RoofViews

Building Science

Designing for Moisture Durability & Energy Efficiency

By Benjamin Meyer

May 06, 2020

A city view through a window pane filled with water droplets

There can be a perception in the market that a "green building" is a better building, and that the risks associated with "building differently" are inherently covered by the green certifications driving the industry forward from a sustainability standpoint. Both better buildings and risk mitigation can be accomplished by green buildings, and this article will discuss some of the key principles to accomplish this for building enclosures and roof assemblies.

Moisture durability of enclosure systems focuses on the interaction of the materials, assemblies, and their design configurations in the building. The goal of managing moisture durability is to establish performance expectations, allow enclosures to perform as intended, continue to perform through the project lifecycle, and be serviced or maintained in a way that minimizes risk of damage to the enclosure and performance of other critical building systems. This discussion is going to focus on the moisture durability aspects of buildings and how they relate to energy performance and lifecycle expectations. While other aspects of resilience are also important, these aspects target risks that are not necessarily related to climate change, but are related to the design of enclosure and roof assemblies directly.

Moisture Durability in Context

The American Institute of Architects defines olor: #333f48;"> as "mitigating risk for hazards, shocks, and stresses and adapting to changing conditions". Resilience goes beyond the minimum code requirements to address issues that influence long-term performance (more here about Sustainability and Resilience). The "hazards, shocks, and stressors" can come from external sources as well as from the design decisions of the built environment. Some are rare extreme events such as tornadoes and wildfires, and some are common and persistent adverse events, like moisture risks in the building enclosure. This perspective of moisture durability as a risk fits within many existing terms and goals that stem from Sustainability, Resilience, Adaptability, and Mitigation initiatives; moisture durability fits within these goals and is not separate from them.

Moisture durability and energy efficiency are part of resilient design

Energy Efficiency is a Moving Target

The minimum or baseline energy efficiency performance expectation has been improving over time. The cost-effective and validated energy saving of one of the underlying national energy standards has increased in each of ANSI/ASHRAE/IES Standard 90.1-2016 (ASHRAE 90.1) 3-year publications. The ASHRAE 90.1 – 2019 version has also recently been published and was validated by the Pacific Northwest National Laboratory as an additional 5% of savings over the previous 2016 version.

Compounding the energy savings, green building rating systems generally require additional savings beyond the baseline and provide points for exceeding the baseline. In addition, the energy performance requirements within green certification systems are also improving. For example, the same energy savings that would have contributed 10 points to the LEED v3 rating system, is roughly equivalent to the starting energy savings required in LEED v4.1, which is currently in the pilot phase.

Increasing efficiency requirements are compounded by green rating systems.

Not every local jurisdiction is adopting the same base codes and standards, which leads to additional confusion in the design and construction industry.

Interactive Complexity and Tight Coupling

The book Normal Accidents by Charles Perrow explains how significant technological advancement can lead to failures. Perrow describes two main components of "normal accidents." The first component being "interactive complexity" as a function of the number and degree of system interrelationships; when this factor is high surprises are expected. The second component is "tight coupling," the degree at which initial failures can concatenate rapidly to bring down other parts of the system; the more highly-linked surprises are not easily isolated and resolved. If a system has only one of the two components then it is still a risk but is more easily managed. When "interactive complexity" and "tight coupling" are combined, accidents could be considered "normal" or expected according to Perrow.

As more materials and additional requirements are added to enclosures, it is important to recognize when materials and assemblies need to change in order to achieve higher energy performance. In a broad sense, as energy efficiency is improved in building enclosures, moisture risks can increase from decreased heat flow across the assemblies. The changes in enclosures can manifest as generally lower exterior surface temperatures (during heating months) as the exterior is less dependent on the interior space conditioning. As we improve energy efficiency, we may also be increasing moisture risks in building enclosures. And the increased risk may be more complex than the historical designs and more tightly coupled to the building's HVAC operations, structural elements, and occupant-use conditions.

