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IMCL 2016 International Making Cities Liveable Conference
Filippo Weber, MArch | Dr. Rosa Schiano-Phan, PhD
1. Context and Background
Global environment is under pressure due to the high waste in natural resources and the unreasonable proportion of energy consumption compared to that really needed.
Cities are the engine of our world  but a polluting one: 78% of the Green House Gas (GHG) emissions produced worldwide are actually produced in, by or for cities. Of this proportion 45% are produced by buildings, and 60% of this is for “comfort” – mainly space heating, cooling, hot water and lighting. Therefore, the impact of “comfort” weighs approximately 30% of the total GHG emissions produced by cities and 20% of the total produced in the world. These figures are even more outstanding if it is considered that cities represent only 2% of the earth’s surface .
This scenario is the consequence of the fact that industrial era and modernism have brought active energy processes and energy related activities into cities and buildings. From then, the world has started consuming resources and energy. This process has been driven by powerful commercial stakeholders, including the energy, construction, and banking industries, which have addressed cities as agglomerations of assets rather than “living organisms” .
As a result, “cities [and buildings] of the industrial era have consciously excluded natural processes, substituting mechanical devices made possible by intensive use of fossil fuels. Rather than using the solar energy falling on their streets and buildings, they dissipate it as excess heat. At the same time they import immense quantities of concentrated energy in various forms, most of it derived from the petroleum coaxed from the ground in distant landscapes… Thus, we might see our overwhelming problems of depletion and pollution as largely outgrowths of our ways of shaping the urban environment.” . Not only have natural processes been excluded, but also its consequences of this exclusion have been, and largely still are, ignored.
As a consequence, especially in urban areas, the built environment and the energy processes have affected the microclimate to the extent that today’s cities are at the forefront of the most rapid environmental and climatic changes ever experienced by mankind, causing reduction in comfort, health and increasing buildings’ energy consumption .
The microclimatic modifications in the urban environment are produced by the interaction of the causes of Climate Change with specific urban issues that are particularly complex to be solved, as their causes and effects are interrelated generating a negative loop in the city.
2. The Urban Situation: the Negative Loop
Not all the urban GHG are related to the negative loop, but those wasted because of it are elevated and mainly caused by the consequences of manmade landscape modifications (or other choices) such as reduction in evaporative cooling potential caused by the substitution of vegetation with buildings and streets; density of buildings and distribution of functions or intended use; reduced surface reflectivity due to the generally dark colours of horizontal surfaces of cities (red, black, grey) that are highly insulated in summer but not in winter; increased re-absorption of the reflected radiation by the urban fabric within urban canyons; high thermal storage properties of the urban fabric such as street and facades; reduced air movement due to urban obstructions; local Green House effect caused by urban pollution (exhausts from gas, coal or fuel); poor building fabrics and buildings designed against the climate; waste heat from mechanical and thermal processes of transportation, boilers and HVAC; human behaviour that generally is highly energy consuming (i.e. A/C or private cars).
In this scenario, for instance, mechanical systems for cooling are excessively used due to overheating of the surrounding in summer but they also further contribute to an increase of the outdoor temperature due to waste heat from compressors. In order to reduce their use both in terms of people’s behaviour and provision of alternative cooling strategies, pollution and heat must be reduced and people’s awareness increased. However, to reduce pollution and avoid the use of mechanical cooling, air quality for natural ventilation must be improved and alternative forms of mobility must be enhanced by offering better opportunities and conditions for the uptake of alternative transportation modes (e.g., walking, cycling, and low-emission public transport). At the same time, buildings use enormous amounts of energy for space heating because they and the surrounding city are not design to maximise the benefits coming from the energy of the sun as a source of free and clean energy.
Buildings and cities are usually designed exactly the contrary of how they should be, and the consequences of this attitude are numerous, detrimental and now well documented.
3. Negative Aspects of the Negative Loop: microclimate matters
The context described in the previous chapters, have a number of consequences on citizen health, urban sustainability, equality and economy.
The “negative loop” reduces the use and enjoyment of open spaces that are extremely relevant for urban prosperity and economic growth in both developed and developing countries . In general, high urban temperatures have a serious impact on the quality of life of urban citizens and affect the local economy by also reducing productivity. Several studies have shown that significant spatial and temporal deterioration of the outdoor conditions results in reduction of the attractiveness of open spaces impacting the local economy [5,6].
