The Potential of Green Roof Habitats in Ireland All Ireland Architectural Research Group 2015 Conference
Noel Hughes
Existing Green Roof Case Studies + Data
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A wealth of research data exists that supports the perception that green roofs in heavily built up areas can support a relatively diverse level of flora and fauna species (Köhler, 2006). The purpose of this document is to present examples of completed green roofs, which demonstrates the scope of habitat that have been created on green roofs. It will illustrate the value a successful green roof can have on the surrounding ecology. Image 1 - Chicago City Hall
The aim of this document is to examine the list of Ireland habitats which can exist at roof level. The specific construction details, cost, structural makeup and ecological impact of green roofing systems shall be explained. Furthermore, the effectiveness of each green roof in emulating its equivalent natural environments shall be discussed.
The table below show the range of natural habitats in Ireland that have the potential to be replicated on green roofs.
Ireland's Habitats which can be readily adapted to Green Roofs Coastal Habitats Grassland Habitats Sand Dunes Lowland Dry Acid Grassland Vegetated Shingles Banks Calcareous Grassland Cliffs and Slopes Lowland Meadow Purple Moor & Rush Pasture Wetland Habitats Limestone Pavement Reed Beds Heathland Habitats Floodplain Grazing Marsh Lowland Heaths Upland Heaths Mountainous Heaths Ireland's Habitats that can be created on Green Roofs with additional Considerations Marine Habitats Peatland Habitats Saline Lagoon Lowland Raised Bog Blanket Bog Woodland Habitats Fens Wet Woodlands Mixed Ashwood Oakwood Table 1 - Habitats Capable of Existing on Green Roofs
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01 Sand Dunes / Shingles Banks Habitat Case Studies Flat gravel roofs are a common roofing system within many urban centres. The material makeup of such roof currently possess some similarities with many coastal environments. The free-draining sandy and gravel covering presents environmental conditions, such as periods of drought and heavy wind exposure (Grant, 2006), which are common to sand dunes and shingles banks (CVNI, 2011).
Sand Dunes
Image 2 - Murlough Dunes, Dundrum Bay
Vegetated Shingles
The stress tolerance vegetation associated with coastal locations is ideal for rooftop occupation (Dunnett & Kingsbury, 2008). The lack of complex soil layer in sand and shingle beach heads (National Museums Northern Ireland, 2010) also means that it is possible to construct artificial soil which have the capability of mimicking organic beach material (Hitchmough, 1994). This presents opportunities to reduce the need for the removal of natural sand or gravel soils in habitat recreation projects. Recent field research into how plant species spontaneously colonized urban areas and habitats (such as pavements, walls, roofs, lawns and roofs) originate disproportionately from coastal and rocky habitats (Lundholm & Marlin, 2006).
Image 3- Kearney, Down
Precedence
Image 4 - National Trust Visitor Centre, Portstewart Strand
An important example of a green roof working to support coastal dunes and beach heads is the National Trust Visitor Centre at Portstewart Strand. A building designed by Donnelly O’Neill Architects is located next to a two mile stretch of protected beach and sand dunes. The green roof is a 400m2 extensive sedum roof, which is expected to be colonised by local dune grass in the future (GreenRoof, 2010).This project is one of the few attempts of habitat recreation at roof level in Ireland. Further information Portstewart Strand's National Trust Visitor Centre can be found from the National Trust, green roofs.com or from Donnelly O’Neill Architects.
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Sechelt Justice Services Centre
The Sechelt Justice Services Centre is located adjacent to the Pacific Ocean in British Columbia and is an example of a low-impact, site-specific roof design. The roof was developed to replace the coastal dune meadow that was consumed during the building process. The roof mimics the local soil conditions and optimise the exposure to sunlight and prevailing winds. The roof is populated by native costal grass species and selected non-native plants such as sedum, mosses and herbs (Earth Pledge, 2005).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium
Soil Depth Cost Weight
Sechelt, Canada 2003 District of Sechelt Johnston Davidson Sharp & Diamond New Extensive 465m2 40% 60% Black Pumice and 40% Soil Amendment 75mm €58/m2 £46/m2 73.2kg/m2
Significance to Ireland's Habitat Green Roofs The construction method utilised by the Sechelt Justice Services Centre shows promise for the recreation of sand dunes / shingles banks habitats here in Ireland. The roofing systems use a lightweight structure that is within the structural tolerances of the majority of Irelands buildings (Adler, 1999). An artificial soil substrate supports coastal grasses, using pumice rock and plant nutrient supplements. A mixture of native grasses and alien mosses and herbs are planted on the rooftop. The mixture of native/non-native species on Ireland rooftops will have to be done in conjunction with the appropriate local and national biodiversity plan.
