Green Roofs: The Future of Combating UHI

Green roofs add a beautiful shade of natural green to a dull urban environment.


Skyler Hall – Plant, Soil, and Insect Sciences

Joseph Lyons – Building Construction Technology Sciences

Anthony Tiso – Pre-Veterinary Sciences

University of Massachusetts, Amherst



HOOK!!!!! Located in Southern California, Los Angeles [LA] is one of the most popular tourist destinations in the United States and draws in millions of people annually. In 2016 alone, nearly 46 million people visited the city (CBS Los Angeles, 2016). LA is the second largest city in the America, rivaled only by New York City. According to Population USA (2019), in the most recent census survey, Los Angeles has a resident population size of roughly 4 million people and it is estimated that by the summer of 2019 it could potentially rise well over that number. It is predicted that by 2050, the population will have increased by 3.5 million people (World Population Review, 2019). This ever increasing population of the city has a significant impact on cities and the urban environment. Increased buildings lead to higher temperatures through trapped carbon emissions, lack of vegetation, and decreased albedo. All of these factors lead to the Urban Heat Island Effect [UHI]. The urban/city area is significantly warmer than the  surrounding suburban and rural areas. In some cases it was noted that temperatures in major cities could be as much as 22℉ hotter in the evenings compared to the surrounding areas (North Carolina Climate Office, 2019). Continue Reading

Why Not Wood? (Mass-Timber Construction)

Jason Norman (Building Construction Technology) ; Miranda D’Oleo (Environmental Science) ; Liya Woldemariam (Envi. Sci.) ; Dylan Haley (Natural Resource Conservation)


The building sector releases greenhouse gas emissions that contribute to climate change and could have a significant impact on the people and town of Amherst. The carbon dioxide that is emitted into the atmosphere has the ability to trap and store heat near the earth’s surface through the greenhouse effect. Just over the past century, there has already been a 2°F increase in temperature in the Commonwealth (Environmental Protection Agency, n.d, p.2). This has raised concerns regarding the damages that will result from the increase in temperature on human health. It is projected that there will be a 50% increase in the number of heat related deaths, increase in asthma and accelerated spread of diseases through pests (Town of Amherst Energy Conservation Task Force, n.d,  p.10). An increase in temperature and precipitation along with the increase of pollution have shown to increase the incidence of asthma. Pollutants such as smog are expected to increase with high temperatures. These pollutants have been linked to cause respiratory issue (EPA, n.d). Also, high temperatures lead to increased spread of diseases through insects. Insects such as ticks that transmit lyme disease function best in temperatures above 45°F. This means that as winters become warmer the length of time that the ticks are present increase (EPA, n.d). All of these risk and consequences to human well-being and health are too high to not implement policies, in the building sector specifically, meant to mitigate against climate change. Continue Reading

Green Roofs: Saving the Air and Saving Lives

Nicholas Lanni: Animal Science

Cole Payne: Building and Construction Technologies

Ben Lasky: Geology

Buzzing from the alarm clock’s warning ushers in the start of a new day. Avoiding the seductive snooze button, you roll out of bed and begin your morning preparations. Between the alertness of being awake and the daze of sleep, you slowly waddle to the dark bathroom to brush your teeth and wash off the last bit the previous night’s trance in the shower. Drying off, you begin to suit up for today’s task, whether its another day at school or a demanding shift on the job. Sizzling fragrant coffee provides the final jolt needed to get you on your way. Nearly walking out the door you almost forget something: your face mask. Leaving the safety of your climate-controlled home and venturing outdoors without it would be foolish. Indeed, taking deep breaths of unfiltered air is very unhealthy and dangerous. Continue Reading

Wildfires and Climate Change, what can we do?

Ivan Chukarov, Chris Clark, Amelia Midgley, Jeffrey Trainor

The devastating Camp fire in California that raged in November of 2018 has left more than 70 people dead and more than 1,000 people missing. In Butte county, the Camp fire has destroyed 12,784 structures, including 9,891 homes (Holpuch & Anguiano 2018). The emotional and physical stress these large wildfires put on residents of burned areas is unimaginable. Lilly Batres, a 13 year old resident of Magalia, a town affected by the California Camp wildfire, was evacuated to a shelter nearby.  Lilly doesn’t know whether her home is still standing and while she seeks refuge at a camp, she cannot grieve in privacy. To Lilly, the camp is “cold and scary”,  and even to some extent she feels like “people are going to come into our tent,” she explains (Anguiano 2018). The Camp Fire is not the only fire that has burned massive plots of land in 2018. The Carr and Ferguson fires in California, burning more than 80,000 hectares, and in Oregon and Colorado have orched more than 100,000 hectares collectively (Selby 2018).   Continue Reading

Hurricane Resistant Building Techniques for New and Restorative Residential Construction in Coastal Communities


Emma Curran- Environmental Science

Erika Smith- NRC

Dean Jenssen- BCT

George Baidoo- BCT

From Webster’s Dictionary, the word ‘claustrophobia’ is the fear of being enclosed in a small space or room and unable to escape or get out. Many people in the world suffer from this phobia, while others simply feel uncomfortable with the idea of being stuck in place. This is a feeling thousands of people have endured, especially in times of a natural disaster, faced with a rising storm surge and trying to escape. This is the fate many residents in hurricane prone areas, particularly the Gulf Coast and Florida have encountered. Unfortunately, a storm surge rises irrespective to one’s claustrophobia. Brendan Smialowski and Gianrigo Marletta interviewed Mexico beach resident Loren Beltran after the recent devastation Hurricane Michael caused. “My house, which is in Mexico Beach, is under water,” said Beltran, distraught after learning that water had reached the ceiling of her damaged home (Smialowski, B et al. 2018, October 11). Climate change is progressing, and factors like storm surge, sea level rise, and sea surface temperature (SST) increase are causing high intensity hurricanes to happen at a higher rate. This has led to more much more flood damage in coastal communities.  The only viable solution to better protect the homes of residents living in coastal areas is building with flood proof materials and methods, such as concrete foundations, to ensure minimal damage possible from the hurricane. Continue Reading

The Effects of Climate Change on Hurricanes and How to Potentially Minimize Hurricane Damages

