Back to Home Page
Home   |   Contact Us Ph: 443-345-1578

Green Roof Technology Blog

Cool Roofs are not Green Roofs

Green Team at Green Roof Technology, - Thursday, January 17, 2013

By: Jörg Breuning


In Physics class we learned basics about thermodynamics and about thermodynamic equilibrium. In simple words the content of a black coffee mug “adjusts” faster to the surrounding temperature than in a white coffee mug assuming the material and material thickness of the mugs are the same.

Exposing these mugs to the sun light the black mug will convert the electronic energy (sun light) into heat faster and no light or shade cools it faster assuming the ambient temperature is lower. The physics behind converting light into heat is called radiation-less transition. White (or bright) colors reflect the (sun) light more effective than black. 

Any macroscopic or microscopic body on our earth is exposed to these physics properties including all particles in the air of which can be plentiful in polluted cities. While the sun light enters in to the earth's atmosphere, all bodies (particles in the air) receive portions of the sun's electronic energy and convert them in to heat. For example, on a high mountain we experience much more sunlight, or electronic energy, because the air is "thinner" or has less particles in which the light has to travel through. On a beach the light intention is also very high and this is caused by the reflection of the light off the the water and sand. Sunburns on the beach are of high risk because of the consistent wind, we don't experience the transition from light into heat on our skin as fast. No living organisms can reflect the light 100% effectively, but they can actively reduce the consequences (heat) by using techniques such as evapotranspiration.

Roof Surface Temperatures
(a sunny day in May, air temperature around 72ºF)

Reflective roofs can't reflect 100% of the light either, but they are good to a certain degree (see roof temps above). However while reflecting the light back in to the atmosphere, this reflected light will meet all the particles (bodies) again and substantially increase their temperature. It is well proven that less than 5% of sunlight is reflected back into space once it's in our atmosphere.

White roofs relocate the transition point of light into heat from the roof into the atmosphere or surrounding bodies (e.g. buildings). They simply don't eliminate the problem of increasing temperatures (heat island effect) caused by human settlements and they don't decrease the environmental foot print of structures. In addition, the white surface has a slow thermodynamic equilibrium. It takes a long time to to heat up in the winter (when heat is necessary) and cools down slower during summer nights.

The kingdom of plants were the only organisms over millions of year who developed a super-efficient mechanism to reduce the heat transitioned from the sun light. It is called evapotranspiration - powerful, miniature AC units powered simply by solar energy. These super little AC units are found naturally on Earth, but can be practically placed anywhere.  By using this naturally occurring phenomenon and installing green roofs, the outcome will go further beyond any man-made machine or material.

In many countries where insulation requirements are more intense than in North America, it is questionable whether reflecting roof material makes sense to start with. From a global environmental perspective and understanding the basic science of physics, reflective roofs are just relocating the heat issue caused by human development. It is similar to building a chimney higher at a coal power plant so not to pollute the air, when in fact the wind will just carry the pollution toward a different city.

Sometimes I wish all LEED™ professionals would have more common sense and follow these laws of nature and their own environmental gut feeling - it is simply better living under a tree canopy rather than under a polar glacier. 

A Nice Gift for Green Roofers - Un Jardin sur le Toit – First Green Roof Fragrance

Green Team at Green Roof Technology, - Monday, January 14, 2013

Un Jardin sur le Toit – First Green Roof Fragrance

by Jorg Breuning

Jardin sur le Toit by Hermès features a little slice of nature perched on the rooftop of the building of the house of Hermès in Paris, France. A feast for the sense and the mind. A fragrance of light and delight, crunchy and cheerful.


Hermes launches the new fourth fragrance from the collection of garden-inspired fragrances Un Jardin, named Un Jardin Sur Le Toit or “A Garden on the Roof” in 2011. Un Jardin Sur Le Toit refers to the especially luxurious garden located on the Hermes’ headquarters building roof. A secret roof garden, hidden in the heart of the city, in Paris.

The garden is full of aromatic herbs, flowers and fruits whose flavors vary as they pass through the metamorphosis induced by the seasons. Its fresh and sweet-smelling atmosphere is captured by apple, pear, rose, green grass, basil, magnolia and compost notes.  This fruity, vegetal, floral eau de toilette is appreciated by both women and men.

The composition is designed by Jean-Claude Ellena.


