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Crafting Green Roofs


Definition: GREEN ROOF

A Green Roof is a technique to establish vegetation/plants on ground disconnected areas and any other man-made, impervious structures. Living Roofs or Green Roofs are also known as Vegetated Roofs, Eco Roofs, Bio Roofs, and Roof Gardens.

Ideally, vegetated roofs consist of different layers that mimic a natural soil profile (soil horizons).

These layers ensure that vegetation can thrive for as long as the structure lasts. Living Roofs or Green Roofs can partially or entirely eliminate the negative environmental impact (footprint) of a man-made structure.

Roof Gardens bring nature back to a location where she was before the structure existed. Depending on the thickness and composition/depth of these layers, specific plant communities will thrive.

Green Roof with Lawn


Because the intended or desired plant community for a Green Roof determines the thickness, so it affects the weight and expected maintenance of greenery. Therefore, the German FLL-Guideline for Green Roofs created three (3) main categories or types standardizing Green Roofs (in 1982). EXTENSIVE, SEMI-INTENSIVE, and INTENSIVE.

Finally, after the last two 2 decades, these three major types are accepted worldwide. In fact, the FLL-Guideline is the mother guideline of modern Green Roof technology. Also it is the blueprint of all other guidelines or standards in the world.

Every desired or intended plant community is only a snap shot. As all experienced horticulturalists know, nature and so any plant community undergoes a natural succession. The speed of natural succession can be managed by specialists but is also influenced by the elements. Since climate change is happening, Green Roof professionals have to adopt new and existing Green Roofs accordingly. New and more advanced Green Roof systems might be required.

Solar Garden Roofs (BioSolar) and Blue Green Roofs are Green Roof Types that increase sustainability and Return of Investment. In short, these are fully integrated combinations. Later changes into one or the other is possible.

Green Roof Types


Based on the Green Roof Type, professionals choose different materials for the layers and different means for delivery. After all, all materials need to be suitable, beneficial, and resilient for the target vegetation. The different materials and means for delivery finally, determine the system. In conclusion. the five basic Green Roof Systems are shown in the picture.

By definition a Green Roof System starts on top of the last functional layer from a structure, typically the roofing or building insulation. This last functional layer of the structure must be resistant against the force of plant roots, microbiological activity or chemical impact.

Therefore, functional layers of the structure are NOT considered parts of the Green Roof System, even when (English) literature tells it differently. For example a Root Barrier is also a functional layer of the structure! Because it adds only value to the roofing if such doesn't come with that in the first place. Again, most English literature is incorrect at this point.

There are plentiful Green Roof Systems on the market and each follows a purpose or a business model. Many systems are purely laboratory data driven, disregard the needs of plants and natural succession. Plants are the heroes on Green Roofs. Any Green Roof System should make things work for them first.

At Green Roof Technology plants have the highest priority. We don't need to test or vet a Green Roof Systems. Our Green Roof Systems are precisely tailored for your design intend and, of course, to ensure all plants feel home for as long as the building will last.

Compare Green Roofs - Green Roof Systems
Green Roofs - Overview Systems
Reducing the environmentally footprint

Without being Tree Huggers, Green Roof Technology is against excessive use of plastics, artificial sponging elements (mineral wool, thick Poly-fabrics), Polystyrene or other unnecessary components on Green Roofs.
Because many of these components have little or no direct benefit for the vegetation. However, they increase costs and decrease reuse after a Green Roof have to be removed (e.g. change of roof use). To summarize, all our designs contain "plant friendly" and plant beneficial materials or components.

Because we are creating ecosystems that can be reused over and over again.

If certain artificial components are necessary, we choose components that enhance the positive effect on the vegetation and biodiversity. Because leaf mass and root mass of plants are in balance, our preference is for porous materials that improve the amount of root growth. Simultaneously we reduce the excessive amount of layers what streamlines the installation process.

By the way: LEED doesn't have sufficient credits for reducing the amount of different components. In short, LEED is not honoring construction means and methods that avoids sandwiched products, Cradle 2 Cradle products and solutions, and eliminating components that are not necessary.

We feel the pulse of the plants!



Arid Climate GreenRoofs


greenroofs arid climate

Climate Zones and Green Roofs

Green Roof Technology tailors green roof systems for any climate zones because we have worked on projects in every climate zone including unique micro climate zones.
Plant biology and soil biology are our strengths because it is important to allow plants developing their healthy relationship between roots, shoots, stems, and leaves.
All this knowledge and experience you find in our Green Roof solutions to reduce environmental stress on plants, to minimize human interference (maintenance), and to avoid wasting natural resources like water.

