BUILDING CARBON NEUTRAL CITIES THROUGH GREEN ROOFS

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?BUILDING CARBON NEUTRAL CITIES THROUGH GREEN ROOFS

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?????????????????????????????????????????????????????????????????????????????????????????????????????????*Jit Kumar Gupta

* [email protected]

In this era of globalization, liberalization, rapid industrialization and urbanization, cities are valued as engines of economic growth. Housing majority of global population, generating large proportion of wealth, providing best of infrastructure and services, cities are driving the growth of communities and nations. Occupying merely 3% of land, consuming?60-80% of global energy, generating 75% carbon emissions and 70% of human-induced greenhouse gas emissions, cities are making planet earth vulnerable to climate change and natural disasters. Growing concentration of people, consuming large amount of energy, emitting harmful gasses, following a pattern of unplanned, uncontrolled and haphazard development, cities are driving and pushing planet earth towards unsustainability, disasters and global warming.Studies made globally has concluded, that more than 95% cities do not meet the air standards set by World Health Organization and 90% of planet inhabitants are breathing polluted air, leading to ?loss of 7 million people annually. In the given scenario, cities are becoming breeding ground for major calamities, accounting for 90 % of cases of ongoing pandemic, COVID-19. Cities remain on the frontline of climate change and could experience catastrophic consequences in the decades ahead. Emerging patterns of haphazard and uncontrolled urbanisation are likely to impact humanity and nations adversely Accordingly, cities need to be made more sustainable and livable by making them low carbon entities.?Considering their role and importance, globally nations are looking at different options, strategies and opportunities to make cities more livable and sustainable. For achieving the mandate given in SDG 11,defined by UNO for achieving global sustainability, cities are sourcing green energy from?sun and wind, creating more open spaces, limiting polluting vehicle population, changing?fuel options of vehicles from fossil fuel to electricity, minimizing human induced pollution, rationalizing transportation and ?incentivizing energy and resource efficient green buildings.

Buildings are known to play critical and important role in making human settlements, productive, efficient, livable and sustainable. No city can be made sustainable, unless it is supported by built environment, which is carbon neutral and generator of minimum waste besides being energy and resources efficient. Buildings, are known to be largest consumers of energy, resources and generators of waste. Buildings use over 40% world’s total energy, 30% global raw material extracted, 25% timber harvested,16% fresh water withdrawal, 35% of world’s CO2 emission, 40% municipal solid waste generated and 50% ozone depleting CFC besides making 30% residents suffering from sick building syndrome. With number of people rushing towards urban centres, energy requirements of cities, due to buildings, are going to rise sharply. As per McKinsey Global Institute Report (April, 2010), ‘India Urban Awakening: Building Inclusive Cities’, India need to create, on annual basis, buildings to the tune of 700-900 million sqmts. ?Considering the large volume of built space to be created, implications of buildings in terms of resources, energy and waste, are going to be enormous. Thus buildings, as a sector, would require close scrutiny and monitoring, for effecting overall economy in the levels of energy consumption and for making cities resource efficient and sustainable. Within built environment ?building envelop, comprising of outer walls and roof of building, accounts for about two- third (60%)of total heat gain and heat loss within built space. Building envelop is known to be major determinant, dictating the urban sustainability besides operation and energy consumption pattern of the buildings. Accordingly, roofs and walls have to be planned, designed and constructed carefully and thoughtfully, for insulating?buildings against natural elements of heat and cold. This paper examines the relevance and context of green roof in making buildings sustainable, energy efficient and zero carbon.

?Green Roofs;

Green roof, as one the roof typology, is fast emerging as a preferred option for promoting sustainability in the buildings. Green roof, is defined as a space on the roof comprising of collection of greenery, planted on top of a man-made structure. Green roofs, as a solution to manage the temperature within the buildings and bringing nature into cities, have been part of the human history.??The Hanging Gardens of Babylon , used an elaborate irrigation system to create terraced gardens while Europeans used traditional sod roofs for insulating houses (keeping the cold out during the cold winter months and keeping the heat in at the same time). Cities of today, are fast becoming spaces filled with buildings made of brick, mortar, glass, steel and concrete, eliminating nature and natural elements including green spaces, flora and fauna. Existing pattern of urban growth and development, has led to making cities both congested and warm, leading to rising temperature, global warming and large greenhouse gas emissions.?Heat islands thus created in the urban areas, has led to sharp rise in demand and consumption of large fossil fuel-based energy, for keeping the buildings cool, warm and livable. Green roofs, offering variety of benefits in making buildings cool and bringing nature back, are fast returning to the cities. More and more urban buildings are opting for installing roof gardens, making addition of rooftop planters and permitting the growth of vegetation. Germany, as a nation, has emerged as the global leader, with more than 14 percent of all roof area already made green.

