Mineral Wool In Green RoofsMay 2015, revised August 2015 v3

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SummaryIncreasingly, North American stormwater regulations require rainfall to be managed within the property lines of any given development. In the urban setting, where virtually the entire site is consumed with structure, the rooftop is often the only available place to manage stormwater. Therefore, maximizing retention capacity of green roofs is paramount, and relying on aggregate media to perform that function is – to be blunt – inefficient. Water retention within the green roof profile can be greatly enhanced with alternative materials that complement aggregate media. The aim of this paper is to provide compelling evidence that validates mineral wool in green roofs utilizing case studies and test protocols designed to simulate green roof conditions. This paper also includes some guidelines for best practices in the use of mineral wool in green roofs.

Mineral wool is a renewable resource with qualities that are highly desirable in green roofs, including high water retention, low weight, durability, dimensional stability, and excellent horticultural properties.Mineral wool has been successfully used in German green roofs for the past three decades and continues to be used in green roofs today throughout Europe and China. Despite mineral wool’s long and successful history overseas, it remains underutilized in North America. Many specifiers are unfamiliar with its use in green roof assemblies. With deeper appreciation of its history and use, these concerns should shift to comfort. Equally, the change to emergent technologies has the potential to upset established market forces and trigger efforts to sow fear, uncertainty, and doubt; however, this paper uses evidence and data to define mineral wool’s performance in green roofs.

ContentsSummary .............................................................1Conclusions .........................................................2 History & Context ................................................3Lightweight ..........................................................5High Water Retention .........................................6Dimensionally Stable ...........................................8Reliable Horticultural Medium ..........................12Best Practices ....................................................13Sources ..............................................................14Errata .................................................................16

AppendicesA. Active Monitoring .........................................A1B. Dry CycleTests ...............................................A3C. Flow Cycle Tests ............................................A7D. Pedestrian Impact Tests ..............................A10E. Calibrated Impact Tests ...............................A16F. Water Quality Tests ......................................A26G. Magnified Images .......................................A32

Special Thanks To Matthias Fischer, Dipl.-Biol., Bonar Xeroflor GmbHKaren Liu, PhD., Bonar Xeroflor GmbHClayton Rugh, PhD., Xero Flor America, LLCLouis Pilato, PhD., Pilato ConsultingThe entire team at Furbish, whose efforts made this report possible.

Authors Brad Garner, Furbish Company, LLCMichael Furbish, Furbish Company, LLC

Figure S.1. 20-year old mineral wool below Sedum mat in Germany

Furbish :: 3430 2nd Street, Suite 100 :: Baltimore, MD 21225 :: 443.874.7465 :: www.furbishco.com

© Furbish 2015. All Rights Reserved

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Absorbent Mineral wool is a high efficiency stormwater retention component.

Lightweight Mineral wool has a very low dry weight, allowing the green roof assembly to be lightweight.

Horticultural Mineral wool is an excellent horticultural medium in green roof applications.

Stable Mineral wool is dimensionally stable in densities as low as 8 pcf, optimally 10-12 pcf. Mineral wool retains material integrity for at least 30 years in exterior applications, likely far longer. Use of a phenolic resin binder is likely to improve dimensional stability.

Durable Mineral wool tolerates the level of foot traffic that can be expected in green roof applications, exhibiting long-term resiliency to short-term cyclic compression.

Clean Mineral wool is chemically stable when unbound or bound with phenolic resin. Runoff from mineral wool exceeds the EPA’s standards for drinking water.

Renewable Mineral wool is a renewable material, utilizing dolomite or basalt - some of the few renewable rocks, and/or slag - a waste stream product.

Conclus ionsMineral wool is a super-absorbent, lightweight material ideally suited for some green roof assemblies.

Mineral wool has three decades of proven success and durability in green roof applications.

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Mineral WoolMineral wool can be described as “cotton candy rock” as the material is formed of molten rock – commonly basalt or slag – spun into thin fibers resembling cotton candy. The spun fibers are typically mixed with a binding agent, compressed to a given density, and cured in a furnace. Due to a very high air void ratio, mineral wool has excellent insulative properties, and thus its most common usage is insulation, and soundproofing. Mineral wool is naturally hydrophilic, but its fibers may be coated with oil to render the material hydroscopic (water-repelling) for use as insulation or sound attenuation. Mineral wool possesses excellent fire-proofing properties as either a hydroscopic or hydrophilic/hydroponic material. A video explaining more about mineral wool manufacturing can be found here.

Slag wool, a form of mineral wool produced from slag, was first discovered in 1840 in Wales. After several production refinements, mineral wool was first produced commercially in Germany in 1871, and became a very common and high-performing insulation material, and was also used in horticulture.

Invention of The Extensive Green RoofFrom the late 1970s to the mid 1980s, the modern green roof was developed in Germany, differing from historic vegetation-on-structure efforts and rooftop gardens, in that extensive green roofs perform a wide variety of functions efficiently and reliably in a very thin profile.

One inventor who was instrumental in the development of the first extensive green roofs is Wolfgang Behrens; after developing innovative green roof technologies for the German government in the 1970s, Behrens founded Xero Flor, now a division of Bonar. From the 1980s until recent years, Behrens obtained numerous patents for green roof systems that take advantage of the properties of mineral wool. Mineral wool is a lightweight material with a very high volumetric water retention capacity and high compressive strength, characteristics which Behrens capitalized upon. As the German green roof industry developed through

H istory & Contextthe 1980s, a few other companies explored using mineral wool in their green roof assemblies, but some of Behrens’ early patents were so broad as to virtually preclude any competitors from using mineral wool in green roofs.

Possessing excellent properties that make it an important component in several green roof systems, mineral wool has an excellent 3-decade track record of success in green roofs throughout Europe, and more recently in North America and Asia.

Diversification and Standardization As the German green roof industry grew, Xero Flor and other companies - notably Zinco and Optigreen - developed different types of green roof systems. This type of industry diversification is often beneficial to the consumer, as a wider range of choices is available to suit different needs. Extensive green roof profiles that were developed and are used today generally fall within a few broad classifications:• Lightweight aggregate over a composite drainage

course (called “single course” by the FLL),• Lightweight aggregate over a drainage aggregate

course (called “multiple course” by the FLL or commonly “dual media” in the US), and

• Mineral wool which might or might not be used in combination with a lower composite drainage layer and upper media layer (classified by the FLL as “single course”).

For purposes of this report, the first two types listed are referred to as “aggregate-based” green roofs.

In 1975, the German FLL Guidelines were developed; reflective of industry diversification these guidelines are regularly updated to address quality control and best practices for a wide range of assembly and material types. The FLL classifies mineral wool as a “substrate board” (page 69 of 2002 English version).

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North American IntroductionExtensive green roofs first arrived in the US around 1995-1997. However, adoption was slow, and prior to the late-2000s, extensive green roofs were fairly rare in most North American cities, but are becoming increasingly more common throughout the mid-Atlantic, Toronto, Vancouver, Chicago, and in many other urban areas.

US Market Growth and Diversification As the US green roof industry has grown, its path has been different from its European predecessors. Unlike in Europe, the US green roof industry is dominated by roofing and waterproofing manufacturers, most of whom are using variations of systems espoused by Roofmeadow, Optigreen, or Zinco - i.e. systems that achieve water retention primarily via aggregate media.

However, US industry diversification is beginning to occur, primarily in response to recent stormwater regulations. Whereas most extensive green roofs easily hold a 1-inch rainfall, now green roofs are being asked to retain 2- and even 3-inch rainfalls, which is not easily accomplished using aggregate-based green roof systems common in the US. In 2012, Baltimore-based Furbish introduced EcoCline, which utilizes mineral wool. Around the same time, Vegetal ID, a French green roof company, responded to the North American stormwater market with their

Early pioneers of the North American green roof such as Charlie Miller of Roofmeadow gravitated toward an extensive green roof profile of lightweight aggregates over either an aggregate drainage course or a composite drainage sheet. Those profiles are also preferred by Optigreen and Zinco, German companies who competed against Xero Flor, and did not utilize mineral wool. Both Zinco and Optigreen began doing business in North America in the late 1990s. Xero Flor did not join the North American market until the mid-2000s. So the North American green roof industry began without any parties utilizing mineral wool in green roof systems. Xero Flor is currently using mineral wool in Canada, China, and Europe, and some locations within the US.

Figure 1. Bus station in Oldenburg, Germany; a twenty-year-old green roof system utilizing mineral wool.

high efficiency Stock-and-Flow green roof system which utilizes a plastic storage reservoir at the base of a modular green roof assembly. Both EcoCline and Stock-and-Flow adapt and leverage established European technologies to better respond to North American needs, and other innovations are sure to follow. The North American green roof market is now beginning to mature and diversify, benefitting owners and specifiers with greater options; the use of mineral wool is simply one example of that diversification.

UsageMineral wool is used in European green roof assemblies by Xero Flor, Knauf, Nophadrain, De Boer, and likely others. In the North American market mineral wool is available in green roof assemblies by Xero Flor, Knauf’s Urbanscape, and Furbish’s EcoCline.

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Mineral wool is a lightweight, durable construction material.

Mineral wool is an excellent material for retaining high volumes of water on a roof, but with minimal weight. It is an open fiber matrix that is typically over 90% void space. The fiber matrix has a very low weight, but voids within the matrix fill with water, which the fibers retain via capillary action, yielding a saturated weight that is only slightly higher than the weight of pure water.

Due to its low dry density, mineral wool should typically be protected from wind uplift. See “Best Practices” for more information.

Mineral wool at 8-14 pcf

Lightweight Green Roof Media

Dry Lbs/sf at 1 inch thick

0.67-1.17 4.5 +/-

Wet Lbs/sf at 1 inch thick

5.5 +/- 7 +/-

Lbs of water at 1 inch thick

4.5 +/- 2.5 +/-

L ightweightRenewable and RecycledMineral wool is a renewable material, commonly made from dolomite, basalt, and/or slag. Slag is a waste stream byproduct of steel manufacturing, and dolomite and basalt are igneous (volcanic) rocks that are abundantly naturally re-curring worldwide.