Energy efficiency improvements can lead to increased moisture risks in a building enclosure

Moisture Management in Green Building Rating Systems

is tempting to assume that the building enclosure will work perfectly and water won't get where it doesn't belong. Such a belief can lead to a lack of risk mitigation from a very likely hazard (water) throughout the useful life of the building. A more realistic mindset is: moisture intrusion cannot be completely avoided, it must be managed. Enclosures should be designed to manage incidental water with minimal long-term impact. The key is for the enclosure design to have a greater capacity for drying than its risk of wetting.

This moisture durability assessment looks at six primary categories for an enclosure. Roughly working across the project life-cycle, they are shown in the figure below:

Moisture durability elements and assessment project life-cycle details

For the moisture durability assessment, the four most common green building rating systems available for new construction projects are compared against the six categories shown in the previous figure. The green building rating systems reviewed are:

  • Leadership in Energy & Environmental Design (LEED®), version 4.1
  • Green Globes®, version 2019
  • Living Building Challenge (LBC™), version 4.0
  • 2018 International Green Construction Code (IgCC®)

Green building rating systems moisture durability summary

This graphic summarizes each of the six individual detailed assessments reviewed across the project life-cycle phases. There is quite a range of results across the green building rating systems assessed.

Key Takeaways

When designing for moisture durability and energy efficiency in enclosures and roof systems, consider all project phases. This includes utilizing the building enclosure commissioning process to more formally ensure the relevant moisture durability risks are being assessed by an enclosure professional. It is important to recognize that overlooking one of the project phases may result in unmanaged risk for the long term building performance. Some of the systems have direct coverage of individual elements of moisture risk mitigation, but the certification frameworks may not be sufficient to rely on to provide comprehensive moisture durability mitigation. This is especially important knowing all four rating systems have mandatory energy efficiency improvements beyond code-minimum requirements, but none of the four have a complete set of mandatory credits to accommodate the increased moisture risk associated with the added enclosure complexity.

Check back for follow-up articles on moisture durability, including notable highlights from the green building rating system detailed assessment and an example applying the elements of moisture durability to a roof system.


For more information on designing for moisture durability considerations with green building certifications and individual credit assessments, register for the Continuing Education Center webinar, Addressing Moisture Durability and Energy Performance in Roof Assemblies: A Critical Review of Multiple Voluntary Green Building Certifications, sponsored by GAF and presented by Benjamin Meyer, AIA, LEED AP and James R. Kirby, AIA.

About the Author

Benjamin Meyer, AIA, LEED AP is a Roofing & Building Science Architect with GAF. Previous experience includes: enclosure consultant principal, technical management for enclosure products, commercial design, real estate development and construction management on a range of projects that included residential, educational, offices, and DuPont industrial projects. Industry positions include: Voting Member of the ASHRAE 90.1 Envelope and Project Committees, LEED Technical Committee member, past Technical Advisor of the LEED Materials (MR) TAG, and Director of the Air Barrier Association of America (ABAA).

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Thermal Bridging Through Roof Fasteners: Why the Industry Should Take Note

