In 2013 ArchDaily published the article “Can We Please Stop Drawing Trees on Top of Skyscrapers,” - its author was frustrated by rampant greenwashing. If you wanted it to look sustainable, you’d just have to put a tree on it. Plants have always been an effective marketing tactic to appeal to the environmentally conscious, but as soon as they are photoshopped in, they are often discarded at the first whiff of value engineering. Given the voluminous flurry of vigorous commentary and debate following that publication (2013, 2016, 2016) it is clear there is something that persists, perhaps a widely felt instinct that in truth, our urban “landscapes” are unsustainable, and often unlivable. Our cities not only take advantage of the ecosystem services of far-off forests and groundwater to support our carbon production, air pollution, and water wastage, exhausting arable land to feed our increasingly urban populations but simultaneously create urban areas devoid of life that increase our carbon footprints and negatively impact human health and well-being.
Currently, the Tallinn Architecture Biennale is also asking architects, designers, and thinkers from around the world to rec-consider our relationship to food. Beyond such alternatives as 3D printing meat, there is a direct and embedded relationship between food and agriculture, between food and growing plants, and rather than growing them in far-flung corners of the world, growing plants in and around the places we live. But there is a difficult relationship between urbanism, buildings, and “nature” whether cultivated or wild. Even though skyscrapers may not be built for trees, there is some grain of truth we hold onto that the concrete jungle isn’t always the proper jungle. We still strive to incorporate more plants, somewhere, somehow. There is increasing acknowledgment, both in the scientific community and the general public that natural systems have evolved far more advanced means of sustaining life than we can even imagine engineering, and therefore we might more wisely design with the intelligence of living systems as opposed to continuing to try to replace them with mechanical and chemical systems.
But how do we bridge the disconnect between an imagined future of living urban landscapes and the realities of creating spaces where plants will thrive and still operate within the tolerances of the building industry as we know it? There is just as much excitement for these systems as there is skepticism, and just as much danger in wholly embracing them as in rejecting them. As interest in Building Integrated Vegetation (BIV) expands across stakeholders, from clients to communities, architects require methods of evaluation that can better articulate the value proposition and enable actionable decisions on their implementation. Before we continue to make what might be baseless claims on their anticipated performance and contribute to market-based greenwashing, thereby further engendering distrust in the potential of BIV, we require accurate data and valid ways of interpreting that data. If not adequately characterized, there is a risk of introducing unfounded claims about these systems, or potentially worse - handicapping what could be more effective solutions.
In an article recently published by the American Society of Heating Cooling and Refrigeration Engineers (ASHRAE), Yale CEA and collaborators have been examining how to qualify and quantify multiple system types of building-integrated vegetation. Research into plant-based living systems has a long history, from the use of algal systems to produce oxygen or food for the aerospace industry since the 1950s, to more recent plant-based systems for gray and blackwater remediation and energy production. Beyond aesthetic gardens, these systems are meant to be performative: to contribute to clean air and water production (bioremediation), thermal comfort, and energy reduction (insulation and evapotranspiration), among other factors of human health and well-being, both physiological and psychological. Many different systems have been measured and tested for a particular performance, but how they are measured, what parts of the system contribute to which functions, and what functions are valued are as diverse as the stakeholders involved in the various sectors of the built environment process. What occupant values in having plants in a building can range from supplying adequate food to improved immunity and executive functioning skills from remediating Volatile Organic Compounds (VOCs) within the air stream of a mechanically ventilated office. Meanwhile, a building owner might be more concerned with potential energy reductions from the insulating and cooling effects of green walls and roofs, and an employer might be most concerned with employee productivity and job satisfaction. All of these factors combined add up to substantial benefits across the spectrum, but impediments remain, particularly with respect to perceived maintenance challenges.
System designs are so diverse that we cannot make blanket statements about vegetation in buildings without getting into the specifics of the design. Building Integrated Vegetation can refer to exterior surfaces (walls and roofs), interior landscapes, indoor green walls, or other instances. These systems each have a vast spectrum of potential remediation benefits, with their own structures, layers, and assemblies: exterior living walls (where plants grow in modular trays or continuous systems) are different from green facades (trellises or climbing plants whose roots are in the ground or planter boxes). Green roofs can be intensive with less soil and sedum-type roofs to extensive roofs and balconies capable of supporting trees. Indoor systems too range from potted plants which may have little to no air cleaning value, to various systems which draw air through the growing media for bioremediation of toxins, either using stand-alone fans or connected to building HVAC systems. In a series of novel explorations, we have also been investigating the potential for a vegetated building envelope that operated as a mediated boundary between indoors and outdoors in certain climates. It is early days in the research and development of these techniques, and like many alternative technologies that make a claim to boost future sustainability, there have been exaggerated and under-substantiated claims both for and against, their potential effectiveness. However, one thing is certain: to lump them all together is causing far more confusion about their performance than providing answers.
Currently, vegetated systems are compared to their mechanical counterparts: in terms of air quality, indoor systems are compared with mechanical ventilation or filters, and in terms of thermal comfort and energy calculations, external systems are compared to other types of insulation. Stemming from a classical scientific method that tends to measure and respond to one variable at a time, mechanical systems can be efficient for their individual functions (ie thermal comfort or air quality). Research investigating these systems follows suit, reporting on specific metrics defined by particular evaluation methods. Yet, in context, we know these systems to be ineffective, energetically or materially intensive, and the source of other unwanted byproducts. Following in that mechanical tradition, architectural legislation often specifies that systems respond to specific efficiency rates. As architects, we know that the delivery of the built environment is not the delivery of a series of additive systems, each specific to its function, but the design of whole interdependent environments. Narrow efficient performance evaluations can stifle novel innovations which seek more effective holistic architectural solutions.
So what if we were to combine performances? What would it mean to evaluate plants not just on their ability to sequester CO2, metabolize indoor air pollutants, or provide insulation (and then compare those to conventional mechanical and material techniques); what if we were to compare vegetated systems on their ability to do all of the above? And further, including the functional outcomes, we cannot achieve with non-living systems, such as producing food or combating depression related to a disconnect with the natural world? Would the same design, or different aspects of the same vegetated system combined, be able to offset more conventional methods? Establishing more effective frameworks for valuing BIV systems requires a shift towards more comprehensive metrics, including life-cycle analysis, various health benefits, or other social values, which could offer a more holistic picture of value.
With support from the EPA and the National Science Foundation, Yale CEA and collaborators have been developing a body of research able to support the design and construction industries that incorporate the effective benefits of adapting buildings and cities with BIV and their biological components, assessing the outcomes of integrating vegetation systems in wall and roofs which are symbiotic with the current anthropocentric built environment systems. Along with the United Nations Environment Programme (UNEP) we have begun to develop BeyondUrbanAgriculture.org, a platform to bring together the world’s leading researchers cataloging the multiple potential impacts of BIV and to translate them in ways that will be accessible to architects and designers. The aim is to provide designers with appropriate methods for evaluating evolving BIV systems, capable of estimating the compound benefits of working with plants and living systems at the scale of the built environment.
At Tallinn, the benefits of adaptation of living systems and their biological components are displayed as mockups of potential modules for active green walls - symbiotic forms and systems for the built environment. These modules are novel, low-tech building components in the form of planted ceramic bricks as structural infills for growing plants including agricultural species. Unlike energy-intensive mechanical systems that provide efficient performance for indoor environmental quality alone, these BIV systems have the potential to operate on multiple levels. This installation demonstrates a series of modules that could redefine the exterior envelope, not only as a performative tool to improve air quality, but could also regulate local temperature, and provide nutritional benefits for the building inhabitants.