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University Hospital of Basel
While every building in Basel hospital complex has a green roof, only the roof of Clinic One was specially designed as a test site for urban bird habitat creation. The roof is covered with sandy loam and gravel from the nearby riverbank, shaped into small hills and perches that are the preferred train of insect-hunting birds (Earth Pledge, 2005). Studies have proposed that in dense urban areas where vegetation and food is scarce; migratory birds select rooftops which resemble their natural feeding and nesting habitats (Brenneisen S. , 2006).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium
Soil Depth Cost
Basal, Switzerland 1999 University Hospital of Basel n/a Stephan Brenneisen New Extensive 1,860m2 60% 60% sand and gravel; 40% topsoil with stones and humus 90mm €12/m2 £10/m2 146.5kg/m2
The green roof has become frequented by an Weight unexpected range of bird species. Black Redstarts, Wagtails, Rock Doves and House Sparrows (typically a rural mountainous species) dominate the roofscape. The common urban bird species are rarely observed on the roof. A number of native grasses were planted during the construction of the roof. However the majority of vegetation has grown from seeds deposited by birds (Earth Pledge, 2005).
Significance to Ireland's Habitat Green Roofs The Clinic One building illustrates the following points for habitat recreation There exists a readiness by both flora and fauna species to habitat gravel roofs, when the roof provides resources similar to their natural habitats. The University Hospital of Basel represents a successful recreated habitat, which required a low financial investment. The ability of plant species to colonise green roofs through seed dispersal by birds, highlights the natural transition of rooftops vegetation in response to the residing fauna species. This makes the Clinic One building an example of an artificial habitat roof reaching a level of symbiosis with local wildlife.
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Laban Dance Centre
The brown roof on the Laban Dance Centre was constructed using debris found onsite during the construction process. Brick and Concrete were crushed and stacked unevenly across the roof to simulate a waterfront gravel/shingle bank supported by local dry grassland vegetation, which was once common to the Thames (Earth Pledge, 2005). The building won the RIBA 'Building of the Year' award, and Herzog & de Meuron won the Stirling Prize for the Laban Dance Centre building in 2003 (GreenRoof, 2010).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
London, England 2002 Laban Dance Centre Herzog & de Meuron Vogt Landscape Architects New Intensive Rubble Roof 400m2 33% Rubble 120-150mm €28/m2 £22/m2 Not available
The rooftop at the Laban Dance Centre has been designed to support the endangered Black Redstart bird species, one of the most endangered birds in the UK (Earth Pledge, 2005). The success of the roof in providing a nesting ground for the Black Redstart has encouraged the adoption of ecological green roofs by neighbouring buildings (Frith & Gedge, 2000).
Significance to Ireland Habitat Green Roofs The Laban Dance Centre illustrates the following points for habitat recreation The Laban Dance Centre is another example of a successful habitat roof project. The nesting of the Black Redstart and use of the building as a part of their feeding area. Demonstrating that green roofs can play an important role in aiding in conservation methods. A use of recycled construction material (crushed brick and concrete) within the artificial soil substrate showcases a more sustainable approach to green roof planting. Crushed building material used as a aggregate layer of green roofs is not widely utilised within the Irish or UK construction sector (Graceson, Hare, Hall, & Monaghan, 2011).
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02 Cliffs and Slopes Habitat Case Studies An estimated 22% of Ireland's coastline consists of cliff and steep slope habitats and is primarily distributed along the southern, western and north-western seaboards (Cooper, McCann, & Rogers, 2009). A diverse array of flora and fauna species inhabit these environments, dominating areas of high exposure and limited soil (CVNI, 2011). Cliffs and Slopes
Image 5 - Carrick-a-Rede Cliffs, Antrim
The widespread presence of hard-surfaced environments within built-up areas and their colonisation by species adapted to rocky habitats has lead to the emergence of the ‘Urban Cliff Hypothesis’. This planning ecology concept states that development of urban areas is more complex than a simply destruction of natural habitat. Rather original habitats are replacement by artificial habitats that function, both structurally and biologically, like rocky outcrop and cliff tops (Larson, Matthes, Kelly, Lundholm, & Gerrath, 2004).
The combination of resilient plant species and a natural affiliation between cliff habitats and urban structure results in a wide number of both flora and fauna species that can readily be applied to many rooftops (Dunnett & Kingsbury, 2008; Lundholm & Marlin, 2006).
Image 6 - Gallie Craig Coffee Shop, Drummore, Scotland
An example of an interesting combination of cliff habitats and green roof environments is the Gallie Craig Coffee Shop at Drummore, Stranraer, in Scotland. The tourist building was designed by IB MacFadzean Architects whose green roof is integrated into the cliff face. A turf roof allows the building to blend into the contours of the land, reducing any detrimental visual effect on the landscape (GreenRoof, 2010). While this is a very direct representation of the combination of cliff and rooftop habitats. The examples does showcase that a direct comparison between the two habitats on ecological terms can be made.
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ACROS Fukuoka
The Asian Crossroads over the Sea (ACROS) building is a public/private development in the centre of Fukuoka city, adjacent to the Tenjin Central Park. The aim of the design was to create public space equal to the land lost due to the buildings footprint. 15 vegetated terraces dominated the structures south façade, with access to the building’s interior at each floor. The majority of the planting species are indigenous to Japan, mostly hardy grasses and perennial flowers, with some non-native annuals and perennials used for their aesthetics (Earth Pledge, 2005).