Jennifer Arthur: Animal Science/Pre-Vet

Abigail Buck: Wildlife Biology

Spencer Rock: Forest Ecology and Conservation


During hurricane Sandy in 2012, many businesses in New Jersey were left badly damaged or completely destroyed. Donovan’s Reef, a local restaurant in Sea Bright, NJ was completely washed away by the storm. The restaurant was not rebuilt or reopened for over 5 years, leaving anyone who relied on the business for their livelihood without jobs and without an income (Murdock, 2017). Following Hurricane Sandy multiple family owned businesses like Donovan’s Reef, Seacoast Marina, and Memphis Pig Out suffered as insurance did not account for anywhere near their total costs. (Murdock, 2017; Quittner, 2015). Memphis Pig Out is a barbecue restaurant that was built from the ground up by a local husband-and-wife team, Strassburg and Mark. Following Hurricane Sandy their restaurant suffered over $65,000 in damages but only received $5,000 in insurance coverage, barely a fraction of the rebuilding costs. Immediately, to get renovations started, Strassburg sold every single piece of jewelry she owned but it wasn’t nearly enough. Just to keep their restaurant open the couple had to take on second jobs that paid barely anything. Strassburg took on a nightly magazine advertising job while her husband became a dog walker. This money kept their business afloat but meant they worked excessive hours, spent barely any time together, and still barely pulled their business out of collapse. Despite their best efforts restaurant sales in the years following Sandy fell by over 30% and the business is only reaching pre-Sandy production six years later (Quittner, 2015).  Global warming is no longer just an inconvenience in our day to day lives, but is starting to have a real impact on communities. Continue Reading

Green Building Materials and Carbon Taxes on the Building Sector: Reducing Emissions from the Built Environment


Kyle Horn: Building Construction Technology

Augustin Loureiro: Geology

Daniel MacDonald: BDIC, Agricultural Research and Extensions

Eric Vermilya: Environmental Science




For those of us looking to do our part to help achieve the goal of preventing climate change and pollution, the answer starts in our homes. Turning off lights, using a clothesline during the warm months, and taking quick showers to save water and electricity are common ways to reduce our impact on the environment. These activities help to cut down on the operational emissions that a home releases into the atmosphere. Unfortunately, there is not much an average individual can do to reduce the embodied emissions that were released when their home was built. In fact, according a study by the Commonwealth Scientific and Industrial Research Organisation, during the construction process of an average residential home, the materials used have embodied emissions equal to 15 years of operational emissions. During the fabrication process of any given material, embodied emission, which are the total emissions produced throughout the entire life of an object, are released. For building materials, this includes emissions from extraction, manufacturing, and transportation (Milne & Reardon, 2013). For people who are trying to do their part to save the environment, this can be a frustrating fact to learn. The building industry which generates new housing and maintains important infrastructure is a major contributor to the emissions that are changing our environment. In fact, according to the IPCC, the Intergovernmental Panel on Climate Change, the building sector accounts for 6% of global greenhouse gas (GHG) emissions (IPCC, 2014). However, this figure does not take into account the embodied emissions of the building materials that are used by the industry. GHG emissions contribute to ambient GHG concentrations which causes the negative effects of climate change. Fortunately, there are a few ways to reduce emissions of GHG’s such as CO2. The first method, is to use materials that have lower embodied emissions. The second method to reduce CO2 emissions, would be to impose a carbon tax on building materials. A carbon tax would deter people from using materials that have high embodied emissions while also providing a source of revenue. This revenue could be funneled into research and development of alternative low emission building materials and/or put into government subsidies on low emission materials which would provide further incentive for people to use materials that are more environmentally friendly. Continue Reading

Cooling Albuquerque, New Mexico, with Green Roofs

A city does what it has to in order to be sure its citizens can stay safe and protected in the midst of so many dangerous events like crime and murder. One dangerous outcome may come traditionally undetected and that is deaths related to heat waves. San Francisco did all that it could to protect against such a disastrous attack like setting up shelters with air condition, making swimming pools open and free to the public, and opening four air conditioned libraries. This was not enough. Over the Labor Day weekend heat wave of 2017, where temperatures reached triple digits, three elderly people, all in their late 70s to early 90s, died due to the heat wave (Swan, 2017). In San Mateo county in California, just outside of San Francisco, the coroner said three more elderly people died from shock because of the heat wave over the same Labor Day weekend. (Rocha, 2017). The Intergovernmental Panel on Climate Change agrees that heat waves are more likely to be more intense in cities due to the already high temperatures from the Urban Heat Island effect. (IPCC AR5, 2014, p.7-8). This exacerbates the conditions usually seen in heat waves, so not only do cities experience higher temperatures, but also more deaths related to these rising temperatures. Only three names were made public, but like the deaths of Patrick Henry, 90, Ernesto Demesa, 79, and Loraine Christiansen, 95, all of San Mateo county, more elderly are at risk during these heat waves compared to the rest of the population. (Rocha, 2017). Green roofs can help alleviate rising temperatures and urban heat island effect in cities.

Cities, on average, are affected more by heat waves than surrounding areas due to the urban heat island effect. The Urban Heat Island (UHI) effect is the heating of urban areas, typically cities, due to the design and material choice of urban architecture and the high volume of emissions emitted from transportation, which it then trapped in the urban environment. (Monteiro et al., 2017). A city like Albuquerque, New Mexico has experienced temperature differences of up to 22°F between the city and the surrounding rural areas on an average summer’s day, Albuquerque is number two in the United States for the greatest difference in temperature between city and rural communities (Hot and Getting Hotter, 2014). Temperatures inside the city have reached up to 100°F five times in 2016 alone, and the hottest day on record in Albuquerque was 107°F on June 26, 1994 (US Department of Commerce, 2016 ). This increase in temperature causes fatal living conditions. (Monteiro et al., 2017).

Rising temperatures from UHI has also been known to cause heat exhaustion, heat cramps, non-fatal heat stroke, respiratory issues and even heat-related mortality (United States Environmental Protection Agency [EPA], 2017). These results are more likely to affect sensitive populations like young children and older adults, like those in San Mateo county. (EPA, 2017).

Cities have little to no vegetation. Vegetation promotes evapotranspiration which can help reduce temperatures by 2° F to 9°F (EPA, 2017). The effects presented by decreased reflectivity, increased heat retention, and lower evapotranspiration is like wearing a black wool sweater on a hot July day in the desert. If you wear a black wool sweater in the middle of the summer, your sweat is going to be trapped in the sweater, and prevent evaporation, unlike a moisture wicking white t-shirt which allows your sweat to evaporate off of you and carry away the heat. One way to think of this in effect is also the way that humid air feels warmer, because your sweat won’t evaporate, whereas dry heat feels cooler because of its ability to absorb moisture and allow evaporative cooling.