What is going on here?No, this roof does not have measles, it has a problem with thermal bridging through the roof fasteners holding its components in place, and this problem is not one to be ignored.As building construction evolves, you'd think these tiny breaches through the insulating layers of the assembly, known as point thermal bridges, would matter less and less. But, as it happens, the reverse is true! The tighter and better-insulated a building, the bigger the difference all of the weak points, in its thermal enclosure, make. A range of codes and standards are beginning to address this problem, though it's important to note that there is often a time lag between development of codes and their widespread adoption.What Is the Industry Doing About It?Long in the business of supporting high-performance building enclosures, Phius (Passive House Institute US) provides a Fastener Correction Calculator along with a way to calculate the effect of linear thermal bridges (think shelf angles, lintels, and so on). By contrast, the 2021 International Energy Conservation Code also addresses thermal bridging, but only considers framing materials to be thermal bridges, and actually pointedly ignores the effects of point loads like fasteners in its definition of continuous insulation: "insulation material that is continuous across all structural members without thermal bridges other than fasteners and service openings" (Section C202). Likewise, The National Energy Code of Canada for Buildings: 2020 addresses thermal bridging of a number of building components, but also explicitly excludes fasteners: "in calculating the overall thermal transmittance of assemblies…fasteners need not be taken into account" (Section 3.1.1.7.3). Admittedly, point thermal bridges are often excluded because it is challenging to assess them with simple simulation tools.Despite this, researchers have had a hunch for decades that thermal bridging through the multitude of fasteners often used in roofs is in fact significant enough to warrant study. Investigators at the National Bureau of Standards, Oak Ridge National Laboratory, the National Research Council Canada, and consulting firms Morrison Hershfield and Simpson Gumpertz & Heger (SGH), have conducted laboratory and computer simulation studies to analyze the effects of point thermal bridges.Why Pay Attention Now?The problem has been made worse in recent years because changes in wind speeds, design wind pressures, and roof zones as dictated by ASCE 7-16 and 7-22 (see blogs by Jim Kirby and Kristin Westover for more insight), mean that fastener patterns are becoming denser in many cases. This means that there is more metal on average, per square foot of roof, than ever before. More metal means that more heat escapes the building in winter and enters the building in summer. By making our buildings more robust against wind uplift to meet updated standards, we are in effect making them less robust against the negative effects of hot and cold weather conditions.So, how bad is this problem, and what's a roof designer to do about it? A team of researchers at SGH, Virginia Tech, and GAF set out to determine the answer, first by simplifying the problem. Our plan was to develop computer simulations to accurately anticipate the thermal bridging effects of fasteners based on their characteristics and the characteristics of the roof assemblies in which they are used. In other words, we broke the problem down into parts, so we could know how each part affects the problem as a whole. We also wanted to carefully check the assumptions underlying our computer simulation and ensure that our results matched up with what we were finding in the lab. The full paper describing our work was delivered at the 2023 IIBEC Convention and Trade Show, but here are the high points, starting with how we set up the study.First, we began with a simple 4" polyisocyanurate board (ISO), and called it Case A-I.Next, we added a high-density polyisocyanurate cover board (HD ISO), and called that Case A-II.Third, we added galvanized steel deck to the 4" polyiso, and called that Case A-III.Finally, we created the whole sandwich: HD ISO and ISO over steel deck, which was Case A-IV.Note that we did not include a roof membrane, substrate board, air barrier, or vapor retarder in these assemblies, partly to keep it simple, and partly because these components don't typically add much insulation value to a roof assembly.The cases can be considered base cases, as they do not yet contain a fastener. We needed to simulate and physically test these, so we could understand the effect that fasteners have when added to them.We also ran a set of samples, B-I through B-IV, that corresponded with cases A-I through A-IV above, but had one #12 fastener, 6" long, in the center of the 2' x 2' assembly, with a 3" diameter insulation plate. These are depicted below. The fastener penetrated the ISO and steel deck, but not the HD ISO.One visualization of the computer simulation is shown here, for Case B-IV. The stripes of color, or isotherms, show the vulnerability of the assembly at the location of the fastener.What did we find? The results might surprise you.First, it's no surprise that the fastener reduced the R-value of the 2' x 2' sample of ISO alone by 4.2% in the physical sample, and 3.4% in the computer simulation (Case B-I compared to Case A-I).When the HD ISO was added (Cases II), R-value fell by 2.2% and 2.7% for the physical experiment and computer simulation, respectively, when the fastener was added. In other words, adding the fastener still caused a drop in R-value, but that drop was considerably less than when no cover board was used. This proved what we suspected, that the HD ISO had an important protective effect against the thermal bridging caused by the fastener.Next, we found that the steel deck made a big difference as well. In the physical experiment, the air contained in the flutes of the steel deck added to the R-value of the assembly, while the computer simulation did not account for this effect. That's an item that needs to be addressed