Mineral wool is a lightweight material, so shipping mineral wool uses less fuel than transporting aggregates. Other energy use concerns related to mineral wool are transportation of the base material to the manufacturing plant, and energy used to fire the rock. Most mineral wool manufacturers are actively working to reduce energy usage, reduce reliance on non-renewable energy, and to be transparent in their sustainability efforts via documents such as the NAIMA EPD Transparency Summary.

Cradle to CradleSome manufacturers have active programs of reclaiming used mineral wool for recycling as a raw material in manufacture of new product. Re-use may also be possible: if the material retains high tensile integrity (as evidenced in Appendix H), intact green roof slabs may be able to be transported and re-used. If the mineral wool exhibits lower tensile integrity, fibers and media can be blended for use in planters or landscape applications or as a potting medium.

Figure 2. Wet and dry weights of various grades of mineral wool. The vertical axis is pounds. The horizontal axis is wet/dry cycling trials described in Appendix B.

Table 1. Comparative wet and dry weights of mineral wool vs. lightweight aggregate green roof media.

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Naturally hydrophilic, mineral wool predictably and efficiently retains water.

Mineral wool typically possesses a maximum volumetric water capacity (VWC) of 80-94% when tested per ASTM E-2397. When monitored in field conditions, actual water retention reliably peaks to over 70% VWC, and has been field-documented to retain up to 94% VWC, an extremely high retention efficiency for green roofs.

It is unlikely that any commercially available lightweight aggregate green roof substrate would have VWC above 25% except immeditately after a rainfall. This is likely due to the fact that green roof aggregate medias are designed to drain very rapidly in the field, but ASTM E-2399 tests the media’s ability to retain water after being fully saturated, a condition that is unlikely to occur on most green roofs.

Research conducted at the University of Maryland included measurement of VWC of two of the leading brands of green roof media in the mid-Atlantic. In multiple tests, one such media was documented to have VWC of approximately 25%, and during Hurricane Sandy, the media peaked at a VWC of 30% (Griffin 2014). In other research including a second leading brand of green roof media, the media was documented to have between 25-30% VWC immediately after watering (Starry 2013).

Conversely, mineral wool that has been tested to retain 94% VWC per ASTM E-2397 (the corallary to E-2399 for fibrous materials) has been documented to retain up to 94% VWC in the field. Mineral wool’s extremely high efficiency is likely due to the fact that mineral wool rapidly absorbs rainwater, and generally only drains once the material approaches saturation, versus lightweight aggregate, which absorbs water more slowly and drains very rapidly.

High Water Retent ion

Material

VWC perASTM E-2397-9

VWC as Field-Verified

Field-Verified VWC / ASTM E-2397-9 VWC

LWA 35% 20% 57%LWA 45% 25% 55%LWA 65% 25% 38%MW 94% 85% 90%MW 94% 94% 100%

Table 2. Comparative VWC of lightweight aggregate (LWA) and mineral wool (MW) when tested after saturation per ASTM E-2397 or E-2399, contrasted with field-verified VWC.

Appendix A describes monitoring of a 20,000 SF installation of EcoCline in Washington, DC, utilizing a 2-inch layer of mineral wool. Monitoring, performed in cooperation with the University of Maryland, reveals that mineral wool very effectively both captures and releases stormwater. Rainfall fills the mineral wool to approximately 70-80% VWC, then VWC quickly drops to approximately 30-50% over a few days, then continues to draw down to approximately 20% over the course of a week. Nearly all reduction of VWC can be attributed to evaporation and evapotranspiration, as visual monitoring of drains reveals negligible flow of gravitational water after rain events. Drawdown of VWC occurs during all seasons of the year.

The project monitored in Appendix A included ten sensors, some of which measured VWC as high as 94%. Data presented averages all ten sensors together, including sensors at the top and bottom of profile, and sensors at highpoints and lowpoints of the roof.

Re-wettabilityFurbish simulated 20 years of saturation/desiccation cycles, simulating worst-case rewettability scenarios of full desiccation of the mineral wool annually, per Appendix B. These tests, performed on mineral wool bound with phenolic resin, indicate no significant loss in material rewettability resultant of wet/dry cycling. Various informal field measurements of mineral wool taken from 2012 to 2015, and various European applications sampled in 2015 support this data, as noted in Appendix H.

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Field monitoring as described in Appendix A demonstrates precisely measured, reliable re-wettability of mineral wool over the course of 17 months; further Appendix A indicates that volumetric water content does not frequently drop below 10% or approach desiccation. An antecedent moisture content (AMC) of 10%+ provides significant water to plants between rain events, and is high enough to ensure a very high degree of absorption during the following rain event, preserving maximum hydrophilia, as AMC is an accurate predictor of a green roof’s capacity to retain the next rainfall. Figure 3 illustrates mineral wool’s highly efficient retention characteristics.

Figure 3. Volumetric water content (orange line) and rain events (vertical blue bars) for July - September 2014. Left axis is VWC expressed as percent of total volume. Right axis is total daily inches of rainfall. Horiztonal axis is time. See Appendix A for full details.

“Our desire is to develop systems that perform as efficiently as nature would on its own.”

~ Michael Furbish

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Dimensional ly StableIntegrityThe basic material of mineral wool is highly durable rock, typically basalt, dolomite, or slag. The rock is blown into fibers that are compressed to a given density. Mineral fibers are compressed tightly in bats or boards that are easily handled while maintaining an open fiber structure. Mineral wool is typically used within some containment (in green roof applications, usually

Mineral wool has a high degree of dimensional stability when manufactured at a high density with an appropriate binder and appropriate installation handling.

Narrowly focusing on physical performance of mineral wool under stresses common in green roofs, and understanding that empirical results will yield the most useful information, Furbish focused on physical testing and case studies, documenting variables in density and binder, versus detailed documentation of fiber structure or production techniques. Interestingly, Steponaitis and Vejelis note that “compressive stress decrease[s] with increasing thickness of mineral wool boards” and “It can be assumed that deformation in mineral wool products is distributed unevenly. In weaker layers deformation is very high, and in stronger layers the deformation is very small.” Though claims of increased thickness have not been included in Furbish’s tests to date, there is a possibility that thicker installations of mineral wool will be even more resilient than thinner installations.

perimeter containment and below at least one other layer of material), and as such separation of fibers is not a significant threat to material integrity. Mineral wool examined in exposed and covered applications, after two to three decades of exposure to the elements, show a high degree of fiber structure integrity, similar to new material.

StrengthFurbish has performed several tests on the deformability and elasticity of mineral wool in green roof applications, per Appendices D and E. Though these are not exhaustive tests designed to determine the ultimate strength of mineral wool or document exhaustive product characteristics of mineral wool, these tests present results consistent with Steponaitis’s and Vejelis’s statement “The mechanical characteristics of mineral wool slabs are subject to structure, density of material, percentage of binder in product, as well as production techniques.” Steponaitis and Vejelis go on to explain that “The structure of thermal insulating materials is complicated and the skeleton structure of fiber is difficult to describe mathematically. Therefore, such investigations are usually restricted to assessment of empirical dependencies between certain thermal-physical or physical-mechanical properties.”

Figure 4. One-inch 8 pcf mineral wool on an EcoCline project in Washington, DC. This measurement is taken approximately 18 months after installation at approximately 1.125 inches, representing 13% expansion, a common phenomenon. Minor expansion and contraction can be expected of this elastic material.

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DensityFurbish researched and tested densities of 2 pcf (pounds per cubic foot), 4 pcf, 8 pcf, 12 pcf, and 14 pcf. The most common density used in European green roofs is 8 pcf, as lower densities exhibit noticeable compression under light foot traffic. Laboratory testing and documentation of two- and three-decade-old roofs in Germany reveal that 8 pcf mineral wool bound with phenolic resin is highly resistant to compression in the absence of foot traffic, and subject to 15% to 35% compression when subjected to high levels of foot traffic. Laboratory and field tests of 8 pcf mineral wool produced with no chemical binder reveal that 8 pcf mineral wool compresses by approximately 25%, but with some noticeable rebound.

Case StudiesAppendix H, Table H.1 summarizes observed density in several case studies. Furbish is actively monitoring thickness/density in several installations not listed, and all those installations are performing similarly. In all projects summarized, the initial density of mineral wool was nominally 7.9-8.0 pcf. In older projects not subject to much foot traffic, expansion of the material was observed in places, yielding effective densities as low as 5 pcf. In projects subjected to low or moderate foot traffic, effective densities remained approximately 8 pcf, or as high as 10.5 pcf. In areas subjected to very high foot traffic, effective densities reached as high as 12.2 pcf. Long-term project monitoring illustrates that 8 pcf is an acceptable density for most green roof applications, but that 12 pcf is a more appropriate density to reliably guarantee volumetric retention and thus stormwater retention. Dimensional changes observed in case studies are typically fractions of an inch, and all test data indicates that full stability is reached when using material in the range of 12 pcf.

Laboratory TestsIn advance of industry-standard test protocols to accurately measure and predict the dimensional stability of mineral wool in exterior applications, Furbish designed and performed tests to determine mineral wool’s resistance to compression over the expected life of a green roof. The predominant threats to mineral wool’s dimensional stability are media weight and pedestrian impact.

Long-term weight of media was not tested due to the following observations: Mineral wool is primarily used to augment the water retention capacity of thin-profile, extensive green roofs, therefore it would be used in conjunction with media of 0 inches to approximately 4 inches thick, which would typically weigh no more than 30 lbs/sf. After manufacture, before shipping to jobsites, high density (8 pcf or higher) mineral wool is stacked and pelletized such that the bottom layers of material may be subjected to several weeks or months of several hundred lbs/sf, with no measurable compression. Further, two- and three-decade-old German green roofs that have areas with as much as 2 inches of media exhibit the same compression as areas with 0 inches of media. Further, pedestrian impacts present far greater force applied to mineral wool at approximately over 800 psf. Therefore, additional testing focused on resistance to compression under the highest applied forces: pedestrian impact.

Tests were performed to simulate 37.5 and 45 years, which roughly correspond with the expected service life of a commercial roofing membrane under a green roof. Tests indicate that the anticipated compression rate is approximately 10% over 40 years, when using a 12 pcf or 14 pcf mineral wool bound with phenolic resin. A compression rate of 10% is likely very conservative due to the following observations:• Two- and three-decade-old 8 pcf mineral wool,

installations stabilized at effective densities of as low as 5 pcf, indicating that in the absence of continuous pressure, mineral wool may expand slightly.