Elevating Urban Farms onto Rooftops

Green Team at Green Roof Technology, - Wednesday, January 09, 2013

By: Jörg Breuning

Photo credit: Kölner Wein Depot

Long before green roofs became necessity and rooftop farming was trendy in North America, Dipl.-Ing Markus Wittling was planning to elevate an entire vineyard on top of the Wine Museum in Cologne, Germany.  Build in 2002, the sloped green roof spans over the entire museum building of almost 20,000 square feet. It is the first vineyard on a roof, the first sloped rooftop farm and the first and oldest organic urban farm on a roof in the world.

In the middle ages Cologne was the most important wine trading town north of the Alps.  The "Weinmuseum Köln e.V." is honoring this factwith a brand new museum with astonishing and educational exhibits on wine. The green roof displays 40 of the most important grape species from around the world situated onto 720 vine stocks.  The soil layer (growing media) including granular drainage is approximately 27 inches deep and consists of a blend of porous volcano material like Lava rock and Pumice - materials in which grapes simply grow best. 

 This rooftop vineyard is a prime example of the performance of modern green roof technology and is ideal for educational purposes.  If you have a chance to visit Cologne, the Wine Museum is a must on your Green Roof Safari and your effort will be rewarded with amazing wine tasting

For more information: or simply contact us.



Common Sense

Green Team at Green Roof Technology, - Thursday, December 20, 2012

By: Jörg Breuning

Recently we have been receiving more and more calls regarding performance issues on extensive green roofs. Most of these roofs have been installed between 2-5 years ago by various green roof companies or supplied by different manufactures. Common complaints include dying plants, drainage system failure, growing media erosion and waterproofing leaks. Especially pre-vegetated systems (planters, trays, modules) mostly don’t meet expectations or even minimum requirements for green roofs. More often than not, green roof failures are the result of simple design or maintenance mistakes.

Many failures start within the design. A poor design leads to a snowballing effect of problems, growing and gaining velocity with every movement forward. Failures also occur during the construction phase when inexperienced installers claim a certain expertise because of a prior job, a way-back education or simply because they once watched a green roof installation. 

But problems can arise even sooner. We also noticed that many initial design and construction decisions are made ‘democratically’ or as a team consensus because no one person wants to carry the full responsibility on their own shoulders. Often these decisions are wrong and unrealistic. Physics, biology and chemistry are natural laws and cannot be compromised, even if done democratically.

Engineers must work within the parameters of reality and the best course of action is to always to use common sense.

In most cases things could be so easy if people would just use their own common sense and experience instead of believing all the nonsense they find on the internet.

Our commitment is to common sense, never nonsense. 

Sun-Root System unfazed by Superstorm Sandy

Green Team at Green Roof Technology, - Tuesday, December 04, 2012

by Ryan Miller

In April of 2012, Green Roof Technology introduced the first Sun-Root solar green roof system to the United States when we installed a 1 kW system (4 Sun-Root Modules) atop the New York Parks & Rec. office on Randall’s Island in New York City. The rooftop, which is eye-level with commuters on the Triboro bridge, creates and stores enough power during the day to power a series of rooftop LED lights throughout the night.  New York City Parks & Rec was drawn to this technology as a means of adding solar power without the need to drill into the membrane to harness the solar array.

Although controlled wind studies have already proven the strength of this system, we are now able to report some real-life wind tests.  Recent Superstorm Sandy made landfall late October, only 6 months after installation, and left without moving the Sun-Root System an inch.  New York City reported maximum sustained winds at 85 mph with some gusts reaching 92 mph .  Upon visiting the site a week after the storm made landfall we found that our original placements of the Sun-Root withstood the winds without a shift.   Jorg could not be happier.

Green Roof Research in North America

Green Team at Green Roof Technology, - Monday, December 03, 2012

Green Roof Research in North America By Jörg Breuning


I am always amazed how much funds, intellectual energy and resources are put into research of extensive green roofs without the consideration of feasibility and without considering the demands of the plants.  Especially in research common sense should be the starting point of any qualified discussion. This raises also the questions, why are extensive green roofs in Europe –in particular Germany – are so successful?

It is solely successful because extensive green roofs according modern green roof technology are a cost efficient (and beautiful) tool to manage stromwater issues. Period. All other highly market benefits or positive “side effects” are generated by the system for free because these are only consequences of successful implemented nature. Focusing on the side effects and improving them will compromise and eventually reduce the main purpose of an extensive green roof by increasing costs for designing, engineering, implementing and maintenance.