The white t-shirt will also be able to reflect more sunlight due to its lighter color compared to the black sweater. Green roofs are the white cotton t-shirt, a good solution to feeling hot while succumbing to the conditions of the black wool sweater as the urban heat island effect. In order to mitigate some of the UHI effects in Albuquerque, New Mexico, the New Mexican government must create incentive programs to help encourage the design and development of green roofs.

A large factor contributing to UHI is the reduced albedo caused by dark surfaces, used on roads and roofs, decreasing reflectivity and increasing heat retention. (Morini, Touchaei, Rossi, Cotana, & Akbari, 2017). Albedo is a measure for how well a surface reflects light without absorbing it in the form of heat (Morini et. al, 2017). Urban architecture plays a big role here. Since pavements and roofs typically constitute over 60% of urban surfaces, increasing reflectivity will drastically increase albedo and decrease UHI (Akbari, Menon & Rosenfeld, 2009). Decreased albedo, or decreased reflectivity, has been known to raise the temperatures of exposed urban surfaces, like rooftops and pavement, to temperatures 50°F to 90°F warmer than ambient air temperatures, whereas shaded surfaces, or rural surroundings, remain closer to air temperatures (EPA, 2017). Because rural areas do not have such an abundance of these dark materials, rural areas are 18°F to 27°F cooler during the day than nearby cities (EPA, 2017).

There is a cycle that begins when UHI occurs in a city. UHI causes an increase in air temperatures and leads to uncomfortable living conditions, that is then countered with an increase in air conditioning. Warmer environments lead to more air conditioning and energy use, therefore UHI will cause an increase in energy use through an increase in air conditioning. Research shows that there is a 1.5 – 2.0% increase in electricity demand for every 1°F increase (EPA, 2017)

An increase in energy demand due to UHI effects will require power plants to produce more energy which will emit greenhouse gases into the atmosphere and add to the already pressing issue of climate change. CO2 is the most prominent greenhouse gas and is primarily caused by the burning of fuel in order to produce energy (EPA, 2017). With multiple days reaching temperatures over 100°F in Albuquerque, UHI and its effects result in huge spikes of energy consumption. Greenhouse gasses trap heat in the atmosphere and increase temperatures (The Greenhouse Effect, 2017). Because of the effects of UHI, power plants will need to produce more energy to meet the demand and emit additional CO2 into the atmosphere in the process. This increase in CO2 will contribute to climate change in the form of a greenhouse gas. All of these causes lead to the urban environment experiencing greater temperatures than before, which brings the cycle back to the issue of having to increase air conditioning usage, it is a perpetual cycle that is harming the environment by contributing to climate change and heating up the urban environment.

The IPCC states that climate change is real and is increasing temperatures at an unprecedented rate. They are “virtually certain” that there will be more hot and fewer cold temperature extremes over as temperatures continue to increase. This rise in temperatures has a direct effect on UHI and heat waves. The Fifth Report put out by the IPCC states that it is very likely that heat waves will occur more often and last longer than previous years and that it is very likely the cause of human activities like burning fossil fuels. (IPCC AR5, 2014, p. 7-8).

Given that this cycle caused by human activity it only seems fit that there should be an initiative taken to break the cycle. The cycle begins with urban architecture increasing the temperatures of an urban environment and inside of buildings, and by using green roofs we can reduce the temperature of both the urban environment and inside of buildings. Green roofs reduce the effects of UHI through its high reflectivity and its ability of evapotranspiration.

A green roof’s reflectivity has drastic effects on the temperature of the outdoor air when compared to a traditional roof. During a normal sunny day, a green roof’s increased reflectivity can cause the temperature of the roof top surface to be cooler than the temperature of the air, as opposed to a traditional roof in which the surface temperatures can be upwards of 104°F warmer than the air (William et al., 2016). By increasing the solar reflectivity of a roof top, the outdoor air temperature will be lower, and will reduce the demand for air conditioning.

Another way that greater reflectivity reduces energy requirements of a building is by reducing the through roof heat gain (TRHG). TRHG flux is higher for roofs with a lower solar reflectivity, regardless of the region (Kibria, O’Brien, Alvey, & Woo, 2016). By increasing the reflectivity of a roof the indoor air temperatures will be lower too, by preventing heat from entering a building through the roof. Reflectivity has two benefits, both lowering the outdoor air temperature of the urban environment and the indoor air temperature of a building.

Green roofs will reduce energy demands by decreasing a building’s ability to absorb heat. Green roofs cause a cooling effect called evapotranspiration. This sensation is essentially to a building like sweating is to a human, the water on the green roof evaporates into the atmosphere and carries away its embodied heat. By having plants on a roof, the water they use and obtain will absorb heat that would have been absorbed into the building. The water then evaporates, reducing the amount of heat that could have potentially been absorbed into the rooftop and into the building. Less heat is absorbed by the rooftop and transferred to the building (William et al., 2016).

Although there are benefits to green roofs some are opposed to them due to the higher upfront cost and higher maintenance cost. The cost per square foot ranges from $10 to $25 and the annual maintenance of green roofs is $0.21 up to $1.50 per square foot (EPA, 2017). These figures are dependent on the types of plants, the media, and the extent of maintenance and irrigation.

This in turns forces a lot of pressure on the owners to absorb this cost of installation and also puts pressure to maintain them as well. In Southern California, if only half of the roofs are green, then $211 million will be saved in heating and cooling cost in the long run (Garrison, Horowitz 2012). In a University of Michigan study, a 21,000 square foot green roof would cost $464,000 to install versus $335,000 for a regular roof. The study also says that the green roof would save up to $200,000 in reduced energy costs (U.S. Environmental Protection Agency, 2008). With green roofs having multiple benefits and the upfront cost being minimal compared to the savings, it seems reasonable to have this cost be a part of buildings plan.

In order to mitigate the negative impacts of urban heat island in Albuquerque, the city must provide an incentive program for green roofs for new buildings. An incentive program would encourage developers by educating them on the benefits of green roofs and by covering a portion of installation cost. There are a number of places in the world that have recognized the many benefits of green roofs and adopted them into their urban development programs. Canada has been one of the leading countries in North America when it comes to green infrastructure legislation, especially in Toronto, Ontario where green roof programs have been implemented since 2006. (City of Toronto, 2017).

