Green Roofs EcoMENA

Green Roofs EcoMENA

Urban green roofs have long been promoted as an easy and effective strategy for beautifying the built environment and increasing investment opportunity. The building roof is very important because it has a direct impact on thermal comfort and energy conservation in and around buildings. Urban green roofs can help to address the lack of green space in many urban areas. Urban green roofs provides the city with open spaces that helps reduce urban heat island effect and provides the human population on the site with a connection to the outdoors. However, we must differentiate between two types of urban green roofs and assess their adaptability to Arab cities. This article provides an insight on green roofs and roof farming in Arab cities.

What are Green Roofs

Green roofs are essentially sustainable and passive design features of vegetation surfaces applied to a waterproofing layer of a suitable conventional roof build-up in rainy climates. In rainy countries such as Austria, Germany and Belgium green roofs are recognized as a significant source-control feature,contributing mainly to storm water management and drainage control. Green roofs not only store water at roof level, but also reduce the run-off rate from the roof, which in turn reduces the underground drainage network requirements. It is also possible to use or harvest rainfall from a green roof, although the amount of rainwater that can be used may be reduced depending on the type of green roof implemented.

Generally speaking, there are no green roofs in hot arid climates. In Arabia it is hardly to find any examples of successful green roofs. According to European norms the minimum annual precipitation rate for a green roof should be more than 450-650mm. Therefore, it is impossible to grow a green roof in Cairo (26mm), Amman (276mm), Riyadh (20mm) or Dubai (10mm). Even coastal cities like Alexandria (190mm), Tunis (450mm) or Casablanca (425mm) witness extreme summers and drought periods that almost eliminates the sedum plants from recovery during the winter season. Facing these facts, there are many voices in Arabia that surprisingly continue pushing the idea of green roofs claiming to sustain it through artificial irrigation. An idea that make us lose the whole point of sustainability in an already water scarce region.

Unfortunately, across the Middle East there are large numbers of students, architects, clients and even researchers who have a wrong perception and a defective understanding of semantic of green roofs,which are essentially associated with the presence of renewable rain water. This is due to the unfamiliarity with word Green Roof in our region and the huge influence of the Northern imaged media. Moreover, there are many researchers who talk about the positive side effect of green roofsthat significantly save energy, enhance the thermal performance and comfort of buildings, particularly in terms of summer cooling, based on readings and studies made in countries with latitude higher than 40 o with temperate or cold climates. What is missing here is local evidence based experimentation and practices that address green roof in the warm and hot climate not from a theoretical copy-paste approach.

The Real Problem

Arab cities suffer from serious problems that are similar to most other large cities in the developing countries. Among the most visible manifestations of the challenges posed by rapid urbanization are many environmental problems, such as pollution, dense urbanization, urban heat island effect and inversed greenhouse effect during winters. In fact, the dense concentration of automobiles and polluting buildings created a negative impact on the environment. In fact, the rapid urbanization not only created environmental problems but also economic problems. For example, air conditioners are running, over the whole summer period, trying to deliver an endless demand for cooling. This leads to increasing prices of electricity bills. This is due to the lack of energy codes, which means that roofs are without or with very poor insulation. Additionally, cities suffer from constant desert sand depositing together with disappearance of green spaces which lead to deprivation of open space.

During the last decade many Arab cities witnessed several times inefficient food production and distribution, inaccessibly high food prices and above all locally grown food, loaded with toxic contaminants. The fast-growing population and the failing government approaches to housing and spatial planning policies contributed to the growth off informal settlements within and around the center. For example, 8 million Egyptian live in informal settlements in Cairo with problems of unemployment, pollution, transportation, inadequate drainage and sewerage, and lack of usable urban open spaces. In Cairo, the amount of green space per inhabitant is roughly equivalent to 0.33 square meters per person (3.5 square feet), one of the lowest proportions in the world. Among the above listed problems stands out a common denominator. It is the building roof.

Roof Farming as an Alternative

Under the influence of the all those issues emerges the idea of roof farming. Urban roof farming has long been promoted as an easy and effective strategy for beautifying the built environment and increasing investment opportunity. Roof farming can help to address the lack of green space in many urban areas. Urban roof farms provides the city with open spaces that helps reduce urban heat island effect and provides the human population on the site with a connection to the outdoors. Challenged by environmental and pollution, Cities suffer from locally grown food, loaded with toxic contaminants that threat the health.

