Green Roofs and Their Implementations in Architecture
The obstacle and challenges in Erbil city
Siba Nadhim Kady
Sahar Mohammed Yahya
In the last five years, the term green roof has taken on ecological and social significance beyond its seemingly simplistic description, this term has become an epithet for the reduction of pollution and improving urban environment.
Green roofs infrastructure promises to become an increasingly important solution for building owners and community planners which provides a significant numbers of social, environmental and economic benefits that are both public and private nature
interestingly recent statistics suggested that the percentage of green areas in Erbil the capital city of Kurdistan region is approximately 6.5%, while according to international standards 30% of urban areas should be green.
Abstract
Research problem
the ambiguity of green roofs implementation techniques in the region.
the goal is initiated to determine the obstacle and challenges of green roofs implementations in Erbil city as case field by analyzing international experiences and concluding Erbil’s green roofs criteria
Research goal
Introduction Erbil city is facing environmental problems such as
waste water treatment, water supply, land preservation, air and noise pollution, although few parks have been constructed during the past few years, the focus has been on the main streets and less in residential areas
Moreover, in Kurdistan, people lack the awareness that planting trees is beneficial for the atmosphere and can lead to a better living environment for them and their children. Ironically, not only do some people not plant trees, they sometimes uproot or cut trees planted by the government
Climate changes, increasing temperatures, storms and flooding’s especially in the our region, it is not a forecast, it is happening now. for example Syria has had its fourth consecutive summer of droughts while Yemen is struggling with what is considered its worst flooding in a decade, morocco also affected by frequent drought, also the country now, Erbil included, experiences five or six droughts every year.
Without a national campaign by the people and the government for increasing greenery areas and promoting nature, there is a little hope for the future
Green Roofs History Green roofs date back to thousands of years. The oldest green roof appears
to be the ziggurat of ancient Mesopotamia, built from the fourth millennium until 600 B.C.E.
During the middle ages and renaissance, roof gardens were owned by the rich and monks.
Germany is known as the birthplace for modern day green roof systems. In the modern time there were two advocates of green roof technology the
architects Le Corbusier and Frank Lloyd Wright. Although Le Corbusier encouraged rooftops as another location for urban green space, and Wright used green roofs as a tool to integrate his buildings more closely with the landscape, neither was aware of the profound environmental and economic impact that this technology could have on the urban landscape
Green roofs now are the new trend of aesthetical, environmental, economic and above all sustainable solution for urban environmental problems
Green Roof definitiongreen roofs are mainly the covering for any built structure at any elevation such as a parking structure, academic or assembly facility, or any commercial or residential structure-and thought of as being programmed and designed for supporting a layer of vegetation to mitigate storm water loss and heat gain or as usable, comfortable open space that helps to improve urban environments.
Extensive Semi intensive Intensive
Maintenance Low Periodically High
Plant Communities Ground covers, grasses
Ground covers, grasses and shrubs
Lawn or shrub and trees
Plant types Grasses and loans, ground covers, seasonal flowers
Climbers, cactus and succulents, shrubs
Palm trees, ornamental trees, aqueous plants
Plant Diversity low plant diversity More plant diversity high plant diversity
System Built Up Height
150- 250 mmThin growing medium
250- 500 mm 250- 500 mm, provide planters for trees and palm 1000mmm Deep soil
Weight approximate
50-150 kg/m2 <150 kg/m² >150 kg/m²
Cost Low Medium High
Use Ecological protection layer
Designed green roof Park like garden, designed more for aesthetics than performance
Accessibility Not Semi accessible accessible
Irrigation Requirements
little or no irrigation little irrigation irrigation system; more favorableconditions for plants
Extensive Semi intensive Intensive
Benefits
• Lightweight; roof generally does not require reinforcement
• Suitable for large areas.• Suitable for roofs with 0 - 30° (slope).• Low maintenance and long life.• Often no need for irrigation and
specialized drainage systems.• Less technical expertise needed.• Often suitable for retrofit projects.• Can leave vegetation to grow
spontaneously.• Relatively inexpensive.• Looks more natural.
• Easier for planning authority to demand as a condition of planning approvals.
• Greater diversity of plants and habitats.
• Good insulation properties• More energy efficiency and
storm water retention capability
• Longer membrane life
• Longer membrane life
Greater diversity of plants and habitats.
Good insulation properties.
Can simulate a wildlife garden on the ground.
Can be made very attractive visually.
Often accessible, with more diverse utilization of the roof. I.e. for recreation, growing food, as open space.
More energy efficiency and storm water retention capability.
Longer membrane life
Downsides
• Less energy efficiency and storm water retention benefits.
• More limited choice of plants.• Usually no access for recreation or other
uses.
• Unattractive to some, especially in winter
• Greater weight loading on roof than extensive
• Higher maintenance costs
• Greater weight loading on roof.
• Need for irrigation and drainage systems requiring energy, water, materials.
• Higher capital & maintenance costs.
• More complex systems and expertise
green roof benefits in different climatic conditions, a comparative review
Climate benefits
Warm Climates -Shading the rooftop layer -reduction of the direct influence of solar radiations -reduction of indoor temperature fluctuations -reduction of indoor air temperature peaks -reduction of energy used for cooling purpose
Warm And Humid Climate -Indoor daily temperature swings depend on the soil depths
Warm And Dry Climate -Reduction of the outdoor air temperature-cooling the indoor ambient temperature
Cold Climates -Reduction of daily -temperature swing , reduction of the heat flow
-doubtful energy performance in winter
-spring and falls, evaporative cooling in the shoulder seasons may lead to increased building heating loads
Green Roof Technical Guidelines Roof Conditions and Suitability for Greening
Roof conditions and suitability for greeningfunction Location Accessibility Climate Wind
the primary functions a specific green roof is required to perform, will have profound effect on its overall design
The height of the roof, its orientation, its exposure to wind, sun and shading by surrounding buildings will have impact
Access to the green roof site is vital for the installation, ongoing maintenance and bringing up materials.
The general climate as hot, humid or cold, dry should be considered on plants selection.
Wind can generate positive and negative pressure forces, which act on structures. the most affected areas by the wind pressure are: Corners where
stress level are very high
Edges, where stress levels are high
Structure and bedding stabilityStructure and bedding stability
Structure and design loads
green roof is part of the initial design of the building
Depth and Weight of media layers
The depth of media layers range between 2.5c.m-200c.m and the weight of every layer in a green roof system is determined at the point of maximum water capacity including materials and stored water.
Roof Slope Intensive green roofs are executed on slopes of up to 5 degrees, while extensive green roofs on slopes of up to 30 degrees and the maximum slope is 45 degrees.
Water Proofing roof membrane
For an existing building, the membrane should be carefully inspected to determine if it needs to be repaired or placed before the installation.
Parapet Design and Protection against falls
A lower parapet design in low rise building may avoid potential air turbulence and help minimize uplift forces, on the other hand high rise buildings are exposed to increased wind pressure resulting in higher positive uplift forces.
Fire Resistance
The integration of fire breaks in all types of green roofs is recommended. Certain plants should be avoided from use on rooftops that are highly flammable, or that develop large root systems and thus high biomass, or that are excessively thirsty.
Green Roofs Implementation Levels There are two main levels for green roofs implementations, city scale level
and project scale level.
By implementing green roofs on city scale level, the benefits will be public for the total urban environment, this level need a lot of support and previous planning from different institutions whether it’s on the leaders, legislators, regulators, planners, designers, builders, and master planning levels.
On the other hand by implementing green roof on project scale level, the benefits will be private for building owners and planners. This level required several procedures like merging landscape and architecture, enhancing urban microclimate, enhancing the integration of parking, surface, structured, and underground parking
Green Roofs samplesMountain equipment coop, Toronto, Ontario, Canada [2]
Implementations Level
project scale level
Green Roof Type extensiveOverview: This inaccessible green roof garden located on downtown Toronto corporate
Headquarters of the mountain equipment co-op. The 903 m2 green roof area Surrounds a skylight located on the second floor of the building. The roof has Full sun exposure and a load capacity of 40 psf. The vegetation is a wild flower meadow mix of sun flower seeds and perennial plants.