Location Completion Date Client Architect Landscape Architect
New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
Fukuoka, Japan 1995 Dal-lchi Mutual Life Mitsui Real Estate Emilio Ambasz Nihon Sekkei Takenaka Corporation New Intensive 930m2 80% Rubble 300-600mm Not available Not available
Significance to Ireland's Habitat Green Roofs The construction method implemented by the ACROS Building presents the following points for habitat recreation. A high percentage of the land consumed by the buildings footprint has been replaced by rooftop vegetation, however this was a design requirement as the structure is located in a dense urban area with few open spaces or public greenery (GreenRoof, 2010). The design of the ACROS Building showcases its rooftop vegetation as a prominent part of its primary façade. The soils substrate layer of the ACROS Building uses a rubble soil system similar to the Laban Dance Centre; however this report was unable to find out if any recycled material was used in the construction process.
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03 Wetland Habitat Case Studies A growing market for organic water filtration systems (reed beds and willow) has encouraged the emergence of wetland habitats on many rooftops (Oberndorfer, et al., 2007). There is over an estimated 5,000 constructed wetlands in Germany, used primarily to treat residential and municipal wastewater in areas where a connection to the central sewage treatment system is too costly. The adoption of wetland rooftops has followed suit (Earth Pledge, 2005).
Reed Beds
Image 7 - Castle Espie, Down
Floodplain Marsh
Wetland plants clean and filter water naturally. Microorganisms in the root systems and in wetland soil absorb and breakdown contaminants, metabolising them into nutrients (Earth Pledge, 2005). Additionally the minimal soil requirements and the ability to recycle nutrients in water runoff, results in the ability of flora and fauna that requires a permanent waterlogged environment. Green roofs designed with an appropriate drainage layers and irrigation systems can accommodate these species (Coffman & Davis, 2005). The ability of rooftops to contain large bodies of water is limited. Partly due to the additional need for waterproofing any underling structure, but also the weight a substantial volume of water imposes.
Image 8 - Insh Marshes, Scotland
Precedence The largest example of a body of water within an artificial roof wetland habitat recreation is the 120m2 miniature lake around a penthouse suite of the BMW D端sseldorf Office Building. The rooftop habitat created by leading green roof manufacture ZinCo GmbH, is an intensive roof garden and large pond located 20 metres above ground on the roof of the BMW office building in D端sseldorf (GreenRoof, 2010). While the ability of static bodies of water to exist at roof level is limited (Dunnett & Kingsbury, 2008). The capacity to provide a habitable environment for wetland grasses and reed species is a more applicable and mature roofing approach (Coffman & Davis, 2005).
Image 9 - BMW D端sseldorf Office Building
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KPMG Building
During a programme of building renovations, a wetland environment was created on the roof of the parking complex in KPMG Dusseldorf. The wetland was a renovation of a previous ornamental pool which would regularly become choked with algae due to the high phosphate level of the tap water used to feed the habitat.
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium
Dusseldorf, Germany 2003 KPMG Eckhard Gardenier Ulrich Zens New Intensive 4,100m2 67% topsoil for grasses; lava mixed with zeolite for wetlands 300- 400mm €840/m2 £660/m2 Not available
The wetland uses a mixture of plant species that are current marketed with organic rainwater filtration systems and expanded into a larger Soil Depth natural system. The roof contains a well, grass Cost landscaped area, an artificial swamp plus stream Weight and the original pond. The well collects rainwater which is pumped to an irrigation system for the landscaped area and the stream which feeds the swamp which drain into the pond. The water bodies are lined with volcanic rocks, which further filter the water and anchor reed species. The roof supports a complex array of insect and bird species. In addition to this, the roofing treatment has saved the building occupiers money through reduction in storm water fees and heat/cool costs (Earth Pledge, 2005).
Significance to Ireland's Habitat Green Roofs The KPMG building illustrates the following points for habitat recreation A mosque of habitat condition has been created on the KPMG roof, which has been proven that a mix of habitats types on a single roof increases overall biodiversity (Brenneisen S. , 2006). The water pumping system used by the KPMG buildings is complex and will have an impact of the maintenance and operation cost of the roof. The construction costs and structural weight of the wetland roof is considerable when compared to other grassland habitat roofs.
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Possmann Cider Company
During a series of schemes to modernise its factory, the Possmann Cider Company required an alternative system to cool its fermentation tanks because of Germany’s high water charges. In 1993, the company installed a similar wetland green wetland roof as the system use at KPMG, creating a closed loop cooling system. Rainwater collected by the wetland is directed to the fermentation tanks and circulated back to the roof. Plants thrive in the warmer water and the dense shaded root systems quickly cool the water.
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
Frankfurt, Germany 1993 Possmann Company Siegfried Ziepke Not available Retrofit Intensive 3,000m2 100% None - hydroponic n/a Not available Not available
The wetland has become populated by local bird species and a 1999 study showed that 20 new plant species had established themselves on the roof (Earth Pledge, 2005).
