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Urban Development

Cooler buildings and lower bills in summer thanks to green walls and roofs

MD Staff

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A 15% cut in the energy bill with a 40% reduction of the direct solar radiation in dwellings and a lower indoor temperature by up to 3 degrees thanks to plants grown on roofs, balconies and external walls. These are part of the outcomes of the Italian pilot project ENEA is conducting at its research center near Rome.

“We developed a green wall based on an extensive roof-garden system and a self-supporting structure positioned at 50cm from the wall of the School of Energies building, where we conduct training courses”, Carlo Alberto Campiotti at the Department Unit for Energy Efficiency, said. “Successively – Campiotti went on – we’ve begun to study the interactions among green coverings, energy flows, the microclimate and indoor comfort, diversifying the species”.

The “plant system” installed on walls, roofs and balconies, has proved capable of creating an actual insulating pad enveloping houses and condos; in this way vegetation can mitigate temperature peaks during summer, capturing most of solar energy, which doesn’t directly hit the building surface, dissipating through evapotranspiration of plants a large amount of thermal energy (up to 1 liter of water daily per square meter) which would otherwise be absorbed by the building and released as heat inside the house.

“In summer this vegetation system allows to reduce up to 15% of energy for cooling- Campiotti pointed out- while in winter savings for heating reach 10% thanks to the chimney effect between the wall and the vegetable blanket; in practice, a natural ventilation system removing moisture from walls and reducing the thermal dispersion of the building”. Each plant has its own type of leaf given by color, thickness, shape, arrangement on the stems and biological cycle, which determines the amount of solar radiation it captures instead of hitting the walls of the building.

The parameter defining the energy and bio-agronomic traits of plants is called green factor (kv) and it varies from a minum of 0 to a maximum of 1. In practice, if kv is 1, it means the green mantle doesn’t exert any shielding towards solar radiation and, in summer conditions, the temperature of the external wall is superior to both that of the air and that inside the building; but if the value is zero, it means that vegetation exerts a total shield and the temperature of the wall is equal to that of the air.

“The Pandorea Jasminoides variegata – Germina Giagnacovo at the Energy Efficiency and Productive Activities Department explained – is a climbing evergreen with an excellent ability of neutralizing solar radiation, as Lonicera hall prolific and Partenocissus quinquefolia do, although slightly less effectively”.

“In addition to an improved thermal and acoustic insulation and living comfort for individual dwellings, these solutions also have advantages for the entire urban context: green roofs and walls, in fact, contribute considerably to the reduction of the “heat island”, which can cause a peak of the electrical load during summer, between 3 and 8% for each additional degree of temperature.

Furthermore, less use of air conditioning means less greenhouse gas emissions such as CO2, methane, fluorinated gas and water vapor. Installing green roofs, balconies and walls also means mitigating the effects of the so called “rain bombs” – roofs and balconies account in fact for 20% of the total surface of cities and covering them with plants would allow to absorb up to 50% of rainwater, regulating its flow into the city’s water system- in addition to improving air quality, since 25 m2 of plant surface generate oxygen for one person, while 1m2 eliminates 0.2 kg of particulate matter in the air.

“For many sectors in distress in our economy, including the building sector, new prospects for recovering are opening up- Campiotti continued- also thanks to the introduction of the green bonus with the last Budget Law, a new fiscal incentive which allows to recover 36% of the costs, up to 5thousand euro incurred for re-greening single dwellings and parts of condos, an intervention which could increase the value of the building itself”.

Green coverings

“Extensive, mildly intensive and intensive are the three types of green coverings we’re experimenting with at ENEA- Susanna Mariani at the Department Unit for Energy Efficiency, explained. We are particularly interested in the experimental use of autochthonous varieties, such as climbers and evergreens, but also rare wild species such as Echium vulgare, also known as viperina grass, much loved by bees, which can guarantee maximum protection of biodiversity, adaptability to climatic variability and resistance to summer droughts “.

In detail, the extensive coverings are characterized by varieties of plants that are easy to grow (of the genus ‘sedum’, a set of various species of succulents, and perennials) that need little maintenance and rescue irrigation (mosquito-proof), since they can store a large amount of water. This type of roofing is particularly suitable for walls and slopes, since the installation reaches a weight of about 100 kg / m2. Intensive coverings, on the other hand, foresees the inclusion of trees, require high maintenance and increased irrigation, involving the installation of a weight on the building ranging from 400 to 1000 kg / m2, while the mild intensive is positioned halfway between the other two varieties of coverings, by type of plants and maintenance, weighing between 200 and 400 kg / m2

The courses

In september, at the School of Energies of the ENEA Casaccia Research center, the Energy Efficiency Department will organize a course on the cultivation of plants best suited for green coverings. The course is free of charge and is addressed to agronomists, land surveyors, architects, biologists and natural sciences graduates.

