If you’re a fan of green roofs no doubt you read the Scientific American article a couple of weeks ago which set off a mini-firestorm in the green roof and broader green infrastructure world. I won’t direct you to all of the sites which reprinted and summarized the article, but they appeared on websites with large followings and active communities (check the comments section of some of those sites!)
Before diving into the comments, let’s take a look at the actual article. As we all know headlines are meant to capture readers and this one certainly did that. The problem seems to be green roofs in America’s biggest, most iconic city are essentially broken, but fixable. In particular the author asserts that they have not fared well in reducing urban heat island and energy usage. That is definitely debatable, as there are several studies which show green roofs can help with both. However, the article offers no evidence for this assertion and actually spends most of its space concerned with another issue, how green roofs planted with primarily sedum species plants do not perform well in regards to stormwater management.
We should take a step back even further and look at the original statement that green roofs are not working because not everyone gets a green roof for the same reason. With over twelve different green roof benefits there are a lots of reasons to get one and yours may be performing exactly as you expected it to. Especially if you bought one to reduce your long term roof replacement costs. Or if you bought one for aesthetics..and year after year it looks amazing!
But one to the stormwater management assertion...
Before reading Scott MacIvor’s work it has been verticiel’s aim to install a range of plants, not solely sedum species, on it's projects. Several grasses can work in 4-6 inches of medium and not a green roof is designed these days without our green roof champs chives and oregano. If you can have a rooftop you can eat from, why not? That's our philosophy, design a roof which provides as many benefits as possible. However we should all be thankful that he is pushing the industry forward and finding out what is best for the environment, even if your practice was to simply install or recommend sedum species plants.
Reading the comments sections I think some people took offense to how he described sedum species plants as “Just being there.” Years ago when I first started in the industry I was surprised at how passionately people felt about certain kinds of plants. Most feel indifferent about plants. Some people LOVE sedum species plants and I have met some who absolutely despise them! To those who abhor sedum species plants, this article means less of them around. And they couldn't be happier.
And to those who love native plants, having someone speak out against plants commonly found in Asia and Europe on North American rooftops, is a cause for a party and gives ammunition to their passionate argument.
Parsing the comment sections further one can plainly see other underlying sentiments. There are those (green roof designers, installers, growers) who have staked their whole business on sedum species plants, Amy Kraft’s article could be one which easily causes their businesses to tailspin...and quickly. And so they react passionately.
I imagine there are other green roof supporters who fear green roofs have plenty of detractors already and now those opponents have even more ammunition against a truly wonderful technology.
But I fear not and neither should you. This article gives us more to discuss. And finding ways to make green roofs better benefits us all, and for that we should be very appreciative!
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