Yesterday, I hustled around downtown looking at green roofs with my advisor. There are three being included in my study. I considered some others, but it seemed like it would potentially be prohibitively difficult to access roofs on residential buildings, and I found one on a courthouse but couldn’t seem to figure out how to contact anyone about it.
The three roofs are all unique! I wouldn’t have guessed that from the google earth views I used to locate them. They’re all fairly established (have been installed for several years), but the approach is different for each one. This dramatically alters the questions I want to (or even can) ask. Actually, I think this makes the project even more exciting.
The first one we saw was essentially an extensive arrangement of shallow plastic bins with soil and sedums in them. I guess that would make it modular and easily replaceable if something goes wrong. It’s clever, but probably not as visually appealing, even during the growing season, as something more continuous. The picture I’m sharing here is of the lower roof level. It has some solar panels a couple of decks with chairs. There are floating concrete tiles all around the outside (where I am standing in the picture) and it sounds like employees in the building are allowed to walk around the perimeter on breaks. They also appear to be populated with all one type of sedum, though it’s hard to say since they’re partially covered in snow. They have installed an irrigation system to keep the plants watered. I wonder if they expected to have to water them, though, since it seems that most people expect green roofs to be relatively maintenance-free.
The second roof was directly planted, in a pattern, with various grasses. It’s beautiful, even in the winter, but I don’t imagine it’s very practical. I don’t know much about the physical structure of this roof, but ornamental clump grasses can have roots that grow to more than a foot deep. The maintenance person who showed us around said that they’ve had some trouble with leaking, so I wouldn’t be surprised if the substrate isn’t deep enough to allow that. Additionally, as you can see from the picture, only some portions of the roof are planted. I think the other parts are just gravel. It seems like this patchwork method, while pretty and fun, would diminish the insulating effects that green roofs are supposed to have.
The third roof is my home roof: the one I studied for years during my undergrad. This a roof I feel like I know more about than probably any single other person. But I don’t know everything about it.
It, like the second roof, has a patchwork design with some areas lacking plants and being covered only in gravel. In this case, I know that building management has complained that it has not lived up to their expectations for insulating the room below it. This roof also has a watering system, like the first roof. I also know that building management has expressed concern about the increased amount of watering and maintenance beyond what they expected when the green roof was installed.
This roof is also populated with sedums, like the first roof. In fact, I think the variety the first roof uses is one of the varieties found here. This roof has around 10 different types of sedums, which makes for varied texture and color during the growing season.
All three green roofs have attractive patios with furniture, which suggests that they were intended, at least in part, to be enjoyed by visitors. But with all the hype going around about insulative properties of soil and plants, reduced rainwater run-off, reduced heat island effect, and improved urban air quality, I don’t imagine providing green space to employees was the only motivation for their installation. I look forward to finding out what the goals were, what the outcomes have been, and how the thing have changed in between. My goal with this project is actually to learn how soil respiration on green roofs is affected by temperature, but I also love talking about practicality and experiences with people who manage these spaces.
I guess you could say that the larger goal of all of my research thus far, and maybe into the future, has been and will be to provide a better understanding of how green roofs really work and whether they are a practical addition to the urban ecosystem.
As a side note: the weather was not on my side. Wearing a mask meant that my glasses fogged up. Then, the air was cold enough to turn the fog to frost which had to be scraped off of my lenses. Thankfully, my advisor doesn’t wear glasses and took pictures so I could see things better later.
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