Green roofs

[Mike K.]

As this article illustrates, neither builders, policy makers or scientists are sure what the benefits or dis-benefits green roofs may present.

Green roofs strike a chord with designers, builders
Garden-topped buildings are suddenly in vogue, but experts disagree as to whether they are worth the expense

DEBORAH JONES
Special to The Globe and Mail

VANCOUVER -- As fear of climate change turns most public policy decisions shades of green, the roof colour of buildings is taking on a murky hue.

Green roofs have existed since the Hanging Gardens of Babylon were built around 600 BC, and have long been common in Europe.

There are a couple in British Columbia, including at the country market in Coombs on Vancouver Island, where goats munch grass on the rooftop, and the ambrosial park atop the Law Courts in Vancouver, a perennial favourite with the downtown lunch crowd. But they haven't really caught on in the province - until now.

"Green roofs," seen as one solution to climate change, are now sprouting everywhere, despite concerns ranging from the costs and benefits to fear of more leaky condos.

There are two kinds of green roofs: membranes covered with a few inches of soil and vegetation that cannot be walked on, for example, the roof on the downtown Vancouver Public Library, and extensions of indoor living space to outside, for example the terrace on the Coast Hotel on Denman Street in Vancouver.

Fewer than 1 per cent of roofs in B.C. are "green roofs," estimates Jim Watson, technical manager of the Roofing Contractors Association of B.C. Most, he said, are on large buildings, and are designed and maintained by professionals.

"What's different now is there's a movement to put rooftop gardens on wood-frame condos," Mr. Watson said. "They're moving into the mainstream, and unfortunately, the people building them value the [professional engineers and architects] out of it. They're going to build as least expensively as they can, and the oversight is a question mark."

Everyone agrees that green roofs are lovely additions to dense urban areas. It's the environmental benefits - and cost - that designers and builders dispute.

Covering buildings with soil and vegetation can help reduce rainwater runoff into sewers, insulate buildings from heat and cold, protect the waterproof covering from degradation caused by the sun, reduce air pollution and cool city temperatures, advocates say.

Critics counter that green roofs are for the birds, arguing that the only beneficiaries are the warblers that alight on them to rest.

Seeds of public controversy were sown after several B.C. municipalities encouraged or required green roofs on certain new buildings. The bloom came off that idea early this year when three insurance companies refused to insure green roofs in the province.

"We're nearing a collision point," said Jan Calkins, spokesperson for the provincial Homeowner Protection Office. To get building permits, she said, developers are required under the Homeowner Protection Act to have warranty insurance, which insurers are refusing to provide. The agency has called a conference on May 29 for insurers, builders, designers and scientists to hash out the problems.

While green roofs are common in Europe, "in a climate similar to our own, there's not a huge track record," said Karen Liu, an engineer and research scientist with the Centre for the Advancement of Green Roof Technology at the B.C. Institute of Technology, which is testing three types of roof structures.

Architect Freda Pagani, the recently retired head of the sustainability office at the University of British Columbia, is a green-roof skeptic.

"People concerned about the environment have taken up green roofs as a cause célèbre. But I don't think they automatically make sense," Ms. Pagani said. "I am concerned that the touted benefits are not that compelling."

In very hot cities such as Houston, Tex., all agree that green roofs would be helpful. The research at BCIT has shown that summer temperatures on traditional roofs can reach more than 65 C, while the same roof with a layer of vegetation reaches just 30.

But in Vancouver's temperate zone, Ms. Pagani said, "you'd be much better, from a cost point of view, to add regular insulation to the roof. To put a green roof on, you have to beef up the structure, and it's much more expensive."

Soil on roofs can help retain water during heavy rainfalls, she acknowledged, but only until it is saturated. In B.C., which has lately endured deluges lasting weeks, cities "might be better to put in a separate storm system compared to the cost of all the additional green roofs."

More cost-efficient ways of tackling climate change, she suggested, might be investment in renewable energy, including microhydro projects, and designing buildings to use passive solar energy.

Green roofs are "two to three times the costs of conventional roofs," Mr. Watson said. "The additional upfront cost factor would take the lifetime of the roof to get close to being any kind of a payback."

