Tag Archives: IBC

Quality Control Issues with Fire-related Laminated Glazing

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Photo courtesy Technical Glass Products

by David E. Sacks, R.A., AIA, LEED AP, and Bradford S. Carpenter, PE, LEED AP
Historically, glazing has been used to provide light and ventilation in building walls as its primary function. In contemporary buildings, specialized glazing can provide numerous other functions, including fire-resistance.

The percentage of glazed surface area on buildings continues to increase. One of the reasons is the link between access to natural light and improved health, comfort, and productivity of occupants. This factor, along with the energy costs associated with internal lighting and the resulting cooling loads, have focused attention on the positive attributes of daylighting, in turn driving both policy and architectural aesthetic toward greater use of glass in the building enclosure.

This desire to maximize glazed surface area has been a major factor in the development and increased acceptance of fire-rated curtain-wall glazing systems. While the development of these products continues and manufacturers look to expand market share, the expectations of professionals and end users do not always reflect actual product performance (in terms of optical clarity and aesthetic factors like color).

Similarly, the newness of these products results in undeveloped standards and codes, not fully equipped to check or maintain quality control. Additionally, the infancy of product to the construction market also causes contractor unfamiliarity. Fire-rated curtain wall assemblies are inherently different from non-rated curtain wall assemblies with respect to physical characteristics and installation and handling requirements.

Background
Fire separation distances between adjacent buildings (and stepped portions of the same building) trigger specific code requirements regarding fire-resistance ratings and maximum area of exterior wall openings (Figure 1). Historically, fire-resistance-rated walls have been solid masonry, concrete, or similar non-combustible construction with limited fire-protected openings to fulfill fire-escape egress and light or vent requirements. These openings would be protected with fire-protective-rated window and/or door assemblies—typically, steel fenestration glazed with wired glass or individual units of glass block. The building code further restricts the height, width, and overall area of each glass panel in a fire-protective-rated opening.

fireglass_Fire Separation

Figure 1: International Building Code (IBC) Figure 705.8.6 (Vertical Fire Exposure of Adjacent Building) illustrates the requirement for opening protectives due to the fire separation distance of two adjacent buildings (less than [4.5 m] 15 ft from the building/structure to an imaginary line between the adjacent buildings). Image courtesy IBC 2012

In 2006, the revision to the International Building Code (IBC) included a new section, Section 706.2.1–Fire-resistance-rated Glazing, which was added to clarify the distinction between fire-resistance-rated glazing and fire-protection-rated glazing.

While both types of glazing limit the spread of flames during a fire, fire-resistance-rated glazing also provides a radiant barrier. As such, this glazing may be used to construct the fire barrier—in other words, it is the fire-resistance-rated wall, not just a protective opening in said wall. The 2012 IBC went a step further in clarifying the role of fire-resistance-rated glazing when it published Table 716.3, “Marking Fire-rated Glazing Assemblies.” This table states the “W” marking classifies an assembly as “meeting fire-resistance-rated wall assembly criteria.” The development of intumescent fire-rated glazing—which meets IBC 706.2.1—was a catalyst behind this change.

Intumescent
The term ‘intumescent’ characterizes a material that swells and chars when exposed to flame, forming an insulating fire-retardant barrier between the fire and the material. The development of intumescent materials—such as hydrated sodium silicate, graphite, and mono-ammonium phosphate (MAP)—has enabled glazing systems to make the leap from fire-protective to fire-resistant. As such, the creation of fire-resistive glazing assemblies has virtually erased the limitations on which building surfaces can or cannot be glazed. This has enabled architects to design with more transparent fenestration systems in an effort to achieve aesthetic goals or maximize daylight.

