A Cool Way to be Sustainable: the Green Roof

We’ve spent the last few weeks learning all about sustainability, and the dangers that we face if we continue our very unsustainable lifestyles. The main issues I’ve taken from our deliberations are the future of energy, living an environmentally friendly, sustainable lifestyle, and the overwhelming need for change. We are seeing the beginnings of change all around us. More people are taking an interest in reducing their carbon footprint and investing in alternative energies, like solar or wind power. Smaller cars are becoming more popular, both because of the lowers costs associated and the smaller environmental impact. Recycling is well on the way to becoming a regular part of life. These and more small changes everyday are the first steps in what is hopefully a new direction in sustainable living.

It’s only a drop in our Earth-sized bucket, but I like to think that this could be the start of something big. A big problem with large-scale changes is that they also come with large-scale costs, and few people want to invest in something that offers returns over such a long period of time. That is a prime drawback for extensive alt-energy proposals – many of them require new infrastructure and lifestyle changes. But I was browsing Google for cool ideas for sustainable/environmental living and I found one that certainly is cool: the green roof.

A green roof is a roof that also functions as a garden, usually found in an urban setting). This means the original roof is covered by a waterproof membrane and soil for the plants to grow. There are two kinds of green roofs: intensive and extensive. The intensive variety is generally the more garden-like variety: they can be 80-150 lbs per square foot and can support shrubs and even small trees. Extensive green roofs are lighter, from 15-50 lb per square foot, and can only support ground cover like grass and other small plants. Intensive green roofs can be accessible to people, and can be park-like or even support vegetable gardens (I read about an upscale New York restaurant growing their own vegetables on the building roof a few years ago, but I couldn’t find the link). Conversely, extensive roofs are usually only used for the environmental benefits, but require less maintenance.

Both extensive and intensive green roofs have myriad environmental benefits. One of the most well known benefits of green roofs is moderation of the Urban Island Heat Effect. The UIF effect is the phenomena that cities tend to be several degrees higher in temperature than the surrounding area – hence, the term heat island. Manmade structures, like asphalt pavement and rooftops, tend to absorb a high amount of light and remit it as heat, increasing the ambient temperature. Since these materials are in higher use in urban rather than rural/suburban areas, heat islands form in and around cities. Evaporative cooling – water from vegetation evaporating and cooling the air around it – is also believed to have a role in the UHI effect, as there is less plant life in cities than in other areas. Green roofs work to combat both these causes of UHIs. They increase the vegetation in the city, and the light that would have been converted to heat is instead applied to evaporative cooling. Green roofs also by reduce the heat-absorbing capacity of the city by reducing the number of black rooftops.

Green roofs can also improve air quality and act in stormwater management. A study conducted in Chicago showed that with the addition of green roofs in the city, there are lower levels of atmospheric pollutants and deposition such as ozone, sulfur dioxide, and nitrogen dioxide. They also have better insulative qualities than traditional roofs, which could reduce energy use and carbon dioxide and other pollutant byproducts that result from energy production. Rain water retention also means that extra water is usually unnecessary to maintain green roofs, and any runoff is naturally filtered. This retention capability also reduces stress on sewer systems.

 

Energy efficiency is another advantage of green roofs. Traditional roofs offer the highest heat loss in winter and retention in summer. Green roofs have greater insulation (because energy that would have gone into heating the blacktop roof instead contribute to evaporative cooling), and this reduces the amount of energy to keep the building temperature stable, lowering levels of atmospheric pollutants. The growing medium and pants provide a lot more insulation than regular roofs, regulating temperature fluctuations. The National Research Council of Canada has shown that a six-inch extensive roof can reduce summer energy demands by 75%! Green roofs are also longer lasting than most roofs, protecting the waterproof membrane from UV and heat radiation. This, along with the use of recycled materials and prolonging heat, ventilation and air conditioning systems, all contribute to landfill diversion – taking waste that would go to a landfill and recycle or dispose of it in some other way.