In 2006 Toronto, Ontario initiated the Green Roof Incentive Pilot Program to promote the design and development of green roofs on privately owned commercial/ industrial buildings. After one year the program was deemed “very successful” by the city and had awarded 16 applications with grants resulting in over 32,290 square feet of green roofs on new buildings (City of Toronto, 2017). After receiving feedback from the applicants about the pilot program it was determined that although it was successful, they could attract more applicants by increasing the incentive to $5 to square foot which was average for similar incentive programs in the country. (Gironimo, 2007). Within 5 years it was reported by the program coordinator that this program supported a total of 112 projects with a total of 2,507,991 square feet, reducing energy consumption by an estimated 565 MWh, avoiding 106 tons of greenhouse gases (Baynton, 2015, para. 3).

In order to be eligible for this grant the developer must have provided documentation of a design and maintenance plan for the green roof of a new building. This program did not offer grants for developers retrofitting green roofs due to the variables with the type of roofing materials and the amount of weight the building was designed to support. Minimum coverage requirements ranging from 20% for small roofs and up to 60% for larger roof tops were also put into effect. Although larger roofs require 60% of coverage there was a cap of $100,000 for the grant (City of Toronto, 2017). This program is in use today in Toronto and is now a key part of their Climate Change Action Plan and is complimented by the Green Roof Bylaw where the installation of eco-roofs is mandatory for new buildings.

Since this program has shown to be successful over a long period of time according to the city of Toronto, this same sort of incentivized program would be viable for Albuquerque. This program would also provide grants for eligible applicants at $5 per square foot for up to $100,000 for new industrial and commercial buildings and have the same eligibility requirements. With a $5 per square foot incentive, this would cover 20%-50% of installation cost on an average greenhouse relieving pressure from the developers. In order for this plan to work, builders must be educated on the number of benefits for this system by providing resources like pamphlets, websites, and seminars in order to communicate the value of these systems and how the long term benefits outweigh the initial costs.

In order to break the UHI cycle and the rapid increase in temperatures in Albuquerque there must be an incentive program run by the city or state government. Government officials need to address this issue since it impacts the health and well-being of its inhabitants. The impacts on health have led to death and other health complications and with temperature continuing to rise, it seems reasonable to assume the amount of deaths, complications, and general discomfort will rise too. In order for people to alleviate themselves from high temperatures, they must turn to cooling technology. Rising temperatures means that buildings must increase the amount of fossil fuels used to cool buildings which increases not only the cost of cooling, but the amount of greenhouse gases, in this case CO2, in the atmosphere. Greenhouse gases then go on to contribute to rising temperatures in cities which then continues the cycle.

Green roofs can help to break this cycle by helping to reduce the amount of heat trapped in these urban areas by increasing evapotranspiration and reflectivity. By increasing these two properties, less heat is retained in the buildings which then decreases the amount of fossil fuels used to cool buildings and reducing the amount of greenhouse gases in the air.  By implementing an incentive policy that educates and encourages developers to install green roofs, the impacts of UHI will decrease. Unless the New Mexico government steps in, like Toronto, and provide incentives to green roof installation the cycle could continue on indefinitely affecting more families like those in San Francisco.


Evan Brillhart – Natural Resource Conservation

Jacqueline Dias – Environmental Science

Michael Pfau – Building and Construction Technologies

Amanda Tessier – Horticultural Science


Akbari, Menon, and A. Rosenfeld, 2009: Global cooling: Increasing world-wide urban albedos to offset CO2. Climatic Change, 94 (3–4), 275–286, doi:10.1007/s10584-008-9515-9.

Baynton, A. (2015, January 16) Toronto’s Eco-Roof Incentive Program. C40 Cities. Retrieved from:

City of Toronto. (2017). Eco roof incentive program. Retrieved from:

Garrison, N., & Horowitz, C. (2012). Looking Up: How Green Roofs and Cool Roofs Can Reduce Energy Use, Address Climate Change, and Protect Water Resources in Southern California. NRDC Report. Retrieved from

Gironimo, L.D. (2007). Green roof incentive pilot program(AFS# 3677). Retrieved from City of Toronto:

Huber, D. G., & Gulledge, J. (2011). Extreme Weather and Climate Change: Understanding the Link and Managing the Risk. Center for Climate and Energy Solutions. Retrieved from

Hot and Getting Hotter: Heat Islands Cooking U.S. Cities. (2014, August 20). Retrieved from

IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.

Kibria K. Roman, Timothy O’Brien, Jedediah B. Alvey, OhJin Woo, Simulating the effects of cool roof and PCM (phase change materials) based roof to mitigate UHI (urban heat island) in prominent US cities, In Energy, Volume 96, 2016, Pages 103-117, ISSN 0360-5442, (

Monteiro, M., Blanua, T., Verhoef, A., Richardson, M., Hadley, P., & Cameron, R. W. F. (2017). Functional green roofs: Importance of plant choice in maximising summertime environmental cooling and substrate insulation potential.Energy & Buildings, 141, 56-68. doi:10.1016/j.enbuild.2017.02.011

Morini, E., Touchaei, A. G., Rossi, F., Cotana, F., & Akbari, H. (2017). Evaluation of albedo enhancement to mitigate impacts of urban heat island in rome (italy) using WRF meteorological model doi://

Rocha, V. (2017, September 8). Six deaths linked to Bay Area heat wave – LA Times. Retrieved from

Swan, R. (2017, September 07). 3 deaths in SF likely caused by weekend heat wave. Retrieved from

The Greenhouse Effect. (n.d.). Retrieved December 2, 2017, from

US Department of Commerce, NOAA, National Weather Service. (2016, September 26). NWS ABQ – 100 Degree Facts for NM. Retrieved from

U.S. Environmental Protection Agency. 2008. “Green Roofs.” In: Reducing Urban Heat Islands: Compendium of Strategies. Draft.

United States Environmental Protection Agency [EPA]. (2017). Heat Island Impacts. Retrieved from

United States Environmental Protection Agency [EPA]. (2017). Overview of Greenhouse Gases. Retrieved from

United States Environmental Protection Agency [EPA]. (2017). Using Trees and Vegetation to Reduce Heat Islands. Retrieved from

William, R., Allison, G., Ashlynn S., S., Meredith, R., Phong V.V., L., & Praveen, K. (2016). An environmental cost-benefit analysis of alternative green roofing strategies. Ecological Engineering, 951-9.