• Two- and three-decade-old 8 pcf mineral wool, installations stabilized at effective densities not typically higher than 12 pcf, indicating that initial densities of 12 pcf may not be subject to any long-term compression.

• Tests were performed with compressive forces applied in rapid succession, without allowing the material time to rebound. Mineral wool has well documented elasticity, and thus would likely rebound between compressive forces over extended periods of time, versus the concentrated forces applied during testing.

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Binders

Inert phenolic resin binders safely improve the properties of mineral wool. Most mineral wool is manufactured with a binder that holds the fibers together and greatly improves dimensional stability as noted by Steponaitis and Vejelis, and also by Gardziella, Pilato, and Knop, and as supported by tests in Appendices D and E and observations in Appendix H.

The most common binder, phenolic resin, technically known as phenol formaldehyde (PF), is a product that is completely safe for use in green roof applications. See Appendix F for water quality tests.

Runoff from PF-bound mineral wool exceeds the EPA’s standards for safe drinking water. Phenol, the primary component of PF, is used in cough drops, throat lozenges, mouthwashes, and pharmaceuticals. Though formaldehyde is a component used to manufacture PF, the finished product of PF has negligible free formaldehyde, as formaldehyde binds tightly with phenol to form a new compound. The tightly bound formaldehyde in PF is no more available than toxic chlorine is available in table salt (sodium chloride, NaCl).

PF is a stable, inert, non-toxic compound present in many common household items and construction materials, including floral foams, plywood, dishware

such as Bakelite, laminated veneer lumber (LVL), glulam, fiberglass and mineral wool insulation, spray insulation, plastic toys and figurines, laboratory countertops, billiard balls, firefighter protective gear, and gaskets for furnaces and ovens. PF is a highly durable, waterproof, inert industrial plastic with excellent chemical- and flame-resistant properties that make it an invaluable component of so many useful products. PF has a long track record of resistance to the elements. PF is used extensively in engineered lumber, particularly for exterior applications due to the materials excellent resistance to water, wetting and drying cycles, temperature extremes, and biological degradation.

Binders are typically sprayed onto mineral wool fibers and perform like spot welds at fiber intersections, rather than coating fibers uniformly. In order to be sprayable, PF is diluted with water and urea into a sprayable form. The diluted (extended) product is then known as “urea-extended phenol formaldehyde” (UEPF). UEPF is by far the most common binder used in mineral wool, particularly in Europe when green roofs first began to use mineral wool.

UEPF is a stable diluted form of PF. UEPF retains the same properties of the parent PF when appropriate urea concentrations are incorporated; however, if urea concentrations are too high a loss of strength can occur, resulting in loss of compressive strength and dimensional stability.

In addition to improving the sprayability of PF, the introduction of urea to PF greatly helps to reduce formaldehyde emissions at the manufacturing plant, per Pilato “depending upon the P/F ratio, the

The following laboratory compression tests were performed:• Simulation of 45 years of actual foot traffic by

workers, per Appendix D, and• Simulation of 37.5 years of foot traffic, using

calibrated compression device, per Appendix E.

Similar Product ApplicationsGreen roofs are not the only exterior applications that utilize mineral wool, as some manufacturers are offering high-density sub-grade mineral wool products. Roxul’s DRAINBOARD® is available in 8 pcf and 11 pcf densities and has been used in Denmark for 35 years, successfully intact, and virtually unaffected by compression.

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reaction mixture upon condensation contains 5-15% unreacted formaldehyde,” therefore scavengers, such as urea, are added to the P/F mixture, to minimize the free formaldehyde level.

The Rockwool Group, the makers of Roxul insulation, note: “The [binder] compounds are used in a fixed or ‘cured’ form, so they are not emitted from the product. Studies show there is no appreciable increase in the levels of formaldehyde in buildings where Rockwool insulation is used and thus does not represent a risk to the health or well being of occupiers nor has it any negative impact on the indoor climate. Tests confirm that Rockwool products meet the most rigorous standards in Europe classifying the release of formaldehyde.”

UEPF meets strict European Union standards for environmental quality in green roofs. LEED v2.2’s EQ Credit 4.4 allows PF, commonly used in interior applications such as hard-surface countertops, and melamine formaldehyde (MF), commonly used in plastic laminates, as both MF and PF are highly stable with negligible free formaldehyde. Conversely, as formaldehyde is less tightly bound in the less stable UF, LEED’s EQ Credit 4.4 precludes the use of UF.

Mineral wool’s compression resistance and long-term durability is determined principally by density, and secondarily by binder. As UEPF is less rigid than undiluted PF, mineral wool bound with UEPF with a urea concentration of approximately 1-3% per mass has exhibited continued elasticity and resistance to compression over three decades of use, particularly at a density of at least 8 pcf.

A variety of binders other than UEFP are used in the mineral wool industry, including sodium silicates, polyesters, melamine urea formaldehyde, polyamides, and furane-based resins. Key differences between PF and urea formaldehyde (UF) are worth noting. UF is commonly used as a coating for slow-release fertilizers. UF is easily decomposed within the temperature range of 70-90 degrees Fahrenheit by microbes common in

most soils, such as Ochrobactrum, rendering UF an unstable binder to use in conjunction with mineral wool in exterior roof applications that demand long-term dimensional stability. UF is also commonly used in several engineered wood products that are not typically exposed to moisture, such as particle board. UF is relatively unstable and is subject to offgassing of free formaldehyde. Due to offgassing concerns, LEED and other environmental rating systems and regulations are actively working to remove UF from interior environments. UF is not recommended as a binder for use in mineral wool in green roofs.

Several companies are actively using or investigating the use of non-petroleum-based and formaldehyde-free binders. At the time of publication, the authors are unaware of availability of binders other than PF that have demonstrated stability in the exterior environment; however, future technologies will likely produce viable alternatives to PF.

Appendix A includes monitoring data for one installed project using UEPF-bound mineral wool, documenting the material’s excellent retention and rewettability.

Appendix G compares 40x magnified images of UEPF-bound mineral wool fibers of new material with fibers exposed to 3 years of weathering; no discernible differences are present.

Appendix H documents two- and three-decade-old mineral wool in green roof applications, which has physical characteristics nearly identical to new material.

Appendix F documents water samples collected from a 3-year old green roof sample using mineral wool bound with UEPF. The water collected exceeded the EPA’s safe drinking level for formaldehyde by 200 times and for phenol by 12 times.

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Mineral wool has been used as a horticultural growing medium almost as long as it has been used as insulation. Companies such as Grodan specialize in production of mineral wool media for nursery, greenhouse, and crop production. The most common type of binder used in mineral wool, phenolic resin, also has a long history of horticultural use; phenolic resin is an inert plastic used to create floral foam, a ubiquitous green foam found in floral arrangements.

Re l iable Hort icu l tura l MediumWater held in pore spaces between mineral fibers is readily available to plants. As plants absorb and evapotranspirate water, volumetric water content (VWC) drops to approximately 20%. Though short-term VWC is very high after a rain, thirsty drought-tolerant plants “stock up” on water and the air-to-water ratio returns to approximately 50%/50% quickly after a rain, as documented in Appendix A, and as evidenced by healthy vegetation observed in Appendix H.

Mineral wool can be very valuable on a green roof not only for stormwater retention, but for plant irrigation between rain events, increasing the viability of rooftop vegetation and possibly increasing the potential for a diverse plant palette even in a very thin profile. For example, as mineral wool’s VWC is typically between 20% and 50% when used in the eastern US, plants are supplied with abundant water to fuel growth, versus most aggregate green roof medias which only retain a maximum of 25% VWC, even when ASTM tests report higher VWC (Starry), and which rapidly drain below 10% VWC.

Mineral wool is commonly used in living wall applications, such as the Sage Living Wall and Sempergreen’s Flexipanel, both of which are used in interior and exterior applications.Handreck and Black document the components of growing media as:• mineral particles - the inorganic

fraction,• organic matter, the remains of

living organisms,• water, the ‘soil solution’ in

which nutrients for plants are dissolved,

• air, which fills the space between solid particles not filled with water, and

• living organisms, smaller animals and microbes.

Once some organic matter is added to mineral wool, and the material is exposed to naturally abundant microbes, mineral wool meets all relevant criteria for growth media.

Mineral wool is highly root permeable and absorbs up to 94% of its volume in water.

When used as part of a green roof assembly, mineral wool is typically used as a water retention layer, water retention and drainage layer, or sometimes as the surface growth media. Appendix H documents green roofs with no media or soil above the mineral wool, a configuration which has reliably supported vegetation for decades.

Figure 5. Young, healthy vegetation on a newly installed green roof utilizing mineral wool

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Best Pract ices

Figure 6. Cross-section of EcoCline profile, illustrating mineral wool as a component within a complete system.

Mineral wool can be a valuable component within a green roof assembly when used according to best practices. As is the case with most construction materials, context, application, and handling are important variables.

Compatibility When selecting any green roof system, select a system whose components have been engineered to work together. In the case of mineral wool, select a green roof system that has been developed and tested to perform as intended with mineral wool as a component; simply adding mineral wool to a green roof profile without testing may lead to unexpected results. Manufacturers of mineral wool green roof systems consider how the mineral wool will interact with underlayment layers and surface layers to engineer appropriate air to water ratio, drainage, nutrient availability and wind resistance.

Nutrient Although mineral wool is an excellent water retention and rooting media, mineral wool possesses negligible cation

Wind ResistanceThe current US wind-resistance standard, ANSI/SPRI RP-14 is primarily written around aggregate-based green roof systems, as the standard is based primarily on ballast or dry weight of the media. Manufacturers of mineral wool based green roofs may have wind resistance ratings based on actual wind testing versus a calculated ballast rating. Specifiers should understand the manufacturer’s wind rating and specify accordingly.

exchange capacity (CEC), a measure of the material’s ability to absorb nutrients and make them available to plants. Typically mineral wool should be utilized in conjunction with components that provide CEC or used with plants that require little nutrient. As plant roots penetrate the mineral wool, organic matter may accumulate within the fibers and provide increased CEC as the system matures, as shown uncovered mineral wool in Appendix H.

