One topic on discussion during the symposium I believe is in need of even more discussion is the implementation of a requirement to monitor the long-term performance of green roofs.
The need for annual green roof monitoring is essential. Too often we encounter failing green roofs. The green roof ecosystem is fragile, especially in its early establishment years, and can fail for many reasons. They can fail due to poor design, poor installation, wrong material choices or negligent maintenance, and none are mutually exclusive. The effect this has on the performance of a green roof is dramatic. A complete failure of a green roof system can occur rapidly and it is a huge liability, both economically and for safety reasons. Let us also not forget that a bad green roof is an image problem for all of us and reflects badly on the entire industry. Each green roof that fails to support its vegetation or leaks is one more stigma the entire industry has to overcome.
A mandatory green roof monitoring system, whether operated by a government agency or an independent 3rd party, would be able to identify failing green roofs and require whatever is necessary to restore the green roof to a proper level of performance. We believe any green roof that is supporting a healthy ecosystem, complete with year-round vegetation cover, is more likely than not properly functioning and meeting leading performance metrics.
Recently, buried within Maryland’s Stormwater Management – Watershed Protection and Restoration Program was a clause that requires annual monitoring of stormwater bmp’s:
(III) PROCEDURES FOR MONITORING AND
ANNUALLY VERIFYING THE EFFECTIVENESS OF THE ON–SITE SYSTEMS, FACILITIES, SERVICES, OR ACTIVITIES IN REDUCING THE QUANTITY OR IMPROVING THE QUALITY OF STORMWATER DISCHARGED FROM THE PROPERTY.
Striking ‘annually’ from the clause is disappointing and the legislators have essentially gutted this clause of its ability to secure long-term performance effectiveness. Once again we believe a mandatory monitoring system is essential and it is only a matter of time until one is implemented. Who will be the first?
By Andrew Yanders
Last Friday I drove up to Newtown Square, PA to check-up on two green roofs we installed earlier this summer at the Episcopal Academy. I was joined by two of our Philly friends from Urban Ecoforms, Zach and Jared.
July was a remarkable month. The extreme heat coupled with the lack of precipitation made the first days of establishment especially stressful. We placed the roofs on a strict regime of water - beginning with the first week and gradually reducing the amount of water week by week until irrigation ceased after 4 weeks.
As expected, many of the plants did exceptionally well. Notably, Delosperma cooperi and Allium schoenoprasum had no problem handling the conditions. Our Sedum cuttings did not fare so well. The surface of the growing media dried too quickly and became too hot for roots to adequately form.
This hot area on the roof where the cuttings did not establish well was planted with a couple of trays of Sedum sexangulare and Sedum reflexum and a five gallon buckets worth of assorted Sedum cuttings was again spread. The weather has cooled significantly in August and we feel the Sedum cuttings should establish nicely this time.
Planting a green roof is not a precise science. Trial and error is the only way to find out if a species is going to work or not in a specific location. We are finding out on the Academy roof that shading is creating two distinct zones on the small 700 sf roof. The temperature and exposure difference between the two zones is dramatically impacting the growing habits of the plants on the roof.
By Andrew Yanders
Photo By Kat Harrold - Featuring Jorg Breuning (left) and Andrew Yanders (right) at ABC Carpet and Home
In 2010, the Bronx Overall Economic Development Corporation (BOEDC), in partnership with the Bronx Borough President’s Office, submitted a proposal to the Bronx River Watershed Initiative to fund a 10,000 square foot green roof on the ABC Carpet Bronx Outlet building at 1055 Bronx River Avenue, Bronx, NY. Green Roof Technology worked with the BOEDC to manage the project, beginning with the design all the way through training and supervising a local workforce to install the green roof. The installation at ABC Carpet was completed in early November of last year.
This past Friday, Jorg, Kat and Andrew traveled to the Bronx to check on the health of the green roof and to construct 4 environmental monitoring stations. All 4 stations are approximately 1 m tall with a 1 m x 1 m x 0.15 m box integrated on top. Two of of the top-mounted boxes are filled with an extensive green roof system and the other two are only lined with a waterproof membrane. Each box is equipped with 3 temperature probes and a tipping bucket. In the coming weeks, a stand alone weather station will be installed on the roof to monitor wind speed, relative humidity, air temperature, and sun intensity.
By Kat Harrold
Photo By Jorg Breuning
Mulching season is upon us the air is ripe it's fragrance. While the good gardener may protect their garden from unwanted weeds with a coat of mulch this can actually kill the functionality of a green roof.
The fine organic matter produced from the decaying mulch creates a hotbed for weeds that take advantage of the added nutrients. These same fine particles also clog the filter fabric and drains which result and standing water and roof load issues.