Green roofs: an analysis on air pollution removal and policy implementation


In October 1948, a thick cloud of air pollution formed above the industrial town of Donora, Pennsylvania. It lingered for five days, killed 20 people and induced sickness in 43% of the town (Environmental Protection Agency, 2007). Pollution poses a serious threat to our environment and health. Nearly one-quarter of the people in the U.S. live in areas with unhealthy short-term levels of particle pollution, and roughly one in ten people live where there are unhealthful levels year-round (American Lung Association, 2010). Air pollution is of particular concern to public health as it is the cause of hazards including upper respiratory irritation, chronic respiratory irritation, heart disease, lung cancer, and chronic bronchitis (Kampa & Castanas, 2008). The most common health-related impacts from air pollution are increased occurrences of respiratory illnesses such as asthma and a greater incidence of cardiovascular disease (Pope, Bates & Raizenne, 1995). Urban environments struggle heavily with air pollution due to the large amount of factories and vehicles that are major sources of air pollutants that accumulate so much that they become a hazard to human health. In Canada, the Ontario Medical Association found air pollution to result in 9,500 premature deaths per year (OMA, 2008) and estimates increased costs of healthcare up to $506.64 million and lost productivity of up to $374.18 as a result of air pollution (OMA, 2005). Conditions will only worsen as pollution grows with population, traffic, industrialization and energy use (Mayer, 1999). There are many pollutants in the air of an urban environment, though particulate matter (PM10), ozone (O₃), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂) are among the most serious to human health (World Health Organization, 2016).

Particulate matter that appears in urban environments is made up of sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water that exist in the air from human activities such as combustion of fossil fuels, vehicles, and factory emissions. According to The World Health Organization (WHO), the limit for PM10 is 50 μg/m3 annual mean. This represents how much particulate matter is allowed in the air annually by law. Chronic exposure to particles contributes to the risk of developing cardiovascular, respiratory diseases, and lung cancer (WHO, 2017).  In countries of Europe that have concentrations of PM above guideline levels, it is estimated that average life expectancy is 8.6 months lower than it would be if PM exposure from human sources was regulated (WHO, 2017).

NO2 is most commonly formed from anthropogenic burning of fuel (heating, power generation, and engines in vehicles/ships). The limit for nitrogen dioxide is 40 μg/m3 annual mean. Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increased in association with long-term exposure to NO2 and at short-term concentrations above 200 μg/m3, NO2 is a toxic gas which causes significant inflammation of the airways (WHO, 2017). Reduced lung function growth is also linked to NO2 at higher concentrations currently measured in Europe and the US. The US EPA (1998) also focuses on the danger of NO2 by stating that Nitrogen oxides (NOx) resulting from combustion of fossil fuels can form ground level ozone that causes respiratory problems, premature deaths, and reductions in crop yields. (EPA, 1998).

Ozone at ground level, not to be confused with the ozone layer in the upper atmosphere, is formed from vehicle and factory emissions and emissions from solvents and industry. The legal amount that is allowed in cities is 100 μg/m3 8-hour mean, which means that by law over 8 hours concentrations of ozone cannot exceed 100 μg per cubic meter of air. In some cases, chemicals like nitrogen oxides (NOx) react with sunlight and also contribute to forms of ozone. The limit for ozone is 100 μg/m3 8-hour mean and once this threshold is passed, O3 can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases (WHO, 2017). The American Lung Association (2007) reported that annually, over 3,700 premature deaths in the United States (premature death is a death that occurs before a person reaches their expected age) can occur as a result of a 10 parts per billion (ppb) increase in O3 levels (ALA, 2007). Bell (2004) found that increased mortality rates in 95 urban areas within the US are linked to elevated levels in ozone, with one of these urban areas being Chicago, where ALA (2007) found over 2 million people at increased risk for health problems resulting from short-term exposure to O3 and particulate matters (ALA, 2007; Bell, 2004).

SO2 is a colourless gas with a sharp odour that is produced from the burning of sulfur-containing fossil fuels (coal/oil) for heating residences, generating power, and motor vehicles along with the smelting (extraction by melting) of mineral ores that contain sulfur. The limit for sulfur dioxide is 20 μg/m3 24-hour mean and this means that air in cities will contain on average 20 μg per cubic meter over the span of 24 hours. When the limit is exceeded, SO2 can affect the respiratory system, lung functioning, and cause irritated eyes. Evidence shows that the effects of sulfur dioxide are felt very quickly and most people would feel the worst symptoms of coughing, wheezing, shortness of breath, or a tight feeling around the chest in 10 or 15 minutes after breathing it in (S02, 2005). Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract (WHO, 2017).

One policy the U.S. government has in place to control pollution levels is the Clean Air Act (CAA) of 1970 (majorly revised in 1977 and 1990). The CAA’s purpose is to reduce air pollution and its harmful effects by setting limits on pollution. This Act requires states to meet specific air quality standards regarding six common pollutants: particulate matter, ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead (EPA, 2017b). The Act contains specific provisions to address hazardous or toxic air pollutants, acid rain, chemical emissions that deplete the ozone layer, and regional haze (EPA, 2017b). The six “criteria” air pollutants are regulated based primarily on human health and secondarily on environmental criteria.

The CAA improved the environment which in turn improved the economy and human health. In the 45 years following the installation of the CAA, national emissions of the six common pollutants dropped an average of 70% while gross domestic product grew by 246% (EPA, 2017c). Forty-one areas that previously had unhealthy carbon monoxide levels in 1991 now meet the health-based national air quality standard. In 1990 alone, pollution reductions under the Act prevented 205,000 early deaths, 10.4 million lost I.Q. points in children due to lead exposure, and a multitude of other health effects (Environmental Protection Agency, 2017d). Despite massive improvements in air quality since CAA took effect, millions of Americans still live in areas with pollution levels exceeding the limits (EPA, 2007). Those who struggle to meet CAA air quality standards may find green roofs a useful tool to bring pollutant levels down.

