Jill Fehrenbacher

American cities have a surprising amount of wasted open space. Even in densely packed urban areas like New York City, the prime real estate atop roofs is given much less consideration than one would expect from a populace that values each square foot of space so highly. This oversight is a real shame, because there is so much that can be done to improve the local environment and quality of life, simply by fixing up a roof.


The average city rooftop is layered with black tar, a material which traps sunlight and heat, raising the temperature of the surrounding area. The heat trapped by dark, flat roofs elevates city temperatures as much as ten degrees Fahrenheit – contributing to what scientists call the “urban heat island” effect.

Cool Roofs
The easiest and quickest solution to combat the urban heat effect is simply to turn hot dark roofs into
“cool roofs” by painting them with a basic coating of light-colored water sealant. In the same way that white clothing helps keep you cool in the summertime, white roofs reflect sunlight and heat. If all the roofs in New York City were ?cool roofs?, the city would save some $100 million dollars per year in cooling costs.

Green Roofs
An even better alternative to cool roofs (albeit one that requires more time and effort) is to turn waste roofs into landscaped Green Roofs. Green roofs having the same cooling effect of white roofs, with the added benefits of:

* Providing amenity space for building users ? replacing a yard or patio
* Increasing roof life span
* Reducing storm water run off
* Providing noise insulation
* Filtering pollutants and CO2 out of the air
* Providing locally grown food (with roof-top vegetable gardens)
* Increasing wildlife habitat in built up areas
* Reducing heating (by adding mass and thermal resistance value) and cooling (by evaporative cooling) loads on a building
* Reducing the urban heat island effect


Cost & city planning

Green roofs add so many benefits to a building and its surrounding area, it’s astonishing that more roofs aren’t green at this point. The biggest roadblock to our green roof future seems to be cost and bureaucratic red tape of city planning laws. Although green roofs cost more up front to install than regular roofs, the savings that they accrue over the years quickly pay off. The biggest hurdle to getting green roofs going in more places, is convincing getting city governments to change their policies and adopt programs which provide incentives to property owners to renovate their roofs.

In this endeavor, the city of Chicago is leading the way. Chicago’s Department of Environment is actually giving away $5,000 grants to any building owners who want to start a green roof project. So if you are a lucky homeowner living in Chicago, you have no excuse for not making your rooftop green!

Meanwhile I’m waiting for New York City to wake up and get on the ball with this. If only this photograph were more than just an “artist representation”

Aesthetics
Frustratingly, another hurdle to green roof world-domination is the fact that ever since the “back-to-the-earth” straw bale movement of the seventies, green roofs have been associated with a sloppy, crunchy aesthetic. This is an unfair and unfortunate connotation, since green roofs can be as clean, modern, and integral to ?good? architecture as glass and steel. Peter Zumthor’s green roofs on the Val Thermal Baths in Switzerland are just one example of a stunning use of green roofing in contemporary architectural design.

Others include Renzo Piano’s proposed redesign of the California Academy of Science in San Francisco. Piano’s green roof design features mounds and valleys of various heights and sizes, creating pockets of shade and opening vistas into the surrounding Golden Gate Park.

The largest “living roof” in the world was designed by environmental architect William Mcdonough, and sits on top of the the Ford Motor Company’s Rouge Manufacturing Plant in Dearborn, Michigan. Other notable green roofs include the international airport in Amsterdam, and the sloped green roofs of the Palais Omnisports in Paris-Bercy.

For more information on Green Roofs check out:

+ Greenroofs For Healty Cities
+ Greenroofs.com
http://jscms.jrn.columbia.edu/cns/2005-03-01/schwartzs-greenroofs
http://www.gothamgazette.com/article/environment/20051028/7/1635

Also, Treehugger posted a fabulous Green Roof Primer back in September. With an extensive collection of photos and diagrams, this helpful primer documents Treehugger volunteers putting up a green roof over a yoga studio in Toronto.

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28 Comments

  1. Nicole Hsu November 26, 2010 at 12:44 pm

    Pls. forward to me, any information promoting active participant in the green rooftop movement. Specifically for green design or landscape development and learning.

  2. Ellen Hymon October 24, 2008 at 9:37 pm

    I would like to know more about the green roof program.

  3. Will June 14, 2008 at 3:58 pm

    It is so good to read about green roofs and green buildings.

    I was in China in January and it was awful. There wasn’t a single clear day out of five. Then you look out onto the city and flat roof, one after the other. If they would just plant green roofs, people could breath easier.