in the next phase of research. Despite this anomaly, both approaches showed the same thing: steel deck acts like a radiator, exacerbating the effect of the fastener. In the assemblies with just ISO and steel deck (Cases III), adding a fastener resulted in an R-value drop of 11.0% for the physical experiment and 4.6% for the computer simulation compared to the assembly with no fastener.Finally, the assemblies with all the components (HD ISO, ISO and steel deck, a.k.a. Cases IV) showed again that the HD ISO insulated the fastener and reduced its negative impact on the R-value of the overall assembly. The physical experiment had a 6.1% drop (down from 11% with no cover board!) and the computer simulation a 4.2% drop (down from 4.6% with no cover board) in R-value when the fastener was added.What Does This Study Tell Us?The morals of the study just described are these:Roof fasteners have a measurable impact on the R-value of roof insulation.High-density polyisocyanurate cover boards go a long way toward minimizing the thermal impacts of roof fasteners.Steel deck, due to its high conductivity, acts as a radiator, amplifying the thermal bridging effect of fasteners.What Should We Do About It?As for figuring out what to do about it, this study and others first need to be extended to the real world, and that means making assumptions about parameters like the siting of the building, the roof fastener densities required, and the roof assembly type.Several groups have made this leap from looking at point thermal bridges to what they mean for a roof's overall performance. The following example was explored in a paper by Taylor, Willits, Hartwig and Kirby, presented at the RCI, Inc. Building Envelope Technology Symposium in 2018. In that paper, the authors extended computer simulation results from a 2015 paper by Olson, Saldanha, and Hsu to a set of actual roofing scenarios. They found that the installation method has a big impact on the in-service R-value of the roof.They assumed a 15,000-square-foot roof, fastener patterns and densities based on a wind uplift requirement of 120 pounds per square foot, and a design R-value of R-30. In this example, a traditional mechanically attached roof had an in-service R-value of only R-25, which is a 17% loss compared to the design R-value.An induction-welded roof was a slight improvement over the mechanically attached assembly, with an in-service value of only R-26.5 (a 12% loss compared to the design R-value).Adhering instead of fastening the top layer of polyiso resulted in an in-service R-value of R-28.7 (a 4% loss compared to the design R-value).Finally, in their study, an HD polyiso board was used as a mechanically fastened substrate board on top of the steel deck, allowing both layers of continuous polyiso insulation and the roof membrane to be adhered. Doing so resulted in an in-service R-value of R-29.5, representing only a 1.5% loss compared to the design R-value.To operationalize these findings in your own roofing design projects, consider the following approaches:Consider eliminating roof fasteners altogether, or burying them beneath one or more layers of insulation. Multiple studies have shown that placing fastener heads and plates beneath a cover board, or, better yet, beneath one or two layers of staggered insulation, such as GAF's EnergyGuard™ Polyiso Insulation, can dampen the thermal bridging effects of fasteners. Adhering all or some of the layers of a roof assembly minimizes unwanted thermal outcomes.Consider using an insulating cover board, such as GAF's EnergyGuard™ HD or EnergyGuard™ HD Plus Polyiso cover board. Installing an adhered cover board in general is good roofing practice for a host of reasons: they provide enhanced longevity and system performance by protecting roof membranes and insulation from hail damage; they allow for enhanced wind uplift and improved aesthetics; and they offer additional R-value and mitigate thermal bridging as shown in our recent study.Consider using an induction-welded system that minimizes the number of total roof fasteners by dictating an even spacing of insulation fasteners. The special plates of these fasteners are then welded to the underside of the roof membrane using an induction heat tool. This process eliminates the need for additional membrane fasteners.Consider beefing up the R-value of the roof insulation. If fasteners diminish the actual thermal performance of roof insulation, building owners are not getting the benefit of the design R-value. Extra insulation beyond the code minimum can be specified to make up the difference.Where Do We Go From Here?Some work remains to be done before we have a computer simulation that more closely aligns with physical experiments on identical assemblies. But, the two methods in our recent study aligned within a range of 0.8 to 6.7%, which indicates that we are making progress. With ever-better modeling methods, designers should soon be able to predict the impact of fasteners rather than ignoring it and hoping for the best.Once we, as a roofing industry, have these detailed computer simulation tools in place, we can include the findings from these tools in codes and standards. These can be used by those who don't have the time or resources to model roof assemblies using a lab or sophisticated modeling software. With easy-to-use resources quantifying thermal bridging through roof fasteners, roof designers will no longer be putting building owners at risk of wasting energy, or, even worse, of experiencing condensation problems due to under-insulated roof assemblies. Designers will have a much better picture of exactly what the building owner is getting when they specify a roof that includes fasteners, and which of the measures detailed above they might take into consideration to avoid any negative consequences.This research discussed in this blog was conducted with a grant from the RCI-IIBEC Foundation and was presented at IIBEC's 2023 Annual Trade Show and Convention in Houston on March 6. Contact IIBEC at https://iibec.org/ or GAF at BuildingScience@GAF.com for more information.

