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Kimberly Powell

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If green roofs were mandatory in cities would there be less development and building?

William McDonough knows the benefits that come from designing and implementing green roofs. McDonough has helped design living roofs for big companies such as Nike and Ford Motors. But many companies and homeowners overlook the benefits of green roofs. One benefit of green roofs is that they keep the internal temperature of a building steady throughout the year. The National Research Council of Canada found that having a green roof reduced the daily energy demand for air conditioning in the summer by 75%. Toronto is the first North American city to pass a law mandating green rooftops for all new residential, commercial and industrial developments. Any new construction with floor space of more than 2,000 square meters must devote between 20 and 60 percent of its roof to vegetation. But with green roofs comes an unwanted financial upfront cost. Will developers decide that the benefits outweigh the costs for installing green roofs?

If green roofs were mandatory in cities would there be less development and building?

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    May 23 2012: I agree with Mike Robinson, but wanted to dig a little deeper: I take it from the phrasing of your question that you are afraid that mandatory green roofs would scare off development. To me, that phrasing already concedes that Big Money has a stranglehold on our priorities. That stranglehold is exactly what we need to reverse if green building, or even environmentalism as a whole, are to take hold.

    Of course, there is such a thing as a thoughtful, well-intentioned benevolent developer/corporation (very exceptional); but is further development--even smart/green development--what we really want? To me, that is just an intermediate band-aid, and not nearly sufficient to the task at hand. It was reported recently that most oceanic life is predicted to be extinct by 2049 unless we humans radically change our ways, and soon. We are hitting an environmental wall right now, and only a few people are even aware.

    Given this situation, the whole paradigm of who develops what, how, and why needs to consciously shift to a much more sustainable path. Essentially psychotic corporations need to be put in their place (purely as tools of the people), and governments need to pull their noses out and get with the program!
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      May 23 2012: I find a lot of what you are saying is very poignant and insightful. The one piece that I would like to touch on is the idea that corporations should be tools of the people. I find it fascinating that people are so easily manipulated into letting business have control over their lives. Mass population has and will always have the upper hand if they unite in a cause. Look at any period in history and this proves to be true over and over again (in both good and bad ways) But, corporations are the one entity that seems to have figured out how to manipulate the masses into thinking a certain way. If people would just unite and simply communicate they could use these money magnates as for their own means instead of simply feeding the machine. Development would be a lot easier if the people that were supplying the money knew the only way they could use the building was to build it a certain way. I don't think laws are the answer to the problem, because time has shown us that corporations will find loopholes or worse simply ignore them and get reprimanded later. It is the consumer that decides the fortunes of companies, but people simply have not seemed to figure it out yet...
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        May 23 2012: Yes, I wholeheartedly agree. I think we are getting a bit off topic, but it's good that this discussion has spurred a deeper related discussion. There are probably other conversations on TED related to this very issue of finding a collective consciousness and following it, but I haven't looked yet.

        This issue of laws not being the answer is also very ripe for further discussion. Laws are really only necessary when and where there are moral/ethical/behavioral differences between people. I don't see fundamental differences fading away anytime soon, so there is still a place for law. However, I would say that virtually all the laws we live by are far too complex (and many are mis-directed), thus difficult to enforce. Laws should be very simple, clear, well-directed, and most importantly easy to enforce. Hopefully, as you imply, we'll someday get to a point where laws are essentially superfluous, and we're all keyed in to a fairly unified purpose (e.g. the sustainability of life on Earth).
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    May 22 2012: I watched a ted talk recently about the issue facing us in future, and that is how to feed a possible 9 billion people in the next century (Jonathan Foley, The Other Inconvenient Truth), when so much of the earth's surface is already devoted to agriculture, and being overtaxed. Perhaps there will be a time where we will all have to produce our own food, because the resources of the world will be unable to cope. Green roofs could be the way of the future, especially in terms of growing our own vegetables, and this would also reduce the use of industrial fertilisers, which apparently account for quite a bit of the world’s emissions due to the fact that they have doubled the world’s levels of phosphorus and nitrogen.
  • May 22 2012: I hope it will stimulate innovation but am also hopeful it will lead to less development. Or more accurately I hope it will lead to less greenfield development and more brownfield development (revitalizing already existing developments).