Significance to Ireland's Habitat Green Roofs The Possmann Cider Company illustrates the following points for habitat recreation The company states that the wetland roof treatment has an annual saving of €5,000/£3,9001 in the buildings cooling cost (Earth Pledge, 2005). Illustrating that wetland green roof are a possible means of sustainable building cooling. This roof type combines sustainable technologies, namely a grey water rainwater storage system to reduce the need for mains water to feed the roof environment. The adaption of hydroponic plant feeding methods has completely removed the need for an artificial soil substrate. The Possmann Cider Company is an example of a habitat roof naturally colonised by a local bird species.
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Figure converted from stated value ($6,000)
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John Deere Works
The manufacturing and assembly process at the John Deere factory in Mannheim, Germany produces an extensive volume of wastewater due to its metal cutting systems. Previously all wastewater in the factor was sent to a treatment plant and discharged to the municipal sewer system at a significant fee. The company did not have the require ground level land to support a natural treatment system, so rooftop system were explored. The roofing technique employed does not utilise a soil base substrate in order to limit the weight on the pre-existing structure.
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
Mannheim, Germany 2003 John Deere John Deere John Deere Retrofit Intensive 42m2 65% None - hydroponic 50mm €480/m2 £330/m2 341.8kg/m2
The plant life receives nutrient from a 50mm deep hydroponic system. The designers of the roof system have found that a combination of Sedges, Rushes and Irises species are the most effective in the breakdown of carbon and nitrogen compounds in discharge water and can accumulate and remove suspended phosphates and heavy metals particles through their root systems (Earth Pledge, 2005). Green roofs can remove over 95% of cadmium, copper and lead in retained water they also remove 16% of zinc and dramatic reduce the level of water soluble Nitrogen (Schmidt, 1990).
Significance to Ireland's Habitat Green Roofs The John Deere factory illustrates the following points for habitat recreation Again the John Deere factory uses a hydroponic plant feeding system A wetland habitat roof system was used in the John Deere factory to reduce the water discharge of the metal works, unlike the Possmann Cider Company which was driven by the reduction of cooling costs. Both the wetland roofs systems of the Possmann Cider Company and John Deere factory were designed as energy saving habitats, dedicated purely to their relationship with their connected buildings. This may present conflicting design drives; between building sustainability and habitat recreation.
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04 Woodland Habitat Case Studies While it is unexpected to have woodland habitats at roof level many examples exist (Peck & Kuhn, 2000). Trees and large bushes are exclusive to intensive green roofs and have the highest visual impact of any planting. However a number of factors need to be considered when creating woodland habitats Native Woodlands
Wet Woodlands
The weight of any planted tree must be calculated, as they induce a considerable concentrated load which can greatly increase during high winds due to the addition of tipping momentum under wind Image 11 - Bonds Glen, Derry Image 10 - Belvoir Park Forest, Belfast pressure (Francis & Lorimer, Mixed Ashwood Oakwood 2011). Trees with smaller leaves and a relatively small crown offer the best wind resistance, and the minimum soil depth for small trees is approximately 500mm. To counteract the debilitating factors of high winds and shallow Image 12 - Glenarm Woodlands, Antrim Image 13 - Breen Oakwood, Antrim soils it is necessary to anchor the root ball to the roof structure below (Dunnett & Kingsbury, 2008). Irrigation systems are also crucial for the survival of tree on green roofs because of reduced root systems. Trees need a continuous flow of water to meet there nutrient and water requirements (White & Snodgrass, 2003). Additionally tree dominated rooftops are heavily affected by restricted size, due to a combination of the volume of single plants and the typical area of many roofs (Brenneisen & H채nggi, 2006).
Despite these restriction successful woodland habitats can exist within a green roof environment, all be it in a heavily managed format (Earth Pledge, 2005). An extreme example of the combination of a tree rooftop is the Hundertwasserhaus, an apartment block in Vienna, Austria by the artist Friedensreich Hundertwasser. The building possesses an earth covered roof supporting numerous grasses and large trees, many of which have sprouted from inside rooms with their trunks protruding through the roof structure and having limbs extending from windows. The structure supports a total of 250 trees and bushes (Earth Pledge, 2005). While the majority of structures accommodating tree habitat do not go to such planting extremes as the Hundertwasserhaus, tree require care consideration before planting. Image 14 - Hundertwasserhaus, Vienna
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The Patterson Garden
The rooftop garden of Glen Patterson at third floor level in the Escala Tower in the Vancouver harbour district was designed to resemble a costal wet forest. The roof supports a number of transplanted mature trees, mostly Black and White Pines, Maple, Cypress and evergreen Oak species (in addition a Gnarled Japanese Maple aged at over a 100years), an artificial pond and stream and a number of species of dwarf rhododendrons and mountain hemlocks as groundcover planting.
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium
Soil Depth
Vancouver, Canada 2003 Glen Patterson K.M. Cheng Architects Nakano Landscape Design New Intensive 185m2 100% black pumice pebbles; graded sand; coconut fibres; zeolite 300mm (600mm for tree roots) Not available Roof strengthened to load-bearing of 1220kg/m2
Two years before the completion of the building. Trees to be relocated to the roof were Cost excavated and their roots cut back to 3-foot Weight diameter planting balls. To allow the plants time to adapted to the compact environments of the roof. Additionally shortly before being replanted at roof level the root balls were bound tightly with plastic strapping, using bonsai techniques, to restrain root growth (GreenRoof, 2010).