Mineral Wool (water retention and drainage layer)

Filter Fabric

Aggregate Media(nutrient layer)

Aggregate Media(weed suppression layer)

Vegetation

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Density Use a mineral wool with a density of at least 8 pcf, preferably 12 pcf if the roof will be subjected to much impact. Ensure that the mineral wool utilizes a binder that has demonstrated stability, or material that has proven stability without use of a binder. Binders technology is likely to change and improve over the next few years.

TrafficAs with any green roof, avoid vegetating areas subject to frequent foot traffic; frequent may be defined as more often than once weekly. Design pedestrian access routes and pedestrian spaces such that the weight of the pedestrian is not transferred to the mineral wool in order to provide stable, level pedestrian surfaces and prevent unnecessary compression of the mineral wool. Mineral wool has adequate compressive strength to support the occasional maintenance worker, but not enough to support frequent pedestrian impact or to level pavers.

InstallationWhen installing, wear protective clothing, similar to insulation installers. Mineral wool may cause itching, which is often best managed by wearing long sleeves and showering soon after handling. Mineral wool is lightweight and easily handled dry, but is difficult to handle when wet, so keep it dry until it is in place. Once installed, minimize construction impact over the installed mineral wool, and cover as soon as practical. Ballast the same day as installation.

Figure 7. Mineral wool installed before covering with media and filter fabric.

Plant Selection Select plants that will thrive in a mineral wool green roof. Mineral wool provides greater water availability to plants than aggregate-based green roofs, which can be a blessing - potential for broader plant palette - or a curse - potential for high weed pressure. Low maintenance green roofs should be designed to provide a certain amount of “stress” to plants to minimize competition and slow species succession. Stress within aggregate-based green roofs is predominantly created via very dry conditions. Stress within European mineral wool green roofs has traditionally been created by utilizing an ultra-thin profile. EcoCline utilizes a harsh media in conjunction with mineral wool in order to suppress weeds and minimize species competition, even within deep mineral wool profiles designed to manage high volumes of stormwater. Mineral wool green roofs are typically around 1 to 3 inches thick, yet support Sedum and similar vegetation that would otherwise require approximately 4 inches of media in a comparable climate zone. As system thickness increases, without some other constraint, higher maintenance plants can easily outcompete Sedums in surprisingly thin profiles.

15

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17

Errata The original publication of Mineral Wool in Green Roofs, dated May 2015 listed Whitney Griffin, PhD., as a contributing author of this report. Dr. Griffin was instrumental in the work of Appendix A; however, upon further review, Dr. Griffin’s contributions are not extensive enough to warrant co-authorship, so her name is removed as a contributing author.

Page 6 was amended to more accurately cite the research conducted at the University of Maryland.

The list of sources was updated to correct the citation date for Dr. Starry’s dissertation.

Appendix 1 was amended to more specifically identify the roles of Furbish and the University of Maryland in this resarch.

A1

Furbish is actively monitoring one green roof in Washington, DC that utilizes mineral wool.

Conclusions • Mineral wool efficiently absorbs rainwater, with

retention nearly matching rain amounts, creating negligible runoff until reaching approximately 80% volumetric water capacity (VWC).

• Water held in mineral wool is available for evaporation and/or evapotranspiration, as evidenced by quick drawdown of VWC without the creation of runoff.

• Between rain events, mineral wool possesses a VWC and air-to-water ratio that is documented to be favorable to a wide range of plant species.

• Mineral wool’s retention performance is consistent through time.

Test ProtocolsMonitoring equipment was installed in November 2013 in cooperation with the Department of Plant Sciences at the University of Maryland. The monitoring package consists of a weather station and green roof system monitoring. The weather station consists of an ECRN-100 High Resolution rain gauge (±0.2mm accuracy); PYR total radiation sensor; VP-3 relative humidity, temperature, and vapor pressure sensor; Davis Cup anemometer (wind speed and direction); and LWS leaf wetness sensor (all supplied by Decagon Devices, Pullman, Washington). The green roof system monitoring consisted of ten 5-TM soil moisture probes (Decagon Devices, Pullman, Washington) inserted into the mineral wool layer. Sensors were placed evenly across a single drainage area of the roof to account for wet spots near the drain and drier spots away from the drain. All data were logged and transmitted by Em50G wireless cellular data loggers (Decagon Devices, Pullman, Washington). Analysis of collected data was prepared by Furbish.

Test ResultsFigure A1.1 plots rainfall and volumetric water retention from November 2013 to April 2015. Volumetric water content (VWC) is represented by the orange line and corresponds to the left axis. VWC is expressed as the percentage of the volume of mineral wool occupied by water (e.g. 10% of the volume of mineral wool is occupied by water, or 90% of the volume of mineral

Appendix A: Act ive Monitor ingwool is occupied by water). The mineral wool utilized in this application retains a maximum of 94% VWC as tested per ASTM E-2397. Note that on several occasions the VWC peaks to between 75% and 85%, approaching the maximum VWC. Also note that the VWC drops sharply to approximately 50% VWC within 1-3 days of peaking, and then gradually drops to approximately 20% VWC over the course of a week. Average VWC drops to 10% or less on eight occasions over the 17-month period, and never drops below 5%.

Rainfall is represented by the blue bars and corresponds to the right axis, expressed in total daily rainfall (inches). Note that most rain events produce less than 0.5 inches of precipitation, which is typical for the Washington, DC region. Also note that VWC rises commensurate with most rain events. For example, on April 8, 2014 (040814), the roof receives approximately 0.61 inches of rainfall. At the same time the VWC raises from 0.21% to 0.51%. As the mineral wool in this application is 2 inches thick, 21% VWC equates to 0.42 inches of water before the rain, and 51% equates to 1.02 inches of water after the rain, and increase of 0.60 inches of water retained, which almost exactly matches the precipitation that occurred. A similar pattern occurs with most other rainfall events, including a few rain events exceeding 2 inches of precipitation. Efficiency of retention is partially a function of the speed of precipitation; a high volume of precipitation in a very short timeframe will be more likely to create runoff than a slower rainfall of the same total volume. Only seven (7) rain events over the 17-month period produced significant runoff, likely due to the speed and intensity of the storm.

Note the consistency of the graph. Rainfall is captured and retained at similar rates throughout the year. The mineral wool dries down to an average ambient condition of 20% VWC throughout most of the year, including winter. Furbish has observed roof drains and observes little to no visible runoff following a rain event, which we interpret to indicates a lowering of VWC primarily via evapotranspiration versus delayed runoff. As the mineral wool typically retains 20% to 50% VWC throughout most of the year, it is an ideal rooting medium for plants, providing a highly desirable air-to-water ratio for a wide range of species, including Sedum.

A2

Figure A.1 Total daily rainfall (inches) and green roof system volumetric water content (%) of a 20,000 square foot green roof in Washington, DC (VWC n = 10 and rainfall n = 1).

Figure A.2 Monitoring equipment installed on rooftop soon after installation.

A3

Furbish conducted a series of trials to test the rewettability of two different mineral wool products that are used in green roof applications: 8 pcf mineral wool that utilizes a phenolic resin binder, and 8 pcf mineral wool that does not utilize any chemical binder.

These tests were performed in order to quantify whether repeated wet/dry cycles affect the hydrophilic (water-absorbing) properties of mineral wool when the material fully desiccates to from-the-factory condition (approximately less than 1% volumetric water content).

Conclusions• Mineral wool bound with phenolic resin retains

slightly more water than unbound mineral wool,• 30 psf of compression reduces volumetric water

content by approximately 15-20% in 8 pcf mineral wool*,

• Wet-dry cycles have no detectable effect on rewettability of either mineral wool bound with phenolic resin or mineral wool that does not utilize chemical binders, and

• During testing a very slight initial hydrophobia was observed in some samples, which quickly converted to hydrophilia once in contact with water for a few seconds.

*Note that following these tests, Furbish confirmed via a more focused test protocol that 12 pcf mineral wool demonstrates negligible loss of volumetric water content under 30 psf compression. Those test results are not included in this appendix.

Tests described in this Appendix were performed before the active monitoring described in Appendix A. Note that the active monitoring field information in Appendix A provides very similar rewettability results as are found in this Appendix.

Appendix B: Dry Cyc le TestsTest AssumptionsBased on a general familiarity with green roofs and familiarity with how mineral wool performs in green roofs, Furbish made the assumption that the mineral wool in green roofs rarely dries below 5% VWC, and very rarely - if ever - dries below 1% VWC (refer to Appendices A and H). Further, Furbish assumes that in climates that are susceptible to severe drought, some form of baseline irrigation would be provided. However, assuming a worst-case scenario of an annual mega-drought with no supplemental irrigation, a test assumption was that the mineral wool will completely desiccate once annually. Based on these assumptions, twenty (20) saturation/desiccation cycles were created to simulate 20 years of full desiccation/saturation events.

Samples TestedFour (4) different conditions were simulated on the two (2) different materials, for a total of eight (8) tests, duplicated, for a total of sixteen (16) samples, as listed below.

1A Unbound, uncompressed1B Unbound, uncompressed1C Bound, uncompressed1D Bound, uncompressed2A Unbound, compressed by 30 psf2B Unbound, compressed by 30 psf2C Bound, compressed by 30 psf2D Bound, compressed by 30 psf3A Unbound, compressed dry 20 times by 170 psf, then compressed by 30 psf3B Unbound, compressed dry 20 times by 170 psf, then compressed by 30 psf3C Bound, compressed dry 20 times by 170 psf, then compressed by 30 psf3D Bound, compressed dry 20 times by 170 psf, then compressed by 30 psf4A Bound, compressed wet 20 times by 170 psf, then compressed by 30 psf4B Bound, compressed wet 20 times by 170 psf, then compressed by 30 psf4C Bound, compressed wet 20 times by 170 psf, then compressed by 30 psf4D Bound, compressed wet 20 times by 170 psf, then compressed by 30 psf

A4

Test ProtocolsSamples in Group 1 (1A, 1B, etc.) were tested with no construction impact and no compression applied to the material to establish a baseline for the mineral wool’s water retention and rewettability. Note that steps 1-4, below, are very similar to ASTM E-2397 which is used to establish the dry weight and maximum water holding capacity of mineral wool or similar fibrous materials used in green roofs.

Process:1. Weigh Dry: Weigh each “from-the-factory-dry” to

establish a baseline dry weight for each sample. Samples were placed in a wire mesh containment to use as “handles”. For all samples, the wire mesh containment weighed approximately 0.2 lbs.

