Towards a Definition of Zero Impact Buildings Shady Attia 24) and André De Herde
25)
Abstract There have been several attempts to define zero impact or near zero impact buildings. Most of these are based on measuring performance or on metric benchmarks regarding the quantity or quality of the various resources employed during a building’s life cycle. However, the problem underlying these efforts is that the resources are measured independent of each other, leading to restrictive overall design approaches. Most existing definitions focus on breaking even with a single resource, such as energy, water or materials, during the building’s life cycle. In fact, the building community needs to set a collective definition for what constitutes a zero ecological impact building, conflating all the resources involved. In this paper, we discuss this deficiency and suggest a shift in thinking necessary to define zero impact buildings. The resulting definition allows us to examine broader criteria including land management, carbon neutrality, energy neutrality, water efficiency and material neutrality. This paper reviews existing definitions or perspectives on zero impact buildings in order to redefine a more comprehensive definition of zero impact.
1
Introduction
The Brundtland Report (1987) and the Intergovernmental Panel on Climate Change (IPCC) Report both agreed in describing the current environmental imbalance as one where in: “the human demand on the planet is exceeding the planet's regenerative capacity.” (Solomon, 2007, pp.996). In order to correct this imbalance, current generations have taken on the challenge of better resource conservation and management. Many scholars and committees have analysed how to close the energy cycle of buildings, or for that matter how to close the land, water or material cycles of buildings (ASHRAE, 2008; IEA, 2009; Nadav, 2008; David, 2010; Raymond, 1998; Rovers, 2009). However, these endeavours rate the different resource flows and cycles separately. At the other end of the spectrum, sustainability indicators such as eco-footprint analysis and life-cycle analysis are too broad, too complex and require the input of variables (food, waste, occupant behaviour and transportation) that are beyond building design practice (EEA, 2008).
24) Architecture et Climat, Université Catholique de Louvain, Louvain La Neuve, Belgium
[email protected]; 25 ) Architecture et Climat, Université Catholique de Louvain, Louvain La Neuve, Belgium;
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In fact, we cannot achieve zero impact buildings (ZIBs) without setting a comprehensive definition of ZIBs. A definition that includes all resource cycles during a building’s life will reveal where the potential lies for maximum impact of environmental decisions on the overall life cycle of buildings. We need a definition that is based on metrics and benchmarks and that therefore can lead and guide the design process. It must also be based on a universal benchmarking standard and provide a framework that allows comparison, analysis and a perspective on opportunities that optimize the use of resources. This paper aims to examine and refine this issue, particularly by comparing existing definitions and reviewing them in light of a more comprehensive ZIB definition. Our goal is to provide a defensible and realistic definition of innovative ZIBs that cater to the cradle to cradle (C2C) philosophy (McDonough and Braungart, 2002). The need for clarity has become increasingly important as the ZIB concept has become more widespread. Yet without a universally accepted definition of what zero impact entails, the issue has become confused. Without consistent parameters to determine ZIB compliance there is no way to achieve our sustainable objectives. Without the performance indicators or metrics, the end result is predictable: buildings will continue to be produced on the basis of the same practice that has produced our existing built environment.
2
Existing definitions and perspectives
The following section explores the different resources contributing to the life cycle of a building, in what way these resources are viewed as zero impact, and how this compares to a more comprehensive definition of ZIBs. We should note that determining if a building is truly zero impact is a complex task. Definitions by default are constricting because they are static, while the reality is that buildings and cycles are dynamic.
2.1
Land use
According to the European Union Directive (2005), land is the scarcest resource on earth, making land development a fundamental component in effective sustainable building practice. Worldwide over 50% of the human population is urban. Environmental damage caused by urban sprawl and building construction is severe and we are developing land at a speed that the earth cannot compensate. Buildings affect ecosystems in a variety of ways and they increasingly overtake agricultural lands and wetlands or bodies of water and compromise existing wildlife. Most contemporary cities must deal with surface runoff, surface temperatures, and urban heat island effects, all problems related to intensive land use. When discussing land resource definitions two aspects have to be taken into consideration. The first is quantitative, involving the degree of density – or the ratio of available building land to the building footprint. The second is qualitative and considers the adaptation of site facilities to the building’s context, including the management of site water, heat island effects, habitats and pollution. However, land use policies are still an open area of research at present and lack definition as to the role of land use in achieving zero impact. Current research is more concerned with the classification of existing urban land use, land coverage, spatial structures, including the housing density, the mean housing and plot sizes, and the spatial aggregation of built up areas (Herold and Menz, 2000; Frohn, 1995). 106
Yet ZIB designers require strategies and performance indicators for sustainable land use that guide decision making and the design process that leads to zero impact buildings (Dunster et al., 2008). Designers are looking for ways to integrate buildings into the biotic and abiotic surrounding context, and to conserve material and land resources through optimized use of land including long-term retrofit plans.
