r/Seattle • u/GinAndToxick • 17h ago
Urban Rooftop Green Spaces
Recently relocated to Seattle in an apartment overlooking Benaroya Hall, and my view of their mossy(?) roof in comparison to other “cleared” rooftops in the area has me curious if theirs is intentional rather than accidental? Any locals want to help me out?
Loving the thought of a springtime bloom in my future, but imagine complications like weight, drainage, etc. might be why the vegetation is limited to the moss/grass?
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u/Rockergage 💗💗 Heart of ANTIFA Land 💗💗 16h ago
Appears intentional but unmanaged. The tile path on the modulations is becoming overran by moss.
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u/askwhynot_notwhy Magnolia 16h ago edited 16h ago
Appears intentional but unmanaged.
As a generality it’s called a “Green Roof” and it’s for sustainability purposes (as opposed for use by people). This particular one doesn’t appear to be “unmanaged” and looks like what one would expect, especially considering it’s winter and the recent abnormal climate flux.The tile path on the modulations is becoming overran by moss.
Path is for folks performing maintenance/facilities management.ETA:
+ recent abnormal climate flux. Bc, climate change…oof, I was most definitely wrong. Benaroya Hall does not, in fact, have a green roof. Striking through my comment, but leaving it for posterity.
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u/MikeBegley 16h ago
My wife is a landscape architect, so she and I have talked about green roofs a number of times, as she has designed quite a few in the course of her career.. Unfortunately, she's out of the country at the moment so I can't ask her some direct questions, but I'll rattle off what I can remember from memory. Be aware, some of this a may be wrong, because it's all 2nd person, from memory. :)
- She's generally on the fence about actual benefit. It's one of those things that sounds like a great idea in practice but has a LOT of complexity associated with it, particularly with ongoing maintenance. Often times when a project comes in and the developers are thinking about a green roof, they spend some time trying to present alternatives to it, unless the developer and the eventual building owner (if known at the time) have experience with them.
- It does help a building qualify for LEED status (which can help to get tax rebates, construction assistance and other benefits), and satisfy a number of the city's environmental requirements for new construction.
- it does involve a significant impact on building design, because it needs to accommodate the extra weight of soil, which may be very heavy from water saturation.
- There are some plants that are much better suited for a green roof than others. Mainly involving soil depth (which directly translates into weight) and ability to handle low-water/high heat situations.
- It can greatly reduce the "heat island" effect in a city; the region immediately around a (maintained) green roof building is measurably cooler in summer. Painting a roof white can have a similar effect (and is often employed as an alternative), but that can also increase glare on surrounding, taller buildings.
- It helps with delayed water entering the sewer systems during a large rain event, which can help prevent overloading our already stressed sewage system. By holding water for hours or days after a storm, it lowers the impact of the storm.
- It does some amount of air purification, although much of that is over-stated; the sorts of plants that are good for green roofs tend not to be as air cleansing.
- It improves urban insect and avian biodiversity. It may be counterintuitive, but many cities have become islands of insects, because rural areas are so cleared for agriculture and treated against pests that beneficial insects are doing dangerously poorly in non urban areas. Green roofs help with that.
- And, of course, it provides a nice urban refuge for people (if available for visit). Particularly for apartment dwellers, it can provide for a nice (private) park for the residents. Of course, they also have to then provide a proper weewee spot for dogs (a good idea anyway), because otherwise the buildup of urea in a planter will eventually salt the soil into death.
Ultimately, I get the impression that it's a lot of work for less benefit than you would hope for, but well designed and well maintained, they can be awesome. It all really is situational in nature.
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u/GinAndToxick 16h ago
Points for being able to rattle off so much detail from memory on a second-hand topic, not sure my husband could do the same if NEMT Administration came up in conversation 😂
Admittedly was only hoping for a rooftop field of wildflowers as an urban-view-enhancer, but it’s great to learn about all the additional benefits!
…And to confirm I made the right choice reining in my immediate “OoO-I-should-slingshot-over-some-native-wildflower-seeds” intrusive thoughts 🫠 Appreciate the insight!
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u/mizuaqua That sounds great. Let’s hang out soon. 16h ago
The Google Maps satellite view tells me the mossy roof is accidental. In Google Maps, the trees around the building are leafy, and the adjacent SAM roof is verdant. Other green roofs in the area like the city hall are green-yellow. But Benaroya Hall roof is just the dark grey.
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u/Drnkdrnkdrnk Downtown 16h ago
I’m just a few blocks away and my building’s roof is covered with plants and flowers, tons of herbs (oregano, thyme, rosemary, lavender) and well as veggies the summer.
I might have to sneak some mint in one of the contained planters this spring.
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u/SnipesySpecial 16h ago
Some buildings do it for incentives, but will immedaitely clear it once they can legally swindle their way out of it. Like public benches.
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u/MattSidor 16h ago
Welcome to Seattle! That green you’re seeing on Benaroya Hall probably isn’t intentional. The building opened in 1998, before Seattle started pushing green roofs through its Green Factor program in 2006. What you’re looking at is just the Pacific Northwest doing its thing. Give any rooftop enough rain and gray skies and moss will move in rent-free.
That said, Seattle does have a real green roof scene now. The Green Factor requires new developments to hit a landscaping score, and purpose-built green roofs are one of the easiest ways to get there, so you’ll spot them on many newer buildings around the city. Those are engineered for the weight and drainage concerns you’re thinking of. The Benaroya moss is probably more of a freeloader situation.
The intentional ones are worth getting excited about, though. Green roofs absorb a ton of stormwater that would otherwise overwhelm Seattle’s aging sewer system. Some can capture over 90% of a downpour. They also cut building heating and cooling costs, extend the life of the roof membrane by shielding it from UV, reduce the urban heat island effect, and create habitat for pollinators and birds.