Technological developments

 

 

 

 

 

 

 

 

 

 

 

 

 

It is important to understand how this engineered product supports long-term stability and stormwater retention performance in outdoor applications such as vegetated roofing. Needled rock mineral wool can be ideal for vegetated roofs, as it acts as a water reservoir and supports plant health, replaces heavy growing media, and performs exceptionally as a rooftop stormwater management tool throughout the lifespan of the vegetated roof.

3) Needled or binderless innovation

The most recent advancement in this industry is the manufacture of needled rock mineral wool—a non-petroleum-based and formaldehyde-free alternative. Products made this way are known as Needled Mineral Hydro Blanket, Cubes or Flocks. The needling process provides dimensional stability without the use of any binders—mineral wool is formed by a mechanical interconnection of pure mineral fibres. This process forms a structurally stable, lightweight, and porous material with longer fibres (Figure 1) that can maintain excellent water-holding properties. It is consistently hydrophilic, even after varying weather cycles throughout the year. The material can hold 90 per cent of its volume in water. When wet, the majority of the retained water is easily available for plants’ uptake. (This was tested by pH curve. The authors can provide data upon request.) A minimum of 10 per cent oxygen is left in the needled mineral wool, enough to support the oxygen levels in the root zone and, therefore, healthy roots. The material is inert, with chemically stable fibres. On the left side of Figure 1, the condition of fibres three years after installation is shown with soil particles attached.

 

 

 

The hydrophilic characteristics of the Needled Mineral Hydro Blanket can offer long-term stability, as nothing rinses away. The physical attraction between fibres and water remains the same throughout the lifetime of the product.  Binderless mineral wool offers hydrophilic characteristics that better support root growth and overall plant health, making particularly suitable for many vegetated roof applications, with long-term survivability in various climatic zones.

 

 

 

 

 

 

Needled or Binderless Mineral Wool is Ideal for Vegetated Roofs

• It is lightweight;
• It can supplement or, in some cases, replace heavy growing media;
• It can act as a water reservoir while supporting plant health;
• It achieves more credits under the Leadership in Energy and Environmental Design (LEED) program (The material contributes to eight additional points under LEED v4. These include credits in the Sustainable Sites [Protect or Restore Habitat, Open Space, Rainwater Management, and Heat Island Reduction], Energy and Atmosphere [Optimize Energy Performance], Materials and Resources [Environmental Product Declarations], and Indoor Environmental Quality [Thermal Comfort and Acoustic Performance] categories.); and
• It performs exceptionally and reliably as a rooftop stormwater management tool throughout the lifespan of the vegetated roof (as seen on Sweden’s Karolinska University Hospital, Rentenversicherung headquarters in Berlin, and various projects throughout Baltic and Scandinavian countries).

Needled Mineral Hydro Blanket comes in a roll and has a density of 286 to 319 lb/35 cf. It is also available as Hydro Cubes (0.8 x 0.8 in) and Hydro Flocks (0.1 to 0.8 in.) and is recommended for containers, patios, terraces and ground level landscaping applications. Cubes and flocks are added to a traditional growing medium and contribute to better soil structure, water-holding capacity, and aeration. The retained rainwater inside the Hydro Cubes or Hydro Flocks is easily available for plant uptake and improves plant survivability.

Research and analyses

As the needled manufacturing process does not require binders, it ensures the product’s natural hydrophilicity remains intact, making it highly reliable for long-term stormwater management performance in vegetated roofs (Figure 2).When it comes to long-term water absorption, research shows needled mineral wool (Hydro Blanket, Cubes and Flocks) designed for growing plants outperforms traditional horticultural RMW by up to three times. Water uptake (WOK) analysis is used to determine this. This method shows the velocity of water absorption in time for specific substrates. After saturating and drying out, the capacity of absorption is measured for 1500 minutes. The results show long-term water absorption of needled mineral wool for growing plants is 70 per cent, whereas traditional phenol-based horticultural mineral wool absorbs significantly less—between 20 and 35 per cent. (Water uptake analysis test method developed by Regeling HandelsPotgronden [RHP], Netherlands.)

 

As experience and numerous studies show, RMWs using binders are commonly recognized as products for hydroponic growing, and the needled or binderless type—due to its unique characteristics—is ideal for outdoor environments. For example, it can be used in vegetated roofs for significant improvement of stormwater performance and roof longevity in different climate zones. Research indicates RMW positively influences plant growth and development on vegetated roofs as well as in other applications. (From D. Majkovič et al.’s 2016 presentation, “Promote Vegetated Roof Stormwater Performance with Mineral Wool Layer,” from Cities Alive in Washington D.C. Also from C. Arkar et al’s 2015 publication, “Lightweight Green Roofs’ Thermal Response Under Freezing Conditions,” from Energy Procedia 78.) It also showed great potential in container substrates as an alternative growing medium in the 1990s. (The study that determined this can be found in W.C. Fonteno and P.V. Nelson’s Physical Properties of and Plant Responses to Rockwool-amended Media, published in 1990 by the Journal of the American Society for Horticultural Science.) Applications of the new generation of Needled Mineral Hydro Blanket confirms this finding. (See A. Šušek et al’s presentation from Ramiran 2015 at the Hamburg University of Technology, “The Impact of Rock Mineral Wool on Water Retention in a Conventional Growth Medium, and Development of Zonal Pelargoniums.”)