Significance to Ireland's Habitat Green Roofs The Patterson Garden illustrates the following points for habitat recreation A 600mm substrate (a substantial soil depth for a roofing system) is needed to support tree species that have undergone induced stunted grown and dwarfism to adapt to roof conditions. Special consideration was given during the roof’s construction to accommodate the additional weight imposed by the planted trees (Earth Pledge, 2005). The roof has a purpose built automatic irrigation system to supply the water needs of the garden (Earth Pledge, 2005). The rooftop was design as an ornamental garden not a natural habitat recreation with all trees species cloud pruned to a 900mm (Earth Pledge, 2005).
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Roppongi Hills
Roppongi Hills in the centre of Tokyo was conceived as an experimental urban development. In combination with a number of other schemes, the developments green spaces was envisaged as a way to revitalize the residences of downtown Tokyo. Who were categorised as have high levels of depressed. Presently Roppongi Hills represents 26% of greens space in central Tokyo. The scheme contains a number of green rooftops, with the Keyakizaha building supporting a rice paddy with a parameter tree line (GreenRoof, 2010).
Location Completion Date Client
Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium
Soil Depth Cost Weight
Tokyo, Japan 2003 Roppongi 6 Chrome Redevelopment Association Cionran & Partners Yohji Saski & Dan Pearson New Extensive & Intensive 13,285m2 26% Soil; Artificial aggregates; Sedum mats 30-1200mm Not available 97.6kg/m2
Significance to Ireland's Habitat Green Roofs The Roppongi Hills illustrates the following points for habitat recreation A requirement for additional structural props was needed to be installed in order to stabilise the planted tree species (Earth Pledge, 2005). Rainwater storage in combination with a drib irrigation system was developed to provide water and nutrients for the roof habitat (Earth Pledge, 2005). Again the Roppongi Hills was designed as an ornamental garden rather than a natural habitat. The majority of the Roppongi Hills is a combination of traditional Japanese and Japanese-British style gardens (Earth Pledge, 2005).
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05 Grassland Habitat Case Studies Grasses are common on many green roofs. Many roof designers state that mimicking natural meadows is their primary goal (Budge, 2009). The shallow roots systems and the pressures imposed by grazing have created a diverse range of stress-tolerant vegetation that is capable of adapting to a green roof environment (White & Snodgrass, 2003).
While certain grassland habitats will require intensive soil layer to support their principle species (CVNI, 2011; White & Snodgrass, 2003). Lightweight extensive green roofs are capable of providing for many grassland habitats (Larson, Matthes, Kelly, Lundholm, & Gerrath, 2004). Many of the grasslands in Ireland rely on a variation of a shallow mineral soil (NIEA, 2010) these conditions are replicable within the substrate of extensive green roofs (Dunnett N. , 2006). Grass roof habitats are a mature green roofing treatment. Numerous examples of grass covered green roofs which have been proven to provide for surrounding wildlife or support rare species (Dunnett & Kingsbury, 2008).
Lowland Acid Grasslands
Calcareous Grasslands
Image 15 - Wangford Warren, Suffolk
Image 16 - Little Deer Park, Antrim
Lowland Meadows
Rush Pastures
Image 17 - Tees Valley, Middlesbrough
Image 18 - Slievenacloy, Belfast Hills
Limestone Pavements
Image 19 - Knockmore, Fermanagh
Image 20 - Ducks Unlimited National Headquarters, Winnipeg, Canada
For example, the Ducks Unlimited National Headquarters and Conservation Centre in Winnipeg, Canada contains a grass roof which supports the surrounding tidal habitats. The grass roof provides resources for nesting birds from the adjacent Oak Hammond Marsh which has many parallels to Lough Neagh (GreenRoof, 2010).
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Hill House
To comply with strict planning requirement for building within a ‘scenic corridor’, a buried dwelling was designed for the Norton family in California. The house used a system of concrete/ fieldstone retaining walls and sod covered roof to create to minimal impact building. The roof was cover with Winter Rye and local wildflowers with boundary of the sloped roof landscaped with Honeysuckle vines and Oak trees (GreenRoof, 2010).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
La Honda, California 1979 George & Adele Norton Jersey Devil Design/Build Jersey Devil Design/Build New Extensive 232m2 100% 50% road base and 50% topsoil 200mm €830/m2 £650/m2 439.4kg/m2
Significance to Ireland's Habitat Green Roofs The Norton Hill House illustrates the following points for habitat recreation The Hill House is an example of a semi-buried structure. While his will allow for the colonisation of additional fauna species it will not affect the rate of colonisation by flora and invertebrate species (Dunnett & Kingsbury, 2008). A mixture of commercially available road aggregate and natural topsoil was used in the development of this roof system, a sustainably questionable material mixture. The direct connection between the building roof and surrounding natural environment was an imposed design feature.
