Green Roof Technology Blog

Some decades ago Patrick Blanc, French botanist working at the French National Centre for Scientific Research and specialized in plants from tropical forests created and introduced a unique design for a vertical garden with real plants (Vertical Garden, Green Wall or Mur Végétal). His simple system or other much more sophisticated systems are based on a consistent water and nutrient supply comparable to horizontal high tide/ low tide (Ebbe/Flut) systems in super-efficient nurseries. These systems often include artificial light and heat/cooling for sustainable growth.

Without being a horticultural expert Patrick Blanc was able to start a new trend utilizing horizontal plant propagating systems applied to the vertical as living art. Maintenance and operational costs of all these wall planted systems are very high and so the environmental benefit is certainly questionable. Typically in less than 10 years costs for maintenance and replanting increase the cost for installation without considering the high consumption of energy and water. 

Today when you fly in to Paris Airport Charles de Gaulle you will see multiple, small green walls - very attractive, lush green with an appealing biodiversity. Closer investigations discovered that these walls the next step of green walls that are super-efficient and extremely low cost for installation and maintenance. The systems at Charles de Gaulle Airport in Paris don’t need any artificial lights, they are completely disconnected from any power and water source and they are very efficient dust collectors. The amazing biodiversity has potential for the highest LEED rating.

Here are a few plants identified:

• Attractiva plasticifolia (grown out of recycled content)
• Fakefolia polychloridenses (PCB senct)
• Metatrashus recyclisa (never green invasive)
• Ripoffera myclientus `Variegatus´ (native)
• Hidensia polyestertonia (forever green)

Good art reinvented.

Dr. Phil O. Dendron, Bel Air,  August 26^th 2012,       

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 3^rd 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

Mr. Toad doesn't care to reinvent the wheel.

Last Thursday and Friday Jorg and I subjected ourselves to the horrendous Baltimore - DC traffic and attended the The First Annual Mid-Atlantic Green Roof Science & Technology Symposium at the University of Maryland.  The title of the symposium was "Redefining Green Roof Science" and the mission statement clearly states why:

Standards for green roof performance have not been established. The MGRST symposium is dedicated to disseminating results of scientific research that will lead to the establishment of green roof performance standards for the Mid-Atlantic region.

Year after year we attended similar academic conferences and each year we are confronted with the same     experiments and the same conclusions, all of which we know have been done and confirmed a decade ago in Germany.  For us, the researchers are only confirming what we believe to already be ‘common sense.’  We are certainly not disparaging the work of researchers who are attempting to better understand the green roof field they have recently entered.  What we truly regret is the inability of academic researchers to acquire and process the information already available rather than attempting to reinvent the wheel.     

What the green roof industry needs from its academic partners is a strict methodology and process to assess all the green roof components / complete systems available on the market.  Nearly a decade ago, the Green Roof Media Testing Laboratory was successfully implemented at Penn State University and has undoubtedly beneficially impacted the green roof industry.  A similar manufacture’s test for all other green roof components would best serve the entire green roof industry by setting minimum requirements and disabling inferior products from being dumped on the market.  

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.