2. Wet: Submerse samples in water for 1 to 5 minutes.3. Drain: Remove samples from water and allow to

freely drain along a ¼-inch per foot slope until water flows slower than one drop per second.

4. Weigh Wet: Weight the drained sample.5. Dry: Place the sample in a dehydration chamber

until the sample’s weight is approximately the same weight as measured in step 1 (“from-the-factory-dry”).

Repeat steps 2-5 twenty times.

Samples in Group 2 tested the mineral wool’s water retention and rewettability under 30 psf of compression, the average maximum weight anticipated to be used over mineral wool, comparable to of 4 inches of aggregate media.

Process:1. Weigh Dry: Same as Group 12. Wet: Same as Group 13. Drain: Same as Group 1, except place 30 lbs of

dry precast concrete pavers directly over the wet sample while the sample is draining.

4. Weigh Wet: Same as Group 1, except briefly remove the precast concrete pavers while weighing.

5. Dry: Same as Group 1.Repeat steps 2-5 twenty times.

Samples in Group 3 tested the mineral wool’s water retention after the mineral wool was subjected to typical dry-weather construction impact, then rewettability under 30 psf of compression. Based on significant green roof installation experience, Furbish estimates that no single area of the roof would typically be stepped on more than 10 times during construction after installation of the mineral wool layer and before installation of media, as mineral wool is typically covered by filter fabric and media on the same day it is installed. High-traffic areas require special protection, which is typical for all green roof installation. In order to simulate a worst-case scenario, the test assumed that each square foot of mineral wool would be stomped on 20 times by a 170 lb person.

Process:1. Weigh Dry: Stomp on dry mineral wool 20 times,

by a 170-lb person wearing construction boots. Then same as Group 2.

2. Wet: Same as Group 23. Drain: Same as Group 24. Weigh Wet: Same as Group 25. Dry: Same as Group 2Repeat steps 2-5 twenty times.

Samples in Group 4 tested the mineral wool’s water retention after the mineral wool was subjected to typical wet-weather construction impact, then rewettability under 30 psf of compression.

Process:1. Weigh Dry: Weigh mineral wool “from-the-

factory” dry to establish a baseline weight. Then fully saturate. Then stomp on fully saturated mineral wool 20 times, by a 170-lb person wearing construction boots. Then re-dry to “from-the-factory” conditions to re-establish a sample baseline weight. Then same as Group 2.

2. Wet: Same as Group 23. Drain: Same as Group 24. Weigh Wet: Same as Group 25. Dry: Same as Group 2Repeat steps 2-5 twenty times.

A5

Test ResultsTesting demonstrated no measurable loss in rewettability of mineral wool over 20 saturation/desiccation cycles. Mineral wool bound with phenolic resin retained slightly more water than unbound mineral wool.

In Figures B.1, B.2 and B.3, the vertical axis is in pounds, and the horizontal axis is cycles (cycle 1 through cycle 20).

Figure B.1. This graph illustrates the dry weight of each of the 16 samples, per Step 1 as noted above. The dry weight is very consistently measured to be between 0.80 lbs and 0.90 lbs for each 1 square foot sample. (Sample 1D was a slightly heavier outlier at approximately 1.0 lbs. Notice that some samples weighed more at the beginning Cycle 5, indicating that Cycle 5 did not uniformly dry all samples; however most other cycles uniformly dried all samples to “from the factory” condition, or slightly drier.)

Figure B.2. This graph illustrates the wet weight of each of the sixteen samples, per Step 4 as noted above. The wet weight is very consistently measured to be 4 lbs and 6 lbs, with an average of 5 lbs for each 1 square foot sample. (Sample 1D was a slightly heavier outlier at approximately 1.0 lb dry weight and proportionately higher saturated weight. Notice that the trend line for all samples is relatively horizontal, i.e. there is no measurable decrease in rewettability.)

A6

Figure B.3 illustrates the average wet and dry weights of each group of sample. Notice that the dry weight for bound samples (T) and unbound samples (K) is uniformly approximately 1 lb/sf. The distance between wet weights and dry weights represents water retention capacity and material efficiency. Generally, bound mineral wool retained slightly more water than unbound mineral wool, and uncompressed mineral wool retained slightly more water than mineral wool compressed by 30 psf.

Figures B.4 (right) illustrates wetting samples per Step 2, above. Figure B.5, (bottom left) illustrates draining uncompressed samples before weighing per Step 3, above. Figure B.6 (bottom center) illustrates draining compressed samples under 30 psf of precast concrete pavers before weighing per Step 3, above. Figure B.7 (bottom right) illustrates weighing fully drained samples per Step 4, above.

A7

Furbish conducted a series of trials to test the rewettability of two different mineral wool products that are used in green roof applications: 8 pcf mineral wool that utilizes a phenolic resin binder, and 8 pcf mineral wool that does not utilize a chemical binder.

These tests were performed in order to quantify whether high volumetric water flow affects the hydrophilic (water-absorbing) properties of mineral wool.

Conclusions• High flow cycles (simulating 160 inches of rainfall)

have no detectable effect on rewettability of either mineral wool bound with phenolic resin or unbound mineral wool, and

• Mineral wool bound with phenolic resin retains slightly more water than mineral wool bound without resin.

Test AssumptionsBased on a familiarity with green roofs in general and a familiarity with how mineral wool performs in green roofs, Furbish designed this test to simulate approximately four (4) years of rainfall in the Eastern US (a total of 160 inches of rainfall). Four years was chosen because only the initial hydrophilic properties of mineral wool were the focus of this test, as longer term applications cannot accurately be modeled without increasing root mass within the mineral wool, and longer term applications are best examined via case studies, such as in Appendix H.

Samples testedTwo (2) different materials were tested, for a total of two (2) tests, duplicated, for a total of four (4) samples, as listed below. Bound samples were bound with phenolic resin.1 Bound, 8 pcf, 1 square foot at 1” thick2 Bound, 8 pcf, 1 square foot at 1” thick3 Unbound, 8 pcf, 1 square foot at 1” thick4 Unbound, 8 pcf, 1 square foot at 1” thick

Appendix C: F low Cyc le TestsTest ProtocolsA total volume of 100 gallons of water was used per sample. One hundred (100) gallons = 23,100 cubic inches = a vertical column of 160.42 inches of water over each 1 square foot (144 square inches) sample. The volume of 100 gallons of water was released via gravity feed onto the samples in twenty (20) cycles, of five (5) gallons per cycle, simulating 8.02 inches of rainfall per cycle. Each sample was weighed before and after each cycle.

Process:1. Each sample was encased in a clear, rigid plastic

casing, open at two sides (top and bottom sides). The rigid plastic was reinforced with wooden ribs to prevent bowing of the plastic. Each sample was inspected to ensure uniform contact between the plastic casing and the mineral wool so that water could only pass through the mineral wool and not through voids between the mineral wool and casing.

2. Weigh Dry: Weigh samples dry (“from the factory”) to establish a baseline dry weight for that sample.

3. Wet: Release five (5) gallons of water through the samples. Gauge water release so that no water flows outside the plastic casing.

4. Drain: Allow samples to freely drain along a ¼-inch per foot slope until water flows not faster than one drop per second.

5. Weigh Wet: Weigh the drained sample.Repeat steps 2-5 twenty times.

A8

Test ResultsTesting demonstrated no measurable loss in rewettability of mineral wool after exposure to 100 gallons/SF. In Figures C.1 and C.2, the vertical axis is in pounds, and the horizontal axis is cycles (cycle 1 through

cycle 20). The dry weight of each of the 4 samples was only taken initially, per Step 2 as noted above, as this test did not include substantial desiccation between cycles. Both wet and dry weights include the weight of the plastic casing, for consistency.

Figure C.1. illustrates the wet weight of samples taken per Step 3, above, The wet weight is very consistently measured to be between 6 and 7 lbs, with an average of 6.2 lbs for each 1 square foot sample. Notice that the trend line for all samples is relatively horizontal, i.e. no measurable decrease in rewettability,

Figure C.2 illustrates the same wet weight results as the chart above, but the vertical axis represents volumetric water capacity (VWC) expressed as percentage of water of the total volume. Note that the two Bound samples (Samples 1 and 2) average approximately 85% VWC, which is consistent with actual field data illustrated in Appendix A.

A9

Figure C.3 (top right). Photo of sample in plastic casing with wooden ribs, per Step 1, above.

Figure C.4 (top left). Photo of samples saturating in water, per Step 2, above.

Figure C.5 (middle right). Photo of samples receiving water, per Step 3, above.

Figure C.6 (bottom right). Photo of samples draining, per step 4, above.

A10

Furbish conducted a series of trials to test the compression resistance of two different mineral wool products that are used in green roof applications: a 12 lb/cubic foot (12 pcf) and a 14 pcf mineral wool, both manufactured utilizing a phenolic resin binder applied at a rate of approximately 6% per mass. The 12 pcf and 14 pcf materials were selected after Furbish determined that 8 pcf mineral wool compressed to an effective density of 10-12 pcf under high foot traffic. The primary goal of theses tests was to ascertain whether mineral wool manufactured at an initial density higher than 10 pcf stabilizes at its initial density without further compression under foot traffic, and whether overburden layers affect compression.

Conclusions• Mineral wool at a 12 pcf density retained

approximately 95% of its volume after approximately 22 years of simulated compression, and approximately 91% of its volume after 45 years of simulated compression.

• Mineral wool at a 14 pcf density retained approximately 99% of its volume after approximately 45 years of simulated compression.

• Mineral wool of both 12 pcf and 14 pcf densities exhibited rebound from compression.

• Use of a shovel guard improved compression resistance. (Note that this conclusion is not consistently supported by tests and case studies in other Appendices.)

Test Protocols1. Workers stepped on unprotected mineral wool

samples 20 times to simulate construction impact (approximately 2 steps per square foot), then covered the mineral wool with overburden layers.

2. Workers walked on the samples, continuously moving, for 31 minutes to simulate 11.25 years of installation and maintenance activities.

3. Workers squatted and/or sat directly on the samples for 60 minutes to simulate 11.25 years of intensive weeding efforts.