But Mr. Watson believes green roofs have their place. "The real benefit to humanity is just providing more green space for people in big centres. ... As we move toward a denser population, why not create some green spaces?"

Ms. Pagani agreed that livability is the best reason to install green roofs, but said the cost-effectiveness has not been proved.

"We have to get a lot more thoughtful and smart," Ms. Pagani said. "People think there are easy answers to a set of complex problems that require much more profound responses than just adding green roofs."

[DanJ]

I definitely agree that the benefits of Green Roofs are somewhat shaky. I have recently been working on a proposal to add a Green Roof to the Philadelphia Free Library, and in doing so I did a good amount of research on the “benefits” of such an addition. Speaking as an engineer studying sustainable design, I certainly don’t see any serious benefit to the environment that would warrant the cost of a Green Roof addition, however, there is a great benefit to the community in general.

The addition of green space in the urban environment is something that I think is very important. Having recently moved from Austin, TX to center city Philadelphia I definitely miss the green that was so prevalent in Austin. Not only that, every tiny green space in Philadelphia is always packed full of people when the weather permits it.

While people should not consider Green Roofs to be something that is going to combat climate change, or win great strides for environmentalism, I think that as the world shifts so seriously towards urbanism, it is a wise decision to plan for as much green space inclusion as possible.

[Mike K.]

Interesting insight, Dan.

Public spaces atop public buildings is a great concept.

[Coyett]

Solar Stadium For 2009 World Games



The main stadium of The World Games 2009 Kaohsiung will be the first in the world to use solar energy in conformity with a "green building code" a Kaohsiung city government official said last week. Lin Chin-jung, director of the Bureau of Public Works, said the stadium's spiral-shaped ceiling will have solar energy plates installed. Lin said the multi-functional stadium will be self-sufficient in electricity needs.

He pointed out that Kaohsiung City has an average of 2,282 hours of sun per year, averaging 5.6 hours daily. If the solar energy plates receive enough sunlight, they will be able to provide 80% of the electricity needs during the operation of the stadium and 100% during the remaining time. Any surplus electricity generated could be sold. Construction of the stadium began on Thursday, July 6, and is expected to be completed in January 2009, six months ahead of the opening of The World Games.

--------------------------------------------------------------------------
A building that generates it's own electricity strikes me as much more beneficial to the environment than simply constructing a roof-top garden. Though, I suppose a garden would help absorb pollutants and decrease energy consumption.

[pseudolus]

California Academy of Science, San Francisco, Renzo Piano architect
under construction

"Sustainable features include the living roof, water reclamation, use of renewable energy, and integration into the park and community."

http://www.calacademy.org/newacademy...abledesign.php

[Evergrey]

The supermarket I shop at here in Pittsburgh has a green roof. It was just awarded LEED certification. It's called Giant Eagle Market District.

http://www.bizjournals.com/pittsburg...l?from_msnbc=1

[Master Plan Dan]

The Public Space that is added is great. I mean provided that the building owners actually let the public up there.

And for a purely cosmetic point of view, they look great. The Woodward's Building that is the "Keystone" to the revitialized East end of Vancouver (have yet to see if it will materialize) has Green Walls as well.

I think the idea of having vertical gardens and large expanses of green space in the urban core is a great idea, regardless of price.

I know that sometimes having the birds chirping outside my window in the morning is annoying... but it sure sounds better than city noise!

It could also help with migratory birds... giving them a place to land.

I say the social benefits out weigh the cost issue.

[MonctonGoldenFlames]

Originally Posted by DanJ

I definitely agree that the benefits of Green Roofs are somewhat shaky. I have recently been working on a proposal to add a Green Roof to the Philadelphia Free Library, and in doing so I did a good amount of research on the “benefits” of such an addition. Speaking as an engineer studying sustainable design, I certainly don’t see any serious benefit to the environment that would warrant the cost of a Green Roof addition, however, there is a great benefit to the community in general.