By Authors Elizabeth Grant

November 17, 2023

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Building Science

Developing Best Practice Solutions for GAF and Siplast Customers

With any roofing project, there are a number of factors to consider when choosing the right design: sustainability profile, potential risks, overall performance, and more. Our Building and Roofing Science (BRS) team specializes in working with industry professionals to help them enhance their roof designs across all of these areas. Leveraging their building enclosure expertise, our BRS team serves as thought leaders and collaborators, helping design professionals deliver better solutions for their customers."We're a consultant's consultant. Basically, we're a sounding board for them," explains Jennifer Keegan, Director of Building and Roofing Science. Rather than solely providing product specifications and tactical support, the BRS team partners with consultants, specifiers, and architects to provide guidance on designing high-performing roofs that don't just meet code, but evolve their practices and thinking. For example, this might include understanding the science behind properly placed air and vapor retarders.As experts in the field, our BRS team members frequently attend conferences to share their expertise and findings. As Jennifer explains, "Our biggest goal is to help designers make an informed decision." Those decisions might be in a number of areas, including the building science behind roof attachment options, proper placement of air and vapor retarders, and how a roof can contribute to energy efficiency goals.Expanding the BRS TeamOur BRS team is accessible nationwide to look at the overall science of roof assembly and all of the components and best practices that make up a high-performance, low-risk, and energy-efficient roof. Our regional experts are positioned strategically to better serve our customers and the industry as a whole. We have the capacity to work with partners across the country on a more personalized level, providing guidance on roof assembly, membrane type, attachment method, or complicated roof details including consideration of the roof to wall interface.Partnering with the Design Services TeamIn addition to our newly expanded BRS team, GAF also offers support through its Design Services team. This group helps with traditional applications, installations, and system approvals. GAF's Design Services team is a great resource to answer any product questions, help you ensure your project meets applicable code requirements, assess compatibility of products, outline specifications, and assist with wind calculations. By serving as the front line in partnership with our BRS team, the Design Services team can help guide the design community through any phase of a project.GAF's Building and Roofing Science team is the next step for some of those trickier building projects, and can take into consideration air, vapor, and thermal requirements that a designer might be considering for their roof assembly. Through a collaborative process, our BRS team seeks to inspire project teams, as Jennifer explains, "to do it the best way possible."Engaging with the TeamsGAF has the support you need for any of your design and roofing science needs. To request support from the GAF Design Services team, you can email designservices@gaf.com. For additional support from our Building and Roofing Science team regarding specialty installations or how a building can be supported by enhanced roof design, contact us at buildingscience@gaf.com.Our Building and Roofing Science team is always happy to support you as you work through complex jobs. You can also sign up to join their office hours here.