    We may also want to consider living underground or underwater if we are looking for niches to occupy that may be more efficient than square boxes exposed to the elements.
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    Aja B. 20+

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    May 22 2012: This discussion has been selected as today's featured TED Conversation on our Facebook (http://www.facebook.com/TEDConversations) and Twitter (http://twitter.com/tedconversation) feeds. Congrats! :)
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    May 22 2012: The saying raining cats and dogs came from animals falling through sod roofs in ole England. My grandparents in central Kansas built their house almost all underground. The temperature was consistant year around (before air conditioning). In Phoenix one of the high schools is underground elminating the need for extensive air conditioning. This is not a new thought nor is it a bad thought. Ideas come around in a circle. However I am against making it mandatory. If I was building in Toronto I would build my factory in 1,900 foot sections and link them with tunnels and walkways. All the best. Bob
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    Jun 1 2012: Personally, I do not believe that by making green roofs mandatory that it will stop the development of new buildings. The price of the building will just increase due to the price increase in the production.
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    Jun 1 2012: I do think that green roofs are a great idea and would increase the biodiversity of a neighborhood and help with energy efficiency. However, I do wonder about the risks of making this mandatory. I feel that if developers are to continue building at the rate they are going now in order to maintain their business and at the same time to implement green roofs, they might cut corners elsewhere. It is no surprise that construction sites go up as fast as possible because it is what will make them the most money. If you require them to add on green roofs and all of the extra work and special materials that go along with building a green roof, I fear that corners will be cut elsewhere and therefore possible cause a greater risk than the green roofs are worth.
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      Jun 1 2012: Theresa, you make a very valid point. Today, our society is big on being cost efficient. A building company would care more about the initial cost then saving earths biodiversity, simply because it is just not their job. If green roofs were to become mandatory, the developers might indeed cut cost somewhere else in the building process. With that said, do you think that there is any way around this obstacle? Is there a way that green roofs could become mandatory without it effecting the quality of the work?
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      Jun 1 2012: It is true that there would be cuts elsewhere but I don't think that the quality of the work would be affected to a point that it was bad. What kind of work do you mean? Like the building itself? There regulations that must be followed so that it is not a poorly constructed building. Now if it is decoration that would decrease in quality , that is not a big deal. If it a reduction in the quality of work of the service provided, then that affects those in charge directly.
  • May 27 2012: Kimberly, your question is really one of economics, and simple economic reasoning is enough to answer it without going into the details of what green roofs are and how they work (although these details are interesting in their own right, to be sure!).

    The effect of compelling producers to add a new component to each of their products is that the cost of production rises. The result is that the marginal producers -- those whose costs have now been driven higher than the revenues they can obtain from the product -- are driven out of business. We end up with reduced supply and a higher market price, which in turn leads to the marginal buyers -- those who were prepared to pay the original price but not the new, higher one -- investing elsewhere, e.g. in other cities.

    Now, of course people can freely purchase a green-roof building, and they will do so if the savings on air conditioning and the other benefits of such a building outweigh the additional cost -- in short, if the choice is economical. Thus we arrive at the conclusion that if green-roof buildings are economical, a government mandate is irrelevant; and if they are not, it's harmful (reduced production and higher prices).