In response to rising air pollutants, people are considering transforming city rooftops into green roofs to mitigate the problem. A green roof is a layer of vegetation installed on top of a roof, either flat or slightly sloped (National Park Service, 2017). The high amount of rooftop space in urban cities creates an opportunity for green roofs to be implemented on a large scale. Roofs represent 21–26% of urban areas and 40–50% of their impermeable areas (Wong, 2005; Dunnett & Kingsbury, 2004). These spaces typically have much unused surface area that could be repurposed to combat the aforementioned effects of harmful air pollutants, a green roof’s main purpose. The plants that compose the roof are able to take up compounds through their natural processes respiration and photosynthesis, which remove the pollutants from the air and improve its quality.WHO has guidelines for the limits of the primary air pollutants that must not be exceeded in urban environments. Green roofs will help keep the levels of PM10 at 50 μg/m3 annual mean, nitrogen dioxide at 40 μg/m3 annual mean, ozone at 100 μg/m3 8-hour mean, and the concentrations of sulfur dioxide in the air of urban environments at 20 μg/m3 24-hour mean.

Literature surrounding green roofs agrees on their impact of particulate matter removal (Speak, Rothwell, Lindley & Smith, 2012; Currie & Bass, 2008; Rowe, 2011; City of Los Angeles, 2005; Yang, Yu & Gong, 2008; Jayasooriya, Ng, Muthukumaran & Perera, 2017). The range of particulate that is annually reduced by a green roof is 0.42–3.21 g/m2 over 500,000 square meters of rooftops (Speak et al, 2012). Rowe (2011) performed a study where 2000 m2 of uncut grass were planted on a green roof. It was estimated that the green roof could remove up to 4000 kg of particulate matter. In a simulation where green roofs were built over 198,000 square meters of roofs in Chicago, 234.5 kg of particulate matter would be removed by green roofs in one year (Yang et al., 2008).  Yang et. al (2008) also did a study where the concentrations of acidic gaseous pollutants and particulate matters on a 4000 m2 roof in Singapore are measured before and after the installation of a green roof. Research found that the levels of particulate matter was reduced by 6% in the air above the roof after installation of the green roof (Yang et al., 2008). Jayasooriya et al. (2017) state that green roofs annually remove 1.53 g/m2 PM10  (Jayasooriya et al., 2017).Currie and Bass (2008) state that green roofs have the potential to reduce annual amounts of PM10 by .89–9.21 g/m2 (grams per square meter) over 486,000-2,430,000 square meters of green roof coverage in Toronto (Currie & Bass, 2008). Jayasooriya et al. (2017) states that green roofs annually remove 1.53 g/m2 PM10 (Jayasooriya et al., 2017). Another study on green roof remediation in Los Angeles (LA) puts these numbers of removed particulate matter into context. The city of LA found one square meter of green roof able to remove approximately 0.1 kg of particulate matter per year and if a gasoline powered vehicle were to release .01 grams of pm per mile of travel and drive 10,000 miles per year, then the vehicle would emit 100 grams per year (.01 kg/year) and therefore, one square foot of green roof would reduce the pollution of this theoretical car for the whole year (City of Los Angeles, 2005). According to the literature, the annual range of particulate matter reduced by green roofs fall between .42 g/m2 and 9.21 g/m2 (Speak et al., 2012; Currie & Bass, 2008; Rowe, 2011; City of Los Angeles, 2005; Yang et al., 2008; Jayasooriya et al., 2017).

Currie and Bass (2008) state that green roofs have the potential to reduce annual amounts of NO2 by 0.6–2.55 g/m2. Yang et. al (2008) found that if green roofs were built over 198,000 square meters of roofs in Chicago, 452.25 kg of nitrogen dioxide would be removed by green roofs in one year. Rosenfeld, Akbari, Romm, and Pomerantz (2008) calculated that emissions from coal fired power plants to the air could be reduced by 350 tons of NOx per day in Los Angeles by implementing green roofs. This value of energy saved from the installation of green roofs relates to a 10% reduction in the causes of smog to the city of Los Angeles, with an active NOx trade program, and results in a savings of one million dollars per day (Akbari, Pomerantz & Taha, 2001; Rosenfeld et al.,1998;  Clark, Talbot, Bulkley & Adriaens, 2005) estimate that if 20% of all industrial and commercial roof surfaces in Detroit, MI, were traditional extensive sedum green roofs, over 800,000 kg per year of NO2 , 0.5% of that area’s emissions, can be removed. Yang et. al (2008) states that green roofs annually remove 2.33–3.57 g/m2, NO2 in an urban environment. Jayasooriya et al. (2017) states that green roofs annually remove .37 g/m2 NO2. In a study done in Singapore, 21% of nitrous acid, a byproduct of nitrogen dioxide, was reduced directly above a green roof (Rowe, 2011). One study implementing green roofs in Kansas City, MO, used by the EPA, estimated that by 2020, green roofs would reduce 1800 pounds (816 kg) of NOx (EPA, 2016). After reviewing the literature, it is found that a green roof can reduce a range of 0.37-3.57 g/m2 (Currie & Bass, 2008; Yang et. al., 2008; Jayasooriya et al., 2017; Rosenfeld et al., 2008) Clark, Adriaens, and Talbot (2008) reported that green roofs yield an annual benefit of $0.45–$1.70 per m2 ($0.04–$0.16 per square foot) in terms of nitrogen oxide uptake. Clark et al. (2005) estimates that NOx reduction from a 2000 ft2 green roof would provide an annual benefit of $895–$3392, resulting in the green roof being 24.5-40.2% cheaper than a conventional roof without vegetation.

Currie and Bass (2008) state that green roofs have the potential to reduce annual amounts of O3 by 1.2–3.58 g/m2. Yang et al. (2008) state green roofs have the potential to annually reduce 4.49–7.17 g/m2 O3 and in their simulation of Chicago, green roofs were built over 198,000 square meters of roofs, the results were measured over the course of just one year, with 871 kg of O3 removed by green roofs. Jayasooriya et al. (2017) state that green roofs annually remove 1.24 g/m2 O3 . Since ozone is formed by the reaction of sunlight with pollutants such as nitrogen oxides (NOx), green house reduction in nitrogen oxides also reduce concentrations of ozone in the urban environment. According to the literature, the annual range of ozone reduced by green roofs fall between 1.2 g/m2 and and 7.17 g/m2 (Currie & Bass, 2008; Yang et. al., 2008; Jayasooriya et al., 2017).

