Green Roof Discusssion

May 19, 2009
10:09 am

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There are two basic types of green roofs: extensive and intensive. The extensive ones, which simply use a layer of hardy groundcovers like sedum, are a lot cheaper (about $10/square foot) than intensive green roofs, which are more landscaped gardens with trees and shrubs in addition to groundcovers.

— brad

2. May 19, 2009
10:10 am

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this article is a good start but i feel like it doesn’t have enough facts about green roofs…yes they are around $25 - 30/ square ft…but they are suppose to help insulate the roof. what are the saving from that? does Daley’s office know how much these buildings save in heating & air conditioning costs? why is it so hard to get permits for this in NYC….just the beehive reason or something else?

— Peri 8

3. May 19, 2009
10:20 am

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On this reasoning, why not replace Central Park with reflective material?

— James Papp

4. May 19, 2009
10:22 am

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I recently put a green roof on my Mercedes GL. I had a welder put a 2 inch rim of aluminum around the edges — not an easy task to weld aluminum. I then layered a quarter inch of gravel, and 1.5 inches of topsoil mixed with Canadian peat moss. Currently I am growing various herbs, carrots watermelons, pumpkins, and corn. In a couple of months, I will be able to just grab some food from my roof instead of pulling into a McDonalds. I can actually seen the carrots growing as i look up through the panoramic roof. I consider my roof garden the equivalent of a carbon credit.

— Lyle Vos

5. May 19, 2009
10:23 am

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One big problem- can existing roofs take all that extra weight? Water, soil, planters, etc. You might have to add some columns all the way down to your basement- and destroy finishes throughout your building. Gotta add those costs in as well. Try putting planters atop masonry parapets, rather than the roof plane. Brick masonry walls can take some more weight, usually- but strap down those planters. Makes your building look like the Hanging Gardens of Babylon for a fraction of the cost.

— john

6. May 19, 2009
10:23 am

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I look at that roof and see HVAC system run amok. Seriously, first do energy efficiency improvements (have they?) then for that price plus a bit, you could have solar panels. Then put the green stuff down on the ground where people actually get to enjoy it. Gardens without people are kind of sad.

— Jennifer

7. May 19, 2009
10:25 am

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How about the cost of replacing a decomposed roof after 10-15 years?

— Paul

8. May 19, 2009
10:29 am

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Wouldn’t “cool” roofing raise atmospheric temperatures locally by reflecting the sun’s energy back upwards where it could only bounce around? At first glance, absorbent green roofing would be more effective by preventing that.

— MrSatyre

9. May 19, 2009
10:31 am

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It will be a lot less expensive to use green or cool surfaces, especially in urban areas which act as heat islands, to increase the Earths elbedo and reduce radiated heat than it will to limit CO2 emissions which account for less than 10% of the greenhouse gas effect.

— Richard Bunce

10. May 19, 2009
10:35 am

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check out sky vegetables. they have found a way to use hydroponics and limit the water weight. http://www.skyvegetables.com/

— melissa

11. May 19, 2009
10:48 am

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For a cheap green roof system, see http://www.flowscapes.org

— Anna

12. May 19, 2009
11:01 am

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For do-it-yourself low-cost green roof systems, see this report:
http://www.flowscapes.org

A green roof pays for itself with its stormwater-management and insulation value.

Not all green roofs are the same or have the same purpose, so it’s important to not compare apples to oranges.

— Anna

13. May 19, 2009
11:17 am

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@ Mr Satyre (comment 8): Cool roofs and other light-colored surfaces (e.g., cool pavements) cause short-wave solar radiation to reflect back out to space. That doesn’t cause local warming. In contrast, dark-colored surfaces absorb short-wave radiation and re-radiate it as long-wave radiation, which does cause local warming. This is known as the urban heat island effect: all those dark-colored surfaces absorb and radiate a lot of heat, which makes urban areas quite a bit warmer than the surrounding countryside.

Some of that long-wave radiation also gets trapped by greenhouse gases in the atmosphere, contributing to global warming.

— brad

14. May 19, 2009
11:19 am

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Mr. Strickland is either ill-informed, lazy, or trying to “whitewash” any reasonable attempts at reducing heat island effect in NYC. He doesn’t have data to support his supposed idea of “cool” roofs, making me think he’s invested in some company that does business in the materials required to build them. Extensive green roofs cost a fraction of what he claims they cost. Green roofs last 75-100 years vs. 20-30 years for a traditional roofing system. That’s the bottom line. Green roofs are much cheaper over time. I won’t even go into the environmental benefits now.