Vegetated roofs constructed with binder-free needled mineral wool are tested and have been applied in various climate zones from moderate to extreme. Going forward, the focus continues to be on stormwater performance in retention testing, where vegetated roofs with a needled mineral wool layer are compared to traditional, engineered-growing-media-based vegetated roofs. One stormwater testing laboratory in Virginia (Figure 4) uses custom technology to apply replicable computerized rain events mimicking real-life rain events to evaluate assemblies 80 sf in size. In Figure 5, the quantity of water retention and transient water is shown as measured on those samples in 90 minutes. Full and dotted blue lines represent the values for a vegetated roof with a binder-free needled mineral wool layer, which is nearly doubled in stormwater performance compared to a 4-in. vegetated roof with traditional engineered growing media only (shown with grey full and dotted lines in Figure 5). The mineral wool layer does not significantly affect the dynamics of the release, but strongly influences the quantity.

The second graph (Figure 6) indicates stormwater performance is equivalent between a 101-mm vegetated roof with a needled mineral wool layer to which 72 gal is applied after 90 minutes (again, shown with blue full and dotted lines) and a 8-in. vegetated roof without a mineral wool layer (with 68 gal applied after 90 minutes). Introducing the needled mineral wool layer on the roof leads to significant load savings and the possibility of applying this solution when retrofitting. (Mineral wool weighs approximately 10 times less than the same amount of soil.)

Conclusion

Technological developments in needled or binderless mineral wool over the last decade have focused on increasing water retention and maintaining long-term performance. Needled mineral wool’s characteristics better support root growth and overall plant health in various climatic zones, from hot and arid to frigid and wet, whether used in indoor applications such as urban farming or outdoor applications such as landscaping or vegetated roofing. Having been used in Europe for the past decade—with the largest projects being in Scandinavia, the Baltic States, and Germany—needled mineral wool has recently become available in North America, providing American designers and engineers a viable solution to landscaping in arid areas and increasing the stormwater management capacity on rooftops where this would otherwise be impossible.

PET STORMWATER TOOL

A performance evaluation tool developed in collaboration with the Laboratory for Sustainable Technologies in Buildings, University of Ljubljana, helps assess the real performance of a defined roofing system in any city in the world or in different climate zones. A software package was created from its results
Photo courtesy Knauf Insulation

To help design/construction professionals more effectively create vegetated roofs, various manufacturers are introducing new tools and software to the industry. In collaboration with the Faculty of Mechanical Engineering’s Laboratory for Sustainable Technologies in Buildings at the University of Ljubljana, Slovenia, one company has developed a performance evaluation tool as a result of a two-year in-situ performance study of different types of vegetated roof systems. This tool helps assess the real performance of a defined roofing system in any city in the world or in different climate zones.

The University of Ljubljana test and evaluation has been ongoing since 2014, and the initial two-year results have been used to create a software package intended to help current and potential users and owners of extensive vegetated roofs understand the real performance they can expect. As well as vegetated roofs’ stormwater performance, this software provides data on how such roofs can improve buildings’ energy performance and how they can reduce heat island effect.

Darja Majkovič is the head of products and applications in green solutions at Knauf Insulation. For nearly a decade, Majkovič was a researcher at the University of Maribor, focusing on agricultural economics and econometrics. Her work includes collaboration on numerous national and international research and development projects. Majkovič was a visiting researcher at the French National Institute for Agricultural Research (INRA) and a university lecturer, and has written more than 160 articles. 

Jure Šumi is the business development director at Knauf Insulation, leading several teams. These include “Urban Green Infrastructure,” which focuses on developing lightweight green roof systems for stormwater management, “Landscaping and Gardening,” which focuses on developing substrates and systems for water conservation in arid climates, and “Horticulture,” which focuses on developing environmentally responsible hydroponic alternatives. Šumi has more than 20 years of experience in business and market development for multinational companies in a variety of sectors. 

Cristina Senjug serves as the communications manager at Stormwater Capture Co.  

Stormwater Capture Co prides itself in being a hassle-free, one-stop-shop supplying vegetated systems that can be customized to local requirements, with warranty and maintenance support. We also offer ​access to a variety of analytical support service​s such as ​stormwater calculations specific to location ​and building/roof type.

We specialize in supplying green roof systems with​ high water retention-to weight ratio such as the StormCap system. Our premium base layers ​include​ the ​Needled ​M​ineral ​H​ydro ​B​lanket and can be easily cut to fit any shape and design.​

Contact us 855-786-7626 or send drawings to info@stormwatercaptureco.com get an estimate for your project.

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