Manufacture and assembly
In order to create intumescent laminated glass, large sheets of annealed glass are set onto horizontal racks with a silicone bead along the perimeter to create a reservoir that is then filled with hydrated sodium silicate in either liquid or prill (i.e. bead) form. Each sheet is then low-baked (<37.7 C [<100 F]); once the intumescent material is set, the perimeter is trimmed off to remove the silicone bead. This process precludes the use of heat-treated glass as the base product in an intumescent laminated glass assembly.

fireglass_Intumescent Glass Illustration rev

Figure 2: This is a section diagram of intumescent laminated glass. Image courtesy The Schott Group

The individual intumescent laminated sheets are then configured according to the desired fire-rating requirements, and baked in an autoclave at a slightly higher temperature to create the final sandwich panel (Figure 2). When that panel is intended for a monolithic installation, an additional layer of glass with a polyvinyl butyral (PVB) lamination is added to one side (i.e. asymmetric) or both sides (i.e. symmetric) of the sandwich panel, depending on the intended use. The panels are then cut to size with a diamond-blade saw and the edges sealed with a special metallic perimeter tape to protect the intumescent interlayer during transportation, construction, and in service.

Material and system limitations
Since the intumescent lamina is not inherently stable, it needs to be protected to prevent deterioration through absorption of atmospheric moisture and general exposure to the atmosphere. Hydrated sodium silicate, which is frequently used as the lamina material, is particularly sensitive to high temperatures, ultraviolet (UV) radiation, and water—a significant challenge, particularly for applications as exterior fenestration glazing. As such, the PVB lamination at the exterior face, the perimeter edge tape, and the unit’s general storage/handling are critical to the sandwich panel’s performance and they hint at the intumescent material’s limitations.

Several intumescent glass manufacturers indicate products must be protected from temperatures at or above 50 C (122 F). This limitation applies to internal (i.e. radiators or halogen lights) and external sources of heat. Additionally, particular attention should be paid to where the external sheet of glass is made of highly absorptive glass (e.g. body-tinted). This temperature sensitivity will limit the applicable climates as well as specific exposures where this glazing may be installed.

Revised Image as requested

Figure 3: This is a sample of 120 intumescent laminated glass with protective metallic tape (arrow) along the perimeter of the glass. Photos courtesy David E. Sacks

The special aluminum tape along the edges provides protection against moisture and general exposure to the atmosphere (Figure 3). Should the tape lose adhesion and become de-bonded before installation in the fenestration system, it must be replaced or taped over prior to installation, and this may have an impact on the product warranty.

One manufacturer’s product warranty, for example, states: “The removal of edge tape from the laminated assembly voids the warranty.” For a full-frame system, where the edges of glass are concealed by the metal frame, the edge tape typically returns to each face of glass 6.35 to 9.5 mm (14 to 38 in.). However, in a butt-glazed configuration, the edge tape does not return to the face of the glass and is much more susceptible to damage during the handling and installation processes.

The application of PVB at the exterior face of all intumescent glazing units reduces UV degradation to the intumescent material, and it is critical for asymmetric units that the non-PVB protected face not be exposed to UV during transport, storage, or installation. Manufacturers provide their products with a stamp readable from the UV-opposed side as 
a guide to installation contractors.

Beyond just the glass orientation, the product’s installation procedure varies greatly from that of a typical curtain wall system. While a traditional curtain wall may use a pressure-glazed system with a pressure bar to seal the gaskets to the glass surface, intumescent laminated glass systems often require only a fraction of that pressure.

On reviewing the product documentation and installation manual of one fire-rated curtain wall system, one manufacturer specifically notes:

Edge pressure must be between 4–10 pounds per linear inch. This pressure is required on the (curtain wall system’s) mullion gaskets. It must be uniformly applied by the exterior-mounted pressure plate, through the glass to the mullion gaskets. Excessive edge clamping pressure will cause deformation and breakage.

The installation manual goes on to describe the pressure plate installation: “Tighten the screw until a maximum of 1.13 to 1.69 Nm (10 to 15 in. pounds) of rotational torque is achieved.” As a point of reference, one non-fire-rated curtain wall system manufacturer states in its literature to torque all pressure plate bolts to 5.65 Nm (50 in. pounds).

As implied by the reduced pressure, intumescent laminated glass manufacturers specifically indicate their glazing systems are not intended for use in pressure-glazed curtain wall systems. Instead, the systems typically employ a glazing tape between the frame and the glass when setting the glass and potentially an additional bead of silicone sealant tooled to be water-shedding on the exterior face. Some manufacturers do not warrant the air and water integrity of a fire-rated curtain wall system if a primary perimeter sealant joint is only installed at the exterior pressure plates or cover caps.