It also affects the health of the inhabitants, by raising the concentration of specific urban pollutants that provoke respiratory diseases, and increasing the risk for the vulnerable urban population during periods of extreme heat [5,8,9]. As reported in Melbourne, Australia, hospital admissions increase by 37.7% when the average temperature during two consecutive days is higher than 27 °C . Other studies from a number of European cities have shown similar results, also associated with increased casualties .
Moreover, microclimatic changes of large urban environments modify the pattern of the local weather. As the urban microclimate amplifies the magnitude of heat waves making cities and their inhabitants more vulnerable, it can also intensify other weather events such as precipitation patterns and storms. Rainfall in Ho Chi Minh City, one of the most flood-prone cities in the world, has been on a steady upward trend for over a decade and this has been attributed to urban microclimatic changes rather than Climate Change .
The negative loop, above all, makes buildings consume more energy. Its impact is particularly crucial during summer when the increment of ambient temperature in cities can go up 10K more when compared to the countryside. Simulations for cities show “that the average heating energy [demand] may decrease between 9% and 17%, while the corresponding cooling energy needs may increase by approximately 40–70% depending on the scenario considered”. These results show that the benefits deriving from the consequences of the negative loop in winter are negligible compared to the disadvantages of the summer. Moreover theses studies only consider the ambient temperature and not the consequences deriving from the impossibility to implement bioclimatic strategies—e.g., natural ventilation and passive cooling for summer or passive solar heating for winter- that could avoid or drastically reduce the use of mechanical systems, in most climatic regions. In order to reinforce these concepts, many studies [14, 15] have identified in the poor quality of urban environments and microclimates one of the main barriers to the implementation of bioclimatic strategies in cities.
4. Current actions to contrast “the urban situation”: The gap
Future projections estimate further growth of global urban population, with 70% living in cities by 2050 . This will put even more pressure on current urban environments and infrastructures and will create a greater demand for space and energy.
Yet, today’s public awareness of the importance of the urban microclimate in the urban energy balance, urban economy and inhabitant health is rudimental and obsolete. For this reason, actions to contrast the negative loop are generally weak and not incisive. International, national, and urban policies are mainly focusing on energy efficiency, especially for new buildings, energy supply, and products in order to reduce CO2 emissions. However, while the building scale policies have imposed minimum thermal conditions for building elements and share of energy from renewable sources, a large proportion of their energy performance will be influenced by and will be influencing the urban environment, for which no policies exist .
Efficiency is a milestone against GHG emissions but it is not sufficient to tackle urban issues and eradicate the causes and effects of the “negative loop” that are happening in cities and it is often not a feasible pathway for emerging, and developing countries especially due to high costs. Moreover, studies have shown how the reduction of GHG emission in cities, though fundamental for the quality of the urban environment, will not yield significant reduction in urban temperatures since its increase is mainly caused by land use modification and waste heat.
This gap in policies between the building and the urban scale is mirrored by a lack of recognition of the strategic importance of the outdoor design as a microclimate modifier in itself, and therefore of its mitigative potential. The main instruments towards implementation of urban microclimatic mitigation strategies are currently found in fragmented technical solutions and sectorial policies that fail to identify the multiple relationships of cause and effect that lie in the various elements of anthropogenic activities. Moreover, very little attention is given to the impact that buildings, their form, position, fabric, colour, etc. have on surroundings. Also, no attention is given to the energy savings potential coming from the implementation of bioclimatic strategies for space heating and cooling for which no energy is required.
5. Avenues for the future architecture and cities: The New Paradigm:
In order to reverse the negative loop a great effort to change a consolidated mindset must be done by public and private realm. The public realm has large responsibility on local Climate Change (CC) through the choice of pavement materials, urban planning, transportation, street design, green infrastructures and more. Nevertheless, buildings and districts cover large portions of the urban landscape and consequently their choices greatly influence the urban microclimate: massing and master planning, functions’ distribution, geometry, materiality, environmental (mechanical) control systems and others. These equally important responsibilities make the traditional dichotomy between urban actions to mitigate local CC and building actions to reduce energy consumption through efficiency outdated. If the synergy between public and private realms is the strongest route to move towards sustainable cities [18,19], buildings should be considered for the impact they have on the urban environment both when retrofitting and especially when new districts are planned.Thus, based on the existing research and experimentation on the urban microclimate, this paper advocates a new paradigm for building: Passive and Mitigative Buildings. Mitigative: that has the ability to make something milder. They will fine-tune the surrounding microclimate in order to improve health, extend the use of passive strategies, reduce energy demand and enhance users’ indoor and outdoor comfort.
