Chem321:Bringing Green Back to the Cities

This is the 2013 paper by Magenta Miller.

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Magenta Miller Final Term Paper Sustainable Chemistry Summer 2013

                    Bringing Green Back to the Cities

As the world begins to learn more about sustainable chemistry and the effects we are currently imposing on the globe as humans, people have been looking much more seriously into more sustainable options. These options move sustainable chemistry practices from the lab to other viable areas as well. These areas range from agricultural practices to how companies run and operate. One aspect that should be following in suit with these changes is building design. Cities are some of the largest contributors to greenhouse gas emissions and by far the largest energy consumers (Peng, 2013). This stems from the considerable amount of buildings that consume energy and burn fossil fuels in the process. These buildings also are replacing the areas where trees and vegetation used to thrive. This vegetation is not to be overlooked because it is a carbon sink. Vegetation can take in the excess carbon in the air and benefit from it. Green roofs are a practical way to lower the carbon footprint of buildings and also lower energy costs. Green roofs also replace some of the vegetation that was lost when the building was erected. Heating and cooling a building requires immense amounts of energy consumption but green roofs have been shown to decrease these costs by cooling and heating buildings naturally (Pompeii, 2011). The US Department of Health has set a goal to increase the energy efficiency of our buildings and creating “net-zero” buildings by 2025(Sailor, 2012). Using green roof techniques would be a valuable asset to help to reach this goal.

Green roofs are a type of sustainable architecture that can be designed into new buildings, but that can also be erected on top of old buildings as well. The definition of a green roof is any man made building that is covered with vegetation and plants (Mirzaei, 2013). Some buildings are covered only on the top of the building while others have plants cascading down the sides connecting to the surrounding grounds. Germany is known as the leading country of green roofs with almost 100 years of experience, and they have been able to implement the design even into their modern suburban homes (Taylor, 2012). There are two types of green roofing designs for a building. One is intensive and requires attention and maintenance of the grower. The plants that this type of roof uses are shrubs, trees, and plants that require deep soil to expand their roots into. Extensive roofs requires much less maintenance and include plants that don’t need as much soil such as herbs, grasses, or mosses (Pompeii, 2011). When choosing which type of roof a building should use, it is important to think about what the building will be using the green roof for. If recreation and replacement of lost land is why the green roof was implemented, then intensive roofing will give off a better atmosphere for its patrons. If the roof is being used to cover a large area, an extensive roof would be a better fit due to it’s low maintenance and cost to put into practice (Johnston, 2011). Rainwater is also harvested to irrigate the plants and decrease the maintenance and water used on the plants.

      A green roof is not simply a roof with potted plants covering the surface. A soft material is set in place of fiberglass or cellulose right above the ceiling of the building. On top of this is a structuring deck for the roof to be placed on. Next is a layer of waterproofing membrane to prevent water from entering the building. Typically used is a product that has soft fabrics on the underside and filter fabric with roof inhibitor on the top-side. This allows for the roof to be protected and prevents damage from roots penetrating into the roof. A final drainage layer of gravel under the growth media allows water to drain away from the roof (Mirzae, 2013). To many people’s surprise a green roof can increase the lifetime of a roof, but it keeps the roof much cooler and prevents cracking from heat or ice (Mirzae, 2013). 

The basic function of a roof is to keep a building protected from the weather and harsh conditions that surround a building. Roofs commonly are made out of a variety of products. These include, natural stones, clay, and concrete. The manufacturing of these products burns fossil fuels and creates carbon emissions. The material chosen for any project depends on the climate and surroundings. The right product can create a cooling or warming effect but it is shown that green roofing has a more drastic impact (Pompeii, 2011). This makes this option better than the typical roofing choices.

         Roofing is not typically associated with the heating and cooling of buildings and many don’t realize the significant impact on the energy efficiency a roof has on the building as a whole. Being the uppermost part of a building the roof is the part of the building that is most exposed to weather conditions such as sun, rain, ice, etc. The sun beating down on a roof causes it to increase in temperature; for example if the air temperature is 95 degrees Fahrenheit the roof could get up to 175 degrees Fahrenheit (Mirzae, 2013). In winter months, ice can line the roof and keep the building cold and decrease the warming of the building. To compensate, the temperature of a building is highly regulated by gas heating and electric cooling such as air conditioning or fans. This creates a lot of excess energy to be put into a building. To exemplify the cost of heating and cooling a building we will take a look at what a typical office buildings annual energy allocation looks like. An office building distributes 23% of energy to heating and 29% of energy to cooling through air conditioners and fans. This is just over half of the overall energy being used in an office building (Sailor, 2012). To heat the building most offices use gas heating which requires the burning of fossil fuels. Air conditioning and plug in fans use electricity, which requires energy as well. These processes create greenhouse gasses that are bad for the environment. This is therefore considered a “dirty” procedure since the emissions that are byproducts hurt the atmosphere and earth.

         Cities are also struck with a phenomenon known as Urban Heat Island where it is commonly seen that the temperature in a city can reach up to 10 degrees Fahrenheit hotter than surrounding areas (EPA).  This urban heat is potentially dangerous and can be accountable for a number of deaths on the hottest days each year. In 1995, a heat wave killed 800 people in the United States with particularly higher numbers within cities such as Chicago where 525 people died (Pompeii, 2011). To alleviate this some cities have replaced dark paving with lighter colored ones. Doing so however, creates more chemicals into the air as the pavement is laid. In a country concerned about the future generations, any small changes to clean up the processes can make a difference. Green roofing has been found as a good alternative to reducing this issue. After struck with the tragedy in 1995, Chicago implemented green roofs on some major buildings, including city hall, in 2001. This roof was studied and it was seen that the temperature on the roof was 12-25 degrees Celsius cooler than a typical black roof (Pompeii, 2011). This has a major effect on the temperature surrounding the building because the building isn’t emitting as much heat. 

