof nor was there any system to keep out unwanted burrowing wildlife.
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
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 ...
s in northern Scandinavia
Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...
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".
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. Germany was the first country to start developing green roof systems and market them on a large scale. 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.
Green roofs are also becoming increasingly popular in North America, although they are not as common as in some parts of Europe. Numerous North American cities offer tax incentives to developers who integrate green roofs in their buildings. Toronto and San Francisco legally mandate new buildings to include green roofs
Rooftop water purification
Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for hu ...
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) or with plant-based ponds. Plants used include calamus
Calamus may refer to:
Botany and zoology
* ''Calamus'' (fish), a genus of fish in the family Sparidae
* ''Calamus'' (palm), a genus of rattan palms
* Calamus, the hollow shaft of a feather, also known as the quill
* '' Acorus calamus'', the swe ...
, ''Menyanthes trifoliata
''Menyanthes'' is a monotypic genus of flowering plants in the family Menyanthaceae containing the single species ''Menyanthes trifoliata''. The North American form is often referred to as ''M. trifoliata'' var. ''minor'' Michx. It is known ...
'', ''Mentha aquatica
''Mentha aquatica'' (water mint; syn. ''Mentha hirsuta'' Huds.Euro+Med Plantbase Project''Mentha aquatica'') is a perennial flowering plant in the mint family Lamiaceae. It grows in moist places and is native to much of Europe, northwest Africa ...
'', etc.)
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
Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature.Hiltrud Pötz & Pierre Bleuze (2011). Urban green-blue grids for sustainab ...
, 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".
Brown roofs
Industrial brownfield
In urban planning, brownfield land is any previously developed land that is not currently in use. It may be potentially contaminated, but this is not required for the area to be considered brownfield. The term is also used to describe land prev ...
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, soil, 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. The original idea was to allow the roofs to self-colonise with plants, but they are sometimes seeded to increase their biodiversity potential in the short term. 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 is a French surname. It may refer to:
Places
* Laban-e Olya, a village in Iran
* Laban-e Sofla, a village in Iran
* Laban, Virginia, an unincorporated community in the United States
* 8539 Laban, main-belt asteroid
People
Surname
*Ahm ...
, a centre for contemporary dance in London, has a brown roof specifically designed to encourage the nationally rare black redstart
The black redstart (''Phoenicurus ochruros'') is a small passerine bird in the genus ''Phoenicurus''. Like its relatives, it was formerly classed as a member of the thrush family (Turdidae), but is now known to be an Old World flycatcher (Muscic ...
. A green roof, 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 is an area of London, England, located near the Isle of Dogs in the London Borough of Tower Hamlets. Canary Wharf is defined by the Greater London Authority as being part of London's central business district, alongside Central Lo ...
. Designed combining the principles of green and brown roofs, it is already home to a range of rare invertebrates.
ASLA Award Green Roof Projects
2017 Award: Seeding Green Roofs for Greater Biodiversity and Lower Costs, Lincoln, NE, USA. ''Richard Sutton''
2013 Award: Green Roof Innovation Testing Laboratory, Toronto, Ontario, Canada. ''John H. Daniels'', Brooklyn Botanic Garden Visitors Center, Brooklyn. ''HMWhite'', and NYC Parks Green Roof: A Living Laboratory for Innovative Green Roof Design, New York, NY. ''NYC Parks''
2012 Award: Lafayette Greens: Urban Agriculture, Urban Fabric, Urban Sustainability, Detroit. ''Kenneth Weikal Landscape Architecture'' 200 Fifth Avenue, NYC. ''Landworks Studio, Inc.''