    This conclusion should really just be common sense: social wealth and well-being can't be increased by ordering the police power to forcibly prevent people from engaging in voluntary exchange.
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    May 24 2012: Mandating green roofs seems like a great idea to spur environmentalism, as well as help people be greener in general. I don't think that developers would have a problem following a new mandate, but I do question what the individual would think. Would purchasing a space or home that has been built with a green roof increase the up front cost, and would individuals still want to shell out the money despite the promise of 75% reduced air conditioning energy demand? For people who don't use air conditioning or heating what is the incentive to purchase a home that has a green roof, especially if it's more expensive than a traditionally built house? If new mandates don't ensure that all newly built spaces require a green roof and therefore an increased purchasing cost I fear that people will tend towards traditionally built spaces and the new spaces would go unoccupied, unless the developer covered the cost of the green roof.
    • May 24 2012: Not only are green roofs great for reducting HVAC costs but they also have implications for global climate change. If new roofs were installed on new private homes, these places would have substantially less carbon emissions than houses without green roofs. The green roofs will be photosynthesizing constantly, making them extremely beneficial. If homeowners are only looking at the short term consequences of green roofs, they might not be as appealing but all the long term benefits are so great, it seems to me like they outweigh any bad things that could arise.
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        May 24 2012: I don't argue that green roofs would be beneficial with regards to global climate change, but I question how many people are willing to pay an extra up front cost for a space with a green roof. Many ways to help the environment are simply options in current society such as being vegetarian or using LED lights rather than incandescent. If the option isn't turned into a requirement I don't believe that everyone will choose something that benefits the environment, especially if there is a larger up front cost. To me the option of buying a home with a green roof is similar to the option of buying an electric car, just because it helps the environment doesn't mean that it will be the choice of every individual, particularly if it is initially more expensive.
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          May 28 2012: I agree, if the savings from heating and air conditioning take many years to match the upfront cost of the home, people will go with the standard home that is much cheaper. I think most people are becoming more aware about the human impact on the environment, but until the cost of green technology becomes affordable to everyone, we will stick with the cheaper option that causes greater environmental harm.
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      May 24 2012: You have to remember that people who would make green roofs wouldn't be just homeowners. You have to think of a renting scenario as well, apartment complex owners, hotel owners, etc. For someone who owns an apartment complex with a green roof, they could charge a bit extra for the green roof and make a bit more profit in the long run, and as a renter that would be justified because you save on heating/cooling costs. There is an incentive for both the building owner and the renter.
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    May 23 2012: I do not think that green roofs would limit building. Building cost are already high and adjusting for a green roof would not add that much cost relative to the cost of the whole building. I personally think green roofs should be mandatory for all new buildings, especially new government buildings. If the government started adopting green policies such as this it would have a positive effect on the industry and the environment. Green roofs are also very beneficial for pollination. If green roof companies created an alliance with pollination biologists and honey producers we could slow the decline of honey bees.
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    May 22 2012: I agree with Mike that I would be happy if something finally slowed the development and expansion of our cities. I also think this is a very innovative idea and am excited to see similar innovations.

    In looking at this question though, we also need to consider that as Kimberly said, buildings can save 75% of energy used in the summer. If businesses took these savings into account it could result in perhaps more new development, and also changing of existing buildings. It would be nice to see something like this required of existing buildings as well, because we shouldn’t be expanding our populations or cities in the first place, but we should be focusing on changing the way we live now, not just in the future.
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    May 22 2012: I think this is a very noble idea and one that will gain momentum over time to help our society live both more within its means and also foster a greater connection with the environment around us. These roofs aid in cooling building, but can also aid in small scale food production as has been seen throughout many cities across the globe that have rooftop gardens. They also can serve as a place for people to relax and meditate, perhaps on a lunch break which can foster a more productive day and a happier workforce.
    Since I'm not an architect I can't give a completely knowledgeable answer but I believe that, with proper government support, these regulations will do little or no harm to the ability to build in a more sustainable manner. In some ways, this may revitalize these urban areas that have fallen into a state of decay and help aid in cooling our cities, making these building more cost effective in the long run and also providing a cleaner aesthetic feel to the city. Obviously this applies only to certain locations as this would probably be ineffective in say an area that has insufficient water to keep the plants moist or a location that freezes, but it is a positive start in the right direction. I think this is the future of architecture and we will only see more and more buildings designed in this manner.
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      May 22 2012: I didn't even think of the green space on the roofs being able to produce food during the proper seasons. Do you feel that if the roofs had to produce food that it would impact if the building grows and by grow i mean possibly start at a new location (add more buildings to the company)?
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    May 22 2012: I like the idea of green a green roof, but I like what McDonough says about the planning of new cities and buildings even better. Mandatory building codes exist all over the world why not implement them in places where the climate allows. I think of places that are cold more often than they are warm and wonder how well the idea would work. Especially since they would require standing water systems that could freeze and impose massive costs to the building owners. To me though the idea that we take advantage of the environment around buildings and design to it should be mandatory. The study of sun, wind and landscapes can mean just as much to a sustainable building that the green roof idea. cheers
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    May 22 2012: I personally think that green roofs are a fantastic idea. I would however have questions about the durability and lasting power of these roofs. Also, how might this roof design system limit architecture in terms of what shapes we can create with buildings? Overall it's a wonderful solution to a long time issue of combing an environmentally conscious design and one that effectively protects us from the elements. As far as making it a mandatory part of building design, I think it would be most effective to implement something like this in large metropolitan regions such as los angeles and new york where air pollution is high and extreme heat pockets in summer can kill residents. Not to mention they are just so visually appealing.
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      May 28 2012: I would agree with you that green roofs could be especially helpful in large cities where pollution levels are high. And as to the durability, green roofs can actually drastically increase the life of roofs. As long as the original roof is properly sealed and waterproofed there are no detriments to roof life span. The organic materials used in living roofs protect buildings from storms, UV radiation, and many other factors that usually age roofs.
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    May 22 2012: I don't think there would be less development, but there would have to be more innovation around design and architechture, to meet the environmental standards as well as the development needs. I lived in Christchurch New Zealand that was partially destroyed last year in a massive earthquake. the new city plan for the central business district which was levelled, is for buildings to include green roofs, and sustainable design as part of the rebuilding process. Included in that are the many earthquake safe provisions and codes that are mandatory in a place like New Zealand (which is split down the middle by the Pacific and Indo-Australian tectonic plates). This disaster has opened the door to a massive jump forward in sustainable and environmentally friendly building. And lets face it, green roofs are also much nicer visually than an ugly concrete rooftop!
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    May 21 2012: I think that if green roofs were mandated, then many different businesses would sprout (pun fully intended) to provide that service, and would need to build, and even if the initial cost went up, people still need buildings. Development and building costs are already fairly high, and green roof initial costs are not that astronomically high that it would be so detrimental that development and building would slow. I feel the benefit outweighs that initial cost, and development would increase to replace the old.
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      May 22 2012: Do you think UO or any other university for that matter would take the initiative to build with green roofs?
      • May 23 2012: The mandatory implementation of green roofs seems like a great idea to me. In addition to the points that many people have made the already high upfront building costs, I really do think that considering the later savings that green roofs can have for building temperature regulation, etc may outweigh or at least equalize the upfront costs. Especially when you consider how long you expect a building to be in existence and how those savings add up over the years.