4. Steps 3 and 4 were repeated 4 times to generate a total of 45 years of impact.

Each sample was gridded using three (3) equally spaced axis lines perpendicular to the long edge, and three (3) equally spaced axis lines perpendicular to

Appendix D: Pedestr ian Impactthe short edge, for a total of nine (9) axis intersections. The thickness of the mineral wool was measured at each axis intersection during testing.

Samples:Two (2) different materials were tested, in three (3) configurations, for a total of six (6) samples, as listed below. Each sample filled a wooden box with interior dimensions measuring 3’-9” x 3’-1” (11.55 square feet) and utilized mineral wool applied at 1” thick. The “shovel guard” material used was J-Drain 300; the intent of testing this material was to determine whether a semi-rigid layer used over the mineral wool would affect compression resistance.C12 Bound 12 pcf, under 2 inches of EcoCline Media B2 and 1 layer of filter fabricC14 Bound 14 pcf, under 2 inches of EcoCline Media B2 and 1 layer of filter fabricG12 Bound 12 pcf, under 1.5 inches of angular gravel and 1 layer of shovel guardG14 Bound 14 pcf, under 1.5 inches of angular gravel and 1 layer of shovel guardH12 Bound 12 pcf, under 1.5 inches of angular gravel and 1 layer of shovel guardH14 Bound 14 pcf, under 1.5 inches of angular gravel and 1 layer of shovel guard

Test Protocol CalculationsThe impact necessary to generate a simulated forty-five (45) years of compressive forces was based upon Furbish’s imperical measurements. Green roof maintenance typically requires approximately 5 visits annually; a 5,000 SF roof requires an average of two workers to be present for approximately 2 hrs/visit (approximately 1,250 sf per manhour). During a visit, the predominant foot traffic is walking and squatting to pull weeds, which might not require any foot traffic over certain roof areas, or might require up to 3-5 steps/sf, with occasional longer periods of squatting in weedy areas. At the high end of average, Furbish estimates a typical maintenance visit would include 4.8 steps per square foot, approximately 5 times annually, and very weedy green roofs would receive intense weeding visits approximately 3 times annually, covering 0.16 sf/minute. Full calculations are shown in Table D.1.

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Table D.1. Typical maintenance impact calculations . Statistical measurement: typical low-weed-pressure 5,000 SF green roof is maintained by 2 people for 2 hours per visit (4 manhours or 240 minutes), with 5 visits annually.

A 5000 square feet of statistical area ImpericalB 240 minutes per visit to service / walk over non-weedy areas ImpericalC 21 square feet per minute A / BD 76 average number of steps per minute in a 16 SF sample, constantly

movingImperical

E 11.55 square feet sample sizeF 0.55 minutes of foot traffic per visit per sample size (about 45

seconds/16sf)E / C

G 4.8 approximate number of steps per square foot per visit D / 16H 5 visits per year ImpericalI 2.772 minutes of foot traffic per sample size per year F x HJ 31 minutes of foot traffic per trial segmentK 11 years of simulated foot traffic per trial segment J / IL 4 completed trial segmentsM 45 total years of simulated foot traffic K x LN 124 minutes of foot traffic per 16SF sample over 32 year test period J x LO 9424 total approximate number of steps taken over sample area over

45 yearsD x N

P 816 total approximate number of steps per square foot over 45 years O / E

Table D.2. Intensive weeding impact calculations. Statistical measurement: typical high-weed-pressure 5,000 SF green roof requires 2 people for approximately 390 minutes (13 manhours or 780 minutes) 3 times annually.

A1 5000 square feet of statistical area ImpericalB1 780 minutes per visit to service / squat or sit and weed areas of high-

weed-pressureImperical

C1 6 square feet per minute A1 / B1D1 0.156 minutes of intense weeding per square foot of green roof B1 / A1E1 11.55 square feet sample sizeF1 1.8 minutes of squatting to weed per visit per sample size E1 / C1H1 3 intense weedings per year ImpericalI1 5.41 minutes of squatting to weed per sample size per year F1 x H1J1 60 minutes of squatting to weed per trial segmentK1 11 years of simulated intense weeding J1 / I1L1 4 completed trial segmentsM1 44 total years of simulated squatting to weed per trial segment K1 x L1N1 240 minutes of squatting to weed per 11.55SF sample over 44 year

test periodJ1 x L1

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Figure D.1. Average of all samples: Mineral wool at a 12 pcf density retained approximately 95% of its volume after approximately 22 years of simulated compression, and approximately 91% of its volume after 45 years of simulated compression. Mineral wool at a 14 pcf density retained approximately 99% of its volume after approximately 45 years of simulated compression.

Figure D. 2. Sample C12: 12pcf mineral wool covered with filter fabric and EcoCline Media B2. Most samples exhibited approximately 5% compression after 20 years of simulated impact, and approximately 25% compression after 45 years of simulated impact.

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Figure D. 3. Sample C14: 14pcf mineral wool covered with filter fabric and EcoCline Media B2. No samples exhibited any measureable compression after 45 years of simulated impact.

Figure D. 4. Sample G12: 12pcf mineral wool covered with shovel guard and EcoCline Media R (angular #4 aggregate). No samples exhibited any measureable compression after 45 years of simulated impact.

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Figure D. 5. Sample G14: 14pcf mineral wool covered with shovel guard and EcoCline Media R (angular #4 aggregate). Samples exhibited temporary compression of up to 10%; however all samples fully rebounded within one week of testing, exhibiting no measureable compression after 45 years of simulated impact.

Figure D. 6. Sample H12: 12pcf mineral wool covered with shovel guard and rounded #4 aggregate). Most samples exhibited no no measureable compression after 45 years of simulated impact. One sample exhibited 10% compression after 35 years of simulated impact. One sample exhibited 25% compression, but rebounded to 100% of original volume within 1 week of testing.

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Figure D. 7. Sample H14: 14pcf mineral wool covered with shovel guard and rounded #4 aggregate. One probe of one sample exhibited temporary compression of up to 25%; however all samples fully rebounded within one week of testing, exhibiting no measureable compression after 45 years of simulated impact.

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Furbish conducted a series of tests documented in this Appendix which are a variation of tests documented in Appendix D. Whereas the tests in Appendix D simulated pedestrian impact under actual foot traffic over a narrow range of samples, the tests in Appendix E simulate pedestrian impact over a much wider range of samples.

Conclusions• Mineral wool at a 12 pcf density retained

approximately 95% of its volume after approximately 22 years of simulated compression, and approximately 91% of its volume after 45 years of simulated compression.

• Mineral wool at a 14 pcf density retained approximately 99% of its volume after approximately 45 years of simulated compression.

• Mineral wool of both 12 pcf and 14 pcf densities exhibited rebound from compression.

• Use of a shovel guard or media type had no discernable effect on compression resistance.

Appendix E : Ca l ibrated ImpactObservations• Most configurations and most material types

exhibited approximately 10% compression at various points during the test. Some samples fully rebounded and others did not.

• Compression occurred at various points during testing. No significant “breaking point” was observed. Compression generally remained constant after occurring, even if early in the process. Compression rebounded often.

• No particular configuration performed significantly better than others. The top four performing configurations (filter fabric and angular stone, filter fabric and media B2, filter fabric only, and shovel guard with media B2) include the full spectrum of configurations tested.

Samples TestedTwo (2) different materials (12 pcf and 14 pcf) were tested, in nine (9) configurations, for a total of eighteen (18) material/configuration combinations, and each combination was tested wet and dry, for a total of thirty-six (36) samples, as listed below. Each sample filled a wooden box with interior dimensions measuring 5.5” x 6” (0.23 square feet) and utilized a 2-inch thick mineral wool bound with phenolic resin. Filter fabric used was a 3.5 oz non-woven geotextile. EcoCline Media B2 is an aggregate media consisting of crushed brick, granite chips and organic matter, with angular particles, and a maximum particle size of ½-inch. The shovel guard used was J-Drain 300.

Description SamplesExposed (no covering) 12pcf A, dry 12pcf A, wet 14pcf A, dry 14pcf A, wetFilter Fabric (FF) 12pcf B, dry 12pcf B, wet 14pcf B, dry 14pcf B, wetFF & 2” EcoCline Media B2 12pcf C, dry 12pcf C, wet 14pcf C, dry 14pcf C, wetFF & 1.5” angular #4 aggregate 12pcf D, dry 12pcf D, wet 14pcf D, dry 14pcf D, wetFF & 1.5” rounded #4 aggregate 12pcf E, dry 12pcf E, wet 14pcf E, dry 14pcf E, wetShovel Guard (SG) 12pcf F, dry 12pcf F, wet 14pcf F, dry 14pcf F, wetSG & 2” EcoCline Media B2 12pcf G, dry 12pcf G, wet 14pcf G, dry 14pcf G, wetSG & 1.5” angular #4 aggregate 12pcf H, dry 12pcf H, wet 14pcf H, dry 14pcf H, wetSG & 1.5” rounded #4 aggregate 12pcf I, dry 12pcf I, wet 14pcf I, dry 14pcf I, wet

Table E.1. Samples tested.

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Test AssumptionsBased on extensive experience in installation and maintenance of green roofs, Furbish assumed that the primary physical impact to a green roof is pedestrian foot traffic. Based on this assumption, the test was designed to simulate foot traffic over a variety of profiles in order to determine the maximum number of footsteps for each profile, and to determine whether profile construction is a significant variable in the mineral wool’s resistance to compression. Refer to Appendix D for a detailed description of typical anticipated construction and annual maintenance impact, which arrives at 4.8 steps per square foot per visit, as shown in line “G” of Table E.2.

Test ProtocolsFurbish constructed a compression device (affectionately known as “Chomp”) to deliver the required force to each sample. Chomp was constructed of an upper cartridge containing ballast, and a lower cartridge containing eleven (11) sample containers measuring 6 inches long x 5.5 inches wide x 5 inches deep. The bottom of the upper cartridge contains eleven (11) wooden compressor pads, measuring 3.5 inches x 3.5 inches. The compressor pads are designed to directly impact the samples below at a given location. The upper cartridge is attached to the lower cartridge via lubricated hinge set approximately 1.5 inches above the top of the lower cartridge. Before each use, the device is calibrated such that 1) each compressor pad comes fully into contact with each sample, and 2) the full weight of the upper cartridge bears on the samples.

