Green Walls

The environment is getting ever more damaged as cities become denser. According to a United Nations forecast seventy percent of the world population will be living in cities by 2050. Denser living environments bring with them several detrimental consequences associated with air pollution, reduced urban biodiversity, degraded air quality and noise, traffic congestion and more waste. 

Therefore, the design and construction industry are crucial businesses to improving the challenging situation. By using solar passive design techniques, energy efficient building materials, being aware of technological developments in energy efficiency, and better integrating nature into the world’s ever expanding cities, the built environment will be going towards a more sustainable and healthier future. Lets then focus on the benefits of integrating nature into urbanisation's in the form of green walls. 

In order to understand the green walls advantages, the context and concept should be explained. It is unknown when people started to keep plants in cities for their beauty alone, but over 2500 years ago the famous Hanging Gardens of Babylon were constructed for this reason. Since that time, to grow climbers on the exterior walls of buildings was a common practice. However, these plants rarely reached more than two storeys high. Green walls as self-sufficient vertical gardens that are attached to the exterior or interior of a building have currently been reaching much greater heights. The reason relies on the modern technologies that are used as supports. 

SYSTEMS

These structural supports that allow the plants roots to grow are what differentiate the ancient techniques from modern green facades. Basically, the plants growing in these gardens receive water and nutrients from within the vertical support instead of from the ground, resulting in much higher green facades. This system to attach plants to walls of buildings and homes has includes many different methods:

• Modular systems - a container filled with a growing medium that is attached to the wall;
• Industrial Felts - placing plants root into the fibrous material, with water and nutrients being delivered through the layers of fabrics; 
• Green Façade - a structure that is attached to the side of a house or building that allows plants to grow from the ground up or from planter boxes; and 
• Active system - also known as Biowalls, can be connected to air conditioning systems;
• Passive system - stand alone systems which deliver fresh air in their immediate area.

BENEFITS

Besides being so different, all this different methods have common benefits regarding the environment and its residents. 

Firstly, space saving benefits can be significant if putting gardens vertically which result in very little floor space. This can be advantageous for city apartments, city terraces and small urban development where space is not abundant and each square metre used can result in severe economic burdens.

Secondly, insulating properties with green-walls can regulate internal temperatures within the building. This results from the relatively constant temperature in the small cavity between the green-wall and the host wall.

Thirdly, growing plants directly on the west wall will regulate temperatures and result in energy savings. The effects of evapotranspiration of green-walls (cooling effect of plants transpiring) can reduce the heat of buildings in hot climates by almost 10oC which can significantly reduce the energy consumption of a building by reducing the need for air conditioning. In cooler climates, there is always the opportunity to select species that allow shade during warmer summer months and that allow solar penetration during winter months where there is leaf loss. This benefit is a very significant one as it lowers greenhouse gas emissions.

Fourthly, increased Green space in the urban environment will reduce the Urban Heat Island Effect . When plants are replaced with urban surfaces such as buildings, asphalts, rooftops, and concrete a phenomenon known as the urban heat island effect is created. This effect relates to an elevation of temperature relative to the surrounding rural or natural areas which generates an additional demand on energetic systems such as air conditioning and refrigeration. By planting vegetation in these urban forms the evapotranspiration explained previously will global warming could be mitigated. Studies have found urban air temperature of up to 12°C higher than surrounding areas and also demonstrated that during summer non- vegetated areas could exceed vegetated areas in temperatures of 25°C. 

Fifthly, living walls can reduce noise pollution. Beside leaves being bad sound absorbents, plants and their planting medium are not. Plants and trees have been used for years as barriers against traffic and other urban noise pollution and can be found worldwide. As these systems have good phonic qualities they can be used to absorb sound waves, to reduce sound reflection from the hard surfaces of roads and buildings and to improve the acoustic of places such as increasingly denser cities. In addition they help to absorb the echo bouncing off buildings, dampening the loud sounds found in modern cities. Therefore, by containing such a large number of plants, green walls the acoustics of the interior of a building can be largely enhanced.

