Last weekend I had the great fortune to spend three days biking, swimming and relaxing along the shores of Lake Tahoe with my family. I’ve spent summer weekends at the lake almost annually since I was a baby, and like many visitors before me, I always find the Sierra Nevada mountain range to be incredibly inspirational. You really can’t beat granite walls that descend to high alpine lakes. Not surprisingly, my Sierra inspirations usually derive from the natural rather than built environment. But lo and behold, while taking in a final hike at Emerald Bay State Park before returning to the city, I stumbled upon inspiration of another kind — this amazing green roof!
Vikingsholm’s green roof, with Desolation Wilderness in the background (photo by Kelly Coplin)
Located at the head of Emerald Bay, this example of what we might today view as modern green design was actually built in 1929 in the Scandinavian tradition, and emulates the style of 11th century wooden churches in Norway and stone castles in southern Sweden. Such historic features replicated at “Vikingsholm” – the name of the estate – include intricate carvings, Nordic fireplaces, and a sod roof seeded with wildflowers! We write about the benefits of green roofs a lot here at NRDC – green roofs help reduce energy costs by providing natural insulation and cooling, and decrease stormwater pollution and sewage overflows by capturing and retaining rainwater. But because of their relative novelty on the North American continent, we often write about green roofs as if they are “new” technology. In reality, green roofs have been around for hundreds of years, for the exact same aesthetic and environmental reasons we’re giving this architectural feature a closer look today.
This got me thinking about the history of green roofs. Are there aspects of the green roof we’ve been overlooking? As policy makers and policy advocates, how fluent are we in the histories of the technologies we hold up as solutions? In the case of green roofs and other technologies with historical roots (no pun intended), what does history have to teach us? To answer such lofty questions would require a dissertation, not a blog post, but it’s worth a ponder. Below are a few facts about the history of green roofs, just to get us started. Some of them may surprise you!
- The Hanging Gardens of Babylon, constructed around 600 B.C.E. in modern day Iraq, are generally considered the first example of “green roof” or “roof garden” architecture. However, despite being one of the “Seven Wonders of the Ancient World,” the Hanging Gardens of Babylon hardly had the same environmental benefits of today’s rooftop greenery – one scholar estimates the gardens would have required 8,200 gallons of irrigation water a day!![i]
- In rural areas in Scandinavia, sod roofs have been around since the Viking and Middle Ages, and were nearly universal until the beginning of the 18th century. Sod for roofs was cut from nearby fields to insulate buildings from the elements – namely, the bitter northern cold. Early North American settlers replicated this technique in the 1800’s due to timber scarcity.
Farm building in Heidal, Gudbrandadal, Norway. Photographer: Roede
- Homesteaders on the North American prairie adapted to the lack of trees and fulfilled the Homestead Act requirement of building a home within six months of filing a claim by building entire houses out of sod. To build walls, “bricks” of newly cut sod were laid root-side-up so the roots would continue to grow into the brick above it. Over time, these bricks grew into very strong walls. While these “soddies” often served as temporary residences before being abandoned for frame houses, homesteaders were generally surprised at how comfortable they were – cool in the summer and warm in the winter – due to sod’s insulating properties.[ii]
- In the early 1900’s, modernist desires for democratizing green space drove architects to incorporate expansive flat green roofs into urban areas in Germany. This is generally cited as the birth of the modern “extensive” green roof.[iii] In the 1970’s, growing environmental concerns created opportunities for green roofs to flourish. Today, 14% of new flat roofs in Germany are estimated to be green.[iv] Interestingly, it is posited that German green roofs were not inspired by northern sod roofs, but rather were the result of curiosity surrounding “unintentional” green roofs – spontaneous vegetation that sprouted from sand and gravel spread over the top of wood and tar roofs as a form of fire retardation.
- Britain benefited from the camouflaging capabilities of green roofs by using them to cover military airfield hangars as turf during World War II.[v]
- The first prominent modern U.S. green roof was built at the Rockefeller Center in New York City between 1933 and 1936.
And that’s just the tip of the iceberg! What other “new” technologies have interesting historical roots? Do you have any stories to share about green roofs? Please share your thoughts and environmental history quandaries below. Click here to learn more about how communities today are addressing stormwater runoff through green roofs and other green infrastructure solutions.
Another view of Vikingsholm’s green roof (photo by Kelly Coplin)