Visual aesthetics and defects
The visual quality of any laminated glazing system will not match that of a non-laminated system, which uses the same glass components. The same holds true when the lamination is an intumescent product. In an effort to mitigate this difference, many manufacturers offer intumescent laminated systems with low-iron glass, which provides higher optical quality (i.e. greater light transmission and less color).

Intumescent laminated glass products are available with low-iron glass. However, sample warranties for these products also include language noting the impact of intumescent interlayers on optical clarity. One product warranty reads:

Due to the nature of its interlayers, (said product) may develop some minor imperfections such 
as small bubbles or a slight distortion which 
will not affect the free vision through the glazing or fire performance. A variation of up to 5% of light transmission or haze shall not be considered a defect.

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Figure 4: This photo displays creasing at the perimeter of the glass, which may occur at one or more of the interlayers.

Unfortunately, expected or allowable visual defects in intumescent laminated glass are not well defined in the United States. (See Figure 4 for an example of creasing and/or streaking.) International Organization for Standardization (ISO) 12543-6, Glass in Building–Laminated Glass and Laminated Safety Glass, Part 6: Appearance, is widely accepted throughout Europe, and several manufacturers base their in-house quality control guidelines on this standard. Currently, there is no equivalent standard published by ASTM or American Architectural Manufacturers Association (AAMA) for the United States. As a result, the only guideline by which to evaluate laminated glass is that offered by the manufacturers.

ISO 12453-6 divides the glazing material into a perimeter section, referred to as the ‘edge area’ and a remainder of the glass, referred to as the ‘vision area.’ The edge area is intended to be concealed by the frame, and therefore the standard allows for more defects in this portion of the glazing relative to the vision area (Figure 5). Published quality control literature for one manufacturer shows a modified version of the ISO 12543-6 (Figure 6).

Glass evaluation

Figure 5: Areas to be examined on finished sizes (of glass) ready for glazing, where 1 = width of edge area; 2 = edge area; 3 = vision area; H = height of pane; and L = width of pane. Image courtesy ISO 12543-6:2012

For a 2 x 2.5-m (6.5 x 8.2-ft) sheet of intumescent laminated glass, this modification effectively increases the size of the edge area by 42 percent, increasing both the total allowable defects in the glass and the likelihood those defects will be visible in service. This modification to the standard implies that the industry struggles with consistency and overall quality control, which places an increased burden on the contractors and design professionals involved.

Conclusion
Intumescent laminated glass can be an effective fire-resistive product, both aesthetically and functionally, for architects and building occupants. Intumescent glass products provide a level of fire-safety far exceeding that of other glazing products. These authors expect intumescent laminated glazing systems will continue to grow in market share in the future. With this growth, it is important building owners, contractors, and architects understand the limitations of these products to better inform their practices and clients, and building standards remain current with building technology.

fireglass_Manufacturer QC Diagram

Figure 6: This shows the modification to size classification of glass areas; this modification allows for an increase to the edge area, where numerous defects are allowed. Image courtesy Simpson Gumpertz & Heger

Until better industry standards for aesthetic quality are developed in the United States, these authors recommend design/construction professionals educate clients on the optical limitations of intumescent laminated glass before specifying those products. If a nearby project used this technology, one should take the client to see it firsthand. It is also recommended specifiers reference the existing European standard, ISO 12543-6, until local standards catch up.

Similarly, a typical curtain wall contractor will likely not understand the nuances of edge pressure and torque limitations or the sensitivity to water and UV of intumescent laminated glass until they experience it for themselves. The lack of industry experience with the installation (and handling) of these products underscores the value of a mockup, which should be created, especially for new products.

David E. Sacks, R.A., AIA, LEED AP, is a senior staff member in the Building Technology Division of Simpson Gumpertz & Heger (SGH), a national consulting engineering firm active in building rehabilitation, enclosure consulting, and structural engineering. He is experienced in the investigation and evaluation of building enclosures, including roofing, below-grade waterproofing, and wall and glazing systems, with a specialty in repair and rehabilitation of existing buildings. Sacks’ professional experience includes the investigation and restoration design of existing low-rise, mid-rise, and high-rise residential and commercial buildings, with exterior envelopes consisting of architectural terra-cotta, brick, stone, and modern curtain wall systems. He can be reached at desacks@sgh.com

