The green building envelope: Vertical greening

Planting on roofs and façades is one of the most innovative and fastest developing fields of green technologies with respect to the built environment and horticulture. This thesis is focused on vertical greening of structures and to the multi-scale benefits of vegetation. Vertical green can improve the environment in urban areas and is becoming a key design consideration in modern building developments. Vertical greening of structures offers large surfaces with vegetation and at the same time contribute to the improvement of the thermal behaviour of buildings, increased biodiversity, aesthetical and social aspects but also reduction of air polluting substances as fine dust, carbon dioxide, etc. There are different concepts of vertical green to vegetate the exterior building envelope; two major categories can be considered namely: green façades and living walls. Green façades are made up of climbing plants either growing directly on a wall or, more recently, growing indirectly against a wall with specially designed supporting structures, such as grids, trellis or meshes. Living wall systems (LWS) are composed of pre-vegetated panels or integrated fabric systems that are affixed to a structural wall or frame, whereas a hydroponical system is required to maintain plant growth. Living wall systems (LWS) is a relative new technology and rarely investigated yet. One of the multi-scale benefits of vegetation is the accumulation of fine dust particles on leaf surfaces. Dust particles smaller than 10 ?m are mainly relevant in dense urban areas, because they can be deeply inhaled into the respiratory system and cause damages for the human health. Results found during the doctoral study confirm the relation between particle origin, compound and particle number between different environments as the woodland and near a traffic road. Using image analyzing software on electron microscope images as shown in the thesis enables to study and examine dust particles directly on leaves; it is a process which is able to identify particle size and number. The productive approach contrasts with past research methods that identified dust concentration on tree leaves through washing or leaching of leaves to determine particle mass. Another important aspect of vertical greening is related to the thermal comfort and behaviour of buildings. The thermal transmittance (and thus insulation properties as well) of a building is among other things dependant by the wind velocity that passes the surface of the building. A study conducted for different greening systems shows the potential of vertical green layers on reducing the wind velocity along building façades. In the case of living wall systems the insulation properties of the materials used can be taken into account, as well as the air cavity between the system and the façade as proofed with the calculations. In order to study the effect of a green layer on the temperature gradient through a façade better, an experimental set-up was built (climate chambers). The experimental set-up as used, allows controlled measurements with different boundary conditions (temperatures), besides the measurements are repeatable and reproducible. The results show that especially the living wall systems have a positive effect on the thermal behaviour of buildings. Greening of the building envelope with living wall systems considering the materials involved, can has a high influence on the environmental profile (life cycle analysis) as shown in the thesis. Although applying vertical green is not a new concept, it can offer multiple benefits as a component of current urban design. Considering the relation between the environmental benefits, energy saving for the building and the vertical greening systems (material used, maintenance, nutrients and water needed) the integration of vegetation could be a sustainable approach (taking into account all the unquantifiable benefits until now) for the envelope of new and existing buildings