— aeneas

15. May 19, 2009
11:37 am

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Green roofs for local produce. Solar panels for local energy.

— paulwesterberg

16. May 19, 2009
12:09 pm

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I agree with -aeneas #14 with regards to Mr. Strickland. Furthermore, those “white” roofs do nothing to help mitigate the storm water run-off, which should be a priority of NYC with their antiquated sewer systems, not to mention the aesthetic benefits to go along with the carbon emissions off-setting that Green Roofs provide. Every city in the USA would benefit from a Mayor like Chicago’s Mr. Daley.

— casey

17. May 19, 2009
12:10 pm

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New York needs to realize how much happier Green Roofs can make its citizens. I would like to see more hotels with Green Roofs as a place to relax and have a nice evening drink!

— Chris Kaiser

18. May 19, 2009
1:23 pm

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Incentives for solar thermal projects are conspicuously absent from New York City’s Green Roof program. For the City’s multi-family residential buildings, which have limited roof area but use a lot of hot water, solar thermal systems are greatly more feasible than photo voltaic (PV) systems as they capture more energy from the sun per unit of surface area. Consequently, compared to PV systems which ARE included in the Green Roof legislation, use of solar thermal systems on NYC multi-family building roof tops would generate greater reduction in of fossil fuel usage (therefore greater reduction in greenhouse gases), greater reduction in pollutants, greater reduction in energy costs, and greater reduction in the City’s contribution to our dependence on foreign energy. The absence of incentives for solar thermal systems in the City’s Green Roof legislation is an expensive and wasteful oversight, but one that could be easily corrected.

— R H Schofield

19. May 19, 2009
2:07 pm

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Mentioned but too little emphasized in this discussion is the potential that green roofs and permeable pavements have to reduce non-point source water pollution (aka storm water runoff) in urban areas. The cost of dealing with non-point source pollution is a tremendous burden on local government even before including the costs to public health and the environment of the harmful effects on aquatic organisms.

Green roof building standards for private buildings also provide the opportunity to offload the costs of reducing non-point source pollution onto the private sector (which after all causes the pollution) and get it off the public balance sheet. Why not require green roofs rather than pay for the costs of treating (at a public wastewater faciity) the runoff that results from impermeable surfaces?

The greatest benefit of green roofs may have nothing to do with climate change. There impacts on water pollution and on local government efforts to cost-effectively comply with the Clean Water Act may be more important.

— Michael Wara, Stanford Law School

20. May 19, 2009
2:28 pm

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When it comes to environmentally conscious, conservation and efficiency America is approximately 10 to 15 years behind Europe. When it comes to sustainability there is a 15 to 20 years deficit.
One single “biggest project in the world” of something “good and green” in the US is nothing in a nation’s eco assessment. Going with LEED will slows things down because it is focused on profits – not on problems. Why is America afraid of looking beyond the plate, can’t America think out of their 2 x 4 and 4 x 8 box and why always reinventing the wheel?
I strongly recommend continue destroying nature and cover it up with a white, reflective plastic film since this is much cheaper. Or, raise first the energy costs to what people pay in the rest of the world – i.e. 1 gal. gasoline 7$ in Europe.

— Jorg Breuning

21. May 19, 2009
2:36 pm

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Researchers at the University of Michigan published a paper last year comparing the expected life-cycle costs and benefits of a 21,000 square foot green roof versus a conventional roof of the same size. While the green roof would cost more to install ($464K versus $335K),it would save $200K over its lifetime compared with the conventional roof. Nearly 2/3 of those savings would come from reduced energy use; the other savings come from improved stormwater management and public health benefits of absorbing nitrogen oxides (NOx).

Here’s the reference: Clark, C. P. et al. Green roof valuation: a probabilistic economic analysis of environmental benefits. Environmental Science and Technology 42 (6): 2155-2161.

Also, since some people have mentioned cool pavements and permeable pavements, note that it’s not just water pollution in the conventional sense that’s reduced by these technologies: hot surfaces cause storm water temperatures to increase, and when that heated water enters aquatic ecosystems downstream it can cause havoc.