2011 Award: Manassas Park Elementary School Landscape, Manassas Park, VA. Siteworks]
2009 Award: California Academy of Sciences, San Francisco, CA. ''SWA Group'', Changi Airport Terminal 3 Interior Landscape, Singapore. ''Tierra Design (S) Pte Ltd'', Corporate Headquarters, San Francisco, CA. ''OLIN'', Macallen Building, South Boston, MA. ''Landworks Studio, Inc.'', and Museo del Acero Horno3, Monterrey, Mexico. ''Surfacedesign Inc.+ Harari arquitectos''
2008 Award: Gannett/USA Today Headquarters, McLean, Virginia. Michael Vergason Landscape Architects, Ltd.
2007 Award: Washington Mutual Center Roof Garden, Seattle, Washington. Phillips Farevaag Smallenberg
2002 Award: Chicago City Hall Green Roof, Chicago, Illinois. David Yocca
Examples by country
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 (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
Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combin ...
, and Condor Tower (2005) with a lawn on the 4th floor.
In 2010, the largest Australian green roof project was announced. The Victorian Desalination Project will have a "living tapestry" of 98,000 Australian indigenous plants over a roof area spanning more than . 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 was designed by ASPECT Studios, ARM / pecvkvonhartel architecture, and will be installed by Fytogreen Australia.
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.
In June 2014 ecological artist Lloyd Godman, with structural engineer Stuart Jones and environmental scientist Grant Harris collaborated to install an experiment using Tillandsia
''Tillandsia'' is a genus of around 650 species of evergreen, perennial flowering plants in the family Bromeliaceae, native to the forests, mountains and deserts of northern Mexico and south-eastern United States, Mesoamerica and the Caribbean to ...
plants in extreme outdoor conditions at levels 92, 91, 65 and 56 on Eureka Tower
Eureka Tower is a skyscraper located in the Southbank precinct of Melbourne, Victoria, Australia. Construction began in August 2002 and the exterior was completed on 1 June 2006. The plaza was finished in June 2006 and the building was offici ...
in Melbourne, Australia. The selected air plants are extremely light, and are able to grow with no soil or watering system, and the plants have been checked at regular intervals since their installation and are still growing and flowering. One species; Tillandsia bergeri
''Tillandsia bergeri'' is a species of plant in the genus '' Tillandsia''. This species is native to Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America ...
, has grown from a single shoot to several thriving colonies. The project is now titled Tillandsia SWARM and has been expanded to include many other buildings across Australia, including Federation Square, National Gallery of Victoria and Essendon Airport. Godman has also experimented with Tillandsia plant screens that can be moved across skylights to create shade in summer and to allow in sun during winter. Temperature readings taken on a 40°C day in summer revealed that the surface temperature on the roof had reached 84°C, while the shadows cast by the plants had reduced the surface temperature on the roof to 51°C.
Canada
The city of Toronto
Toronto ( ; or ) is the capital city of the Canadian province of Ontario. With a recorded population of 2,794,356 in 2021, it is the most populous city in Canada and the fourth most populous city in North America. The city is the ancho ...
approved a by-law in May 2009 mandating green roofs on residential and industrial buildings. There is criticism from Green Roofs for Healthy Cities that the new laws are not stringent enough, since they will only apply to residential building that are a minimum of six stories high. By 31 January 2011, industrial buildings were required to render 10% or of their roofs green. Toronto City Hall
The Toronto City Hall, or New City Hall, is the seat of the municipal government of Toronto, Ontario, Canada, and one of the city's most distinctive landmarks. Designed by Viljo Revell and engineered by Hannskarl Bandel, the building opened in ...
's Podium roof was renovated to include a rooftop garden, the largest publicly accessible roof in the city. The green roof was opened to the public in June 2010. Many green roofs in Canada also use sustainable Rainwater harvesting
Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir w ...
practices.
In 2008, the Vancouver Convention Centre
The Vancouver Convention Centre (formerly known as the Vancouver Convention & Exhibition Centre, or VCEC) is a convention centre in Vancouver, British Columbia, Canada; it is one of Canada's largest convention centres. With the opening of the ne ...
installed a living roof of indigenous plants and grasses on its West building, making it the largest green roof in Canada.
The new Canadian War Museum
The Canadian War Museum (french: link=no, Musée canadien de la guerre; CWM) is a national museum on the country's military history in Ottawa, Ontario, Canada. The museum serves as both an educational facility on Canadian military history, in a ...
in Ottawa
Ottawa (, ; Canadian French: ) is the capital city of Canada. It is located at the confluence of the Ottawa River and the Rideau River in the southern portion of the province of Ontario. Ottawa borders Gatineau, Quebec, and forms the core ...