In the last couple of years, Cairo suffered from an inefficient production and food distribution and inaccessibly high food prices. The population explosion and the tendency to build on agricultural land have acted to limit the resources of city families and their access to healthy edible products. With a little effort and money, roof farming can contribute in improving the families quality of life and provide them with healthy food and raise their income, this is besides the environmental and aesthetical role it plays. For example, Cairo citizens and some governmental authorities acknowledged the problem of food contamination & distribution and are mapping measures and methods that can guarantee safe food.While it is not new, the notion of planting rooftops in Egypt has only recently been implemented. In the early 1990s at Ain Shams University, a group of agriculture professors developed an initiative of growing organic vegetables to suit densely populated cities of Egypt. The initiative was applied on a small scale; until it was officially adopted in 2001, by the Food and Agriculture Organization (FAO).

There are several case studies that represent successful projects implemented by different non-governmental organizations (NGO), public institutions and private civil initiatives. For example Ibn Kassir foundation, in Al-Zawya Al-Hamra, Cairo, created a roof farm from wooden containers (barrels) with plastic sheets filled with peat moss or perlite used as substrates. The drainage is driven through small plastic hoses to buckets. This system is producing leafy crops such as parsley, radish, and carrots. A square meter using this method would cost around 400 Egyptian pounds (LE).

Finally, in many Arab cities, where many environmental social and economic problems exist, a beam of light emerges to contribute in solving many of these interrelated problems. Planting our roof with different kinds of vegetables and fruits or even any kind of green plants will change lots of things. It is certain that roof gardening and farming have measurable qualitative and quantitative benefits. The techniques for implementation are simple and doable and above all cost efficient. However, no roof gardens can be created without the knowledge of the factors affecting the creation and design. The most important factors are the climate, the constructional and economic factors.

Regarding green roofs, we shall only address this issue based on experimental and monitored cases. More importantly, a vision is required to be drawn together with long term strategy, adopting the holistic approach of roof farming and providing support and sustainability. It is this holistic approach that can solve many problems of different background and aspects, and can contribute to improving the quality of life of the dense Arab cities. By exploitation of such roofs, their development and planting; a reasonable ratio of green areas can be reached in the near future. A ratio of 4 square meters per person can be provided once the suitable green framing roofs have been developed and exploited.

Green roofs are emerging technologies that can provide a wide range of tangible and intangible benefits to communities interested in enhancement of their environment. Green roof development involves the construction of a vegetative layer on top of a human-made structure or building adding green space to areas that would otherwise be unused. The major benefits of green roofs are reducing energy use as well as air pollution and greenhouse gas emissions, enhancing stormwater management and water quality, decreasing heat island effect by regulating temperature for the roof and the surrounding areas and providing aesthetic value and habitats for many species.

What are Green Roofs

Green roofs mainly consist of a vegetation layer consisting of trees, plants, and other shrubs, a substrate layer where water is retained and in which the vegetation is secured, and a drainage layer which helps to evacuate excess water. The depth of the substrate layer is how the two main types of green roofs are differentiated.

Green roofs can be intensive or extensive. Intensive roofs are thicker, more than 15 cm deep, which allows for the growth of a wider variety of plants including trees and shrubs. However these roofs are heavier, more expensive and require more maintenance and irrigation. Extensive roofs, on the other hand, are covered in only a light layer of vegetation, less than 15 cm, and are primarily made up of shrubs, low-growing sedums, and herbs. Unlike the plants on an intensive green roof, the extensive vegetation is typically self-sustaining apart from the bi-yearly maintenancewhen the beds need to be weeded and fertilized.

Because of their weight and function intensive roofs are usually used on commercial buildings. Commercial buildings tend to be made out of concrete and can support heavierweight loads than traditional homes. Once the plants are installed and the soil is moist these rooftop green spaces can weigh as much as 150 pounds per square foot. They also tend to have more room to include benches, tables, greenhouses, fountains and walkways that travel between different features of the green roof and provide space where people can interact with the natural surroundings. Intensive roofs tend to be more attractive than extensive roofs and can offer people a place to relax, eat or work in park-like settings.

Extensive roofs on the other hand because of their low weight tend to be more often suitable for residential type buildings or sheds and barns. Extensive green roofs are the simplest to install and are very often added to existing roofs. Depending on the source you look at these roofs may add 10 to 35 pounds per square foot to a roofs load. Drought-tolerant plants and grass are the most common used vegetation on an extensive green roof due to their low water requirements and the shallowness of their roots.