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Heinz 57 Centre
The green roof on the Heinz 57 Centre was part of the refurbishment of the long abandonment building located on the fringe of Pittsburgh historic quarter (Earth Pledge, 2005).
Location Completion Date Client Architect
The high masonry walls that surround the garden have created a sheltered micro-climate which has led to a more diverse range of vegetation. The roof is populated by a number of flowering wildflowers and sedum species, with an all year round blooming cycle (Earth Pledge, 2005). The plant list includes 35 separate plant species, which ranges from lowgrowing groundcover plants like sedum to taller vegetation such as Anthemis and Carex (GreenRoof, 2010).
Landscape Architect
New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
Pittsburgh, Pennsylvania 2001 623 Smithfield Associates Burt Hill Koser Rittlemann Associates Burt Hill Koser Rittlemann Associates Retrofit Extensive 1,115m2 33% 90% mineral; 10% organic 120mm €130/m2 £105/m2 146.5kg/m2
Significance to Ireland's Habitat Green Roofs The Heinz 57 Centre illustrates the following points for habitat recreation No irrigation system is use on the Heinz 57 Centre. Instead the roof drainage layer can hold 30% of its volume in rainwater (representing 55% of predicted annual rainwater). This water retention rate is in line with German FLL standards (Earth Pledge, 2005). The roof structural systems is an example of what can be achieve at the low building costs and roof loading scale for grass roof habitats. The high masonry walls of the Heinz 57 Centre shows that through appropriate building design it is possible mitigate the effects of exposed rooftops or even alter the conditions of a green roof through the creation of microclimates
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Chicago City Hall
In conjunction with a Environmental Protection Agency's programme to negate the urban heat island effect and to improve city air quality. Mayor Richard M. Daley and the City of Chicago began construction of an exhibition semiextensive green roof on The Chicago City Hall in April 2000 (GreenRoof, 2010). The garden was a retrofit development on the century old city Hall and is not accessible to members of the public. The roof supports both native and non-native plant species, with has been organised in a number of colour related planting beds (Earth Pledge, 2005). The City Hall rooftop garden has over 150 species, in addition to 100 woody shrubs, 40 vines and 2 trees, a Cockspur Hawthorn and Prairie Crab-apple (GreenRoof, 2010).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth
Cost Weight
Chicago. Illinois 2001 City of Chicago William McDonough + Partners Conservation Design Forum Retrofit Extensive & Intensive 2,045m2 56% Commercial growth media 100mm 150mm 450mm €380/m2 £300/m2 100mm=146.5kg/m2 150mm=293kg/m2 450mm=439.5kg/m2
Significance to Ireland's Habitat Green Roofs The Chicago City Hall illustrates the following points for habitat recreation It is stated that the city hall has an annual saving of €4100/£32002 in general utility cost due to the cooling effect and rainwater retention provided by the grass roof (Earth Pledge, 2005). Supplemental irrigation systems has been added to the roofs systems to aid in the establishment of plants as well as provide supplemental water during extreme periods of drought (GreenRoof, 2010). The research into the reduction of heat island effect and green roofs is still ongoing. However published figures state that there is a 15oC difference between the green roof and neighbouring black tar roofs in the summer (City of Chicago, 2010).
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Figure converted from stated value ($5,000)
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Moos Water Filtration Plant
The Moos Water Filtration Plant near Zurich built in 1914 (one of the first reinforce concrete structures in the region). It supports nine-acres of species rich rooftop meadows. These roofs were not designed as a green roof, but as a sand/gravel/soil roof to add in the cooling of the building. Plants have naturally colonised the space over the buildings lifetime.
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
Zurich, Switzerland 1914 City of Zurich Not available Not available Retrofit Intensive 9,290m2 100% Topsoil and humus 200mm Not available 488.2kg/m2
The three oldest roofscapes cover approximately 3 hectares and provide habitat for 175 different plant species. Including 9 species of orchids (GreenRoof, 2010) and over 6000 specimens of Orchis Morio, an orchid species thought to be extinct in the area (Earth Pledge, 2005). The roofs are currently under consideration to be granted environment protection orders by the regional government (Earth Pledge, 2005).
Significance to Ireland's Habitat Green Roofs The Moos Water Plant illustrates the following points for habitat recreation The roof’s structure presents excellent evidence for the longevity of green roofs (Dunnett & Kingsbury, 2008) and the ability of green roofs to be naturally colonised by unexpected species (Brenneisen, 2006). The soil substrate consists of 5cm of sand and gravel as a drainage layer, with between 15cm and 20cm of topsoil. This again raises questions of sustainability and the sourcing of substrate material mixture.
