Vancouver started green roofs in the 90s. Developers and landscape architects figured out how to do heavily-planted decks and roofs until it became standard practice, and then compulsory: the expression of sustainability.
It takes a decade at least for this landscape to emerge, and it’s happening now on the foliating cliffs and ledges of Yaletown and Downtown South.
Like this, as seen from the new roof garden of the public library:
Tsawassen Mills didn’t – Amazon warehouse probably won’t. Very disappointing…
One aspect to consider is that any condo at-grade landscaping downtown is likely over an underground garage – so technically, those are green roofs too – they just aren’t high up.
.. and like their high up counterparts, aren’t hard surface materials (whether pavement or roofing materials)
I love the idea, looks great etc… I just wonder how much it’s going to encourage bird strikes into nearby windows. Maybe the extra habitat will offset extra deaths? Guess time will tell.
I think major credit has to go to Arthur Erickson VB for both the BC Law Courts (Nelson/Smythe & Hornby/Howe) and the Evergreeen Building (Hastings & Jarvis). Both these edifices opened in 1980.
To me, these were what Vancouver’s downtown inspiration could have and should have been; the definition of Vancouverism before that became a thing.
This analysis seems a bit form over function to me. A green roof is as good as its design and engineering in a high rainfall environment. Several have failed in the Metro with a lot of damage to retail and residential units below. Failures over parking garages do not get as much attention. I lived in a building where several units were uninhabitable for years due to a roof garden terrace membrane failure (mould deeply embedded into the structural framework was a huge problem). The planters at Robson Square were not just replaced a few years ago, but completely rebuilt with a better membrane and drainage system and no filter cloth (which plugs up). I believe the rooftop ponds have been drained for the same leakage issues.
It has taken 30 years of trial and notoriously expensive error to realize that the most successful green roofs utilize a removable suspended deck separated from the membrane with palletized or otherwise removable planting containers.
The green roofs of Germany were quickly adopted here decades ago merely because they were green and cool looking without fully realizing that, unlike Germany, we live with more a metre of rain falling from the sky in winter. That was a shamefully amateurish oversight by designers that took rainscreen experts, structural engineers and insurance companies to fix by demanding better standards.
The claim to sustainability is more symbolic than real when you take a hard look at green roofs. You will achieve as much or more alleviation of the urban heat island effect with a healthy urban tree canopy and light coloured roofs. That is best performed with underground tree root vaults and automated irrigation. Even today I see new developments where street trees are planted directly into the compacted road base material with a dusting of growing medium, therein ensuring the sidewalks will lift as the trees grow, and that the trees will remain stunted and susceptible to disease and drought. That is not best practices.
Green roofs planted with a monoculture of plants that require intensive maintenance (continuous irrigation and fertilizing) is also not part of the definition of sustainability.
The claim that green space absorbs runoff is also shot to hell after each storm. There simply isn’t the volume of soil to take the vast — and increasing — amount of rainfall we receive on rooftops, and the entire Burrard Peninsula is underlain with a deep impenetrable layer of hard glacial till just below the surface. To require tiny slivers of open ditches otherwise known as “bioswales” in an urban environment is merely a planner’s feel good sop to green. They do not pass the simplest infiltration and drainage test. The best solution in urban areas is to install very large underground cisterns below the parking garages in towers, or in parks, and to build detention ponds in suburban areas (can also double as tennis courts and so forth) and recycle a portion of the water into planting beds and parks. The best solution of all is to design huge regional-scale wetlands at the base of urban storm drainage sheds, thus providing a very effective biofiltration function for all runoff.
Would I live under a green roof? Absolutely not.