If irrigation systems are required, we have smart irrigation solutions that reduce the water consumption by 45-85% comparing to frail sprinkler systems or labor intensive drip irrigation systems. Our solutions do not depend specialized irrigation engineers, electricity, Apps/internet or sensors - although these could be integrated.

Combining local and century old gardening techniques with natural man-refined materials helps to optimize Air-To-Water ratio, effective rooting depth, and regulative hydrology cycles (artesian aquifer). Green Roofs that work with recycled water, grey water, and partially with salinated ground water.

We steer clear of using man-made and structurally unstable sponging elements (poly foams, mineral wool or other fiber sponges) because these create unsuitable conditions (stress) on all desired plants for any type Green Roofs in any climate zone.



Biodiversity and Green Roofs

Biodiversity Green Roof

The American Heritage Scientific Dictionary describes biodiversity as, “the number, variety, and variation of different organisms found within a specific geographic region.”

Consequently, biodiverse environments have it all: native species, introduced species, and invasive species of flora and fauna.
In other words: a mono-culture of native species can be just as detrimental as having a mono-culture of invasive species.

The key word in a biodiverse environment is diversity. For instance, the ecological value of Sedum-only Green Roofs is very limited. Such Green Roofs often suffer because of the lack of competition with other plants species.

Native and Naive

We also saw Green Roof project where plant-nazies insist on native plants. However, on these roofs problems increased faster because natural players are not existing. Furthermore a lot of native species cannot handle the change of micro climate or the exposed location on a roof.

For example an extensive Green Roof in Washington, DC is not native in the first place,because the city was built into marshland, tidal plains and forests.

Also all the structures we built have nothing in common with any native landscape. In many States of North America the building are often taller than the highest mountains of a State.
To summarize, Green Roofs are not necessarily a place for plant specie conservation because the environmental conditions are very different to locations on grade.

Ecology and biodiversity requires more than "knowing some species" it also requires the understanding that we cannot fix on a roof the problems we did to nature on grade. Humans did and still do change the environmental conditions on our planet drastically and very fast. Many of us believe there is an opportunity to slow down these changes.



There is a need to stop thinking, researching, testing, and putting goals out there. It is time to act fast and every plant preferable trees are in need. On roofs, on walls, and any available space including a massive reduction in impervious areas like roads and parking lots. Including Urban Tiny Forests.

Every investment in this regards we do now, saves our next generation to pay for with high interests and compound interests.

However, Green Roofs are an step stone environment and a fragmented habitat. Strategically placed Green Roof can create connectivity and reduce migration challenges for species. Some creative ways that connections can be made are Bird airports on roofs, wildlife bridges over roofs, or other green corridors with high canopies on grade.


Resilience of Green Roofs

Vegetation placed on ground remote locations is a century-old tradition for very different reasons, combined purposes, and always with plants in the focus. Because healthy and thriving plants are part of nature, they do what they are doing at their best. Therefore, we must provide the appropriate foundation.

Nature on roofs and on grade undergoes a natural succession. With maintenance we have some control for the speed of succession but be cannot stop it. If we try, we eventually lose the benefits we were seeking in the first place. For example, an extensive Green Roof will look different in 20 years than it looks two years after the installation.

Data, Data and Data

Unfortunately, some data collectors among us are looking at one Green Roof aspect only: Stormwater runoff, stormwater retention and detention, because this brings the cash flow.

Cities, counties, States, and nations can be better advised by looking at resilience or longevity.

In fact, by desperately trying to increase data driven stormwater means, they forget about natural succession. However, natural succession is the key for resilience - assuming we want healthy plants and plant diversity. No wonder that manufacturers flaunt with scientific test results and do not mention that this is only snapshot from a laboratory before natural succession. Nature is not static and never was.

Stormwater-only "optimized" systems ultimately affect all other natural cycles within a Green Roof. Our experience taught us that natural cycles on Green Roofs are hardly known in North America. In same cases not known, disregarded or even purposeful ignored. Just craving for ROI or profits is mostly not helpful for nature. Green Roof replanting or replacing seems a future business model.