?Context of Roof Space

Looking at the entire context, structure and fabric of the buildings and their role and importance as major determinant of sustainability, critical area for sustainable disruption would be, rooftops. Roofs in buildings, are known to be responsible for one-fourth (25%) of total heat gain and loss in the building. In addition to major implication in modulating heat, roof spaces also remain largely wasted and rarely used productively. Large unused roof space within the buildings, causes enormous loss to owner, occupants, community and city. Hard and black surfaces are also known to be largely responsible for and?promoters of heating and rising temperatures, generating a cascade of problems for cities including; getting?hot in the summer, acting like a desert and heat up the entire city, ?making rainwater to run off the roof system and causing flooding besides having ?no aesthetic value and making no contribution to the biodiversity in the urban spaces.

?Advantages- Green Roofs?

Green roofs are known to be providers of numerous physical, social, economic and environmental benefits not only to the built environment, people and communities but also to the city, climate and human livability, in terms of ;

·??????Creating new frontier of humane and sustainable urban planning; decreasing?stormwater runoff ;?reducing ??air pollution- Increasing oxygen production; improving air quality by purifying air ; encouraging biodiversity,?minimizing greenhouse gas emissions, removing air particulates; reducing carbon-footprints of buildings; improving property value and marketability; promoting economy, generating employment.

·??????Promoting Community gardening projects ,?adding up greenery , creating?visually pleasing green element s; Improving aesthetics in building and neighbourhood;

·??????Impacting positively living, working and promoting well-being of people through green environment; promoting relaxation and reducing stress; making people happy, heathy and more productive in the green environment.

·??????Promoting optimum?utilization of unused space ; ?making addition of a new amenity space within building.

·??????Making building operationally efficient and cost-effective; regulating the indoor temperature and reducing the ambient temperature; reducing energy costs?by absorbing heat instead of attracting heat; providing natural insulation for buildings.; reducing/ lowering air- conditioning demand, Improving efficiency of mechanical equipment.

·??????Reducing rooftop maintenance- elongating the life of roof--offering money-saving opportunities; providing?natural protection against extreme heat –enabling?green roofs to last--?twice as long? as traditional rooftops.

·???????Making solar panel more efficiency; reducing the temperature on the roof; reducing energy costs.

·??????Insulating buildings against noise outside and inside- acting as a sound barrier by absorbing sound and providing a quieter environment, both inside and outside building.?

·??????Making buildings safe against fire by providing additional fire-resistant layer through plants, known to contain lot of moistures.?

·??????Creating ability to?reduce and slow ?stormwater runoff?and avoid flooding in the urban environment.

