The cause and urgency of sustainability hardly needs explanation. The situations and trends signaled decades ago by alarming reports as "Limits to growth" (Club of Rome 1972), "Our common future" (United Nations 1987), "State of the World" (World Watch Institute 1984), "Zorgen voor morgen" (RIVM 1988) and "Nationaal Milieubeleidsplan: Kiezen of verliezen" (VROM 1989) are today by magnitude and message still just as accurate as they were then, despite technological developments.
If sustainability is understood as "meeting the needs of present generations without compromising the ability of future generations to meet their own needs" (Brundtland 1987), we can conclude that we have by far not reached or even approached that situation. The world population consumes much more much faster than the Earth can re-generate, re-new, re-produce. This means: depletion,erosion, pollution, toxification. And both the global population and consumption rates are still growing...
In this way, says Rovers (2011a), our own living environment gets depleted of valuable material resources and valuable forms of energy. Valuable but limited concentrated forms of energy (fossil fuels) get forever lost as they are used. Energy does not get lost, as we know, but the potential of it to deliver labor (exergy) does. Fuels that are burnt lead to a slight increase in ambient temperature that is useless as it is not able to carry out any labor. Useful concentrations of materials get lost in disarray and dispersion. It takes millions of years to generate gas or oil, and we burn it in decades. A similar ratio of unbalance goes for materials. Not to mention biological issues such as the fertility of soil (erosion), eco-systems (degradation), bio-diversity (extinction).
Another word for sustainability could be sufficiency: a situation where the renewable resources are enough for what we need or use, considering energy, materials, water, air and food. Urban Harvest+ (Stremke et al. 2012) provides a clear method for the analysis of the self-sufficiency of an (urban) environment. It places a theoretical box over an area and investigates what resources go in, what can be produced in the box and which resources leave the box while they could be re-used and brought back into the system. Then the closed system can be reorganized, demands can be reduced, demand and supply can be optimized, and provision of needs can be maximized. The aim will often be a balanced situation, whereas currently we have an urban situation of high demand and no or very low production; thus a strong decrease of quality.
Like Urban Harvest+, Rovers (2011a, 2011b) promotes a closed cycle approach of resource management, within a limited system ("The Concept of 0"). Buildings should then completely be based on renewable energy and renewable materials that can be produced within the building sites boundaries, adding that the site needs to provide air, water and food as well. It is fair nor useful to aim for self-sufficiency of an urban system, since cities are the most dense locations with the most consumption and least land available for production. But on the global scale we are dealing with precisely such closed cycle and system. We have one Earth and one Sun, and that is what we have to work with.
While it is relatively easy to define and understand sustainability in overall global terms, it is challenging to quantify or assess the sustainability of, let's say, a building project. Complex integral assessments have been developed to calculate the environmental effects or score throughout the life span or cycle of a building: Life Cycle Analyses (Eco-Quantum, GreenCalc+) for scientific use; rating tools (BREEAM, LEED) for commercial-professional use; and practical hybrids (GPR Gebouw) to give "80% accuracy in 20% of time". The Life Cycle Analyses calculate environmental effects, such as that the building project causes x kg CO2 and y kg NO2 emissions, z GJ energy consumption, etc. throughout its life span or life cycle. The various assessment methods mostly agree up to this point (Schilperoort 2008).
The differences arise once all separate effects have been calculated and established and it has to be decided what effect has what importance or relative weight in the whole. Eco-Quantum considers political ambitions (i.e. the reduction of carbon emissions, energy use, etc.) and the "distance-to-target" to settle the relative weight of the various effects. The "advantage" is "Realpolitik", but the disadvantage is that it hides lack of political insight or ambition. GreenCalc+ uses monetarization: it calculates the money that it would cost to undo all environmental effects, and presents a bill of hidden costs. These costs are so far not being paid by anyone though (Schilperoort 2008).
The assessment method of choice will therefor be another one. MAXergy (Rovers 2011a, 2011b) calculates the space?time footprint of a building project or an urban system (in the latter case it includes not only energy and materials, but also food, water and air). MAXergy is preferred over other life cycle analyses because it is a method that starts and ends with ecology, and nothing but ecology. It does not interpret ecological results in political or economical terms, nor does it blur the vision with whole other issues such as People and Profit, but simply indicates if a system is able to provide the energy, materials, food, water and air that it takes. It is a complete and accurate analysis with an integral and holistic view that prevents us from the common pitfall of sub-optimization.
Rovers says that in the end it is solar radiation, and the ability to convert it into useful resources, that is the common denominator for energy and materials. Everything depends on solar radiation conversion and the space?time needed to grow, generate, produce both energy and materials. For solar energy this is obvious: it takes a certain space?time to get a certain amount. Also bio-based materials such as wood and hemp and flax and straw are easy to see in terms of space?time needed to grow them. But also oil is a renewable product of the Earth-Sun system, be it at very low rates. Metals are less obvious, but once they are gone (these resources are being depleted at high speed as we speak, much much faster then they can ever be regained), it takes a certain amount of space*time to regain them. Metals ultimately corrode, atomize, disperse and end up in the ocean; while it takes electrolysis (energy and space*time) to regain them and bring them back into circulation.
