Green Roof Technology


What is your Green Roof system?

This is a question we hear almost daily. In fact, it is like asking an architect: “What is your house?”
Because architects are able to design any house – from tiny home to skyscraper, so we do with Green Roofs and Green Infrastructure.

Firstly, Green Roof systems are an assembly of different layers and all these layers together create the “system”.
Some companies offer pre-assembled systems (typically in plastic boxes, A.K.A. tray or modular systems). Others offer a specific variety of layers where a certain amount of Green Roof types can be tailored from. Lastly, some Green Roof companies have an exclusivity on a specific component. From there they create their marketing around to differentiate themselves. In addition, many add a “warranty” to attract more customers. Is that good enough to grow plants?

Our System

At Green Roof Technology we understood that every Green Roof is as unique as the location of the structure. Further unique is the design, the usage intend of the building, and the budget. In addition, it is obvious that a warranty or exclusivity on product does not help the plants. We do what is best for the plants and within the design intend. Likewise, architects design within a wide range parameters, so we do.

After all, you don’t needs us when you have prefab or Green Roof trays in mind. The same when your focus is on synthetic sponging elements or “innovative” products developed in space or similar. Also not in our focus are systems with excessive laboratory data sheets or misleading advertising.

Crafting Green Roofs for over 40 years added a substantial portion of experience and knowledge about products. In short, we feel the pulse plants. We know materials and components best suitable for any given design intend in any location on earth. Green Roof Technology’s of independence from manufactures and suppliers is legendary. Consequently, we are able to provide the highest value to our customers and building owners.

Green Roof systems

Schematic Overview of Available Green Roof Systems

Tray System

Plastic Boxes, ContainerOne size fits all
Only Extensive

Urbanscape sponging

Layered SE
Sponging ElementsSeamless from Wall to Wall
Mainly Extensive

Granular Growth Media

Layered GD
Granular DrainageSeamless from Wall to Wall, endless flexibility from extensive to intensive Green Roofs all on one area.Blue Roof Ready

Drainage Board System

Layered DB
Drainage BoardsSeamless from Wall to Wall with limited variations from extensive to intensive within one area
 Blue Roof Options

Klima Roof

Platform Based SystemContinues and seamless from Wall to Wall, highest flexibility from extensive to intensive within one areaBlue Roof ReadySolar Ready

Green Roof Systems

In general, there are five (5) typical Green Roof systems on the world market:

  1. Tray systems.
  2. Layered Sponging Element systems (SE).
  3. Granular Drainage, layered (GD).
  4. Drainage Board, layered (DB). 
  5. Monolithic Platform systems.

Obviously, in young Green Roof markets we see a preference tray systems, layered systems with sponging elements (e.g. Mineral Wool), and Layered Drainage Board systems. After all, young Green Roof markets are: North America, Australia, Middle and Far East, and U.K.. As a result there is still some groundwork to do because, of limited experience. Specifically, layered Granular Media Drainage systems are not very popular there. Although, such systems are around for more than a half century, with still millions of square feet existing. It seems people have more trust in plastic than in plant friendly porous materials.

Nevertheless, the Monolithic Platform-Based Green Roof systems cover this gap. Because this is the most flexible solution with readiness for Blue Green Roofs and Solar Garden Roofs.

Point of View:

To summarize, all Green Roof systems were developed for certain purposes, mostly of economic nature. In contrast stands flexibility to One-Size-Fits-All. Also, resilience, sustainability and biodiversity contrary to quick profits.

At Green Roof Technology longevity, the health of the plants, avoiding unnecessary components, and flexibility for the future have priority. In other words, clients can expect robust and honest engineering, a fresh breeze of common sense, and proven technology worth every penny.

Green Roof Systems

Most Used Green Roof Systems on the Market in Comparison
Tray System Sponging Element Granular Growth Media Drainage Board System Klima Roof
FEATURES / PROPERTIES / SPECS / OPTIONS Tray System Sponging Element System Granular Drainage System Drainage Board System Monolithic Platform System
Requires Instant Vegetation YES NO NO NO NO
Plugs, Cuttings, Seeds NO YES/NO* YES YES YES
Variable System Thickness NO LIMITED YES YES YES
Water Retention and Detention at 6″ MEDIUM HIGH MEDIUM MEDIUM HIGH
Air-to-Water Ratio is key for resilience ACCEPTABLE NOT GOOD PERFECT GOOD PERFECT
Saturated Weight at 6″ depth MEDIUM HIGH MEDIUM MEDIUM MEDIUM
Maintenance at 6″ depth HIGH MEDIUM LOW LOW LOW
Blue Green Roof Option NO* NO YES NO* YES
Solar Green Roof installation at later point NO NO NO NO YES
Overall Value 1= Bad 5= Best 2 2 4 3 5
* Depending on project size, availability, and specific system manufacturer’s customization options for fee-based upgrades.

green roof systems

Tray Systems

Manufactured and grown off-site often in greenhouses and mostly with cheap labor. Tray are always in a plastic or metal containers (sizes vary) for shipping that remain on the roof.

These One-Size-Fits-All containers/boxes are only required for easy growing the plants in a nursery. Additionally, the uniform box help with shipping (grown in the shipping box). However, once the container is on the roof, it has no real purpose anymore. It is considered unnecessary.

The installation of these heavy pre-planted boxes relies on a fixed grid or checker board. Because all planters limit the root spaces of plants and critical in-box drainage, the systems have a tendency to fail. This reduces life expectancy accordingly and replacements creates more trash than necessary.  Also, the high amount of unnecessary parts (that are only needed for shipping), such systems are questionable in regards sustainability and LEED ratings.

