Green Roofs and Puget Sound

[ Garage green roof in Mount Baker designed by Harrison Architects. ]

Earlier this month the Puget Sound Partnership released a draft Action Agenda, “a roadmap for protecting, restoring and cleaning up Puget Sound.” In this astute PI opinion piece, Roger Valdez connects the dots to compact development, and calls for policy changes that would allow for increased density in Seattle’s extensive single-family zones.

A far less controversial strategy for reducing polluted stormwater runoff — identified as the biggest threat to Puget Sound — is the implementation of green roofs. The retention of rainwater on green roofs can reduce their runoff by up to 75 percent. And while rooftops are not nearly as big a source of pollutants as are roadways, reducing runoff from roofs matters because all the stormwater ends up in the same pipe. Less runoff means less load on costly detention and treatment systems, and decreased likelihood that heavy rains will cause overflow events, during which untreated sewerage pours directly into the Sound.

In addition to abating runoff, green roofs help mitigate the urban heat island effect, and provide roof insulation, both of which reduce energy use and associated greenhouse gas emissions. They can also provide wildlife habitat. And they sure do look a heckuva lot nicer than a blank roof.

The only remaining question is: why are they still so uncommon in the Puget Sound region? Sure, we’ve got a handful or two, mostly on municipal buildings, but nothing compared to what’s being done in Europe. And of course the reason for this disparity comes down to ideology: European societies are much more inclined to wield government power in the cause of the common good. In other words, they regulate and significantly subsidize green roofs. (This is also why Germany is the world’s biggest consumer of photovoltaics.)

Green building rating systems such as LEED, and the City of Seattle’s new Green Factor code were crafted to encourage green roofs. But since the upfront costs are so significant — roughly two times a conventional roof — most private developers have remained unenthusiastic. The problem is simple: the free market gets a bit wobbly when it comes to both the future and the common good. The solution is also simple: government incentives.

While the ubiquitous flat roofs of highly urbanized areas are the most facile targets for green roofs, there is also great potential in the vast square footage of impervious rooftop in Seattle’s single-family zones, as in the two accompanying photos. But so far, such projects are extremely rare. If any readers know of other small-scale green roof projects, consider it a good excuse to leave a comment.

[ Single-family green roof in South Park designed by Silo Architecture. ]

11 Responses to “Green Roofs and Puget Sound”

  1. Brice

    Haha! Meredith’s house!

    Dan, check out Wilma Stor*’s house too. she’s got a green roof, if i remember correctly.

    Have you checked out the Green Factor audit that Dave LeClerque has presented at a few public meetings? It seems like the Green Factor is certainly having an impact in affecting the right changes re: more green roofs, but the difficult thing is that those zoning revisions take so awfully long to resolve themselves…Dravus anyone?

  2. rouch

  3. Matt the Engineer

    I had a sloped yard and a flat parking space, and am currently turning it into a flat yard with a retaining wall and garage with a green roof. Because of the elevation difference, I’ll be able to use the roof of the garage to add a lot of green area to our small yard.

  4. michael

    the office building I call home for 8+ hours a day – Park Place – is installing a green roof-the first commercial retrofit project I have heard of in Seattle. The owner – Wright Runstad – is going for LEED-EB. no public access though :(

  5. Troy

    The Seattle Streetcar garage has a green roof.

  6. meg

    there is a house with a (sloped) grass roof in tacoma, a few blocks south of 6th & alder (on 6th)

  7. gregw

    I’m helping a neighbor build a carport/workshop with an extensive green roof- 560 sqft in the Highland Park neighborhood. Way to go Matt, I wish I had some elevation to hide my shop and access a green roof on top of it.

  8. Carports

    Fascinating! That is such an interesting topic, green roofs! Thanks for sharing.

  9. San Diego Roofers

    European societies are much more inclined to wield government power in the cause of the common good.

  10. Eddie Marchal

    Eddie Marchal…

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