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Urban Development

Four Regional Development Banks Launch Joint Report on Livable Cities

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Rapid urbanization has provided most cities in the world with opportunities to provide more sustainable, vibrant, and prosperous centers for their citizens. But they must first address challenges such as inadequate infrastructure investments, pollution and congestion, and poor urban planning, according to a new report released today. 

The report, Creating Livable Cities: Regional Perspectives, looks at urbanization trends across emerging and developing economies in Africa; Asia and the Pacific; emerging Europe, Central Asia, and the Southern and Eastern Mediterranean; and Latin America and the Caribbean. It is a joint publication by four regional development banks (RDBs) operating in these regions—African Development Bank (AfDB), Asian Development Bank (ADB), European Bank for Reconstruction and Development (EBRD), and Inter-American Development Bank (IDB).

“Cities offer access to key infrastructure, institutions, and services for a good quality of life,” ADB President Mr. Takehiko Nakao said. “They can be centers of innovation for a more livable future for all. But realizing that potential requires forward thinking and flexible planning, adequate capacity at the municipal level, and good governance.”

Mr. Nakao took part in a launch event at the IDB headquarters today in Washington, D.C., with the presidents of the other three development banks: Mr. Akinwumi Adesina of AfDB, Mr. Suma Chakrabarti of EBRD, and Mr. Luis Alberto Moreno of IDB.

The world’s urban population has grown from just 750 million in 1950 (or 31% of the total population) to 4.2 billion in 2018 (55% of the total population)—a number that is estimated to reach 5.2 billion in 2030 (60% of the total population). While the majority of leading economic hubs are still in advanced economies, the center of economic activity is moving toward the developing and emerging markets, the report says. Asia and Africa will account for 90% of urban population growth between 2018 and 2050, with more than a third of this growth to happen in just three countries—the People’s Republic of China (PRC), India, and Nigeria.

Although large and still dominant, megacities of more than 10 million people and national capitals are not the fastest-growing urban areas. Urban areas with fewer than 1 million residents account for 59% of the world’s urban population and are experiencing a faster growth rate across the regions, the report says. 

Cities need large scale investments to develop and maintain infrastructure and services such as urban transport, water supply, sanitation, and solid waste management. In the face of rapid growth, overstretched services, skills shortages, and increased vulnerabilities to disasters are adding to cities’ environmental stress.

The publication examines the types of policy interventions and approaches needed to promote competitive, inclusive, equitable, and environmentally sustainable and climate-resilient cities—four factors that taken together make cities “livable.”

“RDBs play an important role in identifying, distilling, and diffusing knowledge and actions that can accelerate progress toward creating more livable cities,” the report says. Making cities more livable is one of the seven operational priorities of ADB’s Strategy 2030. ADB’s Livable Cities approach puts people and communities at the center of urban development, and promotes strengthening urban institutions through holistic and participatory urban planning and sustainable financing, and use of data and digital technologies to improve urban services to the residents.

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Urban Development

Cities Around the World Want to Be Resilient and Sustainable. But What Does This Mean?

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Cities around the world, large and small, face common challenges, especially due to rapid urbanization and climate change. According to United Nations (UN) estimates, four billion people – more than half of the world’s population – live in urban areas today. By 2050, over two-thirds of the global population will be urban, challenging cities to meet accelerating demand for affordable housing, well-connected transport systems and other infrastructure and services, as well as jobs.

In addition, rising global temperatures increase the risks of rising water levels, landslides, droughts, hurricanes, and other disasters. Without urgent action, these climate impacts could push an additional 100 million people into poverty by 2030, according to the World Bank. 

The good news is that, armed with knowledge and creativity, urban centers are finding ways to tackle new and old problems alike, with fewer losses and greater recovery capacity – in other words, creating “resilience”.

The Catalyzing Sustainable Urban Futures global conference held recently in São Paulo, Brazil, which was co-hosted by the São Paulo City Hall, the Sustainable Cities Program, and the World Bank’s Global Platform for Sustainable Cities (GPSC), with the support of the Global Environment Facility (GEF), looked closely at this topic of “resilience”.

Representatives from four continents examined three global issues, with sustainability and resilience as an ever-present backdrop. The first was climate change, a concern that mayors can no longer afford to sidestep. According to the World Bank, cities consume about 2/3 of the world’s energy and account for over 70% of global greenhouse gas emissions.

The second issue was the need for more green spaces – think about public parks with trees, birds, bees, and other species. Today, around one million animal and plant species are threatened with extinction, eroding the foundation of our shared livelihood, society’s ability for adaptation, and nature’s capacity to store carbon. Green spaces do not only help cities mitigate and adapt to climate change, but also serve as important places for human-wildlife coexistence – and a home for conserving urban biodiversity.