Green Roof Technology is very proud of its European heritage. Ultimately, this gave us the opportunity to see the bigger picture. Through traditional and fundamental education, robust experience, and over 4 decades of project monitoring we own resilient and lasting of Green Roofs. Additionally, common sense helps growing healthy plants and resilient plant communities on roofs and this increases the benefits as things progress to a natural ecosystem.

Creating natural ecosystems adopt to climate and weather changing conditions - naturally.



Urban Mining and Green Roofs

Urban Mining and Green Roofs

Urban mining is the safeguarding of the environment and the promotion of resource conservation. Because through reuse, recycling, and recovery of secondary resources from waste, we maximize the resource and economic value of waste streams generated in urban spaces. In short, the majority of materials we need for Green Roofs exist in urban waste. As a result, reusing creates a triple bottom line.

Nevertheless, Urban Mining is currently more common for unused electronics, but it has significant potential for Green Roofs. For example, aggregates and organic waste create major volume issues in cities. Exactly these volumes have high potential in the planning and designing of sustainable cities. On Green Roofs and ground based greenery, this potential could be used within sustainable development goals.

p>For decades Green Roof Technology is one of the few industry experts who actively promotes products and components from urban waste streams. Often these products exceed performance specification from virgin components and reduce transportation.
Simultaneously, we drastically reduce the waste during green roof construction by smart engineering. For instance, certain Green Roof components (like drainage boards, edging, pedestals, packaging etc.) require customization for roofs with a lot of waste accordingly. It is possible to reduce waste already in the Green Roof design! This makes Green Roof Technology very unique in the industry, besides the positive effects for our environment.

Green Roofs without the use of plastics isn't new for us - actually these exist ready for many decades!


Green Roof Benefits

Benefits of Green Roofs

For the Building Owner:

  • Certainly, expands roof life 2x3 times (up to 60 years)
  • Likely, reducing air-conditioning costs
  • Reduce winter heating costs
  • Firstly, Stormwater management tool
  • Up to 15 LEED credits
  • Government and municipality incentives
  • Improve public relations
  • Transform dead space into garden space

For the Community: 

  • Firstly, reduced stormwater runoff
  • indeed reducing city “heat island” effect
  • Lowering smog and improve air quality
  • Muffling noise
  • potentially, lower energy demand
  • Improve aesthetics 
  • Naturally, providing green space

For the Environment: 

  • Of course preventing combined sewer overflow
  • Lowering carbon monoxide impact
  • Removing nitrogen pollution from rain 
  • Neutralizes acid rain effect
  • Absolutely, provids habitat for wildlife

Sketches courtesy of Dachbegrünung: Luxus oder Notwendigkeit - 1976


LEED and Green Roofs

LEED and Green Roofs

LEED®, or Leadership in Energy and Environmental Design, is a green building rating system developed by the U.S. Green Building Council (USGBC).  With the intent in providing a standard certification process that promotes five key areas of human and environmental health.
The idea behind LEED is a roadmap to measuring and documenting processes for every building type and phase of building lifecycle. To receive LEED certification, building projects meet defined prerequisites and earn points by attempting a variety of credits. Because LEED® certification can be very costly, it is voluntary.

In contrast, most ordinary building codes in Europe exceed the LEED rating system. After all, many buildings in Europe meet Passive House standards already. Additionally such different mindset in Europe can  often make construction less costly. Certainly with a higher benefits for humans and environment. In our opinion, LEED is overrated and under qualified as a measurement for sustainable and resilient construction.

Nevertheless, all Green Roof Technology's solutions help earning LEED® points in several credit categories. Because collecting LEED® points is very popular in North America, we also hope that our clients can learn from our European heritage in efficiency.  In general, we want to inspire our clients consciousness and common sense. In fact, reducing the amount of excessive plastics (e.g. in tray systems), vegetation/ Sedum mono-cultures, and permanent irrigation systems on extensive Green Roofs, does more for the environment than any LEED point can do.

Potential LEED Contribution:
  • Site Development – Protect or Restore Habitat (Sustainable Sites)
  • Open SpaceSustainable Sites: Rainwater Management (Sustainable Sites:)
  • Outdoor Water Use Reduction (Water Efficiency)
  • Optimize Energy Performance (Atmosphere)
  • Construction and Demolition Waste Management (Material & Resources)
  • Disclosure and Optimization – Environmental Product Declarations (Material & Resources)
  • Building Product Disclosure and Optimization – Sourcing of Raw Materials (Material & Resources)
  • Disclosure and Optimization – Material Ingredients (Material & Resources)