2.2
Energy
Energy is the building resource that has gained the most attention within the built environment research community. There are several approaches to achieving zero impact from this perspective: energy metrics (kWh or MJ), boundary balance (net zero) and balance period (monthly, seasonally or yearly). Research has also stated the importance of comparing design data to the monitored data and to quantifying on-site production against on-site consumption. There are also discussions on the energy quality (primary), type (solar, wind, CHP) and storage in relation to grids and transmission. In trying to achieve zero impact through energy reduction, many practitioners have aimed for a net zero energy goal per site, meaning the import into the building must equal the export. However, a zero impact building should mean that a building’s energy efficiency is maximized, therefore taking into account the grid generation and transmission losses, utility emission rates, and utility cost structures.
2.3
Material
Building materials are another limited resource within a building’s life cycle. In contrast to energy and water, materials circulate within a near closed-loop system (Rovers, 2009; Rovers, 2008; Bryan and Trusty, 2008). The regeneration period of most materials used in current building construction is extremely long since they were millions of years in the making. The only renewable building materials are organic materials including wood and bamboo. Unfortunately, little research is being conducted to ascertain the viability and sustainability of using renewable organic materials. There are several tools available that aim to assess the environmental impact of building materials, including Ecobau, Green Guide, EcoBat and EcoInvent. However, most existing strategies follow the cradle to grave approach, with no regard for the existing building stock. The soundest methodology for material use in buildings is described by Rovers (2009). In this definition building designers borrow materials as a credit, which they materialize temporarily in the building stock, and are re-used or further refined in future buildings.
2.4
Water
Water is a key resource that lubricates the building sector as much as oil does. Buildings require water during construction and during occupancy. In fact, water efficiency is like energy efficiency (Sharma, 2009). Water efficiency is a key metric in evaluating building sustainability. As yet, there is no procedure that makes zero water consumption in buildings possible. Nor is there a metric that encompasses the demand for water, seasonal 107
fluctuations, variation across geographies and the potential for harvesting water. There are sufficient methods, programs, and regulation controlling the use of water fixtures and devices in buildings (Arpke and Hutzler, 2005). However, the major problem with these approaches is that they consider water as a revenue-neutral resource. It is therefore important to formulate a definition that not only takes the water life cycle within buildings into account, but also the energy costs and carbon emissions associated with obtaining water. Any water usage metric should consider the energy impact of water usage as a whole.
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The problem of existing definitions
Thus far the role of land use, energy, materials and water in achieving zero impact has been reviewed from a conceptual perspective (USGBC, 2010; Lippiatt and Helgeson, 2009; ASTM 2005). The common procedure is to define the parameters of the definition of a ZIB by choosing a metric and setting a boundary limit. To a large extent most of these definitions aim to reach a balance. However, there are major problems with this. This section discusses the major faults of existing definitions from a technical standpoint along with an examination of the relevant characteristics of the zero impact building philosophy. The primary problem that has weakened previous attempts to define a zero impact use of resources is the tendency of researchers to deal with every resource separately, regardless of the total CO2 emissions. In fact, sustainable building design should aim to optimize the use of all resources. More importantly, each and every resource used in the building has a history of energy consumption behind it: the energy of manufacturing, transporting and processing the resource. Therefore, in order to truly achieve zero impact, we need to be willing to see and deal with all the resource’s phases and to pursue a more integrated approach that takes this into account. Additionally, it would be beneficial to create a CO2 index for every resource so that we have a consistent understanding of the resource’s impact within the building process. Secondly, the existing parameters derive from the notion of neutralizing the resource consumption and define this as zero impact. In fact, the “break even” approach is very limiting. Restricting the boundaries to ‘zero' or ‘net zero' is misguided because it discourages the potential to research how buildings can in fact generate a resource. A comprehensive definition of ZIBs would emphasize the viability of harnessing renewable resources. The ‘zero' goal limits innovation and creativity in achieving long-term sustainable building practices. If energy generated on site or water collected on site prove to be abundant resources, why then should we limit our objectives to zero? Thirdly, most definitions focus on linking resource consumption efficiency to building area regardless of occupancy size. In fact, taking into consideration the needs of occupants is equally as important as building area in achieving consumption efficiency. In the energy field, Switzerland is considering a resource efficiency measurement per capita. The Swiss 2000-Watt Society proposes defining energy consumption relative to the number of occupants (Morrow and Smith-Morrow, 2008). Similarly, the United Kingdom is proposing a Personal Carbon Allowance (PCA). The PCA concept is based on setting tradable domestic quotas at around 5 tonnes of CO2 per capita per year. Fourthly, most perspectives neglect context as a factor of influence. Researchers have worked to define universal parameters that do not always correspond with local context or 108
seasonal variations. ZIBs should be defined as context-sensitive, thereby allowing for diversity and flexibility in buildings relative to their context. In brief, existing definitions for ZIB are theoretical and require more refinement to reflect the reality. Up to now, most definitions have not been comprehensive enough to tackle the zero impact objectives. There is a certain urgency to set a definition for zero impact buildings, one that considers energy, water, materials and land simultaneously. Also any definition should seek simplicity and consistency in order to facilitate comparison and provide effective design guidelines. The four resources should have standardized metrics and benchmarks that are debated and agreed upon. A conceptual shift in how to effectively approach ZIB objectives is therefore necessary. This requires a further discussion of the core subject in this research: the zero impact approach (Herold and Menz, 2000).