Unending Benefits

Green roofs can be placed on both old and new buildings.The green roof system can either be modular, with drainage layers, filter cloth, growing media and plants already prepared in movable, often interlocking grids, or loose laid/ built-up where each component of the system may be installed separately. Reports vary on installation costs but on average extensive green roof range between $8 and $20 per square foot and intensive green roofs range between $15 and $50 per square foot. This compared to a traditional roof installation which averages about $16 dollars per square foot the green roof installation costs tend to be much higher. Although a higher installation cost is required, the green roof undoubtedly offers more benefits than a traditional roof may offer.

Green roofs have the potential to reduce energy demands two ways: absorbing heat and acting as insulators for buildings. Adding a layer of soil and plants to a roof adds insulation to the building it covers. Since roofs are the site of the greatest heat loss in the winter and the hottest temperatures in the summer, the greater insulation offered by green roofs can decrease the amount of energy required to moderate the temperature of a building.

Furthermore, reducing the demand for energy consequently reduces air pollution. By lowering air conditioning demand, green roofs can decrease the production of associated air pollution and greenhouse gas emissions such as CO2. coming from power plants. Additionally, because plants through photosynthesis convert atmospheric CO2 into oxygen, the plants on green roofs can help filter harmful noxious gases in the air and reduce CO2 emissions in the atmosphere.

Green roofs are emerging technologies that can provide a wide range of benefits to communities interested in enhancement and protection of their environment. The major benefits of green roofs are reducing energy use as well as air pollution and greenhouse gas emissions, enhancing stormwater management and water quality, decreasing heat island effect by regulating temperature for the roof and the surrounding areas and providing aesthetic value and habitats for many species.

According to a 2013 MENA renewable energy status report, the Total Primary Energy Supply (TPES) in Middle East and North Africa has reached about 800 million tons of oil. This equates to a 15% increase in energy demand since 2007. Increased energy consumption in the region is due largely to population growth, with related increases in demand for liquid fuels and electricity for domestic use and devices, heating, cooling, and desalination of water. With heating and cooling being a reason for the increasing demand on fossil fuels, there is enormous opportunity for investment in green roofs as a way to stabilize or reduce energy consumption in the MENA region.

Enhancing Stormwater Management and Water Quality

Stormwater is rainwater and melted snow that hits impervious surfaces and runs off into streets, lawns, sidewalks, and other sites. The main concern with stormwater is it can pick up debris, chemicals, dirt, and other pollutants and flow into a storm sewer system or directly to a lake, stream, river, wetland, or coastal water. In many places around the world, including MENA region, anything that enters a storm sewer system is often later discharged untreated into a nearby waterway polluting the same waters we swim, fish, and drink from.

In addition, stormwater runoff can cause flooding and an overflowing of sewer sanitary systems causing serious water quality impairments. In developing countries like Morocco and Algeria, where countrywide stormwater management and municipal waste management systems are deficient, stormwater runoff is a big problem. Rainwater flows from roofs straight onto streets carrying things like petrol, household garbage, bacteria, fertilizers and pesticides to nearby receiving waters.

According to an EPA study, green roofs are capable of removing 50% of the annual rainfall volume from a roof through retention and evapo-transpiration. By reducing the amount of impervious surfaces within a developed zone, green roofs reduce the amount of stormwater runoff. Also, because green roofs absorb water, they delay the time at which runoff occurs, resulting in decreased stress on sewer systems at peak flow periods.

For conventional non-living roofs with a slope of 2%, a 96% runoff rate is observed. On the other hand, intensive green roofs may have as low as a 15% runoff rate. The benefits green roofs have regarding stormwater runoff could be amplified by more green roofs in a close-knit area and using green roofs with a deeper substrate layer. Nevertheless, if implemented, countries in the MENA region in which stormwater management systems are not in place could greatly benefit from the use of green roofs to help reduce hazardous runoff and subsequent contamination of water supplies.

Decreasing Urban Heat Island Effect

Since the built environment tends to be constructed from materials that are impermeable and non-reflective they tend to absorb a significant proportion of the suns radiation and release it as heat. Because urban areas are densely populated with buildings, they tend to be hotter than the surrounding areas, a phenomenon known as heat island effect. Urban heat islands have many negative impacts such as an in increase energy demand for cooling, an increase in air pollutants and greenhouse gas emissions, and impaired water quality.