— brad

22. May 19, 2009
4:54 pm

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The Mayor of Chicago has his position because he is looking over his plate, because he thinks out of the box and because he doesn’t see any necessity to reinvent the wheel. During his visit in Germany in 1998 he saw green roofs and understood the idea immediately. For him reason enough to act immediately and making decisions before “tunnel viewers” and “wheel reinventers” jump on it and even much longer before wired ideas popped-up like roof farming, conservation of native environments on roofs, converting roofs into power plants or using roofs to dump trash and selling it as recycling.
I am sure the Mayer made is decision on less information you find in these comments on this page. Having 1.000 more people like him we would probably see more than 600,000 green roofs, the costs would be much lower and the technology would be already common knowledge in most of the population.
Keep it simple and do it.

— Jorg Breuning

23. May 19, 2009
5:21 pm

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Thanks very much for this coverage. In the interest of factual accuracy, we feel it is important to alert readers that this green roofs panel was convened and organized by The Drum Major Institute for Public Policy (DMI) as part of its Marketplace of Ideas series. For more information, please visit http://www.drummajorinstitute.org and check out these highlights of the event on DMI’s You Tube Channel:

Richard Daley:
The Chicago Mayor explained that environmental programs funded by the federal stimulus must hire local workers who can create sustainable communities. http://www.youtube.com/watch?v=rEyPeyn8tlQ

Christine Quinn:
The New York City Council Speaker compared the rooftop garden at Chicago’s City Hall to the scaffolding currently holding up New York’s City Hall. http://www.youtube.com/watch?v=DwKZFINESoI

David Yassky:
The New York City Councilman said the role of government in environmentalism is to provide goals and incentives and allow the private sector to choose among options. http://www.youtube.com/watch?v=GJQ-RqrQAh4

Carter Strickland:
The Senior Policy Advisor in the New York City Office of Long-Term Planning expected costs for green roofs to come down as New York City expands its green economy. http://www.youtube.com/watch?v=ot2o2UG_EtQ

Miquela Craytor:
The Executive Director of Sustainable South Bronx pointed out that green roofs improve public health, increase job opportunities and enhance overall quality of life. http://www.youtube.com/watch?v=OIrvvcw-xGc

— The Drum Major Institute for Public Policy

24. May 19, 2009
10:49 pm

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”
carrots watermelons, pumpkins, and corn. In a couple of months, I will be able to just grab some food from my roof instead of pulling into a McDonald’s. I can actually seen the carrots growing as i look up through the panoramic roof. I consider my roof garden the equivalent of a carbon credit.
— Lyle Vos
”

If you hang the carrot over the radiator thus the engine will rev up in effort to reach the carrot.

In 1996 we had a Nebraska snow storm in Fairfax, VA. I built a laaaarge snowman atop my car. In those days a Cadillac was built to hold up lots more than green watermelons and snowmen. After we got on I66, pavement allowed legal speed and snowman’s head fell off and went rolling along the lane faster than you could say Nathanial Hawthorne.

— AMATI NONYMUS

25. May 19, 2009
11:17 pm

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It’s difficult to respond to such a broad question as to whether or not green roofs are worth it, but from my experience in Chicago, urban green roofs seem to have been very worth their salt for the following reasons:

1) Reduce Urban Heat Island: While this may be manageable in the shorter-term, continual climate change will make UHI mitigation vital to tempering potentially-fatal heat waves during the summer months. The indirect climate implications for this include lowering the ambient temperature that needs to be further cooled by the roof-top HVAC systems- which has been confirmed through A-B comparison’s to the non-green roof side (county) of Chicago’s city hall.

2) Reduce Combined Sewer Overflows: While extensive roofs are more affordable, intensive (deeper) growth mediums allow more water to temporarily be trapped and out of the sewer system. This has positive implications for urban health in preventing CSO’s. Additionally, there is an indirect climate effect of lowering the required water to be treated at the treatment plants.

3) Durability: Green roofs are expected to last more than twice as long as conventional roofing materials- so tend to pay themselves off to the developer/owner after approximately the 20 yr mark.

In the case of the city hall green roof, it’s value is extremely fruitful as an accessible teaching tool, early-adopter (2001), case study (comparison analysis), and improved urban aesthetic given it’s relative short height in relation to other downtown skyscrapers. For these reasons urban green roofs seem to proportionately carry their weight even when accounting for their higher albedo.

— Andy Forquer