Sixthly, green-walls act as a biofilter that captures and denatures pollutants known as VOC’s (Volatile Organic Compounds), improving air quality. According to modern scientific research, indoor environments may be as much as ten times more polluted than the outdoor environment. Also, the average person spends over 90 percent of his or her time indoors (American Physical Society 2008). Therefore, improving indoor air quality is fundamental for a good healthy environment. Not every plant is good for indoors however certain species are really good absorbents and removers of pollutants from indoor air. With the right plants composing the green wall and releasing energy-rich oxygen, indoor air quality is substantially improved.

Seventhly, plants from the living wall can be used to purify slightly polluted water such as grey water and stormwater. Having stormwater or grey water penetrating through a green wall system can lead to a near total elimination of pollution before being released back into the surrounding environment. This process results from the filtering done by the roots and its living microorganisms which break down, remove heavy metals and utilise the dissolved contaminants of the water before releasing or recycling it.Therefore, green walls contribute positively to urban hydrology and inherent sustainability by recycling, reusing, and not unnecessarily using potable water.

Eighthly, green walls increase the value of your property by adding a real green component to the building. Living walls are great marketing tools as they can be used to promote a company’s green image. In addition, a living wall can increase property values as it is a unique trend and a unique way of greening interior spaces and exterior landscaping. “It has been proven that by having greenery in retail shops, malls, restaurants, cafes, bars and other businesses, the number of patrons increases” (Green over Grey 2009). By feeling more relaxed and less stressed, some studies assume that occupants will probably remain longer and spend more in order to extend that feeling.

Ninthly, Living walls can be viewed as mini ecosystems  and thus can be considered as a factor to increase the urban biodiversity. Depending on the selected species, these ecosystems can support many beneficial organisms such as butterflies, bees, ladybugs, and humming birds, returning nature to the urban environments. It has been proved that green roofs increased flora and fauna species and it is expected the same results for vertical landscapes. There is now also another possibility: growing food on living walls . Although it is not commercial available it is a possibility that some architects, designers and enthusiastic are considering, which would improve even more the cities environment and also the city residents quality of living.

Lastly, what the undoubted aesthetic appeal of a green surface can do as a therapeutical mechanism. With the increasing noise and pollution the urban environment became a well of stress and discomfort. This is not considered healthy and it has a profound impact on the physical and mental wellness of the population. Green walls became the connection between man and nature that was missing in the modern concrete jungle. It is yet not known why plants transmit such a peaceful energy. However, it is suggested by some that the reason relies on the biophilia hypothesis. This hypothesis suggests that there is an instinctive bond between human beings and other living systems such as plants. Although it has not been proved, it has been confirmed that plants help people to feel more relaxed and focused, which leads to an increase in productivity, creativity, idea generation, and problem-solving capabilities.

COSTS

Besides all the benefits mentioned above, green wall will always need some maintenance and costs. By designing a building with previous knowledge of such techniques, costs for pruning, feeding and watering would still apply, but some maintenance costs could be reduced. Early considerations with accessibility and good connections to the mechanical ventilation systems are an example of those costs. Another costs saved are the energy costs due to isolative properties and material costs. As such, integrating these walls in the early design stage contributes for a better efficiency of the building, minimises costs and maximises benefits.

TO THINK ABOUT

Concluding, the successful cases of living walls in France and Japan have been inspiring many in the modern days to consider this technology. Green walls are an emerging technology with undoubted environmental, social and economic benefits. This systems control extreme temperature inside the buildings, positively improve temperatures outside the buildings, ameliorate the urban heat island, significantly improve air quality, recycle water, lower building energy bills, and even offer pleasant, relaxing and healthier spaces. Due to its positive benefits and as an innovative and healthy way of bringing nature to the built environment, green tools such as the Australian GreenStar ,the North American LEED and many others worldwide have been crediting buildings that integrate this type of technology, in order to promote good design practices. 

Wouldn't this be advantageous for the hotel industry?