Yang et. al (2008) found that if green roofs were built over 198,000 square meters of roofs in Chicago, 117.25 kg of sulfur dioxide would be removed by green roofs in one year. Currie and Bass (2008) state that green roofs have the potential to reduce annual amounts of SO2 by 0.2–0.84 g/m2. Yang et al. (2008) state that green roofs annually remove 0.65–1.01 g/m2 SO2. Jayasooriya et al. (2017) state that green roofs annually remove 0.1 g/m2 SO2. In a study done in Singapore, 37% of sulfur dioxide was reduced directly above a green roof (Rowe, 2011). One study implementing green roofs in Kansas City, MO, used by the EPA, estimated that by 2020, green roofs would reduce 2600 pounds (1179.34 kg ) of SO2 (EPA, 2016). In one field study, the concentrations of acidic gaseous pollutants and particulate matters on a 4000 m2 roof in Singapore are measured before and after the installation of a green roof. Research found that the levels of SO2 were reduced by 37% in the air above the roof after installation of the green roof (Yang et al., 2008). After reviewing the literature, it is found that a green roof can reduce a range of 0.10-1.01 g/m2 (Currie & Bass, 2008; Yang et al., 2008; Jayasooriya et al., 2017; Rowe, 2011, EPA, 2016)

As an example of the costs of building a green roof in a U.S. city, the installation costs to install green roofs on every roof in Chicago were estimated to be $35.2 billion (Yang et al., 2008). This brings up a high cost of green roofs that deters many cities from considering installation. The EPA projected in 2009 that extensive green roof installation costs, which were ranging from $15-$20/sq. foot should drop to $8-$15/sq. foot as installations increased, and soil substrate and plants became more available (EPA, 2009). Not everyone considers green roofs for their own homes, however, with the amount of pollution removed and human health improvements and the inherent existent pollution in cities, green roofs are critical to pollution removal in urban environments and should therefore be installed. In fact, having a green roof reduces more pollution in an urban environment than simply not having one at all. Agra, Klein, Vasl, Kadas, and Blaustein (2017) compared green roofs to other roofs of buildings with no vegetation at all (control roofs) and found that the control roofs had a CO2 concentration 50 cm above the ground of almost 375 ppm while the three types of green roofs in the study ranged from maintaining concentrations of 365-370 ppm of CO2 50 centimeters above surface (Figure 1). With green roofs being confirmed to be more effective With costs of green roofs accounted for and their associated improvement of human health via reduction in air pollution, green roofs can become even more desirable with the inclusion of governmental incentives/policies for cost reduction.

Seeing cost as one of the main obstacles standing in the way of green roofs, we urge government action to alleviate this issue. The U.S. government must make green roof installation less expensive through an incentive system. Funding should be granted to all major U.S. cities for the installation of green roofs. Depending on design, plant type, and climate conditions the price of green roof construction typically ranges from $15-20 per square foot, though the EPA projects that extensive green roof installation costs should drop to $8-$15/sq. foot as installations increase, and soil substrate and plants became more available (EPA, 2009). The U.S. Government should offer $10 per square foot of green roof for commercial, residential, and private properties. In target areas where pollution is most concentrated, the government should offer $15 per square foot. This proposal makes the initial up-front cost of green roofs more feasible, if not directly profitable.

Green roofs become more attainable and widespread with the help of government incentives, as shown by successful policies in Washington D.C. Currently, Washington D.C. has over 3 million square feet of green roof (Department of Energy & Environment, 2017a). The district set a goal that by 2020, 20% of its buildings will have green roofs. In 2006, the D.C. Department of Energy and Environment (DOEE) launched the “RiverSmart Rooftops Green Roof Rebate Program” to give grants that encourage the installation of green roofs on private property. The grants offer $10 per square foot and up to $15 per square foot if the building is in target watersheds. With no cap on project size, all properties are eligible including residential buildings. To encourage small buildings to install green roofs as well, the program gives funds to offset costs of structural assessments to buildings of under 2,500 square feet (DOEE, 2017a). This incentive plays a large role in the growth in green roof installation per year in D.C. In 2005, building owners installed 0 square feet of green roof as compared to 104,068 sq feet of green roof installed in 2006, the first year of this initiative (DOEE, 2017b). In 2015, D.C. implemented a whopping 712,493 square feet of green roof. Though there is some variation, there is a general increase in total green roof area in Washington D.C. (DOEE, 2017c). An incentive program similar to this on the federal level would increase the total area of green roofs on a broader scale.

Installing green roofs in urban environments is cost-effective. They reduce the amount of pollution in air, improve the health of people living in urban cities, and can be less expensive to install with the implementation of governmental incentives & policies. If all rooftops in Chicago were covered with intensive green roofs, a projected 2046.89 metric tons of pollutants would be removed (Yang et al., 2008).

When discussing the green roofs ability to improve human health, the concentrations of pollutants most commonly discussed in the literature are O3, SO2, particulate matter, and NOx   (Agra, 2017; Clark et al., 2005, 2008; Rowe, 2011; City of Los Angeles, 2006; Rosenfeld, 1998; EPA, 1998) By installing green roofs, the four main pollutants would decrease in concentration enough to create improvements in human health and economic benefits in the reduction of human mortality.  Worker productivity and health is improved along the way, as employees that have a view of nature scenery were less stressed, had lower blood pressure, reported fewer illnesses, and experienced greater job satisfaction (Kaplan et al., 1988; Ulrich, 1984).

The cost-benefit analyses discussed how implementing green roofs would result in savings of a million dollars a day from decreased air conditioning, an overall annual benefit of $895–3392 for each 2000 ft2 green roof, and a reduction in the particulate emissions of one car for a whole year per square meter of green roof. Green roof financial incentives in Washington D.C. greatly increased the total area of green roofs in the area (DOEE, 2017b). An incentive program paired with indirect incentives would be successful if emulated on a federal level. The U.S. has proven that federal environmental policies can be effective as show by the Clean Air Act (EPA, 2015).

Even though green roofs cost 2-3 times as much as a bare roof to install, government incentives can alleviate these costs to bring installation prices down. With the upfront costs lowered, we can reap the benefits of financial, health, and environmental pay-off by green roofs.


