Green façades are an under utilised design approach that incorporates vegetated architectural features on outdoor vertical surfaces, enhancing the urban environment and improving both internal and external thermal performance.
The expansion of urban areas has necessitated he loss of green spaces and exacerbated the heat island effect, which can impact the quality surrounding environment, micro-climate, and ecosystems.
There is considerable potential to alleviate this effect with green façades, which absorb heat through evapotranspiration and promote vertical air mixing. However, their adoption and successful implementation have significantly lagged.
Green façades incorporate plants directly or indirectly along a vertical support structure, whereas living walls are built using various continuous, modular, and linear systems. However, these terms are often used interchangeably.
Green façades are made from materials that minimise heat transfer and embodied energy during construction and installation, while also offering effective thermal insulation.
By reducing heat flux, the amount of heat transferred indoors through hard surfaces, green façades can significantly lower a building’s internal temperature.
Numerous studies indicate that greenery in façades can absorb or reflect 40 to 80 per cent of solar radiation during the summer months.
In addition to indoor cooling, vertical greenery has been shown to reduce surrounding air temperatures by an average of six degrees Celsius, with the cooling effect being more pronounced in hotter climates.”
By creating a gap between the foliage and the wall surface, an insulating layer and cooling breeze can be established. Additionally, watering and hydroponic methods enhance cooling through evaporation.
Studies have shown the air gap between a façade structure and the wall face can improve insulation between 10 and 33 per cent, with a five-centimetre gap sufficient for the insulation boost and a gap any wider providing only marginal improvement.
Plant selection is crucial; for instance, deciduous plants, which shed their leaves in winter, allow more sunlight to enter during cooler months, enhancing a building’s thermal comfort.
In addition to being much more cost-effective than air-conditioning, green façades enhance air quality by absorbing car exhaust, reduce noise pollution, alleviate symptoms like cough, fatigue, and dry or itchy skin, and even improve recovery rates for patients with various physical and mental ailments.
The photosynthesis of plants contributes to increased humidity in the air – plants discharge about 97 per cent of the water they take in, leading to a reduction in the occurrence of dry skin, sore throats, colds, and even dry coughs.
Green façades and green areas in general have numerous benefits for human health and wellbeing, particularly for internal façades and green walls, and they also provide opportunities for social interaction.
People spend between 80 and 90 per cent of their time indoors, so internal greenery and biophilic design can be critical to enabling a sustained human connection to nature.
Plants convert carbon dioxide into fresh oxygen, improving air quality, and can also remove toxins from the air we breathe, such as fumes, bacteria, dust, and volatile organic compounds (VOCs) through the natural process of phytoremediation.
Common indoor VOCs that plants help eliminate include benzene, which is found in some plastics, fabrics, pesticides and cigarette smoke; and formaldehyde, found in some cosmetics, dish detergent, fabric softener, and carpet cleaner.
Plant selection again plays a role, but additionally depends on the foliage’s leaf surface area.
Wellbeing benefits also extend to the wildlife spaces are shared with, as vertical greenery can be designed to attract species that improve biodiversity, such as rare or native birds, bees for pollination, and beetles that feed on pests.
Despite the plethora of benefits, widespread adoption has faced several challenges, including maintenance difficulties, design complexities, and high costs.
A study published in the journal Buildings investigated challenges and solutions to green façade implementation, finding 24 social, political-administrative, economic, practical-technical, and environmental barriers that hindered their adoption.
Importantly, the researchers found that the lack of information and knowledge was a key underlying issue.
They proposed solutions developed in collaboration with local stakeholders and experts, including the provision of informative, regulatory, and financial incentives; the adaptation of political-administrative strategies, regulations, and procedures; and support for the practical implementation process through information and expert guidance.
The researchers said: “Even though scientific interest in green buildings has increased, stakeholders, such as policymakers, planners, and construction companies, remain reluctant to promote the implementation of green façades in contrast to other climate change mitigation and adaptation measures with similar potential.
“In light of ongoing social, economic, and environmental challenges, green façades offer manifold potential benefits to create liveable and resilient cities [but] are rarely successfully implemented.
“We were able to identify general implementation barriers, confirm their local relevance in exchange with Leipzig stakeholders and green façade experts, and co- create locally adapted solutions.”
