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.

Green Roof Types: A Comparative Review

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

Green Roofs Components

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.