    I found a lot of good info at http://www.cleanerairforcities.blogspot.com

  4. shail agarwal February 5, 2008 at 2:23 am

    will green roofs work in trpical climates like that in India?
    will it help cooling the temperatures inside the house?
    what is the cost per sq feet of having a green roof?
    thanks

    Shail

  5. Jorg Breuning October 8, 2007 at 6:50 am

    There was one comment I liked most: Let’s do it!
    75 square miles of extensive green roofs in Germany right now – plus 4 to 5 new square miles every year. I forgot I how much of them I did in the last 30 years but getting there in the US is my goal and the reason why I am here. It only works when the technology is getting standardize and when the right installing techniques are available. It doesn’t work when people are greening their sheds in the backyard, design only pilot projects, doing endless research with incomparable parameters, want to have native environments on the roof or want the roofs for food production. The profit of some manufactures and especially of the installers have to come down too. Dropping the average costs to $5-8 sft will really increase the demand:
    I promote green roofs in the 80′s on my vacations in the US – people kicked me out. In the 90′s they were at least listening (but laughing). Today I am happy that there are so many people promoting green roofs. However it shouldn’t be combined with promoting the “paradise on the roof” dream. Sense, simplicity and functionality is the goal.
    Let’s do it or let’s flip that roof.

    Jorg Breuning

  6. Mahesh August 13, 2007 at 3:17 pm

    I am a researcher who has been working for some years on modeling and analysis of urban heat island effect (UHI) for some of the major cities within US. Its interesting to come across a page where people are interested in the subject and giving it a thought. I appreciate the fact that green roof tops are being considered as one of the options to reduce the heat and save energy and so on. I should first say I do agree it does have advantages (much more as compared to people driving around the cities in their SUVs and Hummers). But at the same time the aspect of green roof tops is not the most suitable solution in many cases. Let me make things a bit technically clear.

    Increasing roof life span: This is not always true. First before creating a kind of additional systems on the roof the design capacity and utility of the roof has to be properly studied. Most of the houses are designed for a particular life span and the design usually takes into consideration the weathering. Theoretically speaking if the construction is good a concrete roof (RCC) should increase in its strength as the time goes by. Therefore it lives for ever. But this is not practically true. The same is the case with planting stuff on the roof tops increasing the life span. It’s a theoretical concept but does not take into consideration many practical aspects. For example a small damage to the water proofing element say half an inch can bring down a 100 year life span roof in 5-10 years. And the possibility of noticing the damage becomes quite difficult in a covered space as in comparison with an open space.

    Reducing storm water run off: This is really funny I would say. In order to make efficient use of the storm water run off people should really think about recharging and infiltration methods to help the ground water system. There are several manuals and procedures available for installation of such systems within the urban environment. While grass on the roof top uses 2% of the rainfall the recharge system if designed effectively utilizes around 80%. This kind of recharging will help in future water supply for drinking and of course some for the grass growing on your roof.

    Filtering pollutants: I am not sure how much one feet of vegetation is going to help. Since my knowledge on plants and their effect on pollution is limited I am not going to comment on this.

    Providing locally grown food and increasing wild life habitat: Yes might be possible but once again depends on the type of vegetation grown (definitely roof top grass is not going help any), the type of the building (i don’t know how much food could be provided by a roof top vegetation on top of a high rise for its occupants and during what period of the year). We have a green house on top of our laboratory but the green house does not help create green spaces the glass on the top still reflects, absorbs and emits quite an amount of heat and the amount of electricity used to maintain the green house is exorbitantly high. Ah I almost forgot of one thing I hope busy people living in the city do think about the time required to maintain these vegetations and stuff.

    Reducing heating and Urban Heat Island effect: Ah that’s a strong statement made over there. Firstly people should be clear about what kind of heat these people are talking about. For a person living in a city there are various kinds of heats which affect them. Ok. Let me put things a bit more clear generally speaking there are two kinds of heat especially when people talk about urban heat islands. One is the surface temperature and the other is air temperature. The surface temperature is the temperature of particular object and air temperature is the temperature of the atmosphere around. It’s like wearing a cotton shirt and going shirtless on a sunny day. It makes a little bit of difference but not enough to make you feel cold. Secondly here the people do not take the sun’s angle and number of storey into consideration. A high rise building for that matter a three storey building having a garden on its roof will have no effect on its lower floors. And generally the heat on the lower floors are caused by the air temperature and the sun’s rays hitting the building sides which are generally made of concrete and glass leading to the heat island effect. The roof in this case could be taken care of by just painting them white. Further from the research its been proved that residential areas (with sufficient trees and grass) around the CBD and near highways are more hot as compared to their rural counterparts. There by a reduction in the use of traffic by incorporating public transportation system might be a little useful.