Patents of tray systems go back into 1970’s and they are common/public knowledge – most existing patents on trays are worthless.

Green Roofs and Mineral Wool

Layered Green Roof systems with sponging elements

installed directly on the roof and typically from wall-to-wall and in separate, single layers. Surely, this reduces double handling comparing to tray systems.

Sponging elements are typically Mineral Wool or thick layers of synthetic fabrics. Because sponging elements retain up to 95% of water, it makes them attractive for stormwater calculation and related marketing. Clearly forgotten with the use of sponging elements is the health of plants. Especially on extensive Green Roofs with succulents, drought resistant plants this is problematic. The wide range of Air-to-Water Ratio (95:5 – 5:95) creates extended and unnecessary stress on vegetation. Consequently, the plant diversity will change and unwanted plants dominate. In European long-term studies, systems with sponging elements failed in around 10-12 years and were replaced.

In short: The desperately search for optimizing stormwater DATA, eliminates the intention of having resilient nature on a roof. Smart roof drain controls are much more efficient and less costly.

Layered Green Roof systems with Granular Drainage Media:

also installed directly on the roof and ideally from wall-to-wall for the best protection of the roofing. Surely, this reduces double handling comparing to tray systems. After all, layered systems with Granular Drainage Media go back into the ancient world but also on patents from around 100 years ago.

The Rockefeller Center, NYC is the most famous layered Green Roof system with granular drainage media in North America. Although, constructed in around 1930, it still performs as intended without replacement. Also, without the use of plastics or metals, it is equivalent with some of our latest Green Roof solutions.

In 1977 Hans Gilgen (Optima) patented and improved this layered systems. Of course with a smart Blue Roof/Irrigation system, where the plants operate the irrigation on demand. Naturally, without electricity or Apps. We consider that as an Artesian System. Additionally, Hans Gilgen is mentor of Jörg Breuning Green Roof Technology. We are proud for having of the original documents (French/German). Layered artesian Green Roof systems with granular drainage work in all climate zones. Also, they are adaptive to climate change because they mimic the natural soil profile. The high performance granular components ensure the best growing conditions for the plants all time.

Layered Green Roof systems with Drainage Boards/Mats

installed directly on the roof and preferably from wall-to-wall for the best protection and function. In a world where plastic is cheap and with high profit margins, drainage boards and mats are flooding the green roof industry. Therefore, in our archives there are around 70 different types piling up. Unfortunately, only two handful of these meet the needs of plants or our criteria.

Especially in younger Green Roof markets most of these components have repurposed from other uses. In particular from vertical building drainage and so no good function for horizontal drainage under Green Roofs. Overall, not specifically engineered components are problematic for healthy growth of the plants. Likewise, sandwich components (where fabrics are combined with board) that are also problematic for recycling, reuse or repair. All Drainage Boards / Mats have to be cut to size on the roof. This creates additional waste and costs for Green Roof installations.

Although, Drainage Boards / Mats have great measurable, reliable drainage, retention and detention function, they also limit the rooting space for the plants. In short, Green Roof Technology has sufficient experience to decide when, where and what type of drainage/retention board is needed.  

Monolithic Platform-Based Green Roof systems

The latest 21st century generation of layered Green Roof systems. Such systems are installed directly on the roof and always from wall-to-wall for the best protection and function. The flexibility of Monolithic Platform-Based Green Roof systems is far beyond any other systems. Nevertheless, it combines century old traditions with modern requirements.

Platform-based Green Roof systems create a second roof deck above the roofing that can increasing structural capacity. Certainly, it maximizes the available rooting space for the plants. Although platform based systems use a limited amount of plastics, such comes from Urban Mining.  The skeleton of the platform acts as a protective structure during construction. Can be used for staging area for other trades and before the Green Roof goes in place.

From there it is a solid foundation for all Green Roof Types – even combined types in one area. The skeleton-like structure allows to secure solar panels, technical roof units, railings, micro wind turbines, and amenity items seamless and easy without penetrating the roofing. Monolithic Platform-Based monolithic Green Roof systems adjust to changing roof pitches and work from flat to sloped roofs (from 0-90 degrees!).

Monolithic Platform-Based Green Roof systems are Blue-Green Roof ready, work perfectly in any climate zone and adopt to climate change thus they last as long as the structure. See Klima Roof.

Over the last 4 decades and with the German evolution of modern Green Roof technology, Green Roof systems have developed further. Certainly, some systems are better for smaller application and other green roof systems are more efficient for large projects. Sometimes, a combination of different products can be the ideal solution.

Green Roof Technology is crafting Green Roofs from scratch for over 40 years because every roof is different. Also local climate conditions vary and the availability of materials. Especially, in regards of performance, installing costs, maintenance and efficiency a tailored solution is unmatched.

Ideally all green roof systems and green roof design comply with the FLL-Guideline and have to last as long as the building. Traditionally, German manufactures meet these benchmarks and with time we will see more resilient and sustainable systems worldwide, too.

Of course, we avoid using repurposed components on Green Roofs. These are components that were originally develop for other purposes (e.g. vertical drainage, erosion control, shipping container etc.). Such components often cause challenges for maintenance or other substantial problems in the years to come. Likewise, sponging elements. These are also considered as repurposed components (building insulation). Additionally these components affect the soil biology negatively and create an unnatural, over saturated soil horizon.

Tray or modular green roof systems are popular since the beginning of the American Green Roof industry at a time when Americans were trying to reinvent the wheel. Luckily many of these tray systems have been replaced by now and only for residential use. Thus, most of these plastic containers are used on small roofs or small retrofit roofs. Potentially a good thing and we will see.