The heat island effect causes internal temperatures of buildings to rise which subsequently increases the demand for air-conditioning to moderate the buildings internal temperatures. This in turn leads to higher emissions from power plants, as well as increased smog production as a result of warmer temperatures. Additionally, hot rooftop surfaces transfer their excess heat to stormwater causing the runoff water to be much warmer than the streams, lakes, and other waterways it enters. In many cases dealing with this rapid change in temperature causes stress to aquatic ecosystems.

Green Roofs EcoMENA

Urban heat island effect is especially worrisome for areas like Middle East and North Africa, where out of a population of 300 million, 170 million people reside in urban areas. Furthermore, according to UN projections the MENA population will reach 430 million by 2020, of which 280 million are expected to be urban. In order to combat the potential for the heat island effect in the MENA region, communities can utilize green roofs.

The vegetative surfaces of green roofs utilize a relatively large proportion of the absorbed radiation in the evapo-transpiration process and then release water vapor into the air which helps to cool air temperatures. Additionally, the shade provided by trees and other shrubbery greatly helps to reduce the rooftop temperatures and the overall heat island effect.

Roof Lifespan

Rooftop vegetation moderates the factors that accelerate a rooftops breakdown such as extreme temperatures, UV radiation, and cold winds, thus dramatically expanding the life of a roof. According to a study in Germany, a vegetated roof on average can be expected to prolong the service life of a conventional roof by at least 20 years. The result of this is not only cost savings to the buildings owner but also a reduction of landfill wastes.

Habitats for Species

One of the more altruistic aspects of green roofs is the creation of wildlife habitats. Green roofs can provide habitat (food, shelter, water and breeding grounds) for many different species. Because of their high density, cities severely restrict green space and threaten or destroy habitats so the creation of such green space assumes particular importance in these areas. Urban habitats are often seen as too degraded and depauperate to support biodiversity.

Various recent studies in Europe have indicated that green roofs in large cities have high potential as habitat for species negatively impacted by land-use changes. For example, in Basel, Switzerland, surveys of birds, spiders and beetles on green roofs found high diversity levels for all groups, including many species considered rare or threatened.

For modern Middle Eastern citiies like Dubai, Jeddah, Cairo, Beirut and Tehran, creation of habitats for species could be very valuable. Across the MENA region natural habitats are few and far, and green roofs can provide living space for plants and animals, especially for species such as invertebrates and birds.

Aesthetic Value

Green roofs have the ability to significantly improve the beauty of buildings, the visual and environmental diversity which can have positive impacts psychological well-being. Studies across several countries have all shown the correlation between daily contact with nature and human well-being. In fact, the results of a large survey in the Netherlands showed that the amount of green space in the residential environment was positively related to the health condition people said they experienced in their daily life.

When people have contact with green space research has indicated a positive effect in levels of stress, health levels due to green space encouraging a higher level of use of the outdoor spaces, and mental well-being due to positive psychological effects plants and nature has on humans.

Current Scenario

While green roofs in Northern Scandinavia have been around for centuries, in North America green roofs are still a relatively new technology. In Europe, these technologies have become very well established mainly due to governments and legislatives financial support. This support has led to the creation of a vibrant, multi-million dollar market for green roof products and services in Germany, France, Austria and Switzerland among others.

Currently, implementation of green roofs is rare in the MENA region. However, there is a definite market potential as the benefits of green roofs address many of the major environmental concerns of this area. Furthermore, the concrete architecture in the Middle East is ideal for a green roof implementation. The structural soundness of concrete buildings has the potential to support the weight load of both intensive and extensive roofs. The swift progress of green buildings industry in the Middle East promises a deeper penetration of green roofs in domestic as well as commercial constructions in the years to come.

However, one issue that may surface is that roofs are often fully accessible and are often used to dry laundry or to hold social events like weddings and other celebrations. This may pose an issue for home owners if their green roof takes up too much of their roof to perform their daily functions. An intensive roof may be more suitable for homeowners in this region as they lend well to daily visits and offer space to hold social functions.

Due to their extensive range of environmental and economic benefits, particularly their insulation and cooling properties, ability to significantly reduce rainwater runoff and urban heat island effect, as well as improve air quality and their value in promoting biodiversity and habitat in urban areas, green roofs have become important elements of sustainable and green construction in many countries. While the green roof industry is growing in popularity, the industry is still young with many areas needing advancement.

The major barriers to green roof expansion in the Middle East include a lack of governmental support, high installation costs, lack of awareness and education about green roofs, and limited data quantifying green roof benefits. However, with proper support these barriers can be easily overcome through research and innovation in design by the green roof industry.

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