, opened in 2005, also features a grass-covered roof.
During the renovation of the Hamilton City Hall
Hamilton City Hall is the chief administration (government), administrative building for the city of Hamilton, Ontario, Hamilton. Located in the downtown core, it is an 8-storey building (34.0 m) at the corner of Main Street (Hamilton, Ontario) ...
in Hamilton, Ontario
Hamilton is a port city in the Canadian province of Ontario. Hamilton has a population of 569,353, and its census metropolitan area, which includes Burlington and Grimsby, has a population of 785,184. The city is approximately southwest of T ...
that spanned from 2007 to 2010, many efforts were taken to enhance the environmentally friendly nature of the structure, which included the addition of a grass-covered roof.
Simon Fraser University
Simon Fraser University (SFU) is a public research university in British Columbia, Canada, with three campuses, all in Greater Vancouver: Burnaby (main campus), Surrey, and Vancouver. The main Burnaby campus on Burnaby Mountain, located from ...
's Burnaby
Burnaby is a city in the Lower Mainland region of British Columbia, Canada. Located in the centre of the Burrard Peninsula, it neighbours the City of Vancouver to the west, the District of North Vancouver across the confluence of the Burrard I ...
campus contains a substantial number of green roofs.
Canada's first LEED Platinum V4 Home in Wakefield QC, EcoHome's Edelweiss House, has a living Green Roof which is sloped at 12 degrees.
Costa Rica
Living green roofs have been built and grown at Saint Michael's Sustainable Community since 2012. Native plants, mostly flowers chosen for the environment, maximum shade and mass provide a colorful and functional living roof. The community has the largest number of green roofs in the country.
Egypt
In Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...
, 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 is a food production system that couples aquaculture (raising aquatic animals such as fish, crayfish, snails or prawns in tanks) with hydroponics (cultivating plants in water) whereby the nutrient-rich aquaculture water is fed to hydro ...
), 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.
Finland
In Finland, green roofs are still scarce. Some experimental green roofs have been built in big cities. However, the capital city of Helsinki has published guidelines for enhancing the building of green roofs in the city. There is on-going research on the topic as the conditions in the southern Europe are very different from those in the north and knowledge acquired there can't be directly applied to colder climates. The fifth dimension
Green roofs and walls in urban areas -research program
aims to produce high-level scientific and broadly applicable knowledge on optimal green roof and -wall solutions in Finland.
France
In France, an extensive, cable-supported green roof has been created on the International School in Lyon. Another huge green roof of roughly 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 () is a commune in the Vendée department in the Pays de la Loire region in western France.
History
The site's origins date from the Gallo-Roman period. According to the etymology, the name Lucus meant "Sacred Wood". This ...
.
Germany
Long-held green roof traditions started in the early industrialization period more than 100 years ago exist in Germany. In the 1970s, green roof technology was elevated to the next level. Serious storm-water issues made cities think about innovative solutions, preferably with living plants. Modern green roof technology with high performance, lightweight materials were used to grow hardy vegetation even on roofs that can hardly support any additional load. In the 1980s modern green roof technology was common knowledge in Germany while it was practically unknown in any other country in the world. In Stuttgart, with one of the most innovative Department of Parks and Recreation and with the world's oldest horticultural Universities, modern green roof technology was perfected and implemented on a large scale.
With the first green roof industry boom in Germany there were quality issues recorded. The FLL formed a committee that is focused on modern green roof technology. FLL stands for Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V. (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 2011.
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 second green roof association after DDV (Deutscher Dachgaertner Verband) in 1985. 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 of new green roofs are being constructed each year. According latest studies about of these are extensive; the last are roof gardens. The cities with the most green roofs in Germany are Berlin and Stuttgart
Stuttgart (; Swabian: ; ) is the capital and largest city of the German state of Baden-Württemberg. It is located on the Neckar river in a fertile valley known as the ''Stuttgarter Kessel'' (Stuttgart Cauldron) and lies an hour from the ...