    Overall I am not against this effect. But I just want people to make a sensible decision before adapting to any of the commercial products. Most of the companies are there to make money and have little or no concern to the chain reaction/ negative role which it might play and they are mostly hesitant to invest on research as they fear that might lead to a hold on their projects. I believe this comment would provide a little bit of insight. There are many ways to conserve electricity and make life more easy for example things like putting solar panel over house might lead to energy saving and at the same time utilizing the natural resource to the fullest. Things like ground water recharge will help not only your house but the whole society for years to come. So think before making any decision. Ask an expert and cortically analyze what’s good for your family, your society and your country.

    I am not a consultant but I do care for my environment so if my research or what I have learned so far so help any one in the society I will be more than happy to do so. If you have any comments or questions do feel free to contact me at rumahesh45@yahoo.co.in.

    Cheers
    Mahesh

  7. Nicolas August 4, 2007 at 8:46 am

    I think the green areas may waste a large quantity of water.Though the water will come back by means of rain,but it will make the current status of the shortage of water more serious.We can built forest city but I think we can’t do like that.Maybe we should make use of every space we can find in the city and plant a tree. And we can make more streames around the residential areas in the city and plant trees by the streame or river.What about the roofs?I think the best way for us to take advantage of it is laying more Solar Panel and wind power equipment as the roof has such a large height.Then every building can have enough electricity.

  8. City Living! « mo... June 7, 2007 at 3:52 am

    [...] from here [...]

  9. Edina April 22, 2007 at 1:28 pm

    Let’s do it! ;]

  10. Raegen February 22, 2007 at 3:16 am

    In response to Craig, there is TONNES of research being put into this concept, it’s just recently catching on here in North America but has been done for centuries in other countries such as Europe. In terms of lowering the Co2 content in the air that’s just one of the bonuses especially when other plants such as trees are put onto roofs – amazing, but yes, it can be done. Largely the benefit comes from reducing the ‘Heat Island effect’ because most anything is cooler than black tar roofs especially plants when they are transpiring (releasing water vapour back into the air) and providing refuge for bird and insect species that are otherwise in danger of becoming extinct due to loss of habitat.
    Yes, lots of TURF grasses do use a huge amount of water – to stay green. Otherwise, the cool season grasses for sure, just go into a dormant period. Most of them are drought tolerant, at least to some extent. And cities are usually ‘choked’ for water because we only rely on one source – the city’s reservoir to supply us with that water. There are lots of other ways to collect and use water on an individual basis. Such as rain barrels for later use in watering plants.
    The drought tolerant, low maintenance plants that seem to be most popular on roof tops are Sedums. And perhaps ‘green’ roofs isn’t always the most accurate term, ‘living’ is far more appropriate in many applications.

  11. craig January 13, 2007 at 4:14 am

    The concept looks simple and out of this world.

    But has anyone done any background one this besides trying to sell it?

    Most grasses don’t really lower the Co2 in the air and bring down heat outside. And they consume huge amounts of water – another very precious resource. Cities are usually choked for water already. What are they kinds of plant life suitable for this?

    Induvidual houses are a different proposition, but high rises usually have associations. They’ll need to maintain it, else the purpose is defeated. But of course, there is hope.

  12. Howard January 4, 2007 at 7:23 pm

    I “Stumbled Upon” this web-site – what a great idea! We have a flat roof above our pub, & I think it would be brilliant to have real grass growing there.

  13. Carlos Abler December 30, 2006 at 4:31 pm

    I would add to that list of green roof benefits, something like the following.
    *Community development benefit. This kind of thing can really excite residents, mobilizing them to interact more around common projects. Benefits from social programming augmentation such as that community garden example. The amenities example almost includes this, but does not speak directly to the social benefit.

  14. Richard Donkin December 13, 2006 at 8:09 pm

    There is a 19th century textile factory in Leeds in the UK called Marshall’s Temple Mills, modelled by Ignatius Bonomi, it’s architect, on the Temple of Horus at Edfu. He needed to insulate the roof to ensure the correct humidity inside for flax spinning. A layer of plaster was covered in pitch. Earth was shoveled on top to prevent the pitch cracking, and grass was seeded to bind the earth together. The final practical ingredient employed to keep the rooftop grass in check was a small flock of sheep. It was a novel solution at the time.

    I mentioned the factory in my book, Blood, Sweat and Tears, The Evolution of Work, published by Texere.