?Marginalizing Heat Island

Cities are always hotter than the rural areas that surround them. Cities in general and core areas in particular suffer from the perpetual problem of concentrated heat and rising temperatures, as compared to the periphery. Heat radiated from asphalt roads, vehicle exhaust, air conditioners, paved surfaces and walls/roof /windows from concrete buildings, lead to rise in temperature and remain responsible for promoting ?heat island, making cities several degrees hotter than neighboring areas. Heat islands seriously impact urban settlements during heat waves generated by climate change, leading to colossal loss of human lives. ?Plants greatly reduce the impact of the sun by absorbing heat. In cities with little to no greenery, there’s nothing but buildings to soak up the sun’s rays. In some cases, cities without adequate greenery are as much as 10 °F warmer than surrounding areas with green landscape. During the summer months in New York City, the daily minimum temperature recorded on average is 7.2oF warmer than the surrounding suburban and rural areas and even more during heat waves.?Heat islands are known to impact both inside and outer surfaces of building leading to rise in temperature. Rising temperature within buildings, has critical implications for the occupants in terms of use of larger energy required to lower down the temperature and bring it at the level of ambient temperature. Green roofs are known for their distinct quality and capacity to reduce/ minimize urban heat island effect, promote energy saving and reduce energy costs. Green roofs can mitigate this phenomenon, making cities more climate resilient, and protecting people most at-risk of heat waves by replacing dark surfaces with bright vegetation. Plants are known for their property to reflects rather than absorb sunlight. In addition to reflecting sunlight, plants also undergo a process called evapotranspiration in the presence of sunlight, they release moisture into the atmosphere, which further cools down cities. Green roofs serve a much greater purpose than simple beautification. They also provide natural insulation for buildings. Adding a roof garden greatly reduces heat island effect by absorbing the sun and putting it to good use. Along with removing heat from the air, it??provides shade and reduces temperatures in the surrounding rooftop space, as well as in the building below. Study conducted by the National Research Council of Canada, has concluded that even a six-inch extensive green roof, can reduce summer energy demands?by more than?75 percent ?by lowering air conditioning demand besides decreasing air pollution and lowering greenhouse gas emissions because plants undergo dew and evaporation on a daily basis. Plants on green roofs and other urban outdoor surfaces can help to cool and reduce the excessive heat that accumulates in cities due to the large amounts of concrete, as showcased by the graph given

Insulating Buildings

Heat is gained and lost in the buildings through roof, doors, windows, walls and the floors. Dark surfaces are known for making surfaces hot by absorbing large proportion of heat falling on it, whereas white/light surfaces reflect majority of the heat and remain cool. Having dark roof over the buildings invariably leads to rise in temperature of air in the rooms below and accordingly involves increased demand/pressure on mechanical systems, making it more difficult and expensive to adequately cool a building. Conventional roof remains major element of building, causing heat loss in the winter and heat gain in the summer. Green roofs help to insulate buildings and lower the temperature of the roof and building itself. The extra layers of a green roof also serve as insulation. During summer, green roofs cool entire buildings down, which reduces the need for air conditioning. Since green roofs improve insulation, they also improve heat retention in buildings during the colder months. As a result, green roofs can significantly lower energy cost of building. Buildings with high roof–to–wall ratio (i.e., buildings with?greater roof area vs. exterior wall area )are known to be best performer,?leading to optimizing energy efficiency. ?In addition to insulating buildings against heat gain/loss, additional layers of green roofing and growing medium also helps in minimizing the noise in the interior of the building from mechanical equipment on the roof. Reduced noise levels from typical extensive green roofs (3” - 4” growing media) is up to 3 dB for reflective sound. Accordingly, green roofs are known for their great quality of insulating building against heat gain and loss besides noise, making buildings operationally efficient and cost-effective.

Prevent Flooding and Promoting Stormwater Management

Stormwater management remains a major dilemma and issue facing urban areas.?Increased urbanization is known to promote large scale construction in town and cities, leading to creation of large impervious surfaces at the cost of green spaces. Genesis of majority of the cities suffering from the perpetual problem of flooding, is the outcome of major land areas of the cities going under built environment, paving of pathways and metaling of roads. Existence of large non-porous and hard surfaces in cities, invariably leads to generation of large volume of runoff, when it rains. It has been estimated that storm water run-off generated by hard surfaces is five times more ,?than when compared to woodland area of the similar size. During rains, storm water from buildings and roads flows into storm sewer and therefrom it either enters a municipal water treatment facility, or directly deposited into the ecosystem via lakes, streams, and rivers. During precipitation, cities rely on drainage systems to prevent flooding, but extreme rains can overwhelm the existing capacity of drains and pipelines, resulting in submerged streets. Pollution remains another critical problem with storm water drainage system. As rain falls, the water gets saturated with?pollutants. Dirt or contaminants, scattered on the roof and streets, are picked up by the run off and flushed into the storm sewer . These pollutants then get carried by underground pipelines to rivers and lakes, which invariably results in drinking water contamination. Rain water, thus emerges as a major source of flooding and pollution of potable water sources in the urban context. Cities with combined sewage system, jointly collecting rain water runoff, domestic sewage, and industrial wastewater for treatment, are worst sufferers due to overflowing/choking of the city’s drainage system, discharging sewage into streams and rivers. This invariably leads to contamination of drinking water; causing flooding; creating problem of pollution, which impacts quality of life for local humans and wildlife.