Bradford S. Carpenter, PE, LEED AP, is an associate principal and vice-president in the Building Technology Division of SGH. He has more than 15 years of experience investigating, repairing, and designing building enclosure systems of all types. Carpenter is a member of the American Architectural Manufacturers Association (AAMA), a past co-chair of the Washington, D.C. Building Enclosure Council (BEC|DC), and a frequent speaker and author on building enclosure topics including design and performance. He can be reached at bscarpenter@sgh.com

Specifiers cautioned in use of adhesive anchors

by Gary Higbee, CSI, AIA

Contractors in Arizona participate in an American Concrete Institute-Concrete Reinforcing Steel Institute (ACI-CRSI) adhesive anchor installer certification program. Photo courtesy ACI Arizona Chapter

Contractors in Arizona participate in an American Concrete Institute-Concrete Reinforcing Steel Institute (ACI-CRSI) adhesive anchor installer certification program. Photo courtesy ACI Arizona Chapter

Designing proper construction details is an important part of architecture and engineering practice that involves more than just a grasp of building technology. If designers are not also alert to market conditions, then their details—no matter how elegant—can be ineffective and hinder the pace of a project. Overlooking the complications surrounding the specification of adhesive anchors is a prime example, as recent code changes regarding their use threaten to stall building projects in some of the United States’ largest jurisdictions.

The complications stem from the International Building Code (IBC) referencing a provision in American Concrete Institute (ACI) 318-2011, Building Code Requirements for Structural Concrete, requiring workers installing adhesive anchors in certain orientations to have ACI certification. In big construction markets poised to enact the provision, such as New York City, contractors are finding a lack of opportunities for their installers to become certified places them in an impossible position. They cannot use adhesive anchors on jobs unless their installers are certified, and if they install without certification, they risk a violation or stop work order.

How did this problem arise? It seems the only path to certification is by completing ACI/Concrete Reinforcing Steel Institute (CRSI) Adhesive Anchor Installation Certification Program—a two-day course costing from $500 to $900 per person and requiring success in both written and skills tests.

The hurdle is ACI restricts the training and testing to entities it designates. Typically, these are ACI chapters, which, in the larger construction markets are ill-equipped to handle the volume of requests. In New York City, the group tapped to provide this training (one of only three sponsoring groups throughout the state) is only able to certify 15 to 20 installers each month.

With many building trades installing adhesive anchors, this will only produce a small percentage of certified installers needed in the city for projects getting underway in 2015. Solutions such as sending installers to programs out of the city for certification are unlikely to make a dent in the need and only add to the training’s cost. Since ACI developed the certification requirement in response to the anchor failures that caused the collapse of several ceiling panels in the Boston Tunnel of Big Dig infamy, it is surprising this deficiency has not received more attention.

Impact on the industry
The bottleneck resulting from this shortage of training opportunities has the potential to interrupt construction schedules citywide. In correspondence with Louis J. Coletti, president/CEO of the Building Trades Employers Association (BTEA), the author was warned “at least 40,000 tradespersons must be certified by the effective date of the new code if we are to avoid stalling major public and private projects in the city.”

For specifiers, steering clear of adhesive anchors in favor of other types is a way to elude this glitch. However, in some applications, these products may be the preferred, or only acceptable, anchorage method because of the superior holding power in cracked or damaged concrete. Thus, it is important to clarify not all adhesive anchor installations require the installer to be certified. Only when anchors are installed in a horizontal or overhead orientation and under a sustained tension load is the ACI requirement applicable.

Due to the history of failures in these orientations, ACI requires special inspection. This adds to both the project team’s responsibilities and expenses. The architect and engineer must identify on plans filed with a building department those adhesive anchors for which special inspection is required. Subsequently, the owner must engage an independent testing laboratory to perform the inspections, which ACI 318-11 requires to be continuous—meaning no drilling and installing of adhesive anchors should occur unless an inspector is observing the installers’ procedures.

The special inspector must furnish a report to the engineer of record and to the building official affirming whether the installation procedures and materials covered by the report conform to the approved contract documents and the manufacturer’s printed installation instructions. However, before any installation is performed—and this is critical—the inspector must verify the installer’s certification. This circles back to the original problem: limited opportