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The Green Factor: A Landscaped Envelope for Urban Buildings
Sarah Rich, 6 May 07
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The city of Seattle recently approved a proposed modification in building codes which would set a new bar for U.S. standards in urban development. Based on similar models in Sweden and Germany, the Green Factor is part of Seattle's plan to bring more greenery to the streets of commercial districts, and to compensate for the limitations urban density imposes on green space. The plan encourages a site-appropriate package of greening possibilities, including green roofs, interior green walls, exterior vertical landscaping, and rain gardens, which can help with building insulation, shading, air filtration, and stormwater runoff management. The city will offer incentives which will grant developers credit against open-space requirements when they install more compact or innovative landscape features, either on their site or in nearby public spaces, which improve environmental health and urban livability.

An article in the Seattle Post-Intelligencer reports that the proposal has raised some skepticism among builders and building owners who worry about things like rat-infestation in the thick vegetation of green roofing or walls, as well as the potential that mitigating runoff in such a rain-soaked region can't be done with these solutions alone. But designers have come a long way in creating effective and beautiful systems for architectural greenery. By looking at models in varying climates, these systems can be intelligently adapted to suit their local weather conditions.

To understand the thinking behind the new rules, consider the forests that occupied this land before they were cleared to make room for city development, suggested Steve Moddemeyer, a senior adviser with the city's Department of Planning and Development.
In such a forest, rainfall first hits the tallest trees, sticking to needles and bark. Then it might trickle down onto vine maples, still 15 feet or more above the ground. Next, it drips down onto salal, a leathery native shrub. From there, it drops onto ground-covering plants such as moss and kinnikinnick. Then, it drains its way through organic debris before reaching the soil. In a thick, old forest, the whole process can take 30 days.
In the city, it takes only a few minutes for rainfall hitting sidewalks, streets, parking lots and other impervious surfaces to pour into storm and sewer drains -- often bringing street pollutants in its wake.

A reduction in runoff reduces the associated costs of managing drainage systems, cleaning polluted groundwater and creeks, and dealing with street flooding. The savings permit the city to incentivize and facilitate more surface greening, and of course, the more developers choose to follow these new rules, the more beautiful Seattle will become, likely leading other cities to encourage similar practices.

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Add edibles to the formula and we're getting close to the prize. In SF there's a movement to plant more edibles around the city -- fruits in Golden Gate Park, neighborhood vegetable gardens, etc... Now, if we're going to start making investments into Green Roofing, let's make them productive in addition to less harmful.

Posted by: Ross on 7 May 07

i myself believe we must move beyond being friends of the urban forest, to being companions of the arboreal conurbation.

Posted by: hibiscus on 7 May 07

There is an interesting article in this week's Portland Business Journal about the battle of the greens...A rival to the popular LEED program emerges
Portland Business Journal - May 4, 2007 by Wendy CulverwellBusiness Journal staff writer

check it out at

Posted by: Seth on 7 May 07

My brother just got accepting into the school for landscape architecture; I'll have to pass this on.

Posted by: Dan on 8 May 07

In response to Seth, while LEED may not be perfect, it works precisely because it is not funded by any particular industry (whereas Green Globes is a product of the timber industry.)

See accompanying link to SCI vs FSC wood. LEED only accepts FSC, Green Globes accepts both.

Posted by: Dan on 8 May 07

The green factor has been operating in select cities in europe since the 70's. It is a blanket solution for a problem that should really be dealt with on a more specific case by case basis. It can cause major problems for buildings(imagine a drought that kills off planted surfaces citywide...first urban dust bowl anyone?) There are currently no metrics that validate the effectiveness of this solution in reducing runoff and heat island effect. I am disappointed to see Seattle fall prey to green-wash idealism over more subtle, measurable, and effective measures.

Posted by: chris on 13 May 07



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