In our rapidly developing urban environments, the fight against climate change is more important than ever. Accelerated urbanization has brought with it the expansion of concrete and asphalt constructions, replacing green spaces with rigid and sterile surfaces. This transition has turned cities from natural and green areas into a gray environment of urbanization, bringing a number of problems such as overheating (Urban Heat Island Effect), air pollution, flooding and loss of biodiversity. As cities expand and our carbon footprint grows, the need for sustainable solutions becomes more pressing. One of the most promising strategies is harnessing the power of nature in urban areas.
By integrating green facades and other urban green infrastructure, we can transform our cities into resilient and green environments that actively combat climate change.
The Heat Island Effect
Green walls and facades, elements also known as plant walls or vertical gardens, represent an innovative and aesthetic way to transform the urban environment and integrate nature in the midst of city constructions. This concept goes beyond simple decoration with plants and ends up having a profound impact on the way we perceive and interact with the cities in which we live. In this context, green walls and facades represent an ingenious and indispensable solution to these problems; they are real oases of nature in the middle of the urban jungle, bringing with them a multitude of benefits. By integrating them into the urban landscape, we can regenerate cities, giving them a vibrant, colorful and life-like appearance.
The rich aesthetic valences of green walls and facades bring a vibrant and fresh touch to the urban landscape, transforming monotonous buildings and structures into living, colorful surfaces. Plants growing vertically on the walls create a special dynamic shape, playing with light and shadow, and give buildings a contemporary and innovative look. These green constructions have a number of ecological and economic benefits:
Pollution reduction, air filtration
Plants absorb CO2 from the air, turning it into oxygen through photosynthesis. Thus, it contributes to improving the air quality in the city and to a healthier environment. A green wall of 1 m2 can remove an average of 2.3 kg of CO2 from the air in one year [1]. According to a study by the Universities of Birmingham and Lancaster, UK, careful placement of green walls could reduce concentrations of nitrogen dioxide and microscopic particles by up to 40% and respectively, 60% at street level[2].
Role of trees & other green infrastructure in urban air quality
Another study suggests that building green walls in urban areas could reduce pollution by up to 30% [3]. Green walls can also help improve air quality, both indoors and outdoors. About 25% of carbon emissions generated by human activity are absorbed by plants [4].
According to a study published in MDPI, green roofs and walls could reduce the air temperature in a city by up to 11.3 °C and could reduce thermal transmission in buildings by up to 0.27 W/m2K [5]. Green walls can also reduce the temperature fluctuation at the wall surface, which, over time, can damage the facade of a building. [6]
Energy saving, thermal insulation
Thanks to the thermal insulation properties, these arrangements can lead to significant energy savings, reducing the need to use air conditioning or artificial heating. According to the American Society of Landscape Architects, green walls can reduce energy costs by up to 23% [6] during the summer, by shading the building and reducing indoor and outdoor temperatures (a reduction of approx. 5 °C of the internal temperatures of a construction) [7].
Sustaining biodiversity
Vegetation provides a favorable environment for various essential creatures such as butterflies, pollinating bees and birds. These creatures find food and shelter in the green walls, thus supporting the diversity of species in the urban environment and the formation of unique ecosystems in the city. Increasing urban biodiversity not only supports local ecosystems, but also strengthens overall environmental resilience, making cities more adaptable to the challenges of climate change.
Sound insulation, noise reduction
Due to the dense foliage and irregular shapes of the plants, green walls have properties of absorbing the surrounding noise. Plants absorb sound vibrations and disperse the waves in various directions, helping to reduce the noise level. Can reduce ambient noise levels by up to 40 decibels[8], this being a significant benefit for urban areas with congested, noisy streets.
Psychosocial effects
Walls with vegetation can intensify feelings of happiness and increase productivity, satisfying our
innate need to be connected to nature, a phenomenon also known as ‘biophilia’. Introducing natural elements into monotonous urban environments can improve mood, focus and promote a positive outlook.
A recent study published in Frontiers in Ecology and Evolution found that the installation of green walls in urban areas can provide multiple ecosystem services beneficial to people’s health and well-being, with these structures contributing to improving public health by providing a range of benefits such as reducing stress levels, improving mood and cognitive function. Also, people who work or live in areas with a high proportion of green walls or roofs have better mental health, recover faster from illness and are more productive at work [9].
Increased aesthetic value
Green walls and facades bring nature into the city, reducing theurban monotony of concrete surfaces. It contributes to the aesthetics and more pleasant atmosphere of the urban space, offering an attractive and relaxing appearance.
