Despite the huge variety in green roof systems as far as vegetation, types of components, and reasons for the install, all green roofs share the benefit of managing significant amounts of the precipitation that falls on the building. Depending on how they are designed, green roof systems can indefinitely hold water in cisterns, in deep trays under the plants, or funnel it toward the drains for use in grey water systems. Most green roofs do not retain all of the precipitation that falls, but slowly release it into the drains after it has percolated through the vegetation, growing media, drainage layer and other water storing components. In many jurisdictions, excess rainwater can be captured at the drain pipe and overflow scuppers for other uses such as in fountains, to flush toilets, for rain gardens or irrigation.
One of the most inspiring residential projects I have been involved with recently is a new home in Hood River, Oregon. The house can only be described as stunning, with clean lines and massive windows framing enchanting views of Mount Hood. The house was designed by Hood River architects Liz Olberding in collaboration with Miloš Jovanović of Spatial Studio LLC, and built by general contractor Craft Homes Northwest. It is on a hillside, with the driveway descending from above so that the full span of the vegetated roof is the first impression you get as you arrive at the gorgeous property.
The designers had fun with the stormwater management on this house, using overflow scuppers on the penthouse roofs that empty onto the lower vegetated roof. These drain features are strategically placed so that the resulting waterfalls can be viewed through windows from inside the home.
Hood River is one of the wind-surfing capitals of North America, situated along the breezy and sometimes destructively windy Columbia River Gorge. The residence itself is perched on the edge of a steep hill above the already deep river canyons, so wind uplift is a primary concern here. However, the weight of the pre-grown vegetated tiles and creative use of parapets and vegetation-free zone minimizes the wind impact to the system. There are a dozen species of shallow-rooted sedum growing together in a thick mat holding the plants and growing medium in place, similarly to how the roots of mangrove trees retain sand and protect coastal ecosystems during tropical storms in the Gulf of Mexico.
livingarchitecturemonitor.com
https://livingarchitecturemonitor.com/articles/residential-green-roofing-a-growing-trend-fa23