??In order to reduce the flooding and pollution caused by stormwater, it is important ?that existing hard surfaces are minimized and?more green, open and ?porous spaces are created to make cities spongy so that majority of rain water gets absorbed /harvested and only limited quantity of rainwater is allowed to outflow and go into the drains. In this regard green roofs offer one of the best options and can prove to be of great help to minimize flooding and polluting rainwater. Planters existing on the green roofs have the ability and capacity to absorb, filter, remove harmful toxins, reduce and slow the flow of the rainwater. A green roof absorbs rain water by the water buffering in the plants, substrata and drainage layer. This delays the discharge of rainwater to the sewage system, purifies the rainwater, and allows the water to evaporate through the plants. This all helps in stabilizing the groundwater level, reduces the peak load on the sewage system and reduces the risk of flooding. Plants need water to thrive and green rooftops feature a moisture absorption layer that safely holds on to water during storms. Rooftop planters collect and filter rainwater in a more natural process. Rainwater is stored by the green roof substrata and then used by plants. The deeper a roof garden, more capacity it has to collect the rainwater.

Studies carried out ?by researchers at the Pennsylvania State University,?Center for Green Roof Research , has ?shown that on an average , green roofs captured up to 80% of rainfall during rainstorms, compared to 24% typical for standard roofs, as against 74% and 26% during peak runoff. ?With the maturing of green roof plants, growth of root systems, storm water retention of green roofs is also known to increase. Another study?has concluded?that a 4” extensive sedum roof has the capacity to collect 60-75% of annual rainfall in a temperate climate. It has also been concluded by researchers that during summer, green roofs can retain? up to 90 percent of the precipitation that falls on them and up to 40 percent in the winter. Considering distinct advantages of green roofs for their contributions in reducing the amount of storm water, minimizing flooding, neutralizing acid rain, trapping dust and airborne particles, globally cities, are incentivizing and promoting buildings having green roofs, in the shape of levying lower storm water management fees, setting-off partially the cost of providing green roofs etc. More cities need to adopt the strategy of providing incentives to make green roof integral part of built environment.

Improve Food Security

City are known to be large consumers of agricultural products, needed on day-to-day basis?for the consumption of urbanites, including fruit and vegetables These agricultural products are sourced from rural hinterland ,both from near and?far off?places. Transporting them?from rural hinterland and keeping them refrigerated, involves ?usage of lot of energy and generation of large GHG emissions, making cities unsustainable. In order to promote sustainability, cities have to reinvent and make themselves self-sufficient in daily human needs including availability of fruits and vegetables. To meet this objectives, cities need to make optimum use of large chunks of land available with individuals, corporates, developers, institutions and parastatal agencies for promoting urban agriculture including growing things needed by people on daily basis. In this context, green roofs offer an excellent opportunity for growing and making available vegetables and fruits?within the communities. ?Although urban agriculture is ?a relatively new and emerging field ,but ?rooftop farming is gaining currency and is becoming increasingly popular. Rooftop farms, despite limitations and harder to implement than standard low-maintenance green rooftops, carry distinct advantages and benefits for individuals, community, city and planet. Rooftop farms have enormous capacity to produce agricultural produce of daily needs and promote city’s food security by ensuring assured and regulated supply of produce. Strength of green roof farming can be effectively leveraged for stabilizing the prices, making them affordable even for the poorest of the poor of urban residents. Being fresh, such produce carry enormous value for improving the health and hygiene of the residents. Using green roofs for fruits and vegetables can also help improve the income of the residents and economy of the city besides generating large employment opportunities. Using green roof for agrictural will not only usher an era of food security but also provide numerous physical, social and economic benefits to the city and the community.?Rooftop farms can also help city become sustainable and livable by minimizing its ecological and carbon footprints, because cities will ?no longer be ?required to import?and transport fruit and vegetables from far off rural hinterland ?and also to refrigerate them, two critical factors involved ?in the food production system, generating major greenhouse gas emissions and promoting global warming. In addition, city will have the benefit of reduced heavy traffic and reduced vehicle driven pollution, generated due to transporting fruits and vegetables.

