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Extensive Green Roofs and Irrigation

Green Team at Green Roof Technology, - Tuesday, November 04, 2014

Thank you for all the comments on the blog post:

Irrigation on Extensive Green Roofs


We believe a lot of people in North America agree with the comment that in some areas Green Roofs can't thrive without irrigation. We at Green Roof Technology don’t disagree nor agree. Allow us to bring the discussion into a fundamental perspective:  

Before you built a structure, you have to remove nature or simpler living plants that nobody watered before. Modern green roof technology is able to mimic this type of environment and allows to promote exactly this drought tolerant and hardy vegetation. With a little more understanding of this technology, it is even possible to increase the plant varieties or the plants density.

Nevertheless  the attractivity might not meet the expectations of us (humans). Our picture in mind of a roof garden is a lush green vegetation form that is created with plants that please us (humans), that are not poison or dangerous. In some areas we can achieve this goal by utilizing resources that haven’t been available at this location before the structure was built.

By using natural resources (and water is the most valuable) we start changing our environment (we take water away from somewhere – from plants somewhere) just for our own comfort. Understanding that and the value of water should create an awareness to green roof professionals or engineers to design modern green roof technology in a way that no water or super highly restricted amounts of water are utilized.

Unfortunately, the irrigation industry and most of the green roof designers grew up in an environment where resources are endless. With that said the current waste of water on green roofs is simply not acceptable to me and in these cases green roofs are an environmental nightmare - just for our pleasure (and cash) and that things look “nice and green”.   

When I drive around in neighborhoods in San Francisco in the morning, my car is being washed by all the sprinklers and nobody has a problem with that…..

Simple and efficient technology is here since many decades but not in the interest of the industry, nor “re-invented” in the US or there is a lack of common sense – maybe it is a combination of all.

Most issues I am confronted with, are a result of high tech irrigation that is just not doing what it is supposed to do, there is not the right app, poorly designed and installed, too complicated for facility people etc. or simply drains the budget of building owners over time this water costs are going up.

Let’s discuss further and email us directly:


Comment by Jure Šumi ((LinkedIn):

Interesting input Jorg. Yes, extensive roofs should be self-sufficient where they can be. But in my mind this is not possible in really arid areas like Jim is saying. With our partners in Abu Dhabi we are now investigating what plants should be used there, where top temperatures are regularly reaching 120 F in summer months (with no rain for years). If you use local plants that are surviving in desert than they are surviving only due to the fact that the roots are extremely long and go deep in to the ground to find some moisture (not possible on the roof). Limited irrigation is still needed but the roof needs design with minimised ET, so also irrigation is as low as possible.

Maybe another thing to consider. Yes or no irrigation is also a question of what someone wants from green roof. Nice look is one aspect, stormwater managment is another. We should not forget Energy efficiency. According to our investigation and perfromance tests, evaporation has big effect on energy efficiency in the summer due to cooling effect. If moisture in the green roof system drops below certain level, the cooling effect is limited. So to have best energy perfromance of the roof, than you need irrigation.


Response Jörg Breuning:

Thank you Jure.

My starting point of thoughts about irrigation on extensive green roofs goes back to a fundamental point and only a handful people make these considerations.

Humans are capable to replace nature with a manmade structure on any location on Earth and they make it suitable for people to live there. In these fundamental thoughts, I expect that humans are also able to create this lost part of nature on top of these structures.

I agree this is not always cheap and not everybody is blessed with creativity or experience. Nevertheless, it is possible and it is our responsibility if we respect nature.

The rooting depth of plants is certainly a key element - it isn’t a road block. It seems it is the preferred excuse that we don’t need to feel responsible in what we re doing and that we don’t feel guilty.

I also think it using water for cooling buildings in an open system (what any green roof is) is considered - in my world - using elementary, limited and precious resources for our convenience. In the case that producing water (in dessert states) for the wasteful irrigation of plants (to make our close environment nice) might be a problem to justify to more than 100 million people that have no access to dependable water resources.

What I am saying is, that growing plants even in areas where plants would hardly grow can be done with extremely low impact on natural, precious resources at costs that are lower in the short or long term. The current hype for green roofs can create significant drawbacks in 15 or 20 years from now to building owners if the costs of water continue to rise. Keep in mind a 20 year old green roof is not even the half of the life span of a green roof (at least that is what I know from experience).

Professionals need to start thinking long term and not for quick profit, they should disregard fancy fashions or get away from desperate LEED point collecting terms if they seriously respect nature. 

Jörg Breuning


Picture: Deep rooting plant on roof with hardly any soil and never intentially planted (in Texas at the border to Mexico).

Uneven Water Supply for West

Green Team at Green Roof Technology, - Tuesday, July 15, 2014


WASHINGTON, June 18, 2014 -- The final water supply forecast for this year shows the West divided into a wet north and dry south while snowpack has already melted in much of the region, according to data from the USDA National Water and Climate Center (NWCC).