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Green roofs have many other benefits, such as increasing biodiversity, noise reduction, improve aesthetic, and providing opportunities for urban agriculture and community education. One of the most famous green roofs is on Chicago’s City Hall. This green roof was designed as a test to gauge the benefits of different types of green roof (4, 6, and 18 inches) compared to traditional roofing. Data from the first summer showed roof temperature reduction of 70 degrees and air temperature reduction of 15 degrees. This is clearly a significant amount, and shows the effectiveness of green roofs in temperature regulation, which has an effect on energy and insulation costs. The green roof saves the City Hall $5,000 per year on utility bills as well, once again underscoring its effectiveness.

A garland of nature crowns Chicago

Green roofs are becoming an increasingly popular way to regulate a city’s impact on the surrounding environment and increasing the city’s sustainability. Green roofs can regulate and reverse the urban island heat effect, regulate rainwater runoff, and improve air quality. Furthermore, their insulative properties increase roof service life, reduce the need for costly heating and cooling, and as seen by the Chicago city hall example, are economically viable while being environmentally friendly. Much of Europe has already adopted the green roof, and 14% of buildings in Germany have green roofs. This is one of many small changes in place today which are building towards a more sustainable tomorrow.

Sources:

http://www.greenroofs.org/index.php/about/greenroofbenefits

http://science.howstuffworks.com/environmental/green-science/green-rooftop.htm

http://www.asla.org/meetings/awards/awds02/chicagocityhall.html

Click to access Quantifying%20air%20pollution%20removal%20by%20green%20roofs%20in%20Chicago.pdf

http://drive2.subaru.com/Win11/_images/green_diagram.jpg

http://ngm.nationalgeographic.com/2009/05/green-roofs/klinkenborg-text

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3 Responses to A Cool Way to be Sustainable: the Green Roof

  1. Leah Galamba says:

    I’d have to agree with both Kaitlyn and Aaron when they say the benefits of these roofs seems to be more than just the environmental impact. I think green roofs are an awesome idea and they way you described them it doesn’t seem like they take too much money or effort to install or maintain and the benefits I feel would definitely outweigh the costs. Like Kaitlyn said, cities are often cold and dark but these roofs make them look so cool and versatile, like you are getting the best of both worlds. The green roofs provide a place for plants and small animals to thrive even in the city. Just to play devils advocate I tried looking up the cons to the roofs and basically all I found was that initial investment is large and that they require maintenance. Well, everything costs money and of course a garden takes work but that is half the fun! To me it seems like this is an all around good idea and I hope to see more of them in the future. Great blog

  2. Kaitlyn Spangler says:

    As somebody interested in farming, food, and community, I really enjoyed this post. I agree with Aaron, that their impact on the grand picture of global warming and environmental degradation would not be the end all cure all, but small scale change is, I believe, a much more sustainable and involving approach. Cities tend to be too gray and cold for me, lacking green vegetation, an open sunrise, and farmland. Yet, this idea could be a great way to make those city-dwellers more consciously and consistently aware of the world beyond their metropolis. Taking the time to care for a garden, be it food, plant, or flower based, requires dedication, rationality, and interest. It is an extremely rewarding experience in my mind to foster and nurture products from the earth, watching them sprout and grow into tangible things. It will enliven the cities, add some green to those gray buildings, and allow people so distant from actual farmland and fields to be reminded of the importance of our green Earth. It seems that, although it is not “the answer,” it does much more good than bad. I do not believe that we will find one answer to our overuse of environmentally damaging practices, so innovations such as this are the stepping stones to slow, gradual, and more individualized change. Empower the individual, have better roofs, and get a green roof. I like the sound of that. Great find, Mustafa! I will definitely look more into this!

  3. Aaron Dennis says:

    Green roofs certainly are a cool idea that have a lot of benefits. They are something I certainly support. However, I believe their benefits are more significant for the community than the planet. Cities are already some of the most environmentally friendly per capital places on Earth and in the big scheme of things, the ecological impact of green roofs would be minuscule. It’s not even close to a solution for global warming. However, the benefits communities would reap from these roofs make me an adamant supporter of green roofs. Not only do they beautify the city, but they incorporate an important part of life into a place that has never seen it before: the production of food. It is important to know and understand the process behind creating our sustenance, and green roofs offer wonderful opportunities for community involvement and education. In fact, if you could involve more city dwellers in ecological activities like green roofs, their attitudes toward the environment and the decisions they make down the road just might make a difference.

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