. Surveys about the status of regulation are done by the FBB. Nearly one third of all German cities have regulations to support green-roof and rain-water technology. Green-roof research institutions are located in several cities as including Hannover
Hanover (; german: Hannover ; nds, Hannober) is the capital and largest city of the German States of Germany, state of Lower Saxony. Its 535,932 (2021) inhabitants make it the List of cities in Germany by population, 13th-largest city in Germa ...
, Berlin, Geisenheim
Geisenheim is a town in the Rheingau-Taunus-Kreis in the ''Regierungsbezirk'' of Darmstadt in Hessen, Germany, and is known as ''Weinstadt'' (“Wine Town”), ''Schulstadt'' (“School Town”), ''Domstadt'' (“Cathedral Town”) and ''Lindenstad ...
and Neubrandenburg
Neubrandenburg (lit. ''New Brandenburg'', ) is a city in the southeast of Mecklenburg-Vorpommern, Germany. It is located on the shore of a lake called Tollensesee and forms the urban centre of the Mecklenburg Lakeland.
The city is famous for its ...
.
Germany is the country with the most green roofs in the world as well as 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.
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'', , 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 . The oikostegi covers , 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
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 ...
s are frequently found on traditional farmhouses and farm buildings in Iceland
Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
.
Switzerland
Switzerland has one of Europe's oldest green roofs, created in 1914 at the Moos lake water-treatment plant, Wollishofen
Wollishofen is a neighbourhood in Zürich's district 2 (Zürich), 2nd district. It was formerly a municipality of its own, having been incorporated into Zürich in 1893. The neighbourhood has a population of 15,592 distributed on an area of 5.75&n ...
, Zürich
Zürich () is the list of cities in Switzerland, largest city in Switzerland and the capital of the canton of Zürich. It is located in north-central Switzerland, at the northwestern tip of Lake Zürich. As of January 2020, the municipality has 43 ...
. Its filter tanks have of flat concrete roofs. To keep the interior cool and prevent bacterial growth in the filtration beds, a drainage layer of gravel and a layer of soil was spread over the roofs, which had been waterproofed with asphalt
Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...
. 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
''Anacamptis morio'', the green-winged orchid or green-veined orchid ( synonym ''Orchis morio''), is a flowering plant of the orchid family, Orchidaceae. It usually has purple flowers, and is found in Europe and the Middle East.
Description
It f ...
). More recent Swiss examples can be found at Klinikum 1 and Klinikum 2, the Cantonal
The 26 cantons of Switzerland (german: Kanton; french: canton ; it, cantone; Sursilvan and Surmiran: ; Vallader and Puter: ; Sutsilvan: ; Rumantsch Grischun: ) are the member states of the Swiss Confederation. The nucleus of the Swiss Con ...
Hospitals of Basel
, french: link=no, Bâlois(e), it, Basilese
, neighboring_municipalities= Allschwil (BL), Hégenheim (FR-68), Binningen (BL), Birsfelden (BL), Bottmingen (BL), Huningue (FR-68), Münchenstein (BL), Muttenz (BL), Reinach (BL), Riehen (BS ...
, and the Sihlpost platform at Zürich's main railway station.
Sweden
What is claimed to be the world's first green roof botanical garden
A botanical garden or botanic gardenThe 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, an ...
was set up in Augustenborg, Malmö
Malmö (, ; da, Malmø ) is the largest city in the Swedish county (län) of Scania (Skåne). It is the third-largest city in Sweden, after Stockholm and Gothenburg, and the sixth-largest city in the Nordic region, with a municipal populat ...
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
Bo01 (also known as the "City of Tomorrow") is a neighborhood in the southern city of Malmö, Sweden known for its sustainable development and design. Bo01 began as part of the European Housing Exposition in 2001 and served as a prototype to help ...
urban residential development (in the Västra Hamnen
Västra hamnen (, "western harbor") is a neighbourhood of Malmö, situated in the borough of Centrum, Malmö Municipality, Skåne County, Sweden. Västra hamnen was an industrial area until the 21st century, when also the last factory closed dow ...