The addition of green space in the urban environment is something that I think is very important. Having recently moved from Austin, TX to center city Philadelphia I definitely miss the green that was so prevalent in Austin. Not only that, every tiny green space in Philadelphia is always packed full of people when the weather permits it.

While people should not consider Green Roofs to be something that is going to combat climate change, or win great strides for environmentalism, I think that as the world shifts so seriously towards urbanism, it is a wise decision to plan for as much green space inclusion as possible.

Being a 'Sustainable Designer', I would think that you would see the environmental benefits to a Green Roof, in a residential setting especially. Every home that gets built typically removes 'green space' equivalent to the building footprint, and replaces it with asphalt roofing. Typical asphalt roofing is dark in color and thus absorbs and retains heat. Another pro to a Green Roof from a City services standpoint, in a rain storm, a Green Roof retains water longer and thus eases the storm water runoff pressures on City drainage. A Green Roof is also a good method to use a 'Rain Capture' system to recycle and reduce water usage, mainly thru a 'grey water' system. These small effects of a Green Roof, really add up when its done in quantity. On top of all that, it's high R-Value (for northern climates) and its STC rating, can really make a difference to many aspects of sustainable design.

[Chef]

Apparently Minneapolis is considering a green roof for the Target Center. There was an article about it in the Star Tribune yesterday.

www.startribune.com/503/story/1152461.html

Green-roof advocates see a big target in Minneapolis
As city officials get ready to plan for a new roof on Target Center, talk has turned to whether it's feasible to use sustainable design.

By Jay Weiner, Star Tribune

These days, replacing a roof on a public building is more than a surface thing. It's a sustainability thing. It could become a symbolic, even money-making thing.

That's what Minneapolis city officials think as they approach a seemingly ho-hum endeavor that carries implications for the planet.

The task? Redoing one of the largest roofs in Minnesota -- 3.3 acres worth -- atop the 17-year-old Target Center. Local architects and sustainable-design advocates say if the city wants to make a bold statement while, over time, saving energy and money, the arena's 144,000-square-foot roof should go green.

"It seems to me we need to lead by example with our own buildings," said City Council Member Lisa Goodman about the prospect of a $2.2 million "green roof" on the city-owned arena. "It would send a huge signal from a public-policy perspective."

No one knows yet whether it's possible. Tom Daniel, business development manager for the city's Community, Planning and Economic Development Department, said an assessment of the effects of the weight of a green roof on the arena's structure hasn't been completed. Target Center's roof is tested often with the tons of speakers that some touring bands hang from the ceiling.

A city-funded study estimated that a green roof would cost $400,000 more than a traditional roof. But the green-roof technology would pay for itself in energy savings in about five years. Electric bills at Target Center are typically $60,000 per month.

If installed, Target Center would become the largest building in Minnesota with a green roof surface. What's more, it could be among the 10 largest green projects in the world.

"Bragging rights," said Minneapolis Finance Officer Patrick Born.

"A priceless branding tool for a city," said Mark Andrew, an environmental consultant to sports teams and facilities.

This discussion among the Timberwolves, the prime tenants of the arena, city officials and environmental and design experts comes at a coincidental time: The Fifth Annual International Greening Rooftops for Sustainable Communities Conference started Sunday and runs through Tuesday at the Hyatt Regency in Minneapolis.

Simply put, a green roof uses grass and vegetation on top of a waterproof membrane. Its benefits include keeping buildings cooler in the summer and somewhat warmer in the winter. In dense urban centers, green roofs tend to cool so-called "heat islands," which are created by lots of cars and the sun beating down on more traditional tar or rock roofs. A green roof retains rainfall, thereby reducing dirty runoff that ends up in the nearby Mississippi River.

A monetary bonus

There's something else green buildings, especially green sports arenas, might be able to do: generate sponsorship and advertising revenues.

The city, which pays $6 million a year on Target Center's mortgage and $1.75 million annually to subsidize building operations, would love to "monetize" the green roof by finding a sponsor for it.

Andrew, a former Hennepin County commissioner, owns GreenMark Sports and advises teams and facilities on how to go -- and make -- green. "Sports buildings become huge billboards for environmental sustainability," Andrew said.