Washington, most of Idaho, Montana, Wyoming and the northern parts of Colorado and Utah are expected to have near normal or above normal water supplies through the rest of summer, according to the forecasts. Far below normal streamflows are expected for the southern parts of Oregon and Utah, southwestern Idaho, California, Arizona, New Mexico and western Nevada.

Many of these areas are in the nearly 500 counties across the country experiencing drought, 57 of them in California alone, according to USDA disaster designations.

This year saw near-record low snowfall in parts of Nevada, California, Arizona, New Mexico and the southern parts of Utah and Oregon. Even with some May precipitation, those areas remain dry.  The biggest change this season was in the Washington Cascades. At the beginning of February the snowpack was about half of normal, but it recovered and most of Washington will have a near normal water supply from snowmelt, according to the Center. 

Spring snowmelt is well underway, according to NWCC hydrologist Cara McCarthy. “A lot of our SNOTEL sites have already melted out, especially those in the southern half of the West,” McCarthy said.

Colorado had mixed weather during May. “They had winter and summer all in one month: snowmelt, snowfall, snowmelt,” said McCarthy. Heavy precipitation combined with snowmelt, causing flooding in parts of the state.

Forecasters monitor conditions all year, but June is the final forecast of the season. “These are snow-based water supply forecasts,” McCarthy said. “Typically by July there won't be enough snow left on the ground (to measure).”

In Western states where snowmelt accounts for the majority of seasonal water supply, information about snowpack serves as an indicator of future water availability. Streamflow in the West consists largely of accumulated mountain snow that melts and flows into streams as temperatures warm into spring and summer. USDA scientists analyze the snowpack, air temperature, soil moisture and other measurements taken from remote sites to develop the water supply forecasts.

The NWCC water supply forecast is part of several USDA efforts to improve public awareness and mitigate the impacts of climate change, including drought and other extreme weather events. Through the creation of the National Drought Resilience Partnership, launched as part of the President’s Climate Action Plan, federal agencies are working closely with states, tribes and local government to develop a coordinated response to drought.

Since 1939, USDA has conducted snow surveys and issued regular water supply forecasts. View information by state.

Source: USDA

In dry years most Therophytes like
Asteriscus aquaticus are able to flower as very small plants and produce seeds that are able to survive evon more unfavourable seasons.

Leave Only Footprints, Take only Memories

Green Team at Green Roof Technology, - Wednesday, April 09, 2014

By: Samantha Yurek


Many people wouldn't think twice when gathering a lovely bouquet of flowers while out for a hike. But maybe this is a lesson we should all be practicing and passing down generations, when out enjoying the great outdoors. Transporting flowers for your own benefit is erroneous and punishable in certain situations. 

Although the United States doesn't have a specific law protecting wildflowers from being violently up-rooted, the Endangered Species Act of 1973 does cover all of the plants that are slowly vanishing.

Many states have specific laws regarding plants. For example, North Carolina's Plant Protection and Conservation Act states that it is unlawful "to possess any protected plant, or part thereof, which was obtained in violations of this Article or any rule adopted thereunder." If caught, fines can rise as high as $1000.

There are many reasons why you shouldn't pick wildflowers or take plants from the wild. Not only does it reduce the vibrancy of the location, but it also can be damaging to the environment. The USDA explains it perfectly, "We don't often realize it, but wildflowers support entire ecosystems for pollinators, birds, and small animals on a micro scale. Butterflies and other insects, small birds, and animals depend on seeds, nectar, and pollen for their food supply and life support system. In addition, some pollinators are not very mobile or have very small home ranges or depend on just one species of plant and die once their habitat has been destroyed."

In some cases, transporting flowers from the wild can also aid in the spread of invasive species.


It may not be your first reaction when someone goes to pick a few flowers, but just keep in mind that they are a living object as well, attempting to survive and reproduce just like the rest of us. And is it really worth picking these plants, only to have them wilt in a matter of hours or days? Especially when you could be enjoying them all spring and summer if you were to simply let them be.

So my advice to you is, instead of pocketing flowers from Mother Nature's garden, it is just as easy to take a short trip to your local nursery. Not only will there be a great selection on plants to choose from, you will directly be supporting your local community.

       Let me reiterate: 

Single Source - Multiple Problems

Green Team at Green Roof Technology, - Friday, January 10, 2014

By: Jörg Breuning

2013 was another very successful year for green roofs and the green roof industry. However, at Green Roof Service LLC/Green Roof Technology we discovered a trend that might affect the industry in the long run. 

The quality of green roof installations didn't improve as much as the industry grew. We have received more calls about poorly installed or poorly functioning green roofs than ever before. Most of these (green) roofs were installed in the last two to three years and the lack of proper engineering and maintenance has caused issues. These issues are time consuming to fix, require replanting, and the installation of additional growing media or even a permanent irrigation system (even in a wet year like 2013!).