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Towards an assimilated definition
From the discussion above we can conclude that there are three important criteria that should converge in a zero impact definition. Firstly, the definition must be based on holistic building design integrating land, energy, material and water. Secondly, the definition must incorporate maximizing on the viability of harnessing renewable resources, particularly in the case of energy and water. Thirdly, the definition must promote a closed-loop use of resources, where land and materials are up cycled either for re-use or given back to nature. This brings us back to the core issue behind this paper: how to define ZIBs from a cradle to cradle perspective and attain a consistency and precision of definition that allows performance comparison and achieves a sustainable built environment in a feasible manner. Whilst addressing the problems previously discussed, with an emphasis on the four essential resources (namely: land, energy, water and materials), a new definition is as follows: A zero impact building seeks the highest efficiency in the management of combined resources and a maximum generation of renewable resources. The building’s resource management emphasizes the viability of harnessing renewable resources including energy and water and achieves a closed-loop of overall material and land use.
The following units are suggested as universal metrics for communicating the resource management efficiency among all stakeholders involved in the building industry. The suggested metrics conform with other international units as closely as is compatible with self-consistency comprehensive, and, in large part, already employed in practice. 1. 2. 3. 4.
Land: area (m2) / footprint (m2) per capita Energy: carbon emissions (CO2) / area (m2) per year per capita Water: water (litre) / carbon emissions (CO2) / capita per year 2 or water (litre) / carbon emissions (CO2) / area (m ) per year Material: materials (ton) / carbon emissions (CO2) / area (m2) / capita and abiotic depletion potential / kg antimony equivalent 109
5
Discussion
The purpose of constructing a combined definition is to create a common framework that can be built upon. Exposing the definition to a wider audience will allow new ideas and tighter constructions to be added. The definition is only the beginning of a further process of definition, which the building design community must pursue. The definition of what makes a zero impact building fits into C2C perspective. Our goal here is not to advocate a fixed, onesize-fits-all approach to defining ZIBs, but to propose a consistent long-term approach. We believe that definitions for ZIBs could be successful concepts if they integrate all aspects of building design and construction practice and are supported by transparent evaluation methodologies. An assimilated ZIB definition recognizes synchronous cycles in resources during the building life cycle. Land, energy, water and materials are interconnected in various ways in ZIBs. Therefore, a proper definition should focus on an overall balance, diverting resources where appropriate and giving them back to nature so that buildings are in equilibrium with their resources. Any zero impact metric should measure the carbon impact of energy consumption as a whole. The usage of each of the resources reviewed is understood in a specific way and makes a specific and unique contribution in relation to carbon emissions. Designers should embrace the proposed standardized metrics and calculation methods as a means towards integrated design. Researchers should also build on existing knowledge and link their findings to back into the definition of zero impact buildings. It would be futile to assert that the proposed collective definition of ZIBs should take precedence over all others since the C2C philosophy is already so influential and broad in scope. There is also an emerging trend to create ecologically positive building footprints where the building design is very efficient and through suitable technologies energy and water become positive resources. There is a need to create buildings that imitate nature so that the footprint is ecological, healthy and beneficial in general and not only on the level of energy consumption. For example, buildings that support life or generate purified air, distilled water and energy or improve on the microclimate. Our role as human beings is to contribute to the health of the planet and this we must pursue with vigour. Finally, a ZIB’s life cycle and performance should be better monitored and documented in databases so that these can help us understand how buildings perform over their lifetime. Vast volumes of information can help establish real-world efficiency benchmarks per resource.
6
Conclusion
The four metric definitions described in this paper promote a sustainable design model leading to zero impact buildings. The value of these definitions lie in their use as a metric for designing ZIBs, particularly in regards to land, energy, materials and water. We must understand that the various resources are merely individual components in the approach to zero impact buildings. These metrics are intended to facilitate zero impact designs so that the management of resources becomes measurable. Combined, they provide a framework that can guide design decisions not only in terms of carbon emissions but also in terms of the impact within other life cycles relevant to land, materials and water. In this way, we avoid cradle to grave processes and supplant them with cradle to cradle metrics. 110
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