Third, there was a constant discussion about solid waste management. Without it, rivers will overflow and the air will be polluted by harmful substances, among other problems. With it, millions of people, including those in the recycling industry, will be presented with new opportunities.

Mitigating and adapting to climate change

Today, 90% of urban expansion takes place in developing countries, and much of it occurs near natural hazards, rivers, and coastal regions, in the form of informal and unplanned settlements. A lack of infrastructure and proper land use plans exacerbates the risks facing residents, especially in view of climate change. Thus, several cities are now devising their own mitigation and adaptation plans. São Paulo, for example, is set to launch its plan in June 2020.

Another Brazilian city, Recife, already has a plan in place, in preparation for the city’s 500th anniversary celebration in 2037. One-third of the local population lives in hill areas susceptible to disasters; another third of the population resides at sea level, which means that flooding is a threat.

“With the participation of civil society and the general population, we have compiled a strategic plan based on a set of urban and environmental plans containing a series of initiatives to mitigate [disaster risks], increase resilience, and adapt to the consequences of the climate crisis,” stated Mayor Geraldo Júlio at the conference.

Plans in developed countries are even more ambitious. Paris, France, has pledged to become a carbon-neutral city by 2050, enacting 500 measures in various industries, such as construction, transport, energy, and food. These measures include goals such as using only green energy (biomass, wind, and solar), banning diesel cars by 2024, and eliminating all cars running on petrol fuels by 2030.

Less asphalt, more forests and parks

“With fewer cars on the street, we will not need as many parking lots or as much asphalt,” said the Deputy Mayor of Paris, Pénélope Komitès. “We can, for example, use garage buildings to plant urban forests that help regulate the temperature.”

Just like Paris, the expansion of green spaces is becoming a trend, from China to Paraguay. These spaces capture carbon and improve air quality, among other benefits. Such changes are most welcome in Chinese cities like Ningbo, which has over 40 square kilometers of protected areas despite its population of 8 million people.

In Latin America, the city of Asunción, Paraguay, is planning to build a green urban corridor – at least 35,000 hectares in size – to take better care of its biodiversity, especially birds. The project is in the preliminary phase.

Parks also help reduce heat, a much-needed improvement in a city like Caruaru in the Brazilian state of Pernambuco, where a linear park (i.e., longer than it is wide) will be built with a bike path connecting 14 neighborhoods, with the potential to benefit 140,000 people.

Together, these measures create opportunities for cities to deliver growth that is green, low carbon and competitive – and to build societies that are resilient, inclusive, and livable.

Waste remains rather unsustainable

According to the World Bank report What a Waste 2.0: A Global Snapshot of Solid Waste Management to 2050, in 30 years the global rate of waste production will be double the growth rate of the population. “Cities and countries are developing rapidly, but without suitable systems to cope with changes in the waste disposed of by citizens,” the study highlights.

Against this trend, São Paulo is gradually enacting initiatives and setting goals to alleviate the problem. For example, this year the local government joined the New Plastics Economy Global Commitment to ensure that 100 percent of plastic packaging can be recycled or reused by 2025.

In addition, there is an initiative in place in São Paulo to increase composting yards. Currently, there are five composting yards that receive waste from public markets with a capacity of up to 10 tons / day. By the end of 2020, the local government has promised a total of 17 composting yards to treat 100 percent of the waste from the more than 800 open markets held each week in the state capital.

Composting yards, waste disposal eco-points (available in São Paulo and Caruaru), or simply improved urban sanitation systems (as in the more precarious neighborhoods of Abidjan, Côte d’Ivoire) are among the various solutions that can be adopted by cities around the world to boost sustainability and resilience. Granted, these ideas are not always easy to implement and can be rather expensive. However, according to the What a Waste 2.0 report, the cost of inertia tends to be much higher for both the environment and the poor.

World Bank

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Urban Development

Cities can fight climate change and improve lives by finding new ways to be cool

MD Staff

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Life has always been hotter in cities. Concrete soaking up and radiating sunlight, and the concentration of people, cars and machinery crank up the temperatures, making them on average 5–9°C warmer than rural areas.

This has led to fast growth of power-hungry air conditioning units delivering cooling. The problem is that this cooling has been pumping out excess heat and greenhouse gas emissions, which warm the planet and so lead to an ever-greater need for cooling.

Cities will still have to keep their citizens cool. We have already witnessed growing heat waves, both in frequency and amplitude. They severely affect the functioning and health of cities and their citizens. Rising temperatures contribute to heat-related deaths, reduced workforce productivity—estimated at 2.2 per cent of working hours lost worldwide by 2030—and poor air quality, which disproportionately affects the poorest communities. Rising temperatures mean that 1.6 billion people could face average summer temperature highs of 35°C by 2050, approximately 1.4 billion more people than today.