(Western Harbour) close to the foot of the Turning Torso
Turning Torso is a neo-futurist residential skyscraper built in Malmö, Sweden in 2005. It was formerly the tallest building in the Nordic region until September 2022, when it was surpassed by Karlatornet in Gothenburg, which is still under const ...
office and apartment block, designed by Santiago Calatrava
Santiago Calatrava Valls (born 28 July 1951) is a Spanish architect, structural engineer, sculptor and painter, particularly known for his bridges supported by single leaning pylons, and his railway stations, stadiums, and museums, whose sculpt ...
) is built on the site of old shipyards and industrial areas, and incorporates many green roofs.
In 2012, the shopping mall Emporia with its roof garden, was opened. The size of the roof garden is approximately equivalent to 4 soccer fields, which makes it one of the biggest green roof parks in Europe that is accessible to the public.
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. The Kensington Roof Gardens
Kensington Roof Gardens (formerly known as Derry and Toms Roof Gardens and later The Roof Gardens) is a private roof garden covering on top of the former Derry & Toms building on Kensington High Street in central London.
Originally opened in ...
are a notable early roof garden which was built above the former Derry & Toms
Derry & Toms was a London department store that was founded in 1860 in Kensington High Street and was famous for its Roof Garden which opened in 1938. In 1973 the store was closed and became home to Big Biba, which closed in 1975. The site wa ...
department store in Kensington
Kensington is a district in the Royal Borough of Kensington and Chelsea in the West End of London, West of Central London.
The district's commercial heart is Kensington High Street, running on an east–west axis. The north-east is taken up b ...
, London in 1938. More recent examples can be found at the University of Nottingham
The University of Nottingham is a public university, public research university in Nottingham, United Kingdom. It was founded as University College Nottingham in 1881, and was granted a royal charter in 1948. The University of Nottingham belongs t ...
Jubilee Campus
The University of Nottingham operates from four campuses in Nottinghamshire and from two overseas campuses, one in Ningbo, China and the other in Semenyih, Malaysia. The Ningbo campus was officially opened on 23 February 2005 by the then British ...
, and in London at Sainsbury's Millennium Store in Greenwich, the Horniman Museum
The Horniman Museum and Gardens is a museum in Forest Hill, London, England. Commissioned in 1898, it opened in 1901 and was designed by Charles Harrison Townsend in the Modern Style. It has displays of anthropology, natural history and musical ...
and at Canary Wharf
Canary Wharf is an area of London, England, located near the Isle of Dogs in the London Borough of Tower Hamlets. Canary Wharf is defined by the Greater London Authority as being part of London's central business district, alongside Central Lo ...
. The Ethelred Estate, close to the River Thames
The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the second-longest in the United Kingdom, after the R ...
in central London, is the British capital's largest roof-greening project to date. Toxteth
Toxteth is an inner-city area of Liverpool in the historic county of Lancashire and the ceremonial county of Merseyside.
Toxteth is located to the south of Liverpool city centre, bordered by Aigburth, Canning, Dingle, and Edge Hill.
The area w ...
in Liverpool is also a candidate for a major roof-greening project.
In the United Kingdom, 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 Limited is a British luxury automobile maker which has operated as a wholly owned subsidiary of BMW AG since 2003 – as the exclusive manufacturer of ''Rolls-Royce''-branded motor cars. The company's administrative ...
, who has one of the biggest green roofs in Europe (covering more than 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).
Fort Dunlop
Fort Dunlop (), is the common name of the original tyre factory and main office of Dunlop Rubber in the Erdington district of Birmingham, England. It was established in 1917, and by 1954 the entire factory area employed 10,000 workers. At one tim ...
has the largest green roof in the UK since its redevelopment between 2004 and 2006.
The UK also has one of the most innovative food preparation facilities in Europe, the Kanes salad factory in Evesham
Evesham () is a market town and parish in the Wychavon district of Worcestershire, in the West Midlands region of England. It is located roughly equidistant between Worcester, Cheltenham and Stratford-upon-Avon. It lies within the Vale of Evesha ...
