Understanding FM 1-52
August 21, 2019
There are two recognized field test methods for determining uplift resistance of adhered membrane roof systems, both of which can be problematic:
  1. ASTM E907, "Standard Test Method for Field Testing Uplift Resistance of Adhered Membrane Roofing Systems," and 
  2. FM Global Loss Prevention Data Sheet 1-52 (FM 1-52), "Field Verification of Roof Wind Uplift Resistance." 
Both test methods provide for affixing a 5’ x 5’ dome-like chamber to the roof’s surface and applying a defined negative (uplift) pressure inside the chamber to the roof system's exterior-side surface using a vacuum pump, like in the photo below. 

An example of a test chamber used for negative-pressure uplift testing

However, ASTM E907 and FM 1-52 differ notably in their test cycles and maximum test pressures for determining roof system deflections and whether a roof system passes or is “suspect”.
  • Using ASTM E907, a roof system is “suspect” if the deflection measured during the test is 25 mm (about 1 inch) or greater. 
  • Using FM 1-52, a roof system is “suspect” if the measured deflection is between ¼ of an inch and 15/16 of an inch, depending on the maximum test pressure; 1 inch where a thin cover board is used; or 2 inches where a thin cover board or flexible, mechanically attached insulation is used. 
Test results' reliability 
The reliability of the results derived from ASTM E907 and FM 1-52 is a concern, especially when the tests are used for quality assurance purposes. A note in ASTM E907 acknowledges its test viability. "Deflection due to negative pressure will potentially vary at different locations because of varying stiffness of the roof system assembly. Stiffness of a roof system assembly, including the deck, is influenced by the location of mechanical fasteners, thickness of insulation, stiffness of deck, and by the type, proximity, and rigidity of connections between the deck and framing system."

For example, when testing an adhered roof system over a steel roof deck, placement of the test chamber relative to the deck supports (bar joists) can have a significant effect on the test results. If positioned between deck supports, the test chamber's deflection gauge will measure roof assembly deflection at the deck's midspan, which is the point of maximum deck deflection. Also, in many instances, field-uplift testing results in steel roof deck overstress and deck deflections far in excess of design values, which can result in roof system failure. These situations can result in false “suspect” determinations of a roof system.

Industry position/recommendations

Because of the known variability in test results using ASTM E907 and FM 1-52 and the lack of correlation between laboratory uplift-resistance testing and field-uplift testing, the roofing industry considers field-uplift testing to be inappropriate for use as a post-installation quality-assurance measure for membrane roof systems.

Conclusion

FM 1-52 is an FM Global-promulgated evaluation method and not a recognized industry-consensus test standard. The scope of FM 1-52 indicates that it’s only intended to confirm acceptable wind-uplift resistance on completed roof systems in hurricane-prone regions, where a partial blow-off has occurred, or where inferior roof system construction is suspected or known to be present.

FM 1-52 was originally published by FM Global in October 1970. The negative-pressure uplift test was added in August 1980 and has been revised several times. The current edition is dated July 2012 and includes an option for "visual construction observation (VCO)" as an alternative to negative-pressure uplift testing. VCO provides for full-time, third-party monitoring to verify roof system installation is in accordance with contract documents.

For more information, contact Craig Tyler
March 4, 2020
ENERGY STAR Roofing Program Phaseout

The ENERGY STAR® Roofing Program will be phased out by June 1, 2022 The U.S. Environmental Protection Agency (EPA) has announced they are sunsetting the ENERGY STAR reflective roof program effective June 1, 2022. Program Partners must cease production of printed or electronic marketing material using the ENERGY STAR mark by June 1, 2021. All references to ENERGY STAR must cease by June 1, 2022. As a leader in the commercial roofing industry and the largest manufacturer of reflective and non-reflective roofing materials, Carlisle Construction Materials supports this change, as it eliminates one source of confusion regarding energy efficient roof design. As a rule of thumb for energy efficiency, reflective roofs are best suited for cooling-dominated climates where buildings' air conditioning demands or costs exceed their heating demands – typically, southern markets in ASHRAE Zones 1, 2, and parts of 3. In heating-dominated climates, a non-reflective roof covering is ideal to reduce heating costs (and the burning of fossil fuels) as well to as mitigate the risk of condensation-related issues within the roofing assembly. Carlisle continues to advocate for careful selection of complete roofing systems based on required performance attributes and considering the building's design, intended use, location, and climatic conditions. Additional Resources For more information on roof condensation, reference the November 2012 Design Advisory on how to avoid condensation issues from occupancy- or construction-generated moisture. November 2012 Design Advisory For more information on the condensation risks of cool roofs, check out this short animation. Condensation Risks of Cool Roofs For further reading, visit the Carlisle SynTec website for a white paper on Mechanically Attached Roof Systems in Cold Climate Zones. White Paper Contact Craig Tyler at Craig.Tyler@CarlisleCCM.com with questions.