        As to your question, Kimberly, I do think that a university may be one of the early places to take on this initiative. Not only is a place like UO full of young people who are passionate about making changes towards a more green future, including architecture, but at least at our university there seems to be constant construction and remodeling. This provides many opportunities for new technologies. Additionally students studying architecture are probably at the forefront of learning about these things and can be key assets for new green architecture implementation. This could provide opportunities for the school to save money, be a pioneer on a new green architectural front and allow students gain experience by using their education to provide input into changes in the university.
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        May 24 2012: I think the University of Oregon would be an amazing place to start a green roofs program. We currently have a sustainability initiative and this seems like a logical next step especially with the work that Jessica Green of the biology department is doing in partnership with the architecture school. It would be interesting to find out how many current building could be retrofit for green roofs on campus as well as how to initiate a mandate for all new buildings.
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    May 21 2012: I don't think so, in fact I think it would remain the same. The builders would merely add any extra expenses into the bill while promoting themselves as an Eco-Friendly company. In Florida mandatory hurricane codes do not hamper building, Miami is growing everyday as well as Orlando.

    It would certainly change the landscape for the better though.
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      May 27 2012: I have to agree with Adam and the view he is taking. The assumption that new construction would decrease because of mandatory green roofs is the same as assuming new construction would decrease because different or more stringent earthquake structure regulations are put into place. The alterations of building codes happen relatively frequently and they do not result in noticeable changes in the amount of development.
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    Jun 1 2012: Hi Allison,
    Many people will not vounteer for a prosocial behaviour but when it becomes mandatory they make the best of it and adapt it to their own purposes so that they do not appear to have been maliable to authority figures. Did you ever notice how many people compost now that recycling is required?
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    Jun 1 2012: I do not think green roofs shouldnbecome mandatory, though I could see it being strongly encouraged such as on top of apartment complexes in large cities where you know at least of the tenants would care for the plants and it would give a common space for neighbors to hang out and enjoy the nature scene together since they would not have a backyard. It would also be beneficial on hospital roofs for patients who cannot leave the premises of the building or for those visiting long hours. A fear I have about making green roofs mandatory is that I know many people would not have the time to care for the plants and it would be an eye sore for neighbors. There are already people who do not care for their lawns, shrubs and trees in their front yard and I would imagine it would cause some complaints in a residential neighborhood.
  • Jun 1 2012: Although it will increase the upfront cost of development, it may decrease the cost over time and will definitely decrease the negative environmental impact. To alleviate the upfront cost perhaps a government assistance program could be implemented. Additionally, the costs of adding a green roof to a development project probably would not exclude a large percentage of the market. Green roofs may even inspire a new type of development which is ultra efficient to minimize the extra cost of a green roof.
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    May 31 2012: Buildings will rise regardless of mandatory green roofs. I doubt there will be less development and building, but there may be less diversity in what buildings are being constructed. With the added cost of green roofs either the design of the building will have to suffer and be less creative in an architecture sense or the amount of companies able to build will be smaller allowing for them to experience more growth. If somehow tax dollars were able to help contribute to the expense perhaps that would maintain development of buildings.
    • May 31 2012: If we could use tax dollars to contribute to the development of green roofs, then I believe we could make positive headway on accomplishing the requirement! Raising taxes would not necessarily be a bad thing either don't you think?
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        May 31 2012: It just depends on whether or not people are willing to create a better living environment for their community. And not everyone cares or feels that tax dollars should be spent this way. Though I do think it would be beneficial in the long-run.
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      Jun 1 2012: If green roofs were mandatory in cities, yes it might not stop development. But, it will make development better. Those companies that are creating new development, have the money and would give back to nature the space that it has altered. If the mandate was to stop development then that would be great as well. I see this as a win-win situation.
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      Jun 1 2012: I agree with the fact that I do not think that development will stop. I do however think that the developers will find a way around the 2,000 sq meter requirement for green roofs in a way to "beat the system.
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      Jun 1 2012: I agree that development will continue, even if if is just replacing older buildings and I think that innovation is important in that process, but it also takes a long time for new ideas and building practices to become widespread because there are so many buildings already and replacing them takes a long time. Maybe in 50 years things will look different.
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    May 30 2012: As many commenters have posted, this ultimately boils down to money. The upfront costs of doing a green roof is prohibitive for some builders, even if the roof pays for itself down the road. I think a better alternative would be to provide some sort of reward for including a green roof in building plans. For instance, a tax holiday for a certain period to help offset the cost. The monetary benefit would be realized sooner and may entice more green roofs. Though it may cost the government some money in lost tax revenue, it may ultimately save money in the long run when accumulated environmental costs are realized.
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      May 31 2012: I think a small tax break for including a green roof is a good idea. The major difficulty is deciding on an amount that will entice businesses without significantly reducing tax revenue. Regardless, it could be a great transition point, allowing people to see the benefit of green roofs as a typical building component without initiating a mandate just yet.
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      May 31 2012: This is a very good point and great idea. There are usually multiple ways of implementing things like this and the options are usually the stick or the carrot. Offering something motivational seems like a more likable change, rather than something that will make businesses comply but simultaneously piss them off.