Modernity in architecture is about providing buildings with the ability of not consuming energy by utilizing natural elements and what is offered by the surrounding while providing them with the ability of tuning the microclimate with the users’ need to reduce their energy dependency.
The level of technological readiness of strategies and techniques now available on the market to help improve urban microclimatic conditions and the level of advancement in performance analysis of outdoor spaces have made possible the design and delivery of Mitigative and Passive Buildings. It has been noted that “during the years the techniques used for these purposes improved, but only today do we have the sophisticated means for an optimized designing of outdoor spaces. In other words it can be possible to improve the quality of an outdoor public space by taking care of those factors influencing the thermo hygrometric comfort[and environment]” .
7. The Passive and Mitigative Building Approach
There is no valid universal solution for Mitigative Building paradigm: every case will be specific for climate, microclimate context, culture etc. Yet, the approach to be followed, holistic and innovative, is universal. The main focus areas will be the following.
The optimization of the master-planning and outdoor design, included the external part of the building fabric is the first step in order to tune the surrounding microclimate to the building needs and to make the most out of passive strategies for indoor comfort. Through the massing of the volumes, the penetration or not of the solar radiation, the surfaces exposure or not to the sun, the reduction or enhancement of wind driven air movement, the use of vegetation, water or only by the choices of materials and colours the majority of the energy flows through the city can be controlled and favourable condition for the implementation of effective passive strategies can be designed. Shading and self-shading can be the most effective strategy in summer in most climates while allowing sun to hit horizontal and vertical facades can be beneficial in winter. Darker colours will be preferred on the surfaces hit by the sun in winter while light and cool colours will be chosen for the irradiated parts in summer: the surface temperature can be 20K cooler or warmer according to the colour chosen. The use of vegetation in those parts of the building or district hit by the sun in summer can help in generating shadows and in cooling the air through processes of evapo-transpiration. The same process can be used to cool the air through the design of water bodies or fountains or water spray. Other design choices relate to the reduction of the noise coming from the streets that can be a barrier for the effective implementation of summer passive strategies.
The mitigated microclimate and the other optimization offer the opportunity to step back from an “active system” based approach for indoor comfort in favour of a low energy model based on maximization of passive strategies that are nowadays mature and innovative at the same time. Heating through the sun or the containment of the internal heat gain, cooling through ventilation and materials properties, light up a space, a desk or an office through the manipulation of the visible solar radiation it’s not obsolete, but the real innovation that clients and users should require to designers in order to enhance comfort, health and productivity while moving to a sustainable built environment where we spend the most of our time.
The first two aspects of the approach needed to move towards Passive and Mitigative buildings unlock the possibility of drastically reduce the dependency on active systems and consequently the opportunity to reduce their dimension and complexity. They will become only back-up systems and the energy produced by renewable sources will easily cover their consumption while it will contribute to cover the dependency of the surrounding buildings from fossil fuel.
8. Benefits of Passive Mitigative and Buildings
Mitigative and Passive Buildings will consume negligible amount of energy compared to the traditional low energy architecture. This will be done at a lower price, but above all they won’t have the negative impact that other buildings have on the surroundings. There are consequently many advantages for moving towards this new paradigm.
The mitigation and tuning of the urban microclimate to the energy and comfort needs will translate into a reduction of building energy demand in the first place. In fact the energy demand for heating and cooling is related to the temperature difference between indoor and outdoor. Moreover, active systems, as traditional heat pumps, will consume less energy due to the fact that they will be able to work at higher efficiency. Even more importantly, the tuning of the microclimate will translate into the possibility of integration of low-tech/low-cost bioclimatic strategies which will reduce or avoid the energy demand for comfort. Such changes will not only affect the mitigative building, but will also positively touch the surrounding buildings, public spaces and environment.
Cities will become more liveable both in winter and summer, streets and space between buildings will become a catalyst for urban economy and interaction. They will return to be an attractive part of neighbourhoods where new experiences can take place.