?Promoting Economy

In addition to the environmental, physical and social benefits, green roofs are also known to provide numerous economic benefits creating win-win situation for both owners and occupants. A roof garden substantially enhances re-sale or rental values of property.?In addition to making value addition to property, roof garden also acts as a valuable amenity that enhances the worth of the structure for a relatively modest expenditure. Despite the fact that installation of a green roof invariably involves higher upfront costs when compared with the cost of traditional roof, but when you look at the life- cycle cost of building, then green roofs make buildings both cost-effective and operationally efficient by saving cost on heating and cooling and maintenance of building. Increased?R–value?of the green roofing system, along with reduced temperatures on the roof, lessen HVAC loads, resulting in energy cost savings. Green roofs also make value addition to property by reclaiming the unusable space at the roof level and making addition to usable space in the building, without increasing the footprints of the building. The natural and sustainable appearance, combined with additional usable space, improved appearance, reduction in energy costs and extension of the life span of?roof, means an increase in value of property. A green roof is universally known for its distinct advantage to improve property value and marketability, especially in urban areas with little green space.

Research carried out in London (Marsh and Parson's) have found that a roof garden or balcony typically adds 10-25% more value to the property in high end neighborhoods. Valuation study was also made by the University of Michigan while comparing a 2,000 square meter conventional roof and a green roof in terms of looking at the range of benefits of green roofs including stormwater management, improved health benefits due to reduced pollution, and energy savings. Study concluded that over its estimated lifespan of 40 years, a green roof would save about $200,000, of which, nearly two–thirds would come from reduced energy costs. The economic benefits of any individual green roof will, however, depend on its design, geographic location, surroundings, and the building itself.

?Bridging Social Gaps and Building Societies

Working or living in a green environment invariably brings people together; making positive effect on social cohesion in communities; providing welcome relief for residents having no access to vegetation. Bringing people near greenery provides numerous physiological benefits ranging from reducing stress, to improving memory, to promoting health.?Green roofs Improves overall well-being of everyone in the building besides providing an incentive for people to socialize on their roofs; helps ?neighbors to get to know one another & during extreme conditions come together allowing ?people to assist one another;?provide an aesthetical pleasing view of environment; educating?occupants and visitors to the benefits of the green roof and need for ?protecting the resource.

?Adding Life to Roof

Typical roofs always remain exposed to forces of the nature and natural elements including sunshine, rain, snow, temperature fluctuations, heat and cold and countless other elements on a regular basis. This leads to contraction and expansion of various components of roof resulting in its wear and tear. This wear and tear of the protecting roofing materials from direct ultra–violet radiation and extreme temperatures, ultimately leads to maintenance and repairs, which involves lot of inconvenience, time and cost. As against the normal roof, green roof offers distinct advantage in terms of; protecting the roof membrane from climatic extremes and physical abuse, thereby greatly increasing the life expectancy of the roof. Major advantage of the roof green roof lies in the fact that by protecting the underlying roof covering, green roof extends the life span of the existing roof fabric up to 60 years or even longer; thus making the maintenance of roof highly cost-effective besides providing numerous other benefits to the occupants and the environment. Studies have shown that additional investment made on making of the green roof, can be recouped within a time span of 8 to 21 years. Germany, home to several rooftop gardens, that were installed 50+ years ago, have yet to experience a leak. Maintenance cost of green roof ?can be?made incredibly low by selecting native plants, investing in self-watering planters and designing?garden layout in order to keep plants in prime conditions based upon preference to sun and. Shade.