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Vancouver Conference Centre
Also known as the Vancouver Convention Centre West, this building includes a six-acre green roof designed to replicate British Columbia costal grassland. It is currently the largest grass roof in Canada and the largest nonindustrial living roof in North America. The building was awarded an LEED Platinum rating on completion, the first conference centre in the world to achieve such a rating (GreenRoof, 2010).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium
Soil Depth
Vancouver, Canada 2008 BC Pavilion Corporation LMN Architects PWL Partnership New Intensive 24,281m2 58% Engineered Soil; sand, organic medium, lava rock 300mm Not available Not available
The green roof is landscaped with more than Cost 400,000 specimens of native plants and grasses Weight from the Gulf Islands, including Sea Thrift and Beach Strawberry. Which provides natural habitat to birds, insects and small mammals. The client required that no existing habitats be damaged in the production of the soil layer for the new green roof (Budge, 2009). As such no peat moss was use in the roof's substrate (Budge, 2009), instead it was formed from dredged dockland sands and recycled organic material (GreenRoof, 2010).
Significance to Ireland's Habitat Green Roofs The Vancouver Convention Centre illustrates the following points for habitat recreation A design decision was made not to use peat moss in the development of the roof’s soil substrate. As such recycled aggregate and organic matter gathered from the building’s kitchen and landscaping activities (Budge, 2009). Post completion it was discovered that meadow wildflowers were more abundant on the north-facing section, and annual species (although present) were less prevalent than on the south-facing section (Grant G. , 2006). The Vancouver Convention Centre is an example of a large scale green roof developed specifically for the purposes of habitat replacement within an urban area.
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06 Heathland Habitat Case Studies Numerous feature of heathland that make them a viable candidate for habitat recreation projects within Ireland’s urban roofscape. The dominance of a limited number of species within a small area, the reliance on a nutrient-poor, heavily mineralised soils in addition to an adaption for a fragmented and restricted habitat range (NIEA, 2010). A continuous exposure to environmental stresses has spawned an array of low dense vegetation, drought-tolerant shrubs (Gates, 1980), and heaths (Cooper & McCann, 2001). All these species have evolved to cope with the condition that are present on many rooftops.
Lowland Heaths
Upland Heaths
Image 21 - Murlough National Nature Reserve
Image 22 - Bloody Bridge near Newcastle
Mountainous Heaths
There exists a growing industrial trend to use heath, mosses and sedum roofs as a method to reducing rainwater runoff across the world (Earth Pledge, Image 23 - Mourne Mountains 2005). Due to the thin soils requirements and a natural tendency for heaths to be near mono-culture plants in isolated locations (NIEA, 2010). A clear parallel exists between the natural conditions of heaths and the leading methodologies involved in installing sedum or moss vegetation mats (Dunnett & Kingsbury, 2008). Therefore heathland species can flourish on the substrate of lightweight extensive green roofs (Brenneisen, 2006).
Precedence
Image 24 - North German Bank, Hanover, Germany
Many buildings already use heath and moss extensive roof on small isolated sections of roof. Because of their ability to created successful natural environments at little monetary cost, structural implications and survive with relatively no maintenance (Dunnett & Kingsbury, 2008). An example of this is the North German Bank (Nord LB0) in Hanover, Germany by Behnisch, Behnisch & Partner Architects. The building supports 13 heath and moss extensive roofs and two larger intensive roofs. The generous use of heath roofs is cosmetic. Creating a more visually pleasing environment for the buildings occupants looking out the structure exclusively glass facades (GreenRoof, 2010).
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Life Expression Chiropractic Centre
The rooftops of the Life Expression Chiropractic Centre was installed for its functional aspect of temperature regulation and runoff control. In addition to the visual quality of the roof vegetation to blend into the surrounding rural Appalachian Valley (Earth Pledge, 2005). The unique roof design and planting allows rainwater runoff to discharge along the full length of the building’s eaves, creating a curtain effect of falling water during heavy rain (GreenRoof, 2010). The roof is planted with a variety of native mosses and sedum species (Earth Pledge, 2005).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
Sugarloaf, Pennsylvania 2001 Life Expression Wellness Centre Van der Ryn Architects Roofscapes Inc. New Extensive 557.5m2 100% 90% mineral; 10% organic 120mm €58/m2 £46/m2 137kg/m2
Significance to Ireland's Habitat Green Roofs The Life Expression Chiropractic Centre illustrates the following points for habitat recreation The green roof demonstrates the ability of lightweight extensive roofs to support dense low-growing groundcover on a sloped roof ranging from 14o to 30o. Believed to be one of the steepest green roofs in North America (GreenRoof, 2010). No irrigation system was installed on the roof. Rather the growing medium was designed to retain an estimated 55% of the annual rainfall (Earth Pledge, 2005). Any innovative approach was taken to protect the roof from wind erosion while the plant species established themselves. A medium surface with a photodegradable wind blanket mesh was installed to cover the sprouting vegetation, which has since degraded (Earth Pledge, 2005).
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Schiphol Plaza
Schiphol Plaza at Amsterdam airport had its green roof designed to reflect the condition of surrounding flat plains. The expanse of heath and sedum species has a wide degree of seasonal colour change acting as visual aesthetic for traveller who utilise the underline train station and airport terminal. The green roof also acts as a measure to reduce water runoff in line with the airports environmental policies (Earth Pledge, 2005).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost
The Vague, The Netherlands 1994 Amsterdam Airport Schiphol Benthem Crouwel NACA Andriaan Geuze, West 8 New Extensive 8,100m2 90% Not available 30mm €33/m2 £26/m2 45kg/m2
Construction of the green roof consisted of the installation of pre-vegetated mats of moss and sedum bound together with coir fibre (made Weight from the husks of coconuts). Which absorb rainfall and contain a mineral-based substrate that provides plant nutrients and eliminates the need for soil (GreenRoof, 2010).