. It is topped with a wildflower roof featuring nearly 90 species of wildflower and natural grasses. The seed mix was prepared in consultation with leading ecologists to try to minimise the impact on the local environment. The pre-grown wildflower blanket sits on top of a standing seam roof and is combined with solar panels to create an eco-friendly finish to the entire factory. The development also won the 2013 National Federation of Roofing Contractors Sustainable Roof Award for Green Roofing.
United States
One of the largest expanses of extensive green roof is to be found in the US, at Ford Motor Company
Ford Motor Company (commonly known as Ford) is an American multinational automobile manufacturer headquartered in Dearborn, Michigan, United States. It was founded by Henry Ford and incorporated on June 16, 1903. The company sells automobi ...
's River Rouge Plant, Dearborn, Michigan, where of assembly plant roofs are covered with sedum
''Sedum'' is a large genus of flowering plants in the family Crassulaceae, members of which are commonly known as stonecrops. The genus has been described as containing up to 600 species, subsequently reduced to 400–500. They are leaf succulen ...
and other plants, designed by William McDonough
William Andrews McDonough is an American architect, designer, and author. McDonough is founding principal of William McDonough + Partners, co-founder of McDonough MBDC, and co-author of ''Cradle to Cradle: Remaking the Way We Make Things'' a ...
; the $18 million assembly avoids the need of what otherwise would be $50 million worth of mechanical treatment facilities on site. Built over Millennium Park Garage, Chicago's Millennium Park
Millennium Park is a public park located in the Loop community area of Chicago, operated by the Chicago Department of Cultural Affairs. The park, opened in 2004 and intended to celebrate the third millennium, is a prominent civic center near ...
is considered one of the largest intensive green roofs. Other well-known American examples include Chicago's City Hall and the former Gap headquarters, now the headquarters of YouTube, in San Bruno, CA. The U.S. military has two major green roofs in the Washington, D.C. area
The Washington metropolitan area, also commonly referred to as the National Capital Region, is the metropolitan area centered on Washington, D.C. The metropolitan area includes all of Washington, D.C. and parts of the U.S. state, states of Maryl ...
: the U.S. Coast Guard
The United States Coast Guard (USCG) is the maritime security, search and rescue, and law enforcement service branch of the United States Armed Forces and one of the country's eight uniformed services. The service is a maritime, military, mul ...
headquarters () and the Pentagon
The Pentagon is the headquarters building of the United States Department of Defense. It was constructed on an accelerated schedule during World War II. As a symbol of the U.S. military, the phrase ''The Pentagon'' is often used as a metony ...
().
An early green-roofed building (completed in 1971) is the 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 largest green roof in New York City was installed in midtown Manhattan
Manhattan (), known regionally as the City, is the most densely populated and geographically smallest of the five boroughs of New York City. The borough is also coextensive with New York County, one of the original counties of the U.S. state ...
atop the United States Postal Service
The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or Postal Service, is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the U ...
's Morgan Processing and Distribution Center. Construction on the 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.
In 2001, atop Chicago City Hall
Chicago City Hall is a 10-story building that houses the official seat of government of the City of Chicago in Illinois. Adjacent to the Richard J. Daley Center and the James R. Thompson Center, the building that includes Chicago City Hall ho ...
, the roof gardens were completed, serving as a pilot project to assess the impact green roofs would have on the heat island
An urban heat island (UHI) is an urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent w ...
effect in urban areas, rainwater runoff, and the effectiveness of differing types of green roofs and plant species for Chicago's climate. Although the rooftop is not normally accessible to the public, it is visually accessible from 33 taller buildings in the area. The garden consists of 20,000 plants of more than 150 species, including shrubs, vines and two trees. The green roof design team was headed by the Chicago area firm Conservation Design Forum in conjunction with noted "green" architect William McDonough
William Andrews McDonough is an American architect, designer, and author. McDonough is founding principal of William McDonough + Partners, co-founder of McDonough MBDC, and co-author of ''Cradle to Cradle: Remaking the Way We Make Things'' a ...