Improving Air Quality

Globally, air quality in urban areas is fast deteriorating in majority of the cities. Studies made globally conclude that 95% cities do not meet the air standards set by World Health Organization; and 90% of planet inhabitants are breathing polluted air. Majority of cities are suffering from prevailing bad quality of air, due to large scale pollution caused by traffic and transportation run purely on the fossil fuel, smoke generated by polluting industries; petrochemical operations generating black energy by using coal, oil and gas; ?consuming large?black energy ?by buildings in its?construction, operation and maintenance etc. The World Health Organization estimates that poor urban air quality accounts for 7 million deaths per year. Unless issue of poor air quality is addressed, death rates will continue to rise. In addition to ?millions of people dying annually due to prevailing poor quality of urban air,?millions ?others are also ?suffering from air borne diseases. Cities like Delhi, are known to come to a complete halt by the invasion of polluting air and smog, causing enormous physical, economic, social, environmental and health related issues. In order to make cities and people healthy, it will be essential that quality of air in urban area needs to be improved and made fit for human consumption, based on the norms and standards prescribed by WHO. In this context, green roofs can help and provide critical support and option to reduce dust, particulate matter, and smog in the city air to make it clean, because plants grown on the green roofs are known for their inherent quality of capturing pollutants and filtering out gases from the urban air that could potentially be toxic to the environment and human health. Plants are known to produce oxygen while consuming carbon dioxide from the air. Plants are also known to trap up to 85% of airborne particulates on their leaf surfaces. These inherent qualities of plants will be valuable to improve the quality of urban air. Elevated gardens in the shape of roof gardens are known to reshape and redefine the urban micro-climate; making it more supportive of human health and urban operations. Relevance of the green roof also assumes importance in the context of natural disasters and pandemics like Covid 19, which involve availability of large volume of oxygen as a pre-requisite to combat the virus. Green roofs can stop the emergence /spread of such pandemics in future.

?Integrating nature and cities

Cities and nature remain anti-thesis and believe in mutual exclusion. Intensity of urban development and growing footprints of built environment, led by human greed and land speculation, are largely responsible for eroding and excluding nature from the cities. In urban environment, available habitat for wildlife has been marginalized to a large extent when compared with rural areas. Non-availability of appropriate habitat, has invariably led to most of the wildlife either getting eliminated or migrating ?out of the urban setting. Carefully creating and promoting vegetative roofs in urban areas, can provide appropriate habitat for birds and insects and act as, so called, stepping stone habitats, between the isolated habitat patches that exist in the middle of cities and built environment. Roof gardens, when planted with indigenous and appropriate flora, can provide important habitats for native bird. Green roofs, filling the void created by loss of flora and fauna at ground level, have enormous capacity to promote biodiversity on large scale. ?Green roofs are also known to provide trees and shrubs, where birds could potentially live. ?Another typology of roof is now providing shelter to wildlife including birds and insects. Called as,?biodiverse?or?brown roofs,?they work in a similar way to green roofs but have individual characteristics that attract certain fauna and might include sand, stones and specific plants. Accordingly, different typologies of green roofs can be planned, designed and created, considering the special habitat character demanded by different birds. However, this would require bringing citizens, communities, urban authorities and experts on the same platform to prepare an agenda and action plan to bring nature into the urban context. Within a dense urban environment everyone needs green space and increased biodiversity is known to promote a deeper appreciation for nature, helping people to become environmental advocates.

Decarbonizing Buildings

Buildings are known to be greatest consumers of energy, resources and also largely responsible for generating enormous volume of waste. Buildings also are known to promote global warming, climate change, rising temperature and produce large carbon footprints. Green roofs empower buildings to achieve reduction in cooling loads and reducing greenhouse gas emissions from fossil fuel combustion associated with the use of HVAC equipment. Adding plants and trees to the urban landscape and making them part of green roofs, increases photosynthesis, reduces carbon dioxide levels produced by vehicles, industrial facilities, and mechanical systems. In addition, green roof also helps in increased production of valuable oxygen. Collectively, green roofs?play critical and constructive role?in reducing GHG emissions and ?decarbonizing the cities.