In the academic world Liebig’s law of the Minimum should be applied in any step of the discussion and research. However understanding the limiting factors – including limiting economic factors – requires a tremendous amount of experience, historical data and common sense. The lack of these factors and the lack of time seem the limiting elements but justified by many unique human properties like vanity, self-promotion and economic restrains. On the other side (consumer side) the humans are also part of nature and it is natural that any of their decisions are made accordingly. If an idea doesn’t fit into this process (controlled by the scarcest or limiting resource) we walk away from it, like plants will “walk away” if their minimum requirements are not met. With the disappearance of plants on an extensive green roof we lose the purpose and the investment.

It is common sense that plants cannot walk away as fast as humans so their disappearance might take 2 decades or more which is still much less than the lifespan of extensive green roofs – the lifespan we promote.

For example measuring and promoting building insulation properties of a thermal mass or heat sinks like extensive green roofs was developed as a selling instrument of the industry (like reflective roofs). Trying to improve that will consequently compromise the main purpose to the negative. The end of this research will find out that it is most efficient and probably 10 times cheaper just to increase the buildings insulation on any surface of the building. It will also perfectly benefit when energy prices will continue to super-proportional increase or when we like to build our settlements that they last longer than just two decades – or when we want that the building has the same lifespan as an extensive green roof.

As I brought modern green roof technology to North America from Europe I expected a higher understanding of common sense and of Liebig’s law since it seemed to work in the social and financial world. Investing the research funds in actual extensive green roofs according proven modern green roof technology (e.g. not pre-planted boxes) would benefit the environment, industry and building owner much more and would help to start an entirely new research generation in 10-15 years from now.

When it comes to living technologies going back to the roots sometimes helps or simply is a necessity.  

DC Green Roof Education and Outreach Event

Green Team at Green Roof Technology, - Monday, November 12, 2012

On Friday, November 16th Jorg and Ryan will be in Washington DC to give a presentation on Solar Green Roofs.  

The event is hosted by the Anacostia Watershed Society and will focus on 3 important issues: a) the benefits and design of solar green roofs, b) the design and plant selection for green roofs, and c) methods to reduce the installation and life-cycle costs of green roofs.

If you wish to join us on Friday, please RSVP to  Space is very limited, as we expect a full house.

Swarthmore College's Little White Grub Problem

Green Team at Green Roof Technology, - Friday, October 26, 2012
A few months ago we were contacted by Swarthmore College to help identify the cause of a disturbance on the roof.  During a routine visit in August about 20% of a large, upper section of a green roof was completely torn up.  The disturbance occurred in areas where low-growing Sedums, such as S. sexangulare, S. album, and S. spurium dominate.  Areas where taller Sedums, such as S. takesimense, S. kamtschaticum grow were left undisturbed.  

Further investigation located the likely perpetrators.  Numerous white grubs were found in soil.  The likely cause of the Sedums being torn up is from birds scavenging for a snack.  The grubs feed off the roots of the Sedums, weakening their ability to resist the damage caused by the birds.  

Our article about the damage inflicted on the green roof and ways to remediate the problem continues in our Autumn 2012 issue of Green Instance.  The Scott Arboretum of Swarthmore College has also written a summary of the events, which can be seen here.

The Enclave

Green Team at Green Roof Technology, - Wednesday, September 05, 2012

The Enclave Gets a Lawn

Last week Green Roof Technology, with the help from some friends from Highview Creations, spent  3 days installing a 4300 sf. sod lawn at The Enclave in College Park, Maryland.  The project was a huge success.  Every step of the way went nearly as smoothly as we had imagined.  

Here's a succession of photos taken over the course of the install.  Enjoy!

Just a note to everyone out there:  Rolling out 4300 sf of sod in 100 degree heat is HARD work.  I spent most of the day soaking myself down under the sprinklers.   

Mid Atlantic Green Roof Symposium Highlight

Green Team at Green Roof Technology, - Wednesday, August 22, 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 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: 


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?

Follow Us!

RSSGreen Roof Tech Blog
RSSGreen Roof Plant Blog

Recent Posts



Latest Blog Posts
  1. Sustainability, Resilience: Green Team at Green Roof Technology, 09-Feb-2018
  2. Health Care and Green Infrastructure Green Team at Green Roof Technology, 06-Feb-2018
Facebook   Twitter   LinkedIn   Google+   YouTube
"We sought Mr. Breuning as a lecturer because his company represents one of the most successful, technically advanced, and progressive businesses associated with green roof technology in the USA."

Duncan H.
Program Manager
New York Botanical Garden
Go To Resources Page