Green roofing can provide a small impact on heating and cooling and is a clean alternative process. This roofing technique does not have the ability to completely replace heating and cooling for a building but it has been shown to alleviate some of the energy used. In buildings with green roofs, the energy cost can be reduced by up to 48% (Sailor, 2012). This has been studied for multiple cities and climates in the United States and it has been found that in almost every circumstance green roofing reduces the overall energy cost of the building. Another benefit of green roofing is that it decreases storm water run off. In some cities when the storms are particularly bad, sewers can overflow and runoff into streams and rivers. Soil in green roofs allows them to retain much more water than an ordinary roof. It was found at Penn State Research Laboratories that during a storm where 0.6 cm of rain fell, the green roof flow rate was 88% lower than the control roof. This means storm water running of the roof was lower in the green roof situation (Bliss, 2009). The amount of water retention the soil can hold is based on the depth of the soil. Soil depths range from 10 mm to 20,000 mm (Johnston, 2011). The roofs also help to improve the air quality due to their intake of carbon dioxide for their natural processes. Plants can also trap harmful particulates and dust that commonly float along in city air (Taylor, 2012).

     A final positive factor of green roofing is that it returns some of the vegetation that was lost when the building was built. If structured for recreational uses, it can be used as a public park space or recreational area. The shrubs and foliage can be used by birds and small animals to seek shelter in (Bliss, 2009). This will allow natural animal life to flourish and the plant life will also allow for an increase in biodiversity. Plants that are endemic to the area can be planted or others that can thrive in the climate can be put onto display. Some areas have even been able to create an agricultural space out of green roofs. A building in Tokyo that has taken its green roof to new heights by planting rice and producing 60 kg of rice per year (Taylor, 2012). The issue of space to grow crops has always been a major issue in China due to their large and increasing population. This shows that there are options to handle their issues in an environmentally friendly way. 

Installing green roofs into buildings that are already constructed is not as daunting as it may seem. There are modular green roofs that are all self-contained and one single application can be done to install the green roof with minimal upkeep after since the soil on these is not too deep (Mirzaei, 2013). New buildings could be designed with green roofing in mind and be made uniquely to fit the building. This makes green roofing a very viable option for the future. Climate has been looked at to see the effects it has on the green roofing. Using a building energy consumption modeling system, researchers were able to predict that many major US cities greatly benefited from green roofs and saved electricity in 3 out of 4 major cities with varying climates. They included New York City, Houston, Phoenix, and Portland. Phoenix was the only city not to see a major benefit in due to their unique climate (Sailor, 2012). Phoenix however would still benefit from the plants acting as a carbon sink and reducing Urban Heat Island effect. All industrialized countries have also turned to green roofing in many of their major cities. However more progress can still be made. Germany is the leader of green roofs due to their storm water issues and their drive to choose the most sustainable option to mitigate the problem. This shows that green roofing is an option for most areas and is more cost efficient.

Germany is a leader in green roofing throughout their country and they make a prime example on how incentives can work to promote green architecture. Germany has been the innovator of green infrastructures including green facades, and permeable pavement along with green roofs. One reason for this is that the federal government gives incentives for those who implement these systems. The country requires restoration of the land that the building is replacing and green infrastructure is a way to fill that requirement (Buehler, 2004). Another example shows how all citizens owning property are affected. The federal government also mandates that each resident is responsible for the storm water that his or her property generates (Buehler, 2004). Since green roofs have a large effect on storm water run off, more people naturally want to install the roofs to decrease their payment.

      Looking to the future the possibilities for green roofs are endless. Any new building being erected should be done so with the future in mind and such sustainable practices such as green roofs would be endlessly beneficial. This includes reducing storm water runoff, additional insulation, carbon sinks, and reducing urban heat island effect. With most major cities looking at their carbon emissions and global responsibility, there will be much more growth of green roofs and other architectural green chemistry to come. 

Work Cited

Bliss, D., Neufeld, R., Ries, R. 2009. Storm water runoff mitigation using a green roof. Environmental Engineering Science. 26:407-417.

Buehler, R., Jungjohann, A., Keeley, M. Mehling, M. 2011. How Germany Became Europe’s Green Leader: A Look at Four Decades of Sustainable Policymaking. Solutions. Web accessed http://www.thesolutionsjournal.com/node/981.

Johnston, J. Newton, J. 2004. A guide to using plants on roofs, walls and pavements. London Ecology Unit. Web accessed http://legacy.london.gov.uk/mayor/strategies/biodiversity/docs/Building_Green_main_text.pdf.

Mirzaei R. 2013. Green Roof and Strategic Performance. Australian Journal Of Basic & Applied Sciences. 7(2):473-479

Peng L, Jim C. 2013. Green-Roof Effects on Neighborhood Microclimate and Human Thermal Sensation. Energies. 6(2):598-618.

Pompeii, W. 2011. Assessing the Impact of Green Roofs on Urban Heat Island Mitigation: A Hardware Scale Modeling Approach. The Geographical Bulletin. 52:52-61.

Sailor D, Elley T, Gibson M. 2012. Exploring the building energy impacts of green roof design decisions – a modeling study of buildings in four distinct climates. Journal Of Building Physics. 35(4):372-391

Taylor R. 2008. Green roofs turn cities upside down. Ecos. (143):18-21.