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      May 31 2012: As you stated, it does all boil down to money. But one aspect that I think it's important for businesses in particular to consider is that they gain positive publicity by going green. Because taking steps toward helping the environment and "going green" is becoming more and more popular in today's culture, I think businesses that decide to put up the extra money up front will see a return on their investment from customers that support their decision and choose to associate with that business rather than a competitor.
      • May 31 2012: To put it simply, it is incredible that going green is becoming a trend in the social and political world. Therefore, pushing the more influential people to make more environmentally conscious decisions. The more those in power do it, the more the masses will follow. Do we think it would be a good idea to demand the companies or individuals with a large enough income be required to install green roofs? Or is that too farfetched?
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          May 31 2012: I think that companies would really fight back if they were made to install green roofs using their own money. However, as time goes on and more and more companies start to install them in response to consumer requests, I think that most companies will follow.
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    May 28 2012: Right now I don't think that the benefits of green roofs outweigh the costs. I think that maybe with time and the right advertising, green roofs will become more desirable and therefore the benefits will, in fact, weigh out the costs.
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      May 31 2012: The right advertisement might be the cities themselves. When you start adding more green and better sustainability to structures and show the people you care about the environment as well as those who live in it...well it will attract more people to live in the city.
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    May 28 2012: I suspect that a mandate for green roofs would simply ensure developers move out of the region with the mandate, like how Portland is having so many issues with suburbs trying to get out of the urban growth boundaries in one way or another. It would have to be state or nationwide to ensure compliance. Beyond that, the cost of keeping all those plants alive with be another problem. In apartment complexes and homes, a little education and a lot of coercion would go a long way into convincing people to keep those plants alive. In office buildings, somebody will have to be paid to keep them alive, or else the space could be rented out to families seeking to grow more than their own space might allow.
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      May 30 2012: I agree with you that developers would likely just of the area that mandated them to build a green roof if they really didn't want to. But with more education about the benefits to green roofs, developers may not be as opposed to having buildings with them. Although it may have more upfront cost, in the long run it would save a lot of money that would have been spent on electricity bills to regulate the temperature of the building. Like most things, I feel like the introduction of green roofs will just take time and cannot be expect to be accepted over night.
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      May 31 2012: Education will definitely be the driving factor here. I think it would be great to see public buildings taking the lead in making this happen. There is also the potential for new jobs to be created in regards to caretakers of the roofs. Although, this may only be a possibility for big businesses that can take on the extra payroll. I agree with Amanda that the green roof movement will probably be a slowly occurring one, but the right idea is there.
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    May 28 2012: I think that green roofs are an excellent way to introduce biodiversity to cities, and they are also good because they help to lower the Urban Heat Island effect. I doubt that many developers would be overly excited to include green roofs on their buildings, but if they were informed of all the environmental benefits, and perhaps also of benefits as to how green roofs can increase roof lifespan and help with the insulation of buildings, they might be more open to using them.
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    May 28 2012: I think green roofs are a good idea since it would reduce energy demand and the cost of heating and cooling the building. However, I don't think developers, if given a choice, would use green roofs if the upfront cost was too high. If the upfront cost is high, that cost would then be passed on to tenants at residential buildings. The fact is that unless developers are forced to, they will go with the cheaper alternative to make more money. But, I think green roofing and other sustainable building practices will gain favor among developers as the upfront cost continues to decrease.
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      May 28 2012: I agree that green roofs are a good idea but that building developers will be less inclined to use them in buildings if the upfront cost is too high. I think that perhaps if green roofs and their benefits were advertised more to the general public, there would be an increase in demand for them and more developers would be willing to supply them.
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      May 31 2012: With "today's economy" I have a feeling this would be an added financial hardship that wouldn't be justifiable. It is hard to get people to see the long term effects when so much start up money is needed. Does anyone know some dollar figures for what this might entail? I'm sure it varies drastically depending on the circumstances...just curious though.
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    May 28 2012: I'm interested in how green roofs would effect urban biodiversity. It sounds like the idea is to make the roof's plant life like the natural plant life of that area(or like a farm, depending), but what about animal, fungal, bag bacterial, etc. life? How would the differences between these green roofs and natural areas hinder or be utilized by them? There's of course the issue of elevation, especially on large buildings and perhaps even more importantly accessibility; for instance, I can't see any mammals other than squirrels or bats being able to interact with the gardens in any meaningful way. There’s also things like soil depth, wind exposure, and some crazy edge effects seeing as how we're talking about little patches of soil and plants separated by a bunch of concrete(which I suppose isn't too different from yards...). I know biodiversity isn't the primary reason why people are considering green roofs but it's still interesting to consider.
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      May 28 2012: That _would_ be interesting. For the lower elevations/height (say 1 or 2 stories), I'd imagine the green roofs probably shouldn't cause too much difference for some creatures to go up there if they truly wish to (like, say, cats). Granted, there probably wouldn't be as many variety of insects or invertebrates like worms, unless they were already in the soil that were already laid down, or planted there by the owners themselves.

