SUSTAINABILITY MISGUIDED: ARCHITECTS AND GREENWALLS

One of the more recent trends in the sustainability movement that architects have co-opted without comprehensive understanding is the green wall. Often interpreted as a conceptual extension of the green roof merely with different plants and substrate, the two systems are fundamentally different as strategies of sustainability in an urban context. SERA Architects’ recent proposition for the Edith Green (no pun intended) / Wendall Wyatt Federal Building caught our attention (http://www.jetsongreen.com/2010/01/living-wall-portland-federal-building...) as an example of green architecture that warrants a more critical assessment.

Decades of knowledge and practice in basics of sustainability such as thermal insulation, shading techniques, passive ventilation and solar energy have established a clear difference between green aesthetic and green practice. As such buildings that are retrofitted with plants as a form of green branding are a poor substitute for critical assessment of the building’s performance in less visible but more effectual areas effectively reducing a polemic of sustainable practice to visual farce.

Plants do not a green building make. There is nothing inherently natural about plantings in an urban environment, since they subscribe to a host of restrictions that defeat or hinder their ability to thrive and reproduce in the long term. Street trees for example, are spaced evenly along pavements rather than grouped that would facilitate a beneficial microclimate, while their canopies and root systems bear punishment from aggressive pruning and poor growing mediums that creates a differentiated stress.

Trees, in ecological terms are however structural and the backbone of a diversified ecosystem. As such, the hardy species routinely selected that have a better survival rate, help reduce the overall temperature by a few degrees, and may even absorb carbon-based pollution particulate during its lifetime although that repository is re-released when it decomposes.

In a similar fashion, green roofs using sedums and other xerophytic-type plantings are well suited to the more extreme temperature changes and evapo-transpiration loss atop a roof. With their ground-hugging growth form, fleshy tissues, and vegetative reproduction capacity, the supporting integrated reservoir design and alpine-type growing medium perfected in Germany years ago helps to assure a near maintenance free regime. “Green” roofs are not above their own form of contrivance - see (http://www.jetsongreen.com/2008/11/roedovre-tower.html); though often portraying trees and intermediate height intensive-type plantings as variations on extensive, low maintenance sedums.

There is neither a pragmatic grasp of the growing requirements of trees, shrubs and grasses, nor the supportive relationship of plantings to one another. Plants are perceived as little more than a plug-and-play component of a reductive green aesthetic. Returning to the fatally flawed green wall, reports of failed vertical hydroponic systems such as £100,000 living wall at Paradise Park Children’s Centre in Islington, North London, (http://www.architectsjournal.co.uk/news/daily-news/the-paradise-park-fal...) and http://www.thisislondon.co.uk/standard/article-23735279-the-living-wall-... , are visible enough to garner not only embarrassing press, but an industry response from horticultural maintenance services like Junglefy (http://www.junglefy.com/news/who-is-maintaining-your-green-wall.html) who anticipate more cure than prevention practice. SERA Architects’ own project description for the Federal Building project is conspicuously devoid of a description of its living wall concept. (http://www.serapdx.com/project.php?category=1&project=104)

The rule of thumb observed analogously in subjects like recycling and down-cycling is to understand the solution through the context of problem. For manufactured items it’s the recognizing the whole lifecycle; from the production, through usage and disposal. For plants proposed as a substitute for an energy efficient curtain wall, one must ask to what end. Firstly plants with modified stems like vines and creepers tend to grow in a companion condition with trees and shrubs, using the stems for support while benefiting from the controlled temperature and reduced exposure. In addition nature tends toward biodiversity and monocultures of the same species and similar growth form invariably suffer from pathogen infestations and the inability to compensate for natural die-back during the regular growing season. Plants do not respond in the same way at different altitudes and orientation to the sun. Attached to a building façade, plants bear the added stress of heat radiated from absorbed surfaces. This requires a combination of more maintenance, poorer growth form and shorter life span. Even more horticulturally sound attempts like Patrick Blanc’s green wall for the Athenaeum Hotel in London (http://www.wired.com/culture/art/magazine/17-09/pl_design) reflect a high maintenance hydroponic scheme that ultimately accessorizes the building facade rather than apply the principles of nature. Put another way, because our expectation is one where plants are perceived in a manner used akin to a flower display or supermarket fruit stand with perfect shape, color and free of imperfection, we neither recognize nor appreciate the value of the plants’ collective response their context and the conditions imposed on them. But to do that, we would have to do what is best horticulturally.

We need to create architectural contexts that are adaptive to the growing environments of plants and have a flexible attitude about the seasonal cycle of plants if we want to call our use of plantings truly sustainable. Die-back, changing growth patterns, re-seeding (self-colonizing), etc. should be sources of knowledge for refinement of our neophytic expressions and architects should look to experts in this regard, rather than presume their vision and self-serving rhetoric is well-informed. For buildings designed with plants as part of a comprehensive the surface treatment, we defer to Yuka Yoneda’s pointed commentary, Top Five Green Buildings that Defeat the Point of Being Green, (http://www.inhabitat.com/2009/08/14/top-five-most-ridiculously-greenwash...). Successful implementation of green walls, whether vines growing from the ground up, or modular hydroponics, are scaled in the range of 1-3 stories. Comparatively, rendering of 250 foot buildings or 27 story apartments defeat the obvious tactile and spatial association with plants at the level of the pedestrian.

As Sean Griffiths, director at architecture practice FAT, puts it: ‘I think living walls have become a substitute for having any ideas.’