Chomp was calibrated to deliver approximately 835 psf of force to each sample, per calculations in Table E.3

(71 lbs per each 0.09 square foot compression pad). A total of 40 pavers were used to weigh the upper cartridge with 880 lbs of ballast versus the minimum of 36 pavers calculated. The additional 88 lbs of force is estimated to compensate (or over-compensate) for any load transferred to the hinge during compression.

Two technicians operate Chomp during each use. One technician depresses an 8-foot long lever attached to the upper cartridge to raise the bottom of the compressor paddles approximately 2 to 3 inches above the surface of the samples. When the upper cartridge is fully raised, the technician releases the lever (lets go of lever so that hands are not touching) to drop the full 880 lb upper cartridge onto the lower cartridge. A second technician observes each raising and lowering of the device to ensure calibration throughout the test (to verify that each compressor pad impacts each sample at uniform times, and that the upper cartridge does not come into contact with the frame, so that all weight is transferred through samples, and not through the frame).

Technicians probed the depth of the mineral wool at the point of impact periodically during sampling to check overall thickness. Testing occurred over several days. Final conforming measurements were taken after samples had had approximately 2 weeks to “rebound” after compression.

(Note that all 11 Chomp sample containers were filled and utilized, though only 9 samples are documented in this Appendix. The other 2 sample containers were filled with various other materials not reported on in this document.)

G 4.8 approximate number of steps per square foot per visit Appendix DQ 1000 steps simulated in testing protocolR 100 steps during construction ImpericalS 900 steps during maintenance Q - RT 188 total maintenance visits S / GU 5 maintenance visits per year ImpericalV 37.5 total years of simulated foot traffic T / U

Table E.2. Typical maintenance impact calculations.

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A 11.5 average shoe length heel to toe, inches ImpericalB 3 average shoe width (3" @ heel, 2" @ arch,

4" @ ball), inchesImperical

C 34.5 square inches of average shoeprint A x BD 144 conversion square inches to square feetE 0.24 square feet per average shoeprint C / DF 200 lbs, average maintenance worker ImpericalG 835 psf (force of average footstep) F / EH 3.5 width of sample compressor pad (inches)I 3.5 length of sample compressor pad (inches)J 12.25 sample square inchesK 144 conversion square inches to square feetL 0.09 square feet of sample J / KM 71 lbs required per compressor pad to gener-

ate 835 psfG x L

N 11 samplesO 781 lbs total per CHOMP device M x NP 22 psf per precast concrete paver ImpericalQ 36 minimum 1SF pavers required as ballast O / P

Table E.3. Calibrated impact calculations.

Test Continuation ProtocolsAfter 1,000 impacts on each of the 36 samples, few tests had produced as much as 10% compression, and no test had compressed 15%, so the test was continued by doubling the impact to test the weight of a 400 lb person (1,670 psf of force) versus that of a 200 lb person. Samples selected for further testing were the 14 pcf dry samples A, C, E and G. In this test, sample ‘C’ compressed by 25%, and samples ‘A’, ‘G’ and ‘E’ compressed by approximately 10%; however, after allowing two weeks of “rebound”, final measurements showed no noticeable compression of any of these samples.

Test ResultsAll samples exhibited excellent compression resistance. Figures E.1 through E.14 illustrate compression resistance as percentage of total original volume on the vertical axis, and number of impacts (1-1000 or 1-1400) are shown in the horizontal axis. In all figures E.1 through E.14 final measurements are the same as measurements noted for 1,000 impacts unless “Final” is included in the horizontal axis. Some graphs include a 1,200 designation on the horizontal axis, which is used only for 1,670 psf testing of the 14 pcf dry samples A, C, E and G, per “Test Protocol Continuation” as noted above.

Figure E.1 shows an average of all 12 pcf and 14 pcf samples. Additional Figures E.2 through E.5 illustrate compression resistance group by mineral wool density and moisture level. Figure E.6 through E.14 illustrate compression resistanced grouped by overburden type.

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Figure E.2. 12 pcf mineral wool samples tested dry

Figure E.1. Average of all mineral wool samples tested by density

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Figure E.3. 12 pcf mineral wool samples tested wet

Figure E.4. 14 pcf mineral wool samples tested dry

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Figure E.5. 14 pcf mineral wool samples tested wet

Figure E.6. Samples of mineral with no covering

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Figure E.7. Samples of mineral wool covered only by 1 layer of filter fabric

Figure E.8. Samples of configuration using 1 layer of filter fabric and 2 inches of EcoCline Media B2

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Figure E.9. Samples of mineral wool covered only by shovel guard

Figure E.10. Samples of mineral wool covered by shovel guard and 2 inches of EcoCline Media B2

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Figure E.11. Samples of mineral wool covered only by shovel guard and angular #4 stone

Figure E.12. Samples of mineral wool covered by shovel guard and rounded #2 stone

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Figure E.13. Samples of mineral wool covered only by filter fabric and angular #4 stone

Figure E.14. Samples of mineral wool covered by filter fabric and rounded #4 stone

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Runoff from mineral wool can be expected to provide clean, safe stormwater.

Furbish tested runoff from mineral wool used in a green roof in order to determine the amount of phenol and formaldehyde that might leach from the mineral wool during rain events. These two chemicals were selected for testing, as they are the only chemicals added to the mineral wool fibers in any significant quantity. Other chemicals used in binders, such as urea and calcium silicate, were not tested due to the very small amounts used, and the generally accepted safety of these components.

The test utilized a 12-inch by 12-inch sample green roof assembly in a clear acrylic container. The sample had been growing in the outdoors for 3 years. Distilled water was applied to the surface media and vegetation of the green roof until the necessary quantity of runoff was produced. Water samples were analyzed by Environmental Testing and Consulting, Inc (ETC), as noted on the following pages.

In order to established a baseline measurement for comparison, one other test was performed by soaking multiple samples of mineral wool in distilled water and agitating the samples to ensure full contact of water and fibers. The samples included new unused mineral wool, and mineral wool used in accelerated weathering tests of Appendices B and C. Water samples in this test were analyzed by ETC, and demonstrated that flow patterns through an assembled green roof have a negligible effect on the quantity of phenol and formaldehyde in runoff versus direct contact with the mineral wool, and that new unused material and used material produces similar results.

Though runoff from green roofs is not intended to be used as drinking water, test results are compared with the US EPA’s 2012 Edition of the Drinking Water Standards and Health Advisories (EPA Standards) as a baseline reference point.

Appendix F : Water Qual i ty

Runoff collected contained <0.050 mg/L of formaldehyde. The EPA Standards allow 10 mg/L, 5 mg/L, and 1 mg/L of formaldehyde in drinking water for one-day, ten-day, and lifetime consumption, respectively. i.e. the water sampled is 200 times safer than the EPA Standards for occasional consumption.

Runoff collected contained 0.498 mg/L of phenol. The EPA Standards allow 6 mg/L, 6 mg/L, and 2 mg/L of phenol in drinking water for one-day, ten-day, and lifetime consumption, respectively. i.e. the water sampled is 12 times safer than the EPA Standards for occasional consumption. (Note that phenol is used in pharmaceuticals, mouthwash, and throat lozenges.)

Test results from ETC are shown on the following five pages.

Figure F.1. Collection of water sample.

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This appendix includes a range of 40x magnified images of mineral wool with a range of densities, including bound and unbound materials.

Mineral wool fibers are typically around 6 to 10 micrometers in diameter (10 micrometers = 3.9370079e-4 inches). These strong fibers are formed into a tightly packed matrix, touching at intersections, but with significant void spaces between the fibers, resembling the classic game “Pick-Up Sticks”. The high ratio of void space, even in high densities, explains mineral wool’s high volumetric water capacity.

Images below visually demonstrate the differences between mineral wool of 4 pcf, 8 pcf, 12 pcf and 14 pcf densities. Though these materials appear similar to the naked eye, the material density is apparent at 40x magnification, explaining the significant increase in compressive strength of higher density materials.

Appendix G: Magnified ImagesIn all images, the terms “top” or “side” are used to define the image perspective. “Top” and “side” correspond with the mineral board as manufactured. A view of the top of the board generally shows fibers arranged in a random pattern. A view of the side of the board generally shows fibers arranged substantially parallel to each other, with a distinct “grain”, though often with a noticeable percentage of the fibers oriented perpendicular to the primary fiber orientation. Note the high ratio of void space to fiber, even in very high densities, which is ideal for fibrous root structures to penetrate to absorb water.

Figure G.1. 8 pcf unbound mineral wool, view from top

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Figure G.2. 14 pcf bound mineral wool, view from top

Figure G.3. 8 pcf bound mineral wool, view from top

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Figure G.4. 12 pcf bound mineral wool, view from side

Figure G.5. 14 pcf bound mineral wool, view from side

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Figure G.6. 8 pcf bound mineral wool, exposed to elements for three (3) years, view from top at edge

Figure G.7. Mineral wool fibers under microscope. Magnification level: 100x. Reproduced with permission of Forensic Science Services. Note the binder, observed as spherical shapes.

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General ObservationsFurbish observed mineral wool performance in green roofs on several projects in Germany, including 5 projects that have been in service approximately 20 years. Furbish is also actively maintaining approximately 500,000 sf of green roofs that utilize mineral wool, and maintenance activities include documentation of plant health, proper drainage, nutrient levels, and volumetric retention of the mineral wool; all projects are performing very similarly, so only three of approximately three dozen projects are listed below.

General findings are:• Compression resistance as observed in the field

very closely resembles laboratory test results.• Bound mineral wool at 8 pcf density exhibited

negligible average compression when exposed to light-duty foot traffic on rooftops, but compressed to an effective density of 10-12 pcf when exposed to high foot traffic in at-grade applications.