By Authors GAF Roof Views

May 08, 2023

Edge metal
Building Science

Edge Metal Design Wall Zones 4 and 5

Keeping water out of a building is undoubtedly the primary function of a roof system. But one could argue that ensuring a building's roof stays in place during high-wind events is equally important. Let's face it, without a roof, it's hard to keep water out! This blog takes a look at one of the subsets of wind design of roof systems: Wall Zones 4 and 5 and their relationship with roof perimeters.IntroductionArchitects, specifiers, and roof system designers are generally focused on the wind-uplift capacity of the roof system itself. Wind resistance of perimeter edges and parapets might not be front of mind, especially given the myriad roof-system Approval Listings that can be found through DORA, FM, and UL. However, rooftop perimeters and corner areas are most vulnerable to high wind, and perimeter edge metal and copings are part of the first line of defense. Codes now include wind-design and system testing for edge metal and copings. FM also just recently (late 2021) updated RoofNav's Wind Rating Calculator to include fascia, copings, and gutters.Edge metal and copingsThe term 'edge metal' encompasses three foundational shapes that are used at a roof's perimeter: L-shaped metal, gravel stop metal, and copings for parapets. The figures below show generic shapes; ones that are often contractor-fabricated. Additionally, there are many manufacturers that provide edge metal. Some of the manufacturer-fabricated shapes are similar to those shown below. However, some are a bit more distinct and some are extruded to achieve more unique shapes.Graphic adapted from National Roofing Contractors AssociationSome examples of GAF's metal details are shown here:Steel and aluminum are common materials used for edge metal shapes and copings. Some are galvanized; some are painted. Commonly used thicknesses range from 20 gauge to 24 gauge for steel and 0.032" to 0.040" for aluminum. The continuous cleat is typically one gauge thicker than the edge metal and coping.Why is wind design of edge metal important?The roofing industry has been investigating high-wind events, primarily through a group called the Roofing Industry Committee on Weather Issues (RICOWI). RICOWI was established in 1990 and has published numerous reports based on post-wind-event investigations of damage caused by hurricanes. RICOWI's most recent report, released November 19, 2019, covers their investigation of the damage caused by Hurricane Michael. RICOWI has published five reports covering their investigations of 6 hurricanes since 2004.One of the most consistent conclusions throughout the series of 5 reports of post-event investigations is that the majority of localized roof damage and roof system failures due to high winds commonly begin at perimeters and corners. This is not surprising as the highest wind loads are at rooftop perimeters and corners. This blog about wind design and ASCE-16, among other topics, discusses the process and factors used to determine wind loads, and it provides additional information about roof zone layout. Localized roof damage and roof system failures due to high winds commonly begin at perimeters and corners. Not recognizing the importance of edge metal design relative to the overall wind performance of a roof system can result in edge metal installations that may not have the appropriate wind-resistance capacity. This could possibly result in localized damage and/or system failures, even when the roof system (i.e., deck, insulation, membrane) is appropriately designed for design wind loads.The following information is intended to supplement the wind design concepts that were discussed in GAF's earlier blog about wind design and ASCE 7-16.Roof and Wall ZonesWind design of metal edges and copings includes an upward and an outward component, unlike the primary roof system which includes an upward component only. (The Edge Metal Testing section of this blog has more information on that topic). ASCE 7 calls the outward pressures acting on metal edges and copings Wall Zones 4 and 5. Wall Zone 4 correlates and is aligned with Roof Zone 2 (the perimeter zones), and Wall Zone 5 is aligned with Roof Zone 3 (the corner zones). The figure shows one example of a building's roof and wall zones. Case studies from this blog provide more specific information related to the figure below.What do the codes say?The International Building Code (IBC) includes requirements for determining the wind-load capacity for metal edges and copings. This requirement has been included since the 2003 version of the IBC. In other words, edge metal and copings should have wind-resistance capacities greater than the design wind pressures. This concept is just like wind design for