Greening Urban Core

Open spaces always remain in demand and command premium in urban areas, due to lesser availability of open area and prevailing high cost of urban land. Rapid urbanization and commercialization of urban land, has led to using major chunk of land under development for residential, commercial, industry, trade and commerce, which command high premium in urban land market, generating lot of profit for land developers and builders. This leads to leaving minimum land for green, which is not salable and has no market/commercial value. Congested core areas in majority of ?old cities have been?suffering from absence of adequate open spaces, adversely impacting the quality of life of its residents. Options for creating open spaces also remain minimal, due to very fabric, structure and operation of these areas and non-availability of land for creating green spaces. These areas remain critical because they form the very heart and souls of the city, housing not only its valuable heritage but also providing space for its major trade and commerce operations. Entire life and economy of the old cities gravitates around these areas. These areas remain choked under the pressure of congestion and large-scale activities and continue to suffer due to non-availability of open spaces. Core areas of the cities, need de-congestion and open spaces. In order to improve the quality of life and improve operational efficiency of such congested core areas, it will be appropriate to use the mechanism of??green roofs to create large open spaces by transforming the existing large black ?roof area into islands of ?greens. Converting available roof terraces into green roofs can add usable open space without increasing the footprints of the building. These green spaces, besides catering to the needs of the owners of the buildings can also provide value to the community. Provision of these green terraces will help in improving the quality of life, reduce energy requirement of the buildings besides improving the visibility of the area. Urban local bodies and city development authorities must prepare a blue print and action plan, in consultation with the local representatives, resident welfare associations, NGOs, CBOs, experts to create large green space in the core areas of the city. Such an option must invariably be included and made integral part of preparing master plans/development plans and framing dedicated plans for the development of the core areas. Dedicated funds must be allocated in the budgets of urban local bodies/city development authorities, for incentivizing and development of the green roofs in the core areas.

?Generating ?????????Employment

When green roofs are designed, built/constructed and maintained in cities, new employment opportunities arise at the local level, to meet the demand of green roof-specific manufacturing, production of components and growth of plants, grass and trees for the roofs, and also for green roof design, thereby creating an entire new ?typology of industry and ?job opportunities associated?with it.

Installing green roof

Making green roof involves skilled manpower and special material comprising of protection board, waterproof membrane, soil, insulation layer and growing medium, which have to be used carefully so that healthy plants can grow without causing any damage to the roof below. To begin with, protection board is installed to covers normal roof, followed by placing layer of waterproof membrane and layer of soil, for planting vegetation.?Roof typology could be either intensive or extensive. Extensive roofs, have a thinner layer of soil and are best suited for plants with shallow roots such as mosses and?sedum whereas,?intensive roof gardens, have a deeper layer of soil or other growing medium so that it can sustain hardier plants including trees with stronger roots. The waterproof membrane is normally made from a material such as ethylene propylene diene monomer, a rubbery material similar to the lining put down for ?a duck pond in the garden. This layer prevents water getting in but also stops roots from the plants growing down into the roof. There is also a possibility of adding a further insulation layer that can be placed either on the roof beams or above the waterproof layer. To effectively maintain and water your garden, filter layer, drainage layer and water retention layer, are placed. These layers also help ensure that the soil is not washed away. On top of that, a mix of porous material and soil is placed which is the growing layer. It is important that the growing medium should be as light as possible but still allows plants to flourish. While installing green roofs, soil is rarely used as the growing medium because it is heavy and packs tight after repeated rains, reducing water retention and aeration for plant roots. Instead, manufactured materials such as granulated clay or shale are commonly applied.?Organic compost ?and fertilizers are added as nutrients.?Selection of plants will depend upon typology of roof selected ie intensive or extensive green roof. Maintaining your green roof is no different to maintaining your garden. Extensive green roofs are easier to maintain when compared to intensive ones, but they all need weeding and cutting and safe and easy access. It is not essential to make the entire roof green, one can opt for part of the roof to be made green. However, before making roof green, one should get the load bearing capacity of the roof tested for safety.

Incentivizing Green Roofs

Consuming large energy and resources, buildings account for?the emissions of the majority of a city's greenhouse gases, carbon dioxide, methane, and other pollutants?into the atmosphere. Making provision of the green roofs??can help large reduction in the use of energy to make cities more sustainable. Urban sustainability is known for its distinct advantages in improving health of the residents and communities in a city by reducing air pollution, lowering temperatures, and promoting exercise. Green roofs help cities and individuals receive return on investment reducing enormous health care costs.?By making?air and water cleaner, green roof?reduce the burden on our health care system because people tend to be less sick and more productive. Considering the numerous benefits green roofs offer in terms of; reducing the amount of storm water, minimizing flooding, neutralizing acid rain, trapping?dust and airborne particles; promoting sustainable; reducing consumption of energy/GHG emissions; making cities less prone to global warming and?promoting health and hygiene;?etc.; mandating provision of the green roofs, as integral part of the?buildings, need to be promoted by incentivizing the owners of property?on the pattern followed in promoting the use of solar and wind energy , to partially offset the cost of a green roof. This will go a long way in converting large black and blank roof area into green and colourful roof area. Considering the inherent value of green roof, New York City has already?passed a?by-law that rewards building-owners, who cover 50 per cent of available rooftop space with a green roof by providing one-year property tax credit up to $100,000. The credit equals to $4.50 per square-foot of roof area that is planted with vegetation, or approximately 25 per cent of the typical costs associated with the materials, labor, installation and design of the green roof. Globally cities, are incentivizing and promoting buildings having green roofs, in the shape of levying lower storm water management fees, setting-off partially the cost of providing green roofs etc. More cities need to adopt the strategy to provide incentives, to make green roof a mass movement.

Conclusions

Green roofs remain valuable for offering enormous social , physical, economic and environmental advantages to the individuals, owners, communities, city , nation and planet earth, in terms of; making buildings cost-effective, energy efficient and least consumers of energy and resources; bringing nature into the city; reducing the urban heat island impact; reducing the intensity of storm water and saving cities from flooding; reducing global warming and lowering carbon footprints of the buildings/city; conserving?rainwater water; meeting deficiency of green spaces in congested parts of cities; making optimum use of available unused roof space; making addition to usable space?without increasing the building footprints; promoting economy; generating employment; promoting socialization and security; making people happy, healthy and more productive; bringing birds back to the cities; growing vegetables and making cities self-sufficient in daily needs; eliminating transportation and refrigeration of vegetables; increasing value of properties; empowering cities to become?zero-carbon.

?Despite numerous benefits green roofs offer, major obstacles in promoting the green roof remains the non-availability of affordable and proven technologies and high initial cost. Green roofs typically cost?two to three times? more than a non-green roof.?Although green roofs are not simple to construct or cheap to maintain, yet numerous benefits they offer in long term outweighs, the initial cost concerns. Over time, green roofs, pay for themselves besides making large contribution to the urban?sustainability?and?urban environment. For?creating awareness about the benefits and?for promoting green?roofs, cities need to launch?pilot programs encouraging the installation of green roofs by offering?financial and other benefits. However, reputed technical institutions like IITs/NITs needs to be roped in to promote research in evolving cost-effective and ?operationally efficient design of green roof, considering the different climate zones prevailing in India.

?Green roofs should also be included as part of study curricula of all technical institutions to make students aware about the principles, concepts and technologies to be used in the planning, designing, construction and maintenance of green roof. Industry also needs to be ?roped in to bring innovative technologies and manufacturing of the components used in the making of the green roof, on large scale to bring cost-effectiveness and economy of scale. Bye-laws applicable at the local level also need review and redefinition to facilitate ??the creation of green roofs in the city. By-laws?should also include the provision of??area going under building footprints to be compensated as green area within the building?constructed or on the roof, for making sure city does not lose the extent and advantage of green spaces and where lost, are invariably compensated within the building itself. Our capacity to promote the acceptability of green roof in the urban context, will hold the key to decarbonizing the cities and make them sustainable, livable and?carbon-neutral.

?Bibliography

·????????????????????????McCarthy J, ?Sánchez E; 6 Ways Green Roofs Protect Cities From Climate Change--From fighting heat waves to stopping floods?

·????????Davis C; 4 Reasons Green Roofs Do A Building Good; July 13, 2015?

·???????Rosenzweig, et.; Green Roofs in the New York Metropolitan Region, Research Report,"

·???????Dhot B P, Gupta JK,, Kaur Jasleen; Planning and Designing Sustainable Cities in India, SPA Vijaywada

·???????Gupta?JK; Site Planning in Architectural Projects- Principles and Approach; unpublished paper

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·??????Note; All images shown in the text are sourced and have genesis in the Google.com which?is?gratefully and thankfully acknowledged and appreciated?by the author

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• Author;-

?Ar Jit Kumar Gupta

?????????????#344/40-a, Chandigarh-160036

?????????????Former, Director College of Architecture IET Bhaddal (Pb)

[email protected]

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