We need better ways to keep cool.

“About 40 per cent of energy consumed by buildings worldwide is used for space heating and cooling,” said Martina Otto, who heads the secretariat of the Global Alliance on Buildings and Construction at the UN Environment Programme (UNEP). “Space cooling is amongst the fastest-growing building end uses, and with higher temperature, more urbanites and rising standards of living, we will need a multiplicity of solutions to provide thermal comfort and protect human health.”

Active cooling needs to be cleaner and more efficient while we design buildings for more passive cooling and include nature-based solutions in buildings and cities’ public space. And we need to shift from the notion of cooling down space to providing thermal comfort.

Cities already starting to deliver

There are global and local efforts to address the energy efficiency and climate impact of the cooling sector, in particular through the Kigali Amendment to the Montreal Protocol. These actions can make a huge difference, but cities can do a lot more.

The Cool Coalition—a global network connecting over 80 partners—is working towards a rapid global transition to efficient and climate-friendly cooling. It will work with C40 cities and its network of more than 90 members to share expertise and integrate urban cooling into their climate action plans, as well as with the GlobalABC, who issued a call: “Buildings—keeping cool, naturally”.

By implementing clean cooling strategies, cities can not only reduce the demand for cooling but align their policies with other areas of importance, such as air quality, public health and energy resilience.

Cities are working on innovative solutions, and C40 cities are delving deeper into them as they meet in Copenhagen this week for the C40 World Mayors Summit. These range from scaling up district cooling initiatives to cool roofs and green roofs and facades, to urban landscaping with nature-based solutions such as green corridors, a well-articulated offer of green public spaces.

“Cities have a critical role to play in delivering efficient, clean cooling for their citizens” said David Aitken, Director, Innovation at Cool Coalition partner the Carbon Trust. “In their role as a facilitator, planning authority, asset owner and financier, cities have many levers to pull that can influence the way cooling is produced and consumed. Taking action on cooling at the local level will also leverage co-benefits relating to health and wellbeing, air quality and living standards.”  

There are examples from all over the world.

Following the 2010 heatwave, Ahmedabad in India developed a plan for cool roofs, awareness raising and cooling stations. Since 2013, the city has avoided an estimated 1,100 deaths per year. It has acted as a blueprint for 30 cities in India, who have now released or are developing their own plan.

As part of their commitment to the Paris Climate agreement, Melbourne, Australia is banking on nature-based solutions. The goal is to plant 3,000 trees—which provide shade, reflect sunlight and release moisture into the air through their leaves—every year and cool the city by 4°C.

Copenhagen, Denmark, uses seawater in its district cooling system, reducing CO₂ emissions by up to 30,000 tonnes per year. The goal is to expand district cooling further and contribute to Copenhagen’s target of becoming CO2-neutral by 2025. Other initiatives in Copenhagen include green roofs for municipal buildings and a smart city energy lab that demonstrates how electricity and heating, energy-efficient buildings and electric transport can be integrated into an optimized system.

Cool roofs and new building materials on the rise

Cool roofs are gaining traction globally. Through its CoolRoofs Initiative, New York City has already painted more than 5 million square feet of its roofs with a reflective coating. Meanwhile, the Global Cool Cities Alliance has launched the Million Cool Roofs Challenge, a US$2 million global competition to rapidly scale up the deployment of highly solar-reflective roofs in developing countries.

“The concept of cool roofs is simple, but implementation faces barriers in the global south,” said Kurt Shickman, Executive Director of the Global Cool Cities Alliance. “We need to raise awareness of the opportunity. The availability of coatings and other cool roof solutions is often limited or non-existent. There is a lack of financing and investment. The Million Cool Roofs Challenge seeks to address each of these challenges.”

Green roofs and facades provide thermal insulation and help clean the air by trapping particulate matter. They offer the opportunity for urban agriculture and onsite wastewater treatment, adding further benefits. Bio-based building materials, which have a lower climate impact than concrete and store less heat, also offer real potential to improve the building envelope. While concrete has a high thermal mass, it’s extremely energy intensive to produce: 8 to 10 per cent of the world’s CO₂ emissions come from cement. “Alternatives such as bio-based materials are increasingly being used and can help reduce environmental impacts, while also providing the desired thermal mass,” said Otto. “For example, we have engaged in a partnership with Yale University to explore the use of such alternatives, from certified timber to bamboo and use of agricultural waste products such as coco fibre.”

It is clear that cities have a wide menu of options to choose from. They can walk the talk through public procurement decisions regarding their own buildings, set performance standards, use their planning authority and enter into partnerships with the private sector. By taking advantage of these options, cities can turn down the heat in the city and help put the world on track for a cooler future.

UN Environment

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