Owner: Mountain equipment co-opConstruction: Installation of the green roof took place in May 1998 and the building Was
constructed during fall 1997- winter 1998.Drivers: Some items in the program had no quantifiable economic benefit, but to the
owner they contributed to social and community leadership. The building was intended to encourage discussion and debate about environmental Issues and the green roof has contributed to this.
Obstacles: The possibilities of added costs of structural redesign allowing for employee accessibility were barriers. Since the roof structure would have had to be further upgraded to accommodate live loads, accessibility was not incorporated Into the design.
Benefits: The green roof does have environmental and community benefits. It will also have some operating cost benefit due to thermal inertia of mass of growing medium successful in the establishment of the vegetation and wildlife
Vancouver Public Library, British Columbia, Canada [11]
Implementations Level
project scale level
Green Roof Type extensive
Overview: This extensive 2 400 m2 green roof in Vancouver can be viewed from surrounding downtown office towers. The inaccessible roof is located on top the 7 story library. It is oriented toward the city and the harbor. Four different types of trees, green and blue/green tufted fescues are planted in a light weight growing medium which is composed of reconstituted vegetable waste, sand and pumice.
Owner: City of Vancouver
Construction: Building and green roof were constructed in 1995
Drivers: Environmental and aesthetic purposes
Obstacles: None
Benefits: The green roof was a great successbut no quantifiable data collected
Vancouver Public Library, British Columbia, Canada [2]Implementations Level
city scale level
Green Roof Type semi-extensiveOverview: This demonstration project is located on the first floor podium roof of the Toronto
City Hall building at 100 Queen Street West. The green roof is accessible to the public. It features eight different plots that represent a variety of green roof applications. The eight plots include:• 2 semi-extensive systems demonstrating a variety of plant types and landscaping techniques• Reproduction of the now rare black oak savannah prairie ecosystem type with native plants drawn from nearby High Par• A bird and butterfly garden with a mixture of native and non-native material• 2 extensive green roof plots demonstrating a wide variety of plants• 2 urban agricultural plots, one of which demonstrates some of the principles and plant types associated with permaculture
Owner: The City of TorontoConstruction: Re-roofing and green roof were constructed in the fall of 2000Drivers: Need for Technical research on performance and demonstrationObstacles: Many constituencies were involved and needed to be accommodated in order to
implement the green roof.Benefits: The green roof provides an excellent opportunity for public and professional
access to a variety of different types of applications in one place.
Green roof in Erbil/ the obstacles and possibilities
Erbil, as increasingly growing city , the green roofs gardens could be implemented in two main levels: city scale level and project scale level with two types of green roofs extensive and semi intensive
ErbilImplementations Level
Project scale level
Roof type IntensiveOverview: This type of a green roof garden can be viewed in newly
planned high rise residential buildings owner Building residence Construction: 1. Planting
2. Intensive soil3. Filter4. Beodrain
Drivers Economic and environmental purposes for building residence
Obstacles This type of green roof should be considered in the design face of the building in order to pre-calculate all the necessary constructional treatment for all the loads and irrigation systems accompanying with it.
Benefits This green roof garden is an ideal social place for rise building families cause it is accessible and it is provided with architecture elements such as walk ways, pavements, water pools, play area, also it contains a great diversity of plants so it could be one of an economic solution
Recommendation Leaders and Planners have to encourage and support these two types of green
roof garden and provide laws and legislation for their implementation in Erbil.
Increasingly the awareness of the environmental importance of green roofs garden as one of the effective ways to increase the green areas in the city.
It is possible to propose an economic and environment-friendly system for irrigation with the help of recycled water and solar energy where possible to reduce the energy consumption needed to irrigate the green roofs.
In order to have a long lasting environmental improvement in Erbil and the region in general, Green roof implementation should be considered in the primary phase of any building or city master plan design, and for every future expanding.
Further studies should be considered in this field to support the field of practice of Green roof.
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