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February 19, 2020
FM’s VSH Testing – Very Severe Hail

FM Global, a leading commercial building insurer, and its code-approved testing agency subsidiary, FM Approvals, have created a Very Severe Hail (VSH) impact resistance classification that could affect design professionals. FM Global Guidelines Traditionally, FM Global has recommended its insured building owners use moderate hail (MH) and severe hail (SH) classified roof systems for buildings located in areas FM Global considers to be susceptible to moderate or severe hail impacts. FM Loss Prevention Data Sheet 1-34 ("Hail Damage") provides a map identifying these regions. In recent years, the insurance industry in the United States has seen an uptick in losses from hail in terms of the number of claims experienced and costs of those claims. A majority of the hail damage occurs to roof systems and other rooftop components. In the latest version of FM 1-34 (April 2019), FM Global identified a new VSH region encompassing Oklahoma, Kansas, Nebraska, South Dakota, most of Texas, and parts of Montana, North Dakota, Minnesota, Iowa, Missouri, Arkansas, Wyoming, Colorado, and New Mexico.  Per FM Global, this area was classified as a VSH region based on data from the National Oceanic and Atmospheric Administration's National Weather Service and National Center for Environmental Protection's Storm Prediction Center. This data shows a concentration of reports of hail greater than 2 inches in diameter in this geographical region. Until recently, FM Approvals did not have VSH-classified roof systems available to satisfy its recommendation in the VSH region. In the interim, FM 1-34 recommended using assemblies tested to a Class 4 rating using FM 4473 ("Specification Test Standard for Impact Resistance Testing of Rigid Roofing Materials by Impacting with Freezer Ice Balls"). FM 1-34 indicates aggregate- and paver-ballasted roof systems can be substituted for MH- and SH-classified roof systems in the MH and SH regions. However, FM Global restricts the use of aggregate-ballasted roof systems on buildings taller than 150 feet, or in areas where the design wind speed is 100 miles per hour or greater. FM has indicated only paver-surfaced roof systems can be substituted for a VSH-classified roof system. FM 1-34 also contains recommendations for skylights, rooftop HVAC equipment, and other critical outdoor equipment in the MH, SH, and VSH regions. Hail Classifications FM Approvals traditionally has tested and classified membrane roof systems for MH and SH impact resistances using FM 4470 ("Approval Standard for Single-Ply, Polymer-Modified Bitumen Sheet, Built-Up Roofs (BUR) and Liquid Applied Roof Assemblies for use in Class 1 and Noncombustible Roof Deck Construction). This is the same test method on which many FM Approvals roof system classifications are based. Using FM 4470's procedure, MH-classified roof systems withstand a 2-inch-diameter steel ball weighing 1.19 pounds dropped from a height of 81 inches in a section of tubing. This results in an impact energy of about 8 foot-pounds (ft-lbs.) on the surface of the roof system test specimen. SH-classified roof systems withstand the same 2-inch-diameter steel ball dropped from a height of 141.5 inches, resulting in an impact energy of about 14 ft-lbs. on the surface of the roof system test specimen. FM Approvals recently updated its impact-resistance test method to include testing for the VSH classification. The new testing involves propelling 2-inch-diameter preformed ice balls at roof system test specimens using an ice ball launcher. The ice balls are propelled at 152 to 160 feet per second, resulting in an impact energy of 53 to 58 ft-lbs. on the surface of the roof system test specimen. With these higher test standards, new materials and assemblies are being developed and tested to meet the new ratings. Carlisle has introduced a new coverboard, EcoStorm, that can achieve the VSH rating. Carlisle currently has 133 approved VSH approved assemblies. For more information on EcoStorm VSH Coverboard, click here. Contact Brian Emert at Brian.Emert@CarlisleCCM.com with further questions.

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February 5, 2020
Spray Foam for Walls – The Perfect Wall

The challenge with every design is making sure that it will work in a specific environment. Through understanding the principles of a "perfect wall" - one which contains a water-shedding layer, an air control layer, a vapor control layer, and a thermal control layer - we can generate a wall solution that will work in every environment. The control layers are listed in order of importance. All are important, but not equally important. The ranking comes from historic experience and the underlying physics. Controlling water in the liquid form (rain and ground water) has been the focus of architects for generations. Controlling air is a much more recent focus - less than a century. The corollary, however, is too often true for many in the industry. There should be no doubt, the water control layer is much more important than the air control layer. Controlling vapor is even more recent - only a generation or two. Air movement transports significantly more water in vapor form than does vapor diffusion and therefore air control is more important than the control of molecular water vapor. "Air barriers" are more important than "vapor barriers". Thermal control dates back millennia - but getting it wrong has rarely led to durability failures. The thermal control layer failures have been typically limited to comfort issues and operating cost issues. Hence, thermal control layers are listed last on the control layer "priority" list. In the last decade we have been successful at combining the water control layer, air control layer, and vapor control layer into a single layer that can be a film, coating, membrane, or sheet goods. We have also had good success with wrapping the exterior of a building with all of these control layers and then enclosing those control layers with the fourth control layer - the thermal control layer. This configuration, with the thermal control layer outboard of the water, air, and vapor control layers, allows the assembly to be constructed in all climate zones: cold, mixed, hot and humid, or dry. Even better, this configuration allows this assembly to enclose virtually all interior environments in all climate zones: offices, commercial, residential, institutional, pools, museums, art galleries, and data processing centers. The sole exception being refrigerated buildings and cold storage facilities. In such assemblies the location of the thermal control layer is "flipped" with the other control layers - the thermal control layer now becomes located on the interior of the other three control layers. Utilizing spray foam technology, you can create the "perfect wall" with spray polyurethane (SPF) which meets; Water Control Layer - SPF is inherently moisture resistant. Air Control Layer - SPF has an Air Impermeability of <0.02 (L/s/m2) @ 1 inch of mercury. Vapor Control Layer - SPF has a water vapor permeability of 1.4 perm @ 1 inch of mercury. Thermal Control Layer - SPF has an R-Value per inch of 6.9. This also allows for thinner walls and continuous insulation without thermal breaks. Visit the Carlisle Spray Foam Insulation website at carlislesfi.com for more information on how your next project could utilize spray foam insulation as a "perfect wall" solution. Contact Brian Emert at Brian.Emert@CarlisleCCM.com with further questions.

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