By: Samantha Yurek
Or does it? We're not talking about baseball caps or a pair of mittens here. Green roofs are a living system that on their own should thrive heartily in the environment in which they reside. Not all green roofs are similar, nor should they be. Diverse climates call for various approaches in construction a green roof to handle precipitation efficiently. The vegetation for any green roof should reflect local climate and growing conditions.
Uniform systems will most likely work out fine, but depending on the region, may need constant maintenance to uphold the health of the green roof. At this point, the question is if the green roof is actually doing its job. A green roof is supposed to thrive naturally, as a part of the ecosystem. It defeats the purpose when an irrigation system is put in place or the green roof is over maintained to avoid natural diversity.
Each green roof should be unique in a way that works most efficiently for that particular location. Here at Green Roof Technology we strive to create a living space that will thrive under specific conditions. There should be very little need for additional time, effort and money once a green roof has been put in place.
The Goodman’s authentic Norwegian log house and accompanying log cabin are located in Great Falls, Virginia. Set deep in the woods of Fairfax County near the Potomac River, the Goodman’s enchanting home transports you back to a simpler time in the old country. Both buildings were imported from Norway in 1971 and were reconstructed with authentic sod roofs.
By 2005 the guest cabin still retained its sod roof but the log house roof had been converted to terracotta tiles by a previous owner. When the guest cabin’s roof started leaking in 2004, Mr. Goodman decided it was time to upgrade both roofs with modern green roof technology. A sloped, single course, extensive green roof was installed on the log house and cabin in August 2005. The goal of the new green roofs was to establish stable, natural looking vegetation with a high biodiversity that through successive change would mimic the surrounding forest.
An upside-down green wall. Parthenocissus quinquefolia, commonly known as Virginia creeper, has established well on the roof and now cascades from the roof, creating a beautiful ethereal green wall.
The issue of root penetration is known to most in the green roofing industry. The relatively complex world of roofing membrane compounds and organic chemistry has resulted in most green roof professionals defaulting to local instructional manuals, which default to FLL testing records. But just because a material is effective does not mean it is not harmful, e.g. lead in paint.
In 1997, Bayer Aktiengesellschaft was the assignee of Patent US 5672568 A titled “Root growth inhibitors for building materials comprising monohydric alcohol esters of mecoprop.” Root-resistant bitumen mixtures were soon marketed.
This past week the Berlin Senate’s Department for Urban Development and Environment and the Berlin State Office for Health and Social Affair published a series of recommendations for the prevention of environmental pollution due to the release of the herbicide Mecoprop from root-resistant bitumen membrane sheets.
The statement reads:
Investigations at the Swiss Federal Institute for Water Resource and Conservation (EAWAG) on behalf of the Swiss Federal Office for the Environment (FOEN) have shown that Mecoprop under natural weather exposure is released from the bitumen sheets and the precipitate is washed out.
Rain water contaminated with Mecoprop can pollute combined sewers or surface waters. Due to the low rate of elimination in sewage treatment plants results in a particularly high risk potential. In a decentralized rainwater infiltration system there is a risk of soil and groundwater contamination. (Translated from the German)
The report goes on to make simple recommendations. The first says the use of bituminous membranes impregnated with Mecoprop should not be used unless absolutely necessary for structural reasons. Second, they should never be used in protected water areas.
Green Roof Technology is against any use of herbicides in green roof construction or maintenance. For more information on how to protect your building against root penetration without the use of poisonous herbicides please contact our office.
On July 9th, three more small extensive green roofs were installed a top the Academy’s High School Building in Newtown Square, PA. The High School has a number of glass walled hallways that look out over unsightly black rooftops. The glass walled hallways provide a spectacular viewing area for the green roofs. This year we covered almost three times as much roof area as we did last year, bring the Academy’s total green roof count to five.
Once again, Micah from Urban Ecoforms joined us to lend his experienced hand at installing green roofs. From the picture below you can see that Micah was in rare form and simply thrilled to be freed from his recent solitary confinement atop his current project in West Philly.
While we were installing the green roofs, we could not help but stop and admire the incredible lushness of the green roofs we installed last summer, especially when last July was brutally hot and dry.