• Unbound mineral wool generally exhibits higher levels of compression. (Note that neither laboratory nor field observations document

Appendix H: F ie ld Observat ions

ProjectsOriginal Density

Observed Comression(Expansion)

Effective Stable Density

Foot Traffic Age (Years) Binder

Allee Center 7.9 pcf* 25% 10.5 pcf Low 20 Phenolic Resin*Allee Center 7.9 pcf* (25%) 6.3 pcf Low 20 Phenolic Resin*Oldenburg 7.9 pcf* 10% 8.8 pcf Low 19 Phenolic Resin*Oldenburg 7.9 pcf* (60%) 4.9 pcf Low 19 Phenolic Resin*Bremerhaven 7.9 pcf 0% 7.9 pcf Low 1 NoneBremerhaven 7.9 pcf 40% 13.2 pcf Low 1 NoneNordstraße 7.9 pcf* 25% 10.5 pcf High 25* Phenolic Resin*Daniel-von-Bueren 7.9 pcf* 25% 10.5 pcf High 25* Phenolic Resin*Daniel-von-Bueren 7.9 pcf* 35% 12.2 pcf High 25* Phenolic Resin*Flughafendamm 7.9 pcf* 25% 10.5 pcf High 25* Phenolic Resin*Potomac Plaza 8 pcf 13% 9.1 pcf Moderate 2 Phenolic ResinPotomac Plaza 8 pcf 0% 8 pcf Moderate 2 Phenolic ResinPotomac Plaza 8 pcf (13%) 7.1 pcf Moderate 2 Phenolic ResinEmbassy Suites 8 pcf 0% 8 pcf Low 2 Phenolic ResinEmory Knoll Farm 8 pcf 0% 8 pcf Low 3 Phenolic Resin

Table H.1. Summary of original and current effective densities of mineral wool in case studies presented. An initial density of 8 pcf is adequate in light-duty applications, but 12 pcf is more stable in high-traffic applications. More than one measurement per project indicates minimums and maximums observed. *Denotes unconfirmed but best available information.

extensive use of unbound material.)• Mineral wool supports long-term healthy root

growth. Root penetration speed into the mineral wool appears to be inversely proportional to the thickness of surface media used.

• Mineral wool supports long-term healthy plant growth, even when not covered by aggregate media.

• Mineral wool feels springy under foot on both newly installed green roofs and within green roofs that have been in service for 3 decades, demonstrating excellent long-term elasticity.

• Mineral wool substantially dries between rain events, both in the German climate when used under 1 inch or less media, and in the US mid-Atlantic region when used under 1 to 4 inches of media.

• Mineral wool can serve as an effective drainage material without the need for an air layer or composite drainage layer below the mineral wool.

• Visual and tactile examination of mineral wool fiber structure reveals that the material remains intact in an almost “like new” condition when in service for over 2 decades.

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Berlin Allee Center, Berlin, Germany Installed: 1995 (20 years old)Size: Approximately 100,000+ SF.Profile:• Prevegetated mat, approximately 1” thick• 20mm (0.78”) mineral wool with binder (likely

phenolic resin). Density 7.9 pcf (110 kg/cubic meter

• MembraneObservations: >95% vegetative coverage. Predominant species are Allium schoenoprasum, Sedum album, S. spurium, S. reflexum, S. floriferum, S. sexangulare, and several mosses. Roots actively grew into mineral wool in all areas observed, particularly deeper Allium roots. Mineral wool measured 15-25mm (25% compression to 25% expansion) in most areas observed. System is noticeably “springy” under foot. Not maintained. Sedum mats were not initially installed with 100% coverage, leaving some areas of mineral wool exposed to the sky. Exposed areas are covered with the same plants as the original mats, though with a higher concentration of mosses. No performance differences (resilience, integrity, compression, etc.) are detected between the material covered by mats and exposed mineral wool. In some areas of exposed mineral wool, birds had disturbed the surface, leaving loose mineral wool fibers in places. This phenomena had apparently occurred for many years (with no significant loss of material), though in some places thick mounds of moss appear to have grown over clumps of fibers.

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Oldenburg Bus Station, Oldenburg, Germany Installed: 1996 (19 years old)Size: Approximately 70,000 SF.Profile:• Prevegetated mat, approximately 1” thick• 20mm (0.78”) mineral wool with binder (likely

phenolic resin). Density 7.9 pcf (110 kg/cubic meter)

• 10mm (0.39”) drainage / aeration layer• MembraneObservations: >95% vegetative coverage. Predominant species are Allium schoenoprasum, Sedum album, S. spurium, and several mosses. Roots actively grew into mineral wool in all areas observed, particularly deeper Allium roots. Bound mineral wool measured 18-32mm (10% compression to 60% expansion) in most areas observed. System is noticeably “springy” under foot. Initially maintained for 10 years, currently unmaintained. Sedum mats were not initially installed with 100% coverage, leaving some areas of mineral wool exposed to the sky. Exposed areas are covered with the same plants as the original mats, though with a higher concentration of mosses. No performance differences (resilience, integrity, compression, etc.) are detected between the mineral wool covered by Sedum mats and exposed mineral wool.

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Kindergarden Bremerhaven, Germany Installed: Early 2014 (1 year old)Size: Approximately 7,000 SF.Profile:• Prevegetated mat, approximately 1/2” thick• 20mm (0.78”) mineral wool without chemical

binder. Density 7.9 pcf (110 kg/cubic meter)• 10mm (0.39”) drainage / aeration layerObservations: >95% vegetative coverage. Predominant species is Sedum album. Roots successfully penetrated mineral in most areas observed. Unbound mineral wool measured 12-20mm (0% to 40% compression) in most areas observed. System is noticeably “springy” under foot. Not maintained.

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Bremen Nordstraße Track Bed Greening, Bremen, GermanyInstalled: Early 1990s (approximately 25 yrs old)Profile:• Media, approximately 1/2-3/4” thick• 20mm (0.78”) mineral wool with binder (likely

phenolic resin). Density 7.9 pcf (110 kg/cubic meter)

• 10mm (0.39”) drainage / aeration layer• MembraneObservations: >95% vegetative coverage. Predominant species are Sedum album and mosses with some grasses. Roots fully penetrated mineral in all areas. Bound mineral wool measured approximately 15mm (25% compression) in most areas observed. High-pedestrian-traffic at-grade location; no barriers to pedestrians crossing or walking on tracks. System is noticeably “springy” under foot. Reportedly not maintained.

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Bremen Daniel-von-Bueren Street Track Bed Greening, Bremen, GermanyInstalled: Early 1990s (approximately 25 yrs old)Profile:• Media, approximately 1/2-3/4” thick• 20mm (0.78”) mineral wool with binder (likely

phenolic resin). Density 7.9 pcf (110 kg/cubic meter)

• 10mm (0.39”) drainage / aeration layer• MembraneObservations: >95% vegetative coverage. Predominant species are Sedum album and S. spurium (in deeper areas) with mosses. Roots fully penetrated mineral wool in all areas. Bound mineral wool measured approximately 15mm (25% compression) in most areas observed with a minimum thickness of 13mm (35% compression). High-pedestrian-traffic at-grade location; no barriers to pedestrians crossing or walking on tracks. System is noticeably “springy” under foot. Reportedly not maintained.

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Bremen Flughafendamm Track Bed Greening, Bremen, Germany Installed: Early 1990s (approximately 25 yrs old)Profile:• Media, approximately 3/4-1” thick• 20mm (0.78”) mineral wool with binder (likely

phenolic resin). Density 7.9 pcf (110 kg/cubic meter)

• 10mm (0.39”) drainage / aeration layer• MembraneObservations: >95% vegetative coverage. Predominant species are Sedum album, S. spurium, and grasses with some mosses with. Roots fully penetrated mineral in all areas. Bound mineral wool measured approximately 15mm (25% compression) in most areas observed. High-pedestrian-traffic at-grade location; there are some barriers to pedestrians crossing or walking on tracks, but barriers appeared to be recently installed. System is immediately adjacent to a large turfgrass field, which is a likely cause of high grass coverage. System is noticeably “springy” under foot. Reportedly not maintained.

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Potomac Plaza, Washington, DC Installed: Fall 2013 (2 yrs old)Profile:• Media (angular gravel), approximately 1-1/2” thick• 2” mineral wool with phenolic resin binder. Density

8 pcf• Insulation• MembraneObservations: >90% vegetative coverage. Predominant species are Sedum album, S. sexangulare, S. spurium, S. reflexum, and S. rupestre. Roots have penetrated mineral wool in several areas observed. Bound mineral wool measured approximately 1.75” (13% compression) for approximately 12 months following installation, likely due to very high construction impact due to challenging installation logistics. After the winter of 2014-2015 mineral wool rebounded to 2”-2.25” (0% compression to 13% expansion). System is noticeably “springy” under foot. Actively maintained.

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Embassy Suites, Springfield, VAInstalled: Fall 2013 (2 yrs old)Profile:• Media, 2” and 4” thick• 1” mineral wool with phenolic resin binder. Density

8 pcf• 1/4” protection & air layer• MembraneObservations: >85% vegetative coverage. Predominant species are Sedum album, S. sexangulare, S. spurium, S. reflexum, S. rupestre, S. kamptschiaticum, and several taller perennial plants. Roots have penetrated mineral wool in several areas observed. Bound mineral wool measured approximately 1” (0% compression). System is noticeably “springy” under foot. Actively maintained.

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Emory Knoll Farm, Street, MDInstalled: 2012 (<3 yrs old)Profile:• Media, 3” thick• 2” mineral wool with phenolic resin binder. Density

8 pcf• MembraneObservations: >80% vegetative coverage. Species are planted in mono-specific rows as a demonstration, including Sedum acre, S. kamtschaticum, and S. reflexum. Actively weeded but no nutrient has ever been applied. Roots have penetrated mineral wool all areas observed (see bottom right photo). Bound mineral wool measured approximately 2” (0% compression). System is noticeably “springy” under foot. This installation is part of a side-by-side comparison with a traditional aggregate-based green roof system. In summer 2013, after 5 weeks of drought with no irrigation, both green roofs were probed to gauge relative moisture content through the substrate. The traditional aggregate green roof was “dusty” and dry at the surface and throughout the profile, and Sedum plants had entered drought-induced dormancy. The mineral wool green roof was dusty and dry at the surface, but the lower 1-inch of the 3-inches of media was cool and moist to the touch, and the surface of the mineral wool was slightly moist. Plants in the mineral wool green roof were actively sprouting new buds, even after 5 weeks with no rain.

Mineral Wool In Green Roofs

May 2015

Furbish :: 3430 2nd Street, Suite 100 :: Baltimore, MD 21225 :: 443.874.7465 :: www.furbishco.com

© Furbish 2015. All Rights Reserved

Roots of Carex flacca, Phlox subulata, Eupatorium hyssopifolium, Tradescantia ohioensis after 2 years of growth in an EcoCline mineral wool green roof.

www.mineralwoolingreenroofs.com