Thus a key benefit of the new paradigm is its potential to allow people’s behavioural shift. In fact, changes in behavioural choices, which are also “strongly influenced by changes in the built environment” , have been agreed on one of the main strategies towards mitigation of CC, with a potential reduction in energy consumption by up to 20% . However, the decoupling of CC from the geography and timescale of people’s lives, produced by the global scale of the issue and the difficulty for some to grasp the importance of energy and CO2 savings, produces a considerable impediment to behavioural change . The short-term improvements coming from the application of Mitigative Building in the urban environment can potentially have the benefit of connecting public awareness directly to the issues of local Climate Change and, indirectly, to that of global Climate Change. Hence the implementation of the new paradigm will be more likely to produce the behavioural changes required for the radical transformations needed to enable the transition to a clean, low-carbon, sustainable and resilient society.
Benefits from this transition could be much higher for low income citizens and other vulnerable groups due to the poorer conditions of their housing, the lower affordability of high efficiency goods and lower level of health care they can afford – helping in reducing social disparities and energy poverty.
Hence, especially in developing countries, there is the need to pursue alternative strategies for “clean energy” buildings. Also the UN recognizes that “a more suitable strategy for these countries is the use of ‘passive’ technologies that combine flexibility, accessible know-how and traditional knowledge […]. Urban areas might want to consider combining such ‘passive’ methods with some features of modern technology taking advantage of their declining cost in recent years (solar photovoltaic/thermal energy, water harvesting, etc.).”
From a review of the well-studied problems and opportunities facing our built environments globally and locally, it is apparent that there are a number of strategies applicable to the urban and building scale in order to tune the local microclimate to the inhabitants’ need for health and comfort and to reduce energy consumption. Nevertheless the dichotomy between urban scale policies, slow and often ineffective, and building scale interventions based mainly on improvements in efficiency, has highlighted a crucial gap which has to be bridged: in order to move towards more sustainable and just cities, the buildings’ role in the urban environment must be reconsidered. A new paradigm of building and urban environment is proposed based on the unexploited potential of considering urban environments, buildings and users as part of the same system working in balance between each other. A whole-system thinking is advocated to yield significant improvements in terms of energy, comfort and behavioural shift. Given the technological maturity of present times, most of the strategies and techniques needed to mitigate the microclimate are well known and available.
So far the public nature of the urban environment has implied that if mitigative strategies to improve the microclimate need to be applied, these are mainly the responsibility of the public authorities, while the private stakeholders mainly focus on aspects related to the improvement of their private assets (such as efficiency of buildings, products, appliances, etc.). However, the concept of mitigative buildings places emphasis on the contribution and responsibility that also private buildings have on the public and shared space. Their impact on the urban microclimate, have benefits not only for the outdoor shared comfort but also for the indoor private comfort due to the extension of the applicability of passive strategies.
Having showed the importance of the urban environment under so many aspects, it is necessary to find an international agreement on its value as a social good  and to integrate this concept within the discussion on public spaces and on their quality. The challenge is to provide cities in developed countries with the opportunity to meet the GHG reduction targets and cities in emerging and developing countries the grounds to leapfrog from an energy-based model to a more sustainable and more feasible model of growth.
The innovative potential of this concept lies in a new and more holistic way of conceiving urban environments and buildings as microclimate modifiers. The associated innovation potential of the proposed new paradigm is also found in the almost universal relevance of its message. Although urban environments vary greatly between each country, region, and city and between developed, emerging, and developing countries, there is a commonality in the challenge that all urban inhabitants face with respect to local and global CC. Clearly the answers to the same question posed by microclimatic changes will be different and contextual to each city’s cultural, socioeconomic, and technological development level. However, the proposed approach of reducing energy dependency by improving outdoor conditions – mitigating the urban environment- and reducing the impact of anthropogenic activities and climatic unresponsive buildings is equally valid both in developed and developing countries. In fact, these pathways can unlock the potential for those clean, passive, and bioclimatic strategies that are particularly applicable in developing countries due to their low-cost impact and are equally desirable in developed countries due to their low-carbon potential.
Just as the advent of the arch, steel, reinforced concrete or mechanical systems have each changed the architecture of buildings and cities, today the new paradigm will shape the future of our cities. A paradigm that acknowledges and respects the weak balance of our world system and transforms buildings into thermodynamic systems in harmony with the climate.
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