Next sections get into more detail on exergy, energy and materials:
Rovers (2011a) says that while people commonly refer to an "energy" crisis, we don't have an energy problem, since the first law of thermodynamics states that energy never gets lost. We have an eXergy problem. At least for as long as we are burning our fossil fuels and don't use renewable sources.
Exergy is defined as the labor potential of a certain form of energy. It is often also referred to as the "quality" of this energy form. Burning fossil fuels results in high temperatures, that can be used for labor, to produce bricks and steel for example. The same amount of Joules at lower temperatures, such as in solar heated water of 30 degrees Celsius, is however useless for that type of labor, hence has a lower quality, as it has limited use. Fossil fuels and electricity have a much higher exergetic value (Rovers 2011a).
The result of the dropping exergy of our environmental system is that we end up with low quality energy in the form of ambient temperature, while high quality energy forms such as fossil fuels are depleted. Producing bricks, steel, concrete may become very expensive once we are through our fossil fuel reserves. Another effect of burning our best, high quality energy carriers is CO2 emission and global warming.
What would constitute an 0-energy building? Zero energy referring to Operational Energy used.
A best practice in Operational Energy savings in the climate of the North of Europe is passive building. It was first developed in Scandinavia and Germany. The idea is to use "passive" principles to minimize the Operational Energy for a building: the building opens towards the sun, the other facades are mostly closed; sun shading lets the low winter sun in and keeps the high summer sun out; a compact building design reduces the shell/space ratio; the shell is extremely well-insulated, closed and open parts alike; ventilation is balanced with heat recovery; there are no thermal bridges; no leaks, air tight design; summer night ventilation; (Very) Low Temperature heating; energy-saving lighting; shower heat recovery. The result of these combined measures is a building related energy consumption for heating of <15 kWh/m2/year.
According to Freek den Dulk (Schilperoort 2010), passive measures will bring a well-designed and well-constructed passive house to an EPC of circa 0,4 (the Energy Performance Coefficient EPC is a measure to indicate the theoretical Operational Energy performance of a building. It is calculated in the design stage. The Building Code 2012 prescribes that new dwellings have an EPC of < 0,6. This will be lowered to < 0,4 in 2016 and < 0 in 2018/2020).
If we want to cover all building related Operational Energy use (EPC = 0), the above mentioned passive house needs approximately 24 m2 photo-voltaic panels to produce the energy to cover cooling, heating, lighting and ventilation, according to Den Dulk (Schilperoort 2010). The solar radiation in The Netherlands is circa 1,000 kWh/m2 /year. Photo-voltaic cells are able to convert circa 15% of this radiation energy into electric energy (Rovers 2011a). This EPC=0 still doesn't mean the household is "0-energy" though. There is a total of approximately 60 m2 photo-voltaic panels needed to also cover the Operational Energy consumed by the dwellers for computers, laundry, showers, television, etc.
It may be useful here to stress that the pv-estimate above departs from the common assumption that we need to provide in local energy production. This is not necessarily so in the future though. The amount of solar radiation that reaches the Earth, is more than enough to cover all human energy consumption. The problem is that this energy is not always available in the right form, at the right time, at the right place. If and once technology for storage (hydrogen) or transport (super-conductors) is indeed successfully developed though, as some promise or expect, huge amounts of solar energy can easily be produced in desert areas (Sahara Forest Project) and stored or transported without much loss. It is hard to tell if and when such technology will indeed become available, but if it does, this would be an absolute "game changing" event that makes all current assumptions irrelevant.
The Embodied Energy (harvesting, production and transport of materials) can be substantial. The production of 1000 kg bricks takes 5000 MJ of energy. Which equals 350 kg of dry wood (Egmond et al 2006)! While this is an eye-opener in itself, it does still "only" represent 18% of the total energy consumption in Joules. Operational Energy making up for the other 82%!
If these materials are produced with fossil fuels, as is the case with brick, concrete and steel, it takes enormous amounts of space*time to re-produce these fossil resources once they have been used. The space?time needed to produce/generate the fossil fuels is hundreds of millions of times bigger than the space*time needed to run photo-voltaic panels for the same purpose!
This is where MAXergy may seem a bit "radical": these excessive figures express that if we want to keep or restore the exergy of fossil resources in our system, we would have to wait millions of years before new fossils are produced. The conclusion is: we have to be very careful with out fossil fuels, for once they are gone, we will not easily get them back.