. With an abundance of flowering plants on the rooftop, beekeepers harvest approximately of honey each year from hives installed on the rooftop. Tours of the green roof are by special arrangement only. Chicago City Hall Green Roof won merit design award of the American Society of Landscape Architecture (ASLA) competition in 2002.
The of outdoor space on the seventh floor of Zeckendorf Towers
The Zeckendorf Towers, sometimes also called One Irving Place and One Union Square East, is a , 29-story, four-towered condominium complex on the eastern side of Union Square, Manhattan, in New York City. Completed in 1987, the building is loca ...
, formerly an undistinguished rooftop filled with potted plants, make up the largest residential green roof in New York. The roof was transformed in 2010 as part of Mayor Michael Bloomberg
Michael Rubens Bloomberg (born February 14, 1942) is an American businessman, politician, philanthropist, and author. He is the majority owner, co-founder and CEO of Bloomberg L.P. He was Mayor of New York City from 2002 to 2013, and was a ca ...
's NYC Green Infrastructure campaign, and supposedly serves to capture some of the rain that falls on it rather than letting it run off and contribute to flooding in the adjacent Union Square subway station.[One Union Square East Opens City's Largest Residential Green Roof](_blank)
Zeckendorf Towers press release of 15 November 2010.
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 6 seconds/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 5 gN/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.
One of the oldest American green roofs in existence is atop the Rockefeller Center in Manhattan, built in 1936. This roof was primarily an aesthetic undertaking for the enjoyment of the center's workers, and remains to this day, having been refurbished in 1986.
With the passage of Denver's Green Roof Initiative in the November 2017 elections, effective January 2018, new buildings or existing buildings meeting the initiative's thresholds are required to have rooftop gardens, optionally combined with solar photovoltaic panels.
Seattle
Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...
is another city in which green roofs have been used on an increasing basis. This phenomenon is in large part due to efforts on behalf of the city to encourage green roofs through new and improved building code
A building code (also building control or building regulations) is a set of rules that specify the standards for constructed objects such as buildings and non-building structures. Buildings must conform to the code to obtain planning permission ...
s. In 2006, the Seattle Green Factor program was approved. The program rewards the incorporation of landscaping in new building developments in an attempt to reduce stormwater
Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed la ...
runoff and associated pollution, stabilize temperatures, and create habitats for birds and insects. These changes were expanded in 2009 to recognize the specific stormwater benefits of green roofs, and to reward developers who used them accordingly.
By 2010, Seattle was home to approximately of green roofs. Despite initial hiccups in the city stemming from weeds, lack of irrigation during dry summer months, and a need for continuous replanting, the project has continued to succeed as understanding around the best soils and plants and the need for monitoring and upkeep has increased. A 2010 survey of the green roofs in Seattle acknowledged that while the initial costs of implementing a green roof may deter businesses or homeowners, it is likely that green roofs actually preserve the roofing material and cut costs in the long run. In light of the success in Seattle, other cities such as Portland, Chicago, and Washington, D.C. have all made efforts to develop their own Green Factor programs.
The Seattle City Hall has led the way by implementing a green roof project that has involved the planting of more than 22,000 pots of sedum, fescue, and grass. The City hopes that the project can reduce the annual stormwater runoff
Runoff, run-off or RUNOFF may refer to:
* RUNOFF, the first computer text-formatting program
* Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed
* Runoff or run-off, a stock market ...
for the building by 50 to 75 percent, which will in turn reduce damage to local watershed areas that provide habitats for native species such as salmon. The historic Union Stables building has used green roofs alongside other efficiency
Efficiency is the often measurable ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without ...
based changes to reduce stormwater runoff and decrease the building's energy use by 70 percent. The Park Place building in Seattle's downtown provides a leading example of the use of landscaping to recapture rain water with the hopes of cutting back spending on utilities.
Washington D.C.