Matas Rudzinskas – Environmental Science

Aaron Lutz – Turf Grass Science

Tara McElhinney- Natural Resource Conservation



Agra, H., Klein, T., Vasl, A., Kadas, G., & Blaustein, L. (2017). Measuring the effect of plant-community composition on carbon fixation on green roofs. Urban Forestry & Urban Greening, 24, 1-4. doi:10.1016/j.ufug.2017.03.003

Akbari, H., Pomerantz, M., & Taha, H. (2001). Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas. Solar Energy, 70(3), 295-310. doi:10.1016/s0038-092x(00)00089-x

Australian government, Department of the Environment and Energy (2005). Sulfur dioxide (SO2).

Bell, M. L. (2004). Ozone and Short-term Mortality in 95 US Urban Communities, 1987-2000. Jama, 292(19), 2372. doi:10.1001/jama.292.19.2372

City of Los Angeles Environmental Affairs Department. 2006. Report: Green roofs – cooling Los Angeles

Clark, C., Adriaens, P., & Talbot, F. B. (2008). Green Roof Valuation: A Probabilistic Economic Analysis of Environmental Benefits. Environmental Science & Technology, 42(6), 2155-2161. doi:10.1021/es0706652

Clark, C., Talbot, F.B., Bulkley, J., & Adriaens, P.. (2005). Optimization of green roofs for air pollution mitigation Proc. of 3rd North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Washington, DC. 4–6 May 2005, The Cardinal Group, Toronto (2005)

Currie, B. A., & Bass, B. (2008). Estimates of air pollution mitigation with green plants and green roofs using the UFORE model. Urban Ecosystems, 11(4), 409-422. doi:10.1007/s11252-008-0054-y

Department of Energy and Environment. (2017a). [Graph of green roof installation (in sq ft) per year in Washington D.C. from years 2001-2017]. Green Roof Installation. Retrieved from

Department of Energy and Environment. (2017b). Green roofs in the District of Columbia. Retrieved from

Department of Energy and Environment. (2017c, November). Green roofs in the District of Columbia November 2017. Retrieved from

Department of Energy and Environment. (2017d). RiverSmart rewards and clean rivers IAC incentive programs. Retrieved from

Department of Energy and Environment. (2017e). Stormwater retention credit trading program. Retrieved from

Dunnett, N., & Kingsbury, N. (2010). Planting green roofs and living walls. Portland: Timber Press.

Environmental Protection Agency. (2007). The Plain English Guide To The Clean Air Act

Environmental Protection Agency. (2015). Progress cleaning the air and improving people’s health. Retrieved from

Environmental Protection Agency. (2016).

Environmental Protection Agency. (2017a). Benefits and costs of the clean air act, 1970 to 1990 – Study design and summary of results. Retrieved from

Environmental Protection Agency. (2017b). Clean air act requirements and history. Retrieved from

Environmental Protection Agency. (2017c). Progress cleaning the air and improving people’s health. Retrieved from

How healthy is the air you breathe? (American Lung Association). Retrieved November 13, 2017, from

Jayasooriya, V., Ng, A., Muthukumaran, S., & Perera, B. (2017). Green infrastructure practices for improvement of urban air quality. Urban Forestry & Urban Greening, 21, 34-47. doi:10.1016/j.ufug.2016.11.007

Kampa, M., & Castanas, E. (2008). Human health effects of air pollution. Environmental Pollution, 151(2), 362-367. doi:10.1016/j.envpol.2007.06.012

Mayer, H. (1999). Air pollution in cities. Atmospheric Environment, 33(24-25), 4029-4037. doi:10.1016/s1352-2310(99)00144-2

National Park Service (2017). What is a Green Roof—Technical Preservation Services,

Ontario Medical Association (2005) Illness Costs of Air Pollution

Ontario Medical Association (2008) Ontario’s Doctors: Thousands of Premature Deaths Due to Smog (2008) www.oma.orf/Mediaroom/PressReleases/Pages/PrematureDeaths.aspx

Pope, C. A., Bates, D. V., & Raizenne, M. E. (1995). Health Effects of Particulate Air Pollution: Time for Reassessment? Environmental Health Perspectives, 103(5), 472. doi:10.2307/3432586

Rosenfeld, A. H., Akbari, H., Romm, J. J., & Pomerantz, M. (1998). Cool communities: strategies for heat island mitigation and smog reduction. Energy and Buildings, 28(1), 51-62. doi:10.1016/s0378-7788(97)00063-7

Rowe, D. B. (2011). Green roofs as a means of pollution abatement. Environmental Pollution, 159(8-9), 2100-2110. doi:10.1016/j.envpol.2010.10.029

Speak, A., Rothwell, J., Lindley, S., & Smith, C. (2012). Urban particulate pollution reduction by four species of green roof vegetation in a UK city. Atmospheric Environment, 61, 283-293. doi:10.1016/j.atmosenv.2012.07.043

Ulrich, R. (1984). View through a window may influence recovery from surgery. Science, 224(4647), 420-421. doi:10.1126/science.6143402

United States General Services Administration (2011). The Benefits and Challenges of Green Roofs on Public and Commercial Buildings.

WHO 2016 (World health organization) – Ambient (outdoor) air quality and health. (2016). Retrieved November 14, 2017, from

Wong (2005) Green roofs and the Environmental Protection Agency’s heat island reduction initiative Proc. of 3rd North American Green Roof Conference: Greening Rooftops for Sustainable Communities, Washington, DC. 4–6 May 2005, The Cardinal Group, Toronto

Yang, J., Yu, Q., & Gong, P. (2008). Quantifying air pollution removal by green roofs in Chicago. Atmospheric Environment,42(31),7266-7273.doi:10.1016/j.atmosenv.2008.07.003



Green the Heat


Image result for green roofs

Green roof in city (Klinkenborg, 2009).


Tall buildings consisting of dark roofs and roads with black asphalt remove much of the vegetation that used to thrive there. It is now evident that these changes in the landscape caused severe environmental challenges. Urban areas became vulnerable to the impacts of climate change and the rapid expansion of the population only worsened the cause because of the demand for new accommodation made it normal to ignore existing problems. According to the U.S Census Bureau, 62.7 percent of the U.S. population now live in urban areas (“U.S. Cities are Home to 62.7% of the U.S. Population but Comprise 3.5% of Land Area”, 2015). Many of the environmental challenges in urban areas can be seen in forms of temperatures rising, worsening the urban heat island effect, and pollution from the release of CO2 into the atmosphere. All causing major health threats to citizens living in these areas and more sadly affecting children and the elderly who in many cases were diagnosed with heat related illnesses. Continue Reading