The majority of these under-performing green roofs were under a Single Source Warranty and so our first response was: "Go back to your warranty provider." For green roof owners, this was typically the start of a long odyssey. Odysseus never gave up- but with all the issues presented, my clients were quick to give up because the Single Source Warranties are well-phrased and manufacturers are more likely to argue than take action. Arguing with a piece of paper, written by attorneys, twisted and tweaked by companies' legal departments is an uphill battle. No wonder these numerous stranded people decide to call us.

If the client would have taken his money to the bank, rather than spending it on the warranty (typically $1-$3 per square foot) things could have been much easier and cheaper. On top of that, our costs for designing, engineering and overseeing the installation and maintenance would have saved additional money and no problems to start with.


In any construction process we are meticulous with our details, quality of materials, craftsmanship and maintenance. We also offer low bureaucratic, simple and efficient solutions to make your green roof last far beyond three decades. Our green roofs wouldn't need any artificial irrigation, and will prove to not cost as much initially, as well as having the potential to be paid back in less than seven years.

It is our goal for the future to support the growth of the green roof industry (and the plants), one by one making our clients happy. Only happy clients can help us - and the green roofing industry.

Akron University Green Roof Sees Season's First Snow

Green Team at Green Roof Technology, - Tuesday, November 19, 2013

Located on top of the Sydney L. Olson Research Center, Akron University's first green roof is an 18,000 sf extensive green roof with over 15 varieties of perennial plants.  After its first full growing season, the plants are well established and ready for a winter nap.  Initially planted in October 2012, we established this roof without ever irrigating and only lightly fertilizing at a rate of 5 g / m2 (0.0164 oz / ft2) pure Nitrogen.  As you can see from the pictures below, the green roof is growing in very nicely and is home to a variety of insects.

Back in mid-September:  Nearly 1 year of growth. 

The Oldest Existing Green Roof in the World

Green Team at Green Roof Technology, - Friday, August 09, 2013

By: Samantha Yurek

Photo Credit: Flickr - Michel Rodriguez

Located in the city of Lucca, tucked into the rolling hills of Tuscany, Italy, you will find a most magnificent scene. The medieval architecture of the city is gorgeous, but one tower stands taller than the rest.  Attracting more attention as a consequence of the oak trees flourishing on the roof. Seven oaks were originally planted on the roof of the Torre Guinigi back in the 14th or 15th century. Although replacements have been planted over the decades, the seven residing today are still said to be hundreds of years old. Their roots grew together, penetrating the ceiling and creating a more sturdy structure. Oak trees were specifically chosen by the Guinigi family to represent renewal and rebirth. If visiting Italy, this is a great place to visit, for a few Euros you may climb to the top and see this view for yourself! 

Photo Credit: Flickr - Sidstamm

Akron University Green Roof Update

Green Team at Green Roof Technology, - Thursday, August 08, 2013

Right before Superstorm Sandy came roaring into our lives last October, Akron University had just installed their first green roof. Located on top of the Sydney L. Olson Research Center, this 18,000 square foot extensive green roof has approximately 15 varieties of perennial plants. Grown by seed and sedum cuttings, these perennials made it through the storm and flourished on top this Ohio roof. Without any irrigation systems and very little fertilizers, the green roof is starting to finally show its true colors during these summer months! 

Goodman's Norwegian Log House with Sloped Green Roof

Green Team at Green Roof Technology, - Wednesday, July 31, 2013

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.

Episcopal Academy Installs More Green Roofs

Green Team at Green Roof Technology, - Wednesday, July 10, 2013

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.  

Micah Shapiro (Urban Ecoforms) striking a pose with the beautiful Academy's quad in the background.  

Andrew after spreading the last of the Sedum cuttings.  Seen below is one of the green roofs we installed the previous summer.

Fireworks and Green Roofs

Green Team at Green Roof Technology, - Thursday, July 04, 2013

Fireworks and Green Roofs

Practically all dry organic materials are combustible at relative low temperatures. Roof shingles or many waterproofing membranes on roofs are typically petroleum-based products (including Asphalt) and they is hardly a difference to dry organic materials. Some products are equipped with chemical fire retardants that could decrease the risk of spreading fire, not the risk of leaks cause by impact.

The living vegetation of functional and well-engineered green roofs contain high moisture contents and most plants (especially succulent plants on large extensive green roofs) have a fraction of the energetic potential comparing to all other components used in a building. The green roof growing media (soil for the green roof plants) is a blend of different mineral components with an organic content of typically less that 15%. It is practically impossible to set this material on fire – not even considering the natural moisture content.

Many fires or leaks on roofs caused by consumer or display fireworks could have been prevented if the building would have had a fully functional green roof or a well-maintained conventional roof (regular removing of organic debris from the roof and gutters).

A fire is the worst-case scenario; however in most cases smoldering firework parts (and cigarettes) are causing leaks on unprotected roofs that are discovered much later. These problems are unknown on functional green roofs. When a green roof prevents a leak or even a fire it is typically not recognized but the payback is right there.

Nature is (literally) so cool.

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