  15. Joe Levi: All that R... August 13, 2006 at 5:27 pm

    [...] Not long ago my wife and I saw a telivision show where they installed a “green roof.” Basically, they made a 4 inch deep “growing box” on the roof, lined it with pool liner, placed a couple sheets of carpet padding down (to help hold in the water), placed some soil and netting down (to hold the soil in place), then planted it with ground-cover (sedums and the like). [...]

  16. Inhabitat » Blog ... August 1, 2006 at 5:57 am

    [...] And now for some more green roof love from Inhabitat… [...]

  17. Inhabitat » Blog ... July 20, 2006 at 10:24 pm

    [...] With research and architectural planning, they figured out how to plant out a 1,200-sq-ft sedum roof that wouldn’t compromise the structural integrity of the building. On the contrary, it would offer natural insulation and prevent excessive storm run-off, all while enabling the owners of the top floor apartment to rock in their porch swing and overlook a tranquil green expanse, against the backdrop of the New York City skyline. [...]

  18. Andreas Paulsen July 18, 2006 at 1:01 pm

    Green Roof.
    Take a look at Norway, look at the countryside-rural log houses. They have had green roofs for a long time. I remember goats on the roof.

    Andreas

  19. Inhabitat » Blog ... July 18, 2006 at 7:44 am

    [...] As far as green roof designers go, you can’t get much more committed or accomplished than the team at Rana Creek. While their name often gets partially eclipsed by the names of their starchitect collaborators, such as William McDonough and Renzo Piano, it’s Rana Creek’s genius that yields such massive marvels as the rooftop of the Gap corporate headquarters and the California Academy of Sciences. [...]

  20. Jim Maurer July 13, 2006 at 12:22 am

    I like the idea, but it seems problematic. A green roof would add substantial weight, likely more than lower floors were designed to support – or am I wrong? Also, wouldn’t repairs like leaks be complicated?

  21. Angie Durhman July 7, 2006 at 10:51 am

    TectaAmerica, the largest roofing contracting company in the country, has completed green roof projects across the US. My background is in horticulture, with specific interest in green roof plants and systems. Currently, I am the green roof specialist at Tecta, and am in charge of planning, installing, and maintaining green roofs (primarily on the East Coast). We have done a few small residential projects, but the majority has been extensive roofs for commercial application. The TectaGreen system is a single source for your entire roof project. If you would like further information to move your green roof project forward, please visit http://www.greenroof.com and contact us!
    Angie Durhman

  22. amy lou stein July 7, 2006 at 1:29 am

    What about a 100 yr old townhouse? We would be totally interested. I grew up with the River Rouge disaster and I am in awe of what they have done (+ i read Cradle to Cradle) it’s actually unbelievable to someone from Detroit. How do we try and actually get grants from the city? oxoxox amylou
    ps again thanks!

  23. James July 5, 2006 at 4:49 pm

    Would it be cost effective to green an existing flat roof ( EPDM/Modified) 4 to 7yrs old in good condition?
    Hope to see more on this subject.

    Peace,
    James

  24. Inhabitat » Blog ... July 5, 2006 at 4:52 am

    [...] And for you advanced players in the heat dissipating game, there’s no place left to go but up – Green Roofs!! Here at Inhabitat, our preference for green roofs runs a close second only to prefab buildings. There is a huge variety of green roof construction systems to fit nearly every building type and location. Stay tuned to Inhabitat for more on greening your roof in the near future. [...]

  25. Emilia E. de la Sienra S. November 23, 2005 at 6:51 pm

    Hello,

    I am writting you because I am a biologist, with a masters in Environmental Planning, and working at Ecological Culture, a NGO located in Mexico City.

    We are very interested in creating as many green roofs as possible in the city buildings. We already wrote down the project but we need some training and finance support.

    Would you give me some advice?.
    I really appreciate your time.
    Best regards,
    Emilia.

  26. bo November 16, 2005 at 9:49 pm

    as much as i like the concept of a green roof , i’m not sure how appropriate they are to areas prone to drought , like southern california . is there such a thing as a low-water green roof ?

  27. Brent Bucknum November 15, 2005 at 6:25 pm

    Rana Creek Restoration Ecology…

    -We are a Habitat Resatoration company specializing in “living roof” design among other things and we are based in Carmel Valley, CA

    -We did the research and development and plant selection for the California Academy Living Roof.

    -We have internships for people interested in designing and building living roofs both in our nursery department and our living architecture design department.

    -We also designed and built the landscape highlighted in another feature..Fernwood Cemetery..

    -Feel free to contact me if you are interested in any of our projects or are intersted in building a living roof.

    cheers,

    brent

  28. Lloyd November 13, 2005 at 8:37 pm

    You should also check out Green Roofs for Healthy Cities, url above.

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