the primary roof system—the capacity of the system needs to be greater than the anticipated loads.Chapter 15, Section 1504.5 from the 2015 IBC includes requirements for determining the capacity of metal edges and copings."1504.5 Edge securement for low-slope roofs. Low-slope built-up, modified bitumen and single-ply roof system metal edge securement, except gutters, shall be designed and installed for wind loads in accordance with Chapter 16 and tested for resistance in accordance with Test Methods RE-1, RE-2 and RE-3 of ANSI/SPRI ES-1, except Vu1t wind speed shall be determined from Figure 1609A, 1609B, or 1609C as applicable."Chapter 16 of the IBC indirectly includes requirements for determining the wind loads acting on metal edges and copings. In Section 1609.1 Applications, the IBC states "Buildings, structures and parts thereof shall be designed to withstand the minimum wind loads…" The "parts thereof" encompasses metal edges and copings. The requirement in Chapter 15 to design and install metal edges and copings means the outward pressures for Wall Zones 4 and 5 need to be determined.It's worth noting that the scope of the ANSI/SPRI ES-1 test method does not include gutters, which is why gutters are specifically excluded in the code language through 2018. However, SPRI, in 2016, published ANSI/SPRI GT-1, Test Standard for Gutters, which was first included in model codes in the 2021 IBC.Edge metal testingDetermining the design wind pressures (in pounds per square foot) for Wall Zones 4 and 5 is generally the responsibility of the design professional, such as the architect or structural engineer. On the other hand, determining the capacity of metal edges and copings is generally the responsibility of the manufacturer, which may be a manufacturing company or a roofing contractor that fabricates their own metal edges, coping, and clips and cleats.The IBC specifically lists ANSI SPRI ES-1, Test Standard for Edge Systems Used with Low Slope Roofing, as the test method to be used to determine capacity for metal edges and copings. ES-1 includes three (3) test methods (RE-1, RE-2, RE-3), each for a different edge condition.The RE-1 test method is for 'dependently terminated roof membrane systems'. Essentially, a mechanically attached or ballasted membrane is considered to be dependently terminated if a "peel stop" or row of fasteners is not included within 12" from the roof edge. Without a peel stop or a row of fasteners close to the edge of the roof, the edge metal is acting as the mechanical attachment of the perimeter of the membrane. (The RE-1 figure below is rotated clockwise 115 degrees to show the as-tested configuration of the metal edge. ES-1 presumes a ballasted or mechanically attached membrane will flutter and apply load to the metal edge at 25 degrees. The rotated configuration accommodates a hanging load.)The RE-2 test method is for essentially all metal edge types as long as the "horizontal component" is 4" wide or less.The RE-3 test method is for copings, and RE-3 includes two tests. One test includes an upward load and a 'face' load; the second test includes an upward load and the 'back leg' load.The wind-resistance capacity of metal edges and copings is provided in "pounds per square foot" (psf). This is appropriate because the design wind pressures are also in PSF values which makes the comparison of design wind pressures to wind-resistance capacity simple.Where to find Approval Listings for edge metalSimilar to approval listings for roof systems, there are approval listings for metal edges and copings. Approval Listings are found on FM's RoofNav and UL's Product IQ. An account (free) is required for both. Additionally, NRCA has Approval Listings for contractor-fabricated metal edges and copings which are housed on UL's Product IQ and Intertek's Directory of Building Products.ULKnowing UL's Category Control Number is key to navigating UL's Product IQ. . For metal edges and coping, UL's Category Control Number is "TGJZ". After logging in, performing a search using "TGJZ" provides a list of the manufacturers that have Approval Listings with UL. Clicking on GAF's Approval Listings allows users to easy find rated Roof-edge Systems, Metal, for Use with Low-slope Roofing Systems.Within UL's TGJZ category, GAF has 16 metal-edge products rated using the RE-2 test method and 8 coping products rated using the RE-3 test method. For example (as shown in item 3 in the screen capture above), GAF's M-Weld Gravel Stop MB Fascia B made with aluminum is rated "190 psf". That means this product can be used when the design wind pressures, which include a safety factor, for Wall Zones 4 and 5 are less than or equal to 190 psf.FM's RoofNavWithin RoofNav, Approval Listings for metal edges and copings can be found under "Product