Living green façade systems: contribution to near zero emission buildings

Abstract

With industrial revolution the transport of people and goods generalized. Industries started to be located near raw materials extraction, more for economic than environmental reasons, as this centralization of production increased the average distance of building products from the extraction to the work sites – with consequences on transport energy costs and pollutant emissions. Many building materials result from high energy demanding industrial processes. The North of Portugal is characterized by a sprawled territory occupancy, what is problematic due to infra-structures and transport increased costs. This reality has diverse causes: accented topography, division of soil due to multiple transmission of property, small delocalised industry, among others. The generalized access to individual transport in the last decades accentuated this phenomena. More recently, the Portuguese economic context is changing drastically. Energy cost increasing, small industries closing and unemployment are impelling the return to individual means of subsistence, such as poultry. But the urban sprawled occupancy frequently limits access to productive soils and sun exposure. Apart from being very efficient on passive cooling by shading and evapotranspiration, living green facades present very low embodied energy in comparison with other building cooling systems. They allow rainwater retention decreasing the risk of flooding and contamination of rivers and streams. Green facades are still able to create dynamic changes on buildings’ envelope, according to seasonal variations and plant ageing. It is desirable to make use of native plants and agricultural techniques in accordance with its capability to be used in such structures. This ensures the preservation of the cultural and economic values of a region, contributing to the local identity. However, the use and appreciation of native flora has not been sufficiently valued or studied with a view to integrating these vegetable systems. This study comments on some technical aspects of living green façade systems, integrating the constraints that impose vertical live plant. This strategy is especially relevant for South oriented facades, more adequate for plant growing, contributing to reduce heat island effect, lower emissions and even a positive balance by absorbing CO2 due to photosynthesis. Green facades can also contribute to reduce visual impact from buildings on landscape.