Significance to Ireland's Habitat Green Roofs The Schiphol Plaza illustrates the following points for habitat recreation The Schiphol Plaza can showcase an example of a large scale green roof developed specifically to replicate a mountainous habitat that surrounds the built up area. The planting choices and roof structure is extremely lightweight green roofing approach, being less than a third of the loading requirement of the UK’s domestic buildings (153 kg/m2 (Adler, 1999).
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Somoval Garbage Treatment Plant
The Somoval treatment plant in Monthyon is located less than a mile from the Paris city limits and contains a 4-acre green roof to aid in the minimal visual impact of the structure. The vibrant sedum and moss roof was designed to allow the building to better blend into the surrounding countryside after complaints by local residents. The roofs vegetation turns from red into summer to a green during winter and provides an insulation effect for the treatment plant (Earth Pledge, 2005).
Location Completion Date Client Architect Landscape Architect New Build/Retrofit Green Roof Type Roof Size Roof Coverage Soil Medium Soil Depth Cost Weight
Monthyon, France 1997 Somoval S’PACE Not available New Extensive 15,329m2 Not available Commercial growing medium 70mm £14.50/m2 178kg/m2
Significance to Ireland Habitat Green Roof's The Somoval Treatment Plant illustrates the following points for habitat recreation The Somoval Treatment Plant is another example of a large green roof designed to replicate and blend in with a surrounding mountainous habitat. The low construction cost of the Somoval Treatment Plant is noteworthy, being the second lowest costing of all the presented case studies. Again the Somoval Treatment Plant is an example of a large roof at a scope with contains extensive planting.
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07 Practical Implications of Rooftop Habitat Recreation The research undertaken in the development of this document has provided a number of values in regards to the physical and economical attributes associated with habitat recreation on building rooftops. The following table details the type of environments capable of be recreated depending on the type of green roof installed. Recreated Habitat Type Coastal
Roof type Extensive & Intensive
Woodland
Intensive only
Wetland
Intensive only
Grassland
Extensive & Intensive
Heathland
Extensive
Table 2 - Required Roof Type for Habitat Recreation
Furthermore, by combining the legal structural requirements for roofs under BS6399 and the information gather on completed green roof habitat projects, a comparison can be made between typical building usage and the types of habitat roofs they can support. Roof Structural Requirements (Adler, 1999) BS6399 Category Domestic Offices Retail Warehousing Factories, Workshops
N/m2 1.5 2.5 4.0 2.0 5.0
kg/m2 153 255 408 204 510
Table 3 - Required Roof Loading (Adler, 1999)
These figures represent the general structural requirements for all new buildings in the UK and Ireland. These values are the legally required minimum for any construction system (Adler, 1999), so are reliable reflections of the strength of Ireland’s buildings. Range of Green Roof Weight Loads Recreated Habitat Type Coastal
Weight/m2 75 - 145kg
Wetland
350kg
Woodland
1250kg
Grassland
150 - 490kg
Heathland
45 - 180kg
Table 4 – Imposed Roof Loading for Habitat Recreation
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It is important to note that the above values are derived from completed examples of green roofs. Green roof weight range are typically organised by the type of roofing structure (extensive, intensive, etc) and not ecological environments. Cost And finally the last table demonstrates a typical cost range to the construction and planting of an artificial habitat at roof level. Cost/m2 €15-€60 / £10-£45
Recreated Habitat Type Coastal Wetland
€350-€750 / £300-£600
Grassland
€150-€850 / £100-£650
Heathland
€20-€60 / £15-£45
Table 5 – Estimable Cost Range for Habitat Recreation
Woodland
Heathland
Grassland
Wetland
Building Type Domestic Offices Retail Warehousing Factories, Workshops
Coastal
Habitat
Types of Habitat Roofs capable of occupying Non-Reinforced Structures Through cross-comparison of the two above tables, the following assessment on the structural viability of green roofs on Ireland’s building stock can be achieved.
Table 6 – Building Types Capable of Carrying Habitat Roofs
Coastal, Grassland and Heaths are the most adaptable roof habitats as they are comprised of lightweight substrates and vegetation. Conversely woodland habitats, with their weighty planting, are outside the structural norms of nearly all of Ireland’s structures. The typical architecture of Ireland is dominated by pitched roof structures. While green roofs can occupy the slopes common to most roofs, these systems require additional support and an associated weigh. Pitched lightweight sedum/moss/heather roofs weight 100-130kg/m² (Optigreen, 2011) and grassed pitch roofs generally impose a loading of 160190kg/m² (Optigreen, 2011). These figures present Coastal and Heath habitats as structurally viable options on non-strengthen domestic roofs within Ireland.
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