Washington D.C. started implementing incentives for green roofs within their city at the beginning of the 21st Century. In 2003, the Chesapeake Bay Foundation introduced a “green roof demonstration project” in combination with the D.C. Water and Sewer Authority. This program issued grants to several pilot green roofs, which would assist with the cost of construction for the building owner. From this project the city began to understand how beneficial these roofs could be and more programs were implemented over the years. In 2007, the Riversmart Rewards Program introduced a RiverSmart Rooftops Green Roof Rebate Program that would lend a $3 per square foot subsidy to potential green roof projects within the District. This culminated to assist 12 projects that year. A year later, the subsidy was raised to $5, incentivizing even more developers to use this program within their design. There is also possibility through the RiverSmart Rewards program for “residents and property owners to receive a significant discount on their water utility fees” if they install approved stormwater management features. In 2016, a rebate of $10-$15 per square feet was introduced, “promoting the voluntary installation of green roofs for the purpose of reducing stormwater runoff and pollutants”. $10 per square foot rebates were set for installation within a combined sewer system. $15 per square foot rebates were set for installation within a municipal storm sewer system. The greatest aspect of this incentivized project is the lack of restriction of building type that qualifies. There is no size cap on properties that qualify whether it’s residential, commercial or institutional. In 2016 there was a total of 2.3 million square feet of green roofing within the district. As of 2020, there is 5.1 million square feet of green roofing.
See also
*Arcology
Arcology, a portmanteau of "architecture" and "ecology",. is a field of creating architectural design principles for very densely populated and ecologically low-impact human habitats.
The term was coined in 1969 by architect Paolo Soleri, who be ...
*Blue roof
A blue roof is a roof of a building that is designed explicitly to provide initial temporary water storage and then gradual release of stored water, typically rainfall. Blue roofs are constructed on flat or low sloped roofs in urban communities wh ...
*Ecovillage
An ecovillage is a traditional or intentional community with the goal of becoming more socially, culturally, economically, and/or ecologically sustainable. An ecovillage strives to produce the least possible negative impact on the natural envi ...
*Energy-efficient landscaping
Energy-efficient landscaping is a type of landscaping designed for the purpose of conserving energy. There is a distinction between the embedded energy of materials and constructing the landscape, and the energy consumed by the maintenance and ope ...
*Hanging Gardens of Babylon
The Hanging Gardens of Babylon were one of the Seven Wonders of the Ancient World listed by Hellenic culture. They were described as a remarkable feat of engineering with an ascending series of tiered gardens containing a wide variety of tre ...
* Low-impact development
*Rainwater harvesting
Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir w ...
* Ralph Hancock, designer, The Rockefeller Center Roof Gardens
*Roof garden
A roof garden is a 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, recreational oppo ...
*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 ...
, traditional roof in Scandinavia
*Sustainable city
The sustainable city, eco-city, or green city is a city designed with consideration for social, economic, environmental impact (commonly referred to as the triple bottom line), and resilient habitat for existing populations, without compromisi ...
* Subtropical climate vegetated roof
References
Further reading
*
*Snodgrass, E. and McIntyre, L., ''The Green Roof Manual: A Professional Guide to Design, Installation, and Maintenance'' Publisher: Timber Press (2010).
*Dunnett, N. and Kingsbury, N., ''Planting Green Roofs and Living Walls'' Publisher: Timber Press (updated 2008).
*Miller-Klein, Jan. ''Gardening for Butterflies, Bees and other beneficial insects'' has large section on green and brown roofs and brownfields, including how to make your own, with contributions from several UK practitioners.
*
*Hilary, David. ''Creating My Green Roof: A guide to planning, installing, and maintaining a beautiful, energy-saving green roof.'" (2015).
*Roland Appl, Reimer Meier, Wolfgang Ansel: ''Green Roofs – Bringing Nature Back to Town''. (Proceedings) Publisher: International Green Roof Association IGRA, (2009)
*Diversity of Fauna on Green Roofs
Diversity of fauna
External links
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{{Authority control
Roof gardens
Roofs
Sustainable architecture
Sustainable gardening
Sustainable building
Garden features
Types of garden
Landscape architecture
Urban agriculture
Hydrology and urban planning
Environmental engineering
Roofing materials
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