Sustainable construction approaches are gaining increasing interest in the building sector, with many innovative active and passive methods based on novel materials and technologies explored in recent decades. Green roofs are easily-introduced ways to improve biodiversity and curb carbon emissions in urban areas.
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Improving the Sustainability of Urban Areas
Urban growth demands the provision of suitable domestic dwellings, commercial buildings, and infrastructure. Conventional construction, however, plays a role in climate change and increasing environmental damage due to the carbon-intensive processes and materials used in building projects.
Renewable energy is playing an important role in the decarbonization of power grids and urban areas, with photovoltaic solar panels increasingly becoming a commonplace sight on urban rooftops across the world. Alternative materials such as recovered steel and low-carbon concrete have been explored extensively in new and retrofitted construction projects.
Alternative strategies inspired by nature have piqued the interest of researchers, industry, and consumers in the past few decades. Biophilic design, where buildings include elements such as plants, natural ventilation, and natural lighting, aims to improve the sustainability of construction and urban areas whilst connecting inhabitants with nature and improving their physical and mental health.
Amongst the various biophilic design options available to homeowners and architects, green roofs have gradually gained popularity. Constructing these green options either in new builds or retrofits requires several factors to be taken into account, but a well-designed green roof can bring vast benefits for homeowners and companies.
Building a Green Roof
Before installation, key factors which can affect the efficiency and quality of green roofs must be considered. Extensive green roofs can weigh a lot; therefore, the structural integrity of the roof they will be installed on needs to be comprehensively assessed to prevent damage and safety issues.
Another key consideration is the roof’s angle; flat roofs are simpler, with angled roofs requiring considerations such as water retention issues and how to ensure soil stays in place. Installing a green roof on a flat roof does also need some consideration to ensure water run-off in periods of heavy rain, however. Decking quality and the roof’s ability to manage waterproofing capacity and load need to be evaluated.
Layers and Components of Green Roofs
The first layer which is installed on a flat roof is the waterproofing layer or root-proof membrane. If the roof already has a waterproofing layer, it is not necessary to install one. Then, a root barrier is installed to help prevent roots from infiltrating the roof structure and causing damage to the building.
After the waterproofing and root barrier layers are installed, a water drainage membrane, which can be as simple as a layer of pebbles, is essential to allow stormwater to drain away from the roof and into any guttering. This also prevents the over-saturation of vegetation. Additionally, water storage mechanisms must be incorporated into the green roof’s structure to ensure that plants get the water they need.
The next layer is a filter layer. This prevents debris, substrates, and soil from blocking the drainage membrane, preventing over-saturation, improving efficiency, and mitigating the risk of structural damage. Polypropylene, geotextile fleece, and breathable roofing felt are suitable materials for filter layers.
An optimal growing medium is an essential part of the system, ensuring the growth of vegetation whilst ensuring that nutrient levels are controlled to prevent overgrowth. Substrates must also allow sufficient drainage. The vegetation layer can then be installed once all these elements are in place.
Different plants can be used in the vegetation layer, depending on the load-bearing capabilities of the roof structure, drainage capacity, and the individual’s preferences. Vegetation can either be placed in pre-vegetated trays and mats or directly planted. Succulents and wildflowers are suitable choices for green roofing installations. Finally, a frame is installed to contain the vegetation, but this frame must not block run-off.
Green Roofs – Benefits
Green roofs have several environmental, economic, and societal benefits. Whilst the initial cost of converting a conventional building roof to a green option may be prohibitive for some homeowners, over time the benefits can far outweigh the drawbacks associated with this economic outlay.
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Plants are a natural carbon sink, reducing the amount of atmospheric CO2, thereby helping to remove this greenhouse gas from urban areas and playing a small part in mitigating the effects of climate change. Green roofs can also improve air quality by absorbing air pollution, such as exhaust and industrial emissions.
Green roofs also reduce temperatures on the roof, improving the efficiency of solar panels and reducing the need for air conditioning in warmer months. This has the effect of reducing energy consumption in urban areas, which limits the need for energy generation and, consequently, reduces carbon emissions. Additionally, green roofs help to insulate houses in the winter, reducing energy consumption in colder months.
In summary, the lifespan of roofs can be increased, vegetation provides protection against erosion and fire, green roofs promote biodiversity, ambient noise can be reduced inside dwellings, there are increased feelings of well-being for inhabitants, and a green roof can increase a building’s value.
Green roofs are an environmentally friendly biophilic design option for homeowners and commercial building operators. Increasing vegetation in urban areas and promoting a connection with nature have vast mental and physical health benefits for urban populations, and green roofs can have significant economic benefits as well.
Constructing a green roof is a simple process, but certain key factors such as drainage and structural integrity must be considered before a project is undertaken. This article has provided a brief overview of how to construct a green roof and the many benefits it can bring to the growing world population.
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References and Further Reading
Sempergreen (2022) Benefits of a green roof [online] sempergreen.com. Available at:
Clarkson-Bennett, H (2022) What is a Green Roof? [online] greenroofguide.com. Available at: