Green roofing and rooftop gardening – where vegetation is introduced to a building’s roof or terrace – has become a prime factor in sustainable urban landscaping. Through a more effective utilization of limited space, they not only improve the aesthetics of our contemporary urban environments, but also bring significant environmental and business benefits.
These benefits are necessary in the GCC, where massive construction projects have resulted in over 70% of the population living in built-up areas, and in countries like Qatar, where almost 100% of the population now live in urban developments. In such significantly urbanized environments, any significant and positive improvement to the local ecosystem is especially welcome, and green roofing can facilitate this by expanding biodiversity, reducing heat levels and increasing carbon capture. They can help both body and soul, improve mental health and expand food production.
To know more about rooftop gardening, BQ Magazine spoke to Rania Obead, a lecturer at Jubail University College, Saudi Arabia. She recently visited Doha to attend the International Conference on Energy and Indoor Environment for Hot Climates, presenting findings and innovative thoughts that have emerged from her research, more specifically from ‘Roof Garden Applications in Hot, Humid Climates’. Rania explains her innovative approach to rooftop gardening that will help existing buildings in GCC countries to enjoy both the environmental and economic benefits of green roofs.
“In hot climates, roof gardens provide excellent levels of insulation, reducing the levels of energy required to heat and cool the building”
Beauty aside, rooftop gardens have a number of advantages, providing environmental benefits like expanding space for agriculture, increasing air quality and reducing heating and cooling costs. In desert countries like Qatar, rooftop gardens can keep buildings cooler than traditional roofs. Because the latter sit in direct sunlight for many hours, the temperature of those traditional rooftops often rises above the actual air temperature. The heat produced, radiates back into the environment, making urban areas much warmer than rural or suburban ones.
Rania says: “Actually roof gardening is very interesting given current concerns regarding energy efficiency. In hot climates, roof gardens provide excellent levels of insulation, reducing the levels of energy required to heat and cool the building. This also reduces roof maintenance, because such gardens also act as a cover for the roof, protecting it from deterioration.”
She goes on to point out that: “They also reduce something called the ‘heat island effect’ – the difference in temperature between cities and the rural areas that surround them. An urban heat island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas, due to human activities. In this context, adding plants is very important because plants absorb carbon dioxide (CO2). We recommend that every person should have a minimum of three plants in their roof gardens.”
A fresh approach to roof gardening
“Plant selection is an important factor in successful roof gardening”
Business aside, constructing a domestic rooftop garden is still relatively rare in GCC countries, because it is is perceived as being more complicated than creating a ground level garden. As Rania clarifies: “Less people construct roof gardens in GCC countries, and as part of my research, my primary question was why? The majority answered that, although they knew about the benefits of roof gardening, they were fearful of creating one because of construction costs, complications, maintenance costs and maintenance problems.”
She goes on to add: “In truth, the main concern when thinking about creating a rooftop garden is the weight-bearing capacity of the roof. Roof gardens are very heavy, because the soil has to be placed on the roof and then plants introduced, and this can affect the structure of the building. Considering this, prior to construction, we calculate the potential load-bearing capacities of the building. When we plan a roof garden, the overall design and all other related matters are made with this primary factor in mind.”
And she also notes that: “With regards to existing buildings which have been built without a roof garden in mind, I focus upon a specific way to minimize the effect. The two most common forms of roof garden – intensive and extensive – require construction grade wire frames because the garden is quite literally immediately above your roof, so that isolation system will protect your roof from water ingress – which can be very dangerous for your roof and needs professional and skilled care. In the main, we don’t have this type of garden in the GCC region, so I do not recommend it because as not every building, or client, can handle it.’
“My solution is, quite simply, containers! With container gardening, you just need someone to take care of the plants, and more importantly it doesn’t need any construction, is very simple and can be used by everyone. Basically, I recommend it because I think it is much easier for the owner, it is not heavy and therefore perfect for existing buildings.”
Rania’s portable gardens (in containers) recommend specific designs, sizes and dimensions for the planting containers. Plant selection is an important factor in successful roof gardening, and Rania’s research paper suggests the use of native and desert plants and certain types of vegetables and herbs for the containers. She also recommends suitable soil for those plants and solves irrigation concerns by using an atmospheric water generator.
As she points out: “I recommend the use of high containers (80cm) because I find most people in this region prefer to maintain plants in high containers as it is more difficult to work on lower pots because you have to bend your body more. I then select the dimensions that will make them light and portable. Here in our region we have excessive solar heat, so weight is crucial as you can move the container and change its location, as many plants are very sensitive. Given this, I also constructed a shade from very light material which also covers the roof.”
Qatar’s as well as other GCC countries’ climate and soil does not provide ideal conditions for growing many kinds of fruits and vegetables. The hot weather is tougher on plants than it is on people, and some plants tolerate the heat better than others. Knowing which plants like it hot and which do not will help your garden survive — and even thrive — in hot weather. Tomatoes, peppers, eggplant and melons are crops that do fairly well in a hot climate like Qatar.
A green future
“The idea of creating rooftop gardens in high-rise buildings is now becoming a common trend in many countries and green roofs on buildings are becoming mandatory”
Roof gardens add another dimension of green space to the urban landscape without taking up an extensive area of land in densely populated places. Every one square meter of green space helps remove 500 grams of particulate matter per year, and plants that grow higher than buildings can produce even more oxygen. Furthermore, green roofs can also nurture wildlife, particularly birds, lower urban air temperatures, and improve air quality.
Edible roof gardens where fruit and vegetables are grown can assist businesses by supplementing the produce that they already purchase. Such urban agriculture can also play an important role in strengthening the resilience of cities and their populations against the impacts of climate change.
Besides the environmental benefits, rooftop gardens can also bring significant economic benefits that are clearly transferable across the GCC region. Opportunities for companies to emerge in the field of services related to roof gardening, for example, design, construction and maintenance, are plentiful.
Employee engagement and productivity can be improved in such a beneficial environment, and green roofs can save businesses millions in energy costs. They can even improve the commercial value of real estate. And the social impact of roof gardens cannot be underestimated, providing space for family gatherings and social activities. Indeed, in her research, Rania discusses the benefits of a roof garden in a certain town (Jubail Industrial City – Eastern Province – Saudi Arabia) and measures the trust of the citizens in this practice through a detailed questionnaire.
The idea of creating rooftop gardens in high-rise buildings is now becoming a common trend in many countries and green roofs on buildings are becoming mandatory.
Rania say: “In some countries, for example, in Japan, it is a part of the building code to have 20% of your roof as garden, so it is not a matter of personal selection, it is insisted upon by codes and legislation. In the future, companies will not be allowed to construct a building without roof gardens.”
“The use of roof gardening is really rare in the GCC region and as a consequence, we need to educate people about the benefits of roof gardens, whilst making it more practical, convenient and easier for users”
However, green rooftops in GCC countries are still at a nascent stage. As Rania says: “The use of roof gardening is really rare in the GCC region and as a consequence, we need to educate people about the benefits of roof gardens, whilst making it more practical, convenient and easier for users.”
Many GCC countries have yet to consider such measures in construction policies. Although there are several eco-friendly and green building programs, Qatar in particular needs to further improve and develop rooftop gardens. A guiding policy providing standards with supportive regulations can bolster green infrastructure and although planners have a long way to go, if the right combination of new technologies, educational initiatives, community support, and economic incentives align, it is possible that we may soon be able to create a greener, more sustainable future for our cities.
This article is from BQ Magazine’s Issue 43 – April 2017.
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