The concept is this: A contractor seeking such a high-profile job may trade a signage deal with the Wolves for a reduction on the cost of installation. Or a corporation will want to be linked to the trendy green vibes and seek naming rights for the roof.

But a final decision on whether to go green isn't expected until fall. A new roof, green or not, is expected to be installed in the summer of 2008.

[sentinel]

Green roofs are a HUGE business in Chicago, which currently has about 2.5 million sq. ft. of Green Roofs in existence (and growing exponentially), the largest in the Nation; it's becoming more and more common because as the number of projects incorporating green roofs increases, the cost is going down considerably, and I think it will continue to do so as time goes on.

[mhays]

An ENR story last week discussed several test green roof plots in Seattle. Apparently they're much more effective than the designers predicted in reducing rainwater runoff. Long term, this will be a reason for a lot more green roofs in Seattle. Along with new encouragement from the City.

[Mike K.]

What about saturated green roofs? The PacNW receives a lot of rain and this past winter was exceptionally wet. How do these things hold up under abnormal weather conditions? Or rather, what is in place to protect green roofs and their structures when the weather doesn't cooperate?

[zilfondel]

How about these benefits:

• reduced heat-island effect in cities
• during on/off rainfall patterns, reduced demand on storm sewage system

[DanJ]

Originally Posted by MonctonGoldenFlames

Being a 'Sustainable Designer', I would think that you would see the environmental benefits to a Green Roof, in a residential setting especially.

I certainly agree with all the points you make, and mentioned most of them in my first post. Especially that both residential and new developments get the greatest benefit from Green Roofs, while I was talking more about retrofitting existing commercial buildings with Green Roofs. The point I was trying to make was that while Green Roofs are beneficial from a sustainable point of view, and I would certainly advocate their use when possible, I feel as if because of their very visual and obvious presence, they get a lot more attention than other sustainable practices that really pose a greater benefit to sustainability.

Originally Posted by Mike K.

What about saturated green roofs?

This is something I’ve wondered about as well. I know there are certain part of Washington State that get so much rainfall that there are laws about how much or your planed you are allowed to develop on. The concern being that any serious development would contribute to large things like flooding, as well as things like devaluing neighboring properties by making them absorb the extra runoff. My initial thought was that Green Roofs would be a huge benefit to such places, since you would be able to develop on the land you own without cause such side effect. However, I am unsure about what the difference in absorption would be. Would a Green Roof be a comparable absorber to of rainwater in places that get so much of it?

[Mike K.]

I don't think it would absorb as much water as the land it sits on. And that's perhaps the biggest challenge. Dealing with run-off is one thing, but protecting the plants on the green roof from too much water in their soil is another. At least on the ground excess water has much more volume to flow through whereas on the limited space and depth of a roof it will reach capacity much quicker.

Please don't tell me we're introducing universal building features that work in one part of the continent and may spell disaster in another (i.e. leaky condo crisis, thanks to adapting California's condo construction techniques and materials up in the PacNW and southwest BC).

[F-Misthebest]

The Hotel Donalson in downtown Fargo-which was voted best hotel between Chicago and Seattle-has an upscale green roof. Plus three more buildings downtown are going to go green.

[mhays]

The runoff issue was a core part of the question ENR discussed. I don't have the article since I'm at home. Apparently it works well in our soggy winters. But I'd guess that in a rainier area, like our own coast or nearby rainforests, it might not. (Seattle's 37 inches compare to 100+ in some parts of the Northwest.)

Green roofs aren't about reducing runoff. They're about spreading runoff over a longer period of time. If your soil can collect rain while it falls and then release it over a period of several more hours or days, you're effectively reducing the runoff during peak times.

[Chitabaca]

Now in mexico city, exist new ecological legislation, and buildings with solar cells, have a financial discount and benefits , at the time to pay local taxes.

and also for residencial exist a Greenroof program.

[Coldrsx]

an example of a simple greened roof with a 10,000sqft rooftop green patio on top of 2 level of office space and an urban grocery in Downtown Edmonton

[skyscraper_1]

^ Such a beautiful Sobeys! I wish they had some like that in Halifax.