Rovers (2011b) calculates for a house made entirely of renewable materials and using renewable energy, that only a tiny part of the Embodied Land (space*time) is for energy while by far most Embodied Land is for growing materials. With "0-energy" buildings (zero Operational Energy) in sight, he says, the energy related to used materials (Embodied Energy) and the occupation of land (Embodied Land) becomes the largest fraction. This has surprising consequences: using more and more insulation material (as is the trend in Passive House Building) even from renewable bio-based sources like straw or hemp or flax, face a maximum: there is a point where renewable energy input to heat the house is more environmentally friendly and effective then to add extra insulation. Thus with a materials productive landscape we should aim for a "0-materials" building.
Now, what would constitute such "0-materials" building?
A highly effective strategy for 0-materials buildings is using renewable materials. Schumacher says that these materials can be defined as "made from fibers or materials that are replenished by natural processes at a rate comparable with or faster than its rate of consumption by humans or other users" (Rovers 2011a). This strategy in line with the Cradle-to-Cradle (McDonough & Braungart 2002) principle of the closing cycles, in this case the Natural Cycle. Bio-based materials such as wood, straw, flax, hemp, paper and also earth (Minke 2009a, 2009b, 2010; Alinn 2005; Bevan & Wooley 2008; Haas 2011; Holst 1985), grow back without too much space?time and they are biologically degradable.
Cradle-to-cradle (McDonough & Braungart 2002) also defines a Technical Cycle of assembled (industrial) material factions or parts that can be dis-assembled and re-used without degradation. MAXergy calculations show however that using bio-based materials results in a far lower footprint than re-using industrial materials. Concrete and metals (also reinforcement steel plays a big part) would have to be recycled hundreds of times to approach a balance with the Earth's capacity to (re-)generate them. Actual recycling - as in removing them and using them somewhere else - of large building parts is rare. Most recycling comes along with intense energy consuming processing. Dividing components in small standard parts is key (McDonough & Braungart 2002, SEV 2007).
Another strategy that can be applied, especially for the occasions where we cannot use bio-based materials, is using less materials, designing light-weight buildings. Most buildings are very heavy. The building tradition in The Netherlands and neighboring countries is to use massive materials for floors, walls and facades. Lichtenberg (2005) says that buildings weigh 1000 to 1500 kg/m2 (floor surface). Floors themselves weigh 400-600 kg/m2, and up to 750-800 kg/m2 for layered buildings.
It is often thought that light-weight floors cannot meet contact noise insulation demands, but Bron van de Jagt (2004) shows that the demands and user expectations can be met by only circa 8 cm (or more) mass and one or two flexible detached layers for floors. A double layered, separated, flexible light-weight wall is accurate for walls. So: light-weight is a mature method, yet it takes some extra design and construction effort, especially for us, since we are used to other building traditions.
Gijsbers (2011) researched and developed an innovative contribution to lightweight building. He developed a structure based on small floor spans (3-4m) with movable columns that can be moved once they are bothering the use/users of the space. Beams are locally given additional strength and stiffness if needed, and as long as needed. Because the floor span is so little, the floors can be very thin, and the weight of the floors and the entire building decreases substantially. More light-weight inspiration can be found with (a.o.) Konrad Wachsmann, Frei Otto, Buckminster Fuller and Shigeru Ban, who have all become famous for lightweight architecture and engineering (Beukers 1998).
Life span optimization
The third strategy is life span optimization. The energy and materials used for the production (and demolition) of a building are obviously best spent when the building lasts a long time. The life span of a building depends on the rate of either technical a/o economical a/o architectural expiration. All of these are fatal flaws.
A building can be technically so outdated that it is too expensive to renew it (technical expiration). It is therefor important to design it as such that it is relatively easily adaptable (Brand 1994; Scheublin & Pronk et al 2006;). A technical separation between its casco, shell, infill and services & infrastructure is helpful for this purpose (Lichtenberg 2005).
A building can also become redundant when there is no demand or use for it anymore in the local real estate market (economical expiration). It is therefor important to design it as such that is at least somewhat flexible in use, and multi-functional. Scenario planning and design should be helpful for this purpose. The multi-use potential depends mostly on location, access and circulation, structural grids (dimensions) and principles (open is generally better), but also facades and technical services & infrastructure. Scenarios should look at things like floor plans, finance and regulations (OBOM 1992; Geraedts 2001, 2002, 2006; Lingotto & ANA 2001; Habraken 2008).
Last but not least a building can expire when it has no qualities that people appreciate and attach to (architectural expiration). Bijdendijk (1997, 2006) thinks that people on one hand need longevity and permanence to be able to love their environment, to attach to it; while on the other hand they need the freedom to do whatever they want to do in their own space inside. This is an architectural and ecological variation on the democratically motivated idea of Open Building (Habraken 1961). Bijdendijk proposes to invest in monumental casco's (structure and facade) that are built for a very long life span (100-200 years), on quality locations. These casco's are open, meaning that they are technically prepared and inviting to accommodate a lot of freedom in interior use and design. The long lifespan of the casco justifies - to some extent - the use of less ecological materials, while the short lived infill and services & infrastructure will be light-weight and aim for a low footprint.
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