To protect your green roof from unwanted plants there are two main things you can do. The first is if it is a sedum roof, don't irrigate unless extreme drought lasting more than a month. The dry conditions often fry the seeds before they get a chance to germinate. Use only a small amount of slow release fertilizer twice a year for the first 4 years. Poor soils with a low level of nutrients are ideal for sedums. Excessive fertilizer can actually be detrimental to sedum growth while simultaneously providing excellent conditions for weed growth.
By Kat Harrold
Photo ~ Green Roof Technology
In 1988 fire research testing on green roofs was begun by the Research and Material Testing laboratory of Baden-Wurttemberg in Stuttgart Germany. Initial testing began with the evaluation of bituminous waterproofing layers. It was discovered that the bituminous waterproofing when burned produced 50 kWh/m2. Alternatively when this burn test was done on an extensive green roof with dry grasses only 3 kWh/m2 were produced.
Tests were then done to see if it was possible to establish a fire that would spread across an extensive green roof and or start a glowing/burning of the growing media. After several tests the conclusion was made that it was nearly impossible to create a fire on an extensive green roof that would spread across the roof or ignite the growing media. Conversely it was discovered that a bare regular bituminous waterproofing membrane was 15-20 times more likely to catch fire than an extensive green roof with grasses and perennials. It is for these reasons that many Germany insurance companies offer a 10-20% discount on fire insurance when a building has a built in place green roof.
By Joe Devoy ~Tellus 360
Photos by Tellus 360
A year has passed since the Tellus 360’s green roof was installed and we caught up with Tellus 360’s owner, Joe Devoy. We asked Joe to write a few words reflecting on his new urban oasis.
“One day we were standing on our big flat roof, the sun shining down, the wind gently blowing, having a chat. We were looking at the Marriott and Convention Center being built next door. Coming up to the roof had become a kind of ritual, a pleasant place to relax and reflect.
When we were on the roof we were still part of the city, but it was a different part of the city. Captured all around us were the sounds of city but we were still removed somehow. After a few of these trips the decision was made; a green roof must be built on our roof. We all needed a therapeutic place where city and nature could meet, where the sounds of life relax not excite.
As we talked to Fritz Schroeder of LIVE Green Lancaster and met Jörg and Kat from Green Roof Technology, our vision of a community oasis developed in our mind. “A better way to live and a better life for our building.” Our vision for our building has always been for it to be alive, that it could breathe with the city. We want it to expand and contract, to participate in our life and to help us be better in the way we live.
Our new green roof has achieved that and the life it has brought to our building and our community has been equally amazing. Now I return each morning for my daily ritual. The smell of earth and the sounds of a city alive surround me as I enjoy my breakfast from the local farmers market. I love to hear the city breathe, I love to hear our building breathe.”
By Andrew Yanders
Here at Green Roof Technology we are often confronted with a perplexing industry occurrence. Frequently we visit extensive green roof sites or monitor extensive green roof projects online that have installed an irrigation system. It is difficult to justify the necessity of an irrigation system for extensive green roofs. Sedums, other low growing succulent species, many grasses, and herbaceous plants require no irrigation. The proper selection of plant species is crucial and species not suited for extensive green roof purposes should not be used. An irrigation system wastes potable water on plants that do not need it. This excess water only serves to promote the growth of unwanted plants from foreign origins.
- In extensive roof planting a minimal depth of soil is used (generally less than 15 cm), with the objective of being able to leave the planting to its own devices after an initial establishment phase. Plants selected for such conditions are able to survive on a long term basis with minimal reserves of moisture and nutrients.
- The construction of an extensive roof garden is the same irrespective of the system that is employed. The first layer, a root protection membrane, is laid directly on top of the waterproof roof surface. Above this comes a drainage layer, then filter mat and on top of this the planting medium.
A diligent maintenance schedule is a principal we take very seriously. Without proper maintenance a green roof has no chance of thriving and looking its best. There is even serious threat of long term damage to the underlying roofing materials when maintenance is neglected. There is even a likelihood of an overall failure of the roof’s main purpose, to keep the building’s interior dry. Because of the grave consequences of not properly maintaining a green roof we continue to insist on a strict maintenance schedule with all our clients.
Here in the Northeast of the United States winter is upon us and we are eagerly awaiting the first blanket of pristine white snow. There are 4 key maintenance aspects we wish to highlight that are essential for the health of the roof during the winter season.
Similar to any typical roof, when snow begins to accumulate heavily on a green roof make sure it is evenly spread out; snow drifts should be mitigated to avoid exceeding load limits.
In areas where snow accumulation on the roof is a hazard particular attention must be made not to damage the green roof during snow removal. So far as we know, there has been no literature on this subject and no recommendations have been made. We are recommending a 4 inches, 20 cm, buffer layer of snow. To remove any more snow allows for the potential to disturb plants and dig into the growing media.