Vertical Green. An Environmental Solution to Improve Thermal Behavior of Timber Buildings

The use of installation of vertical green systems (VGSs) on buildings envelopes can be evaluated as a shielding element which may increase energy efficiency, human comfort levels and may have many other environmental benefits. Examples of use of green envelopes are green walls and green roofs. Green walls started to be implemented in the last decades due to fast urban growth, and the lack of space to design new green areas. They became a solution to increase the green density in urban areas and improve the air quality. Beside this, VGSs offer benefit in term of thermal performance under different climate conditions. VGSs installed in individual buildings can provide cooling in warm weather being an insulator and decreasing the need for heating thus saving energy. Installed in a group of buildings, VGSs can lower the buildings surface temperature preventing the urban heat island effect at the urban scale. Their effectiveness is however influenced by the site and the installation system. In the former case, the efficacy may depend by the surrounding environmental parameters, wall orientation, and windows existence, in the latter by the type, number, and extension of the implemented system, substrate layer composition, type of plant species, etc. Analyzing feasible VGSs to be installed on existing buildings, the literature offers different construction types. They can be defined as direct, which means the plant climbs on the façade, or indirect, which means plants climb on a trellis, cables, or mesh. These last structures can be designed with other materials and technology to support the panels where the plants climb. In the cases of large structure as Living Walls, the construction material can have big importance since the whole wall cover may consist of modular panels. An environmentally sustainable way to improve the system design can contribute to reduce the environmental burdens while benefit from the system capabilities as much as possible. Furthermore, the performance of VGSs depends on the types of structure that will be assembled on the wall. Timber can be used as a more sustainable and environment friendly material instead of common ones in the market. For instance, the supporting structure for climbing plants, planting containers and pots, studs as attachment profiles to existing wall could be substituted with wood material. In the manufacturing stage of these panels, wood can be a more sustainable method to be implemented on existing buildings among other possible materials (e.g., aluminium, steel, and plastic) because of its low CO2 emissions. Even though the main part of emissions is caused in the manufacturing phase, it has to be considered its environmental impact in other phases as well i.e., transportation, installation, maintenance, and disposal. In addition, at the end of life in its lifecycle, VGSs mounted on timber panels structures could be a more sustainable choice than other materials since they could be recycled or reused thus increasing the service life capability of VGSs components. The Life Cycle Assessment (LCA) is the proper methodology to analyse the impacts of the VGSs construction material and to estimate the performance of the panels