      As you go higher up, it would stand to reason that there would be a selection for organisms in their ability to reach up to the higher stories (probably mostly birds) and whatever else that may be brought up there by humans (again, whether they be on purpose or accidental).

      That actually sounds like a cool experiment to conduct. 'Would you find a general trend of losing biodiversity as green roofs go to higher elevations?' or something in that line of thought. I wonder if anyone has thought of testing that out?

      It might also depend on what type of plants people want to grow up there, such as purely aesthetic plants, or as people have mentioned before, garden plants for growing food.
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    May 28 2012: I think green roofs are a good idea, but it may not be practical in every situation, an alternative could be solar panels, particularly in areas that get more sun/less rain, where solar panels might produce more energy than a green roof would save. Is it possible to have both solar panels and a green roof?
    I don't think that this would necessarily hinder building development, although in my opinion we could do with less individual homes instead building urban areas upwards to increase density and get rid of suburbia. People may not be willing to pay the extra costs, some may not believe that it will save them heating/cooling costs and others may consider it a hazard, but I think if they became mainstream and all new houses were equipped with them then there would be less resistance.
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    May 28 2012: I think there might actually be more especially if restaurants and families used that space to grow food.
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      Jun 1 2012: Debra, you make a good point. Our society can greatly benefit from green roofs. However, since green roofs can be built now, why would production increase only if it was mandatory?