Search" using the "Flashing" category. Most likely, users of RoofNav are familiar with the "Assembly Search" function which is regularly used to locate roof systems based on their wind-uplift ratings.The search can be further refined within "Subcategory" by selecting Expansion Joint, Gutter, or Perimeter Flashing.Currently, GAF has 59 Approval Listings in RoofNav: 12 for Coping, 41 for Fascia, and 6 for Gutter products. A screen capture from RoofNav shows GAF's first 20 products.Looking closely at the Listing, the EverGuard EZ Fascia AR – Steel provides detailed information about the product itself and the installation requirements. As shown below, the listing includes multiple Ratings (i.e., wind-uplift capacity) based on material type and thickness, and face height.While the Listing is for a steel fascia, an aluminum fascia is also shown in the detailed information. It's important to note that the chart with the "steel" listing's detailed information is the same chart that is available for EverGuard EZ Fascia AR – Aluminum, as well. Therefore, it's prudent for designers and specifiers to provide appropriate information in the specification to avoid mis-communiction about intended product use.Take note of the material and gauge of the "retainer" (i.e., the continuous cleat). The continuous cleat is required to be 0.50 aluminum, regardless of fascia material type for this Listing. Because the strength of the cleat is a significant factor to the overall wind-uplift capacity of the metal edge (or coping), increasing the thickness of the cleat proves to be an effective method to increase performance.FM RoofNav and Edge SecurementFM announced on its website on October 28, 2021 that "The Wind Ratings Calculator has been updated to return separate flashing ratings for roofs." The red-highlighted area shows the required capacity for Fascia, Coping, and Gutter products.Comparison of the Minimum Wind Uplift Approval Ratings Needed (1-75, 1-90) to the Perimeter and Corner Ratings of the EverGuard EZ Fascia shows that each product type provides the required capacity, and in most cases the required capacity greatly exceeds the required rating.Load PathThe 3 test methods included in ANSI/SPRI ES-1 standard determine the wind-resistance capacity of edge metal attached to a substrate. In other words, the measured capacity (Rating) is of the metal edge or coping attached to the wood blocking; the tests do not measure the capacity of the attachment of the wood blocking to any substrate. The National Roofing Contractors provide information on this topic. The NRCA Roofing Manual: Membrane Roof Systems—2019, on page 289 states:"Wood Nailers and Blocking: Many of the construction details illustrated in this manual depict wood nailers and blocking at roof edges and other points of roof termination. Wood nailers must be adequately fastened to the substrate below to resist uplift loads. This especially is true at parapet walls/copings and roof edges where edge-metal shapes are fastened to wood blocking.Among other advantages, the nailers provide protection for the edges of rigid board insulation and provide a substrate for anchoring flashing materials. Wood nailers should be a minimum of 2 x 6 nominal-dimension lumber. To provide an adequate base, nailers should be securely attached to a roof deck, wall and/or structural framing. In the design of specific details for a project, a designer should describe and clearly indicate the manner in which wood nailers and/or blocking should be incorporated into construction details. A designer should specify the means of attachment, as well as the fastening schedule for all wood nailers and blocking."To that end, FM Global Property Loss Prevention Data Sheet 1-49, Perimeter Flashings, provides a number of recommendations for anchoring wood blocking to various types of walls and structural framing. One example of a roof/wall intersection shows the bottom nailer bolted to the bar joists to ensure an adequate load path.In SummaryArchitects, specifiers, and roof system designers are required by code (always check specific local requirements) to determine wind loads not only for the primary roofing system, but for the metal edges and copings as well. Manufacturers and fabricators are responsible for determining the wind-uplift capacity of their metal edge and coping products, as well as their primary roofing systems.Given the relatively new requirements in the IBC for edge securement, designers, consultants, and specifiers should become familiar with both UL's and FM's approval listings for metal edges and copings. Manufacturers of metal edge and coping products are available to assist designers with selection of edge securement.

By Authors James R Kirby

April 24, 2023

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