Vertical greening in urban built environments

Change log
Gunawardena, Kanchane 

To meet the challenge of implementing green infrastructure enhancements to address climate risks in densely built cities, attention has been directed in recent times towards encouraging surface greening approaches. The thesis presented here acknowledged this trend and examined how the typology described as ‘vertical greening’ contributes to this climate resilience enhancement of urban built environments. The project engaged with case study-based quantitative measurements and simulation methods to answer research questions concerned with the microclimate modification and resultant energy use influence presented by installations, in building-scale sheltered environments (e.g., an indoor atrium and a semi-outdoor court), and outdoor neighbourhood-scale canyon environments. It also engaged with qualitative interview and observational methods to address concerns related to the maintenance and sustainability of wider application of installations.

The key monitoring findings from temperate climate sheltered applications highlighted hygrothermal and airflow modifications to be most apparent within the 1-2 m proximate zone, with other phenomena typically introducing airflow mixing to disrupt influence distribution. The potencies of these were relatively modest, and less than those presented in the literature for outdoor installations (maximum mean air temperature reduction of 0.3 K and relative humidity increase of 5.5% at the indoor atrium study, in contrast to 0.9 K air temperature reduction and 13.7% relative humidity increase at the semi-outdoor court study). The modifications nevertheless presented thermal sensation and diversity opportunity to occupants as a significant benefit. The building-scale simulation findings of the same temperate climate case studies highlighted these influences to contribute to thermally moderated microclimates. For the semi-outdoor court this translated to surface flux reductions, with living wall application offering the most (84-90%), followed by green façade application (37-44%). Such reductions could translate to energy use savings if the occupied environments implement mechanical cooling. This was exemplified by the indoor study simulations, where a net annual energy consumption saving for the atrium zone was estimated (69% with living wall and 71% with green façade application). The neighbourhood-scale simulation results also demonstrated widespread outdoor application to have improved the thermal climate of street canyons to benefit pedestrians (summer daytime cool island occurrences increased by 39% for central urban and 3.4% for suburban canyons), as well as present annual net energy use savings to the canyon buildings (between 0.8 and 5.2%). These benefits were pronounced most for the central urban than suburban context, while living walls presented greater influence than traditional green façades in both urban backgrounds.

The synthesis of both observational and simulation findings broadly supports the wider applicability of such installations in densely built temperate climate cities; with the thesis discussing concerns and making recommendations for installation designers. Furthermore, the project presents two novel model coupling pathways for assessing building and neighbourhood-scale vertical greening influence, which would enable urban planners, architects, and installation designers to expediently utilise this typology of green infrastructure to enhance urban built environments and benefit the health, comfort, and wellbeing of their ever-growing occupant populations.

Steemers, Koen
Environmental Design, Green infrastructure, Sustainable architecture, Vegetated architecture, Vertical greening, Vertical greening model, Living walls, Green façades
Doctor of Philosophy (PhD)
Awarding Institution
University of Cambridge
EPSRC (1930753)
Engineering and Physical Sciences Research Council (1930753)
The work described in this thesis was funded by the UK Engineering and Physical Sciences Research Council, doctoral studentship 1930753.