Regarding the contribution of green walls to optimizing the aesthetic value of the environment, research has shown the increase in perceived visual quality with a high percentage of vegetation [10] and with the presence of color contrasts. There is also a positive correlation between visual preferences and a medium to high diversity of plant species and their color
composition (eg complementary colors).
The Main Types of Green Walls and Facades
Green wall and facade systems can be realized in different ways, and the concept of green walls is divided into two main categories: green facades and living walls.
Green facades
Represents the traditional greening of walls and is based on climbing plants. The plants are connected at ground level, planted in the existing soil or in a special substrate near the walls. This system allows plants to develop their roots and benefit from water and nutrients from the soil. Different types of climbing plants are used with the ability to give a natural and vibrant look to the buildings: ivy (Hedera sp.), Russian vine (Fallopia sp.), Virginia vine (Parthenocissus sp.) and wisteria (Wisteria sp.). However, many other climbing plants can be very decorative, including clematis (Clematis sp.), honeysuckle (Lonicera sp.) and jasmine (Jasminum sp.).
According to the fastening system, green facades can be:
Facades with autonomous climbing plants
Climbing plants capable of growing and clinging to the wall without a special support are used. Plants have their own hanging and holding system, providing a simpler and more natural solution.
Green facades with special support
Climbing plants require a special support (netting, wire, trellis) to cling to the wall and climb. As they grow, the plants gradually cover the entire height of the facade, offering a spectacular and natural look.
Living walls installed in a modular system
Represents a more complex solution, involving modular panels and irrigation systems. Pre-built panels are used, provided with compartments or pockets where plants can be placed and grown.
Each panel has its own drainage and irrigation system, ensuring the proper amount of water and nutrients. The panels are easy to install and adapt to different sizes and architectural requirements.
System Design Recommendations
When designing green wall systems, it is essential to conduct thorough research and planning to ensure that the installed system will perform properly. It is recommended to analyze the area where the green wall will be located in order to identify all the additional requirements it may have, so that it can develop properly.
When choosing plants, several factors are taken into account, and the selection must be made carefully, according to the project specifications. Light and shade, location, wind, temperature and rainfall must be considered to determine whether plants will have enough light and water to grow or whether regular watering or an irrigation system is required.
The most suitable type of green wall system for the application must also be chosen, it’s important that the system selected meets the needs of the project. For example, a modular system may be the best option for a project where instant greening is required, while a stainless steel trellis system may be more suitable when cost and environmental factors are more important, as these systems are typically more cost-effective, require less maintenance and are fully recyclable at the end of their life.
It is essential that thorough research is carried out to ensure that the retaining wall/ structure has the capacity to support the weight of the green wall once it is fully planted, and engineering calculations may be required to determine the safety of the project.
The need for maintenance of different types of plants and systems must also be considered: once a green wall has been installed and the plants are established, it is vital that it is maintained to keep the plants healthy.
Fire Resistance Of Green Walls and Facades
Considering all the benefits, it is also necessary to consider the challenges that the introduction of green walls creates for the safety and insurability of the building in which they are installed. In the past, the solution was adopted in the form of small decorative areas on buildings, but now it is proposed for much larger areas, covering an entire facade or even all the walls of tall buildings. This fact explains the current increased level of interest in addressing the potential implications of vegetated building surfaces in case of fire.
Nowadays, green wall designs are enjoying increased popularity; however, when not well maintained, they can be a significant fire hazard. In many European countries there are still no up-to-date building laws and no fire safety procedures for green walls and facades. It is therefore recommended that systems are fire tested and that appropriate policies and regulations are in place.
Plants and greenery are often thought of as fuel for a fire. However, according to European fire studies, vertical gardens and green walls have a sufficient degree of fire safety, provided they are properly maintained. The key is to ensure regular pruning and maintenance of the plants, the vegetation must remain hydrated, the correct operation of the irrigation system must be checked frequently, and it is important to use low combustible materials in the system (eg using soil, substrate with high water retention, within a green wall fire protection system can help further protect the area).
In an age where urbanization has reached unprecedented levels, facades and living walls are becoming more and more necessary; they represent effective and aesthetic solutions for greening and improving the appearance of buildings, contributing to increased biodiversity and reducing the impact on the environment; represent a sustainable solution for ecological constructions and are an essential innovation that can be successfully integrated into contemporary urban strategies.
