When it comes to energy efficiency in buildings, the first thought often goes to thermal insulation, a widely used solution to improve a building's insulation and thus reduce its energy consumption. In addition to this traditional system, in recent years, an ecological alternative with a unique design has spread: the vertical garden. This solution, often described as a "green coat," wraps the facades of buildings with a layer of vegetation. Thanks to their structure, vertical gardens contribute to the thermal insulation of the building. In this article, let's see how.
To fully understand how a vertical garden can function as insulation, it's essential to start with the basics of thermal insulation. In simple terms, thermal insulation is a fundamental process that maintains the internal temperature of a building as constant as possible, minimising heat exchange with the outside. This results in cooler indoor environments in summer and warmer ones in winter, and a significant reduction in the need for artificial heating and cooling. To achieve insulation, it's important to choose insulating materials with high-performance heat resistance, such as fibreglass, rock wool, but also panels made from natural fibres or recycled materials.
The basic principle of a vertical garden as thermal insulation is to create a natural barrier against extreme weather conditions. This vegetative layer prevents direct sunlight from heating external surfaces, reducing overheating during the summer months and keeping indoor spaces cooler. Additionally, plants release water vapour into the air through the process of evapotranspiration. This natural phenomenon helps cool the surrounding environment. When water evaporates from the leaves, it takes heat from the environment, functioning similarly to a natural air conditioner. Finally, the substrate in which the plants grow provides additional thermal mass that helps stabilise the internal temperature. According to a study conducted by ENEA, the national agency for new technologies, the installation of green facades on buildings can lead to a reduction in the city's air temperature of about 1°C. Furthermore, the same study found that such green coats can lower indoor temperatures by up to 3°C.
To select suitable plants to function as thermal insulators, it's important to consider various factors such as resistance, maintenance, and water retention capacity. Some species, such as Sedum, Lavender, and Rosemary, are particularly suitable for vertical gardens due to their robustness and low water requirements. Additionally, climbing plants like ivy, wisteria, and vine are excellent for covering large vertical surfaces. These plants not only create dense foliage that helps shade walls during the warmer months, but also offer a natural barrier against cold winds in winter, further improving overall insulation.
One of the most significant benefits of vertical gardens is their ability to reduce energy consumption. Acting as an additional insulating layer, they reduce the need to use internal air conditioning systems, leading to significant annual energy savings.
In addition to energy benefits, vertical gardens also improve the quality of life for building occupants. Plants enhance air quality, reduce external noise, and provide a relaxing, green view, which can be particularly valuable in densely populated urban contexts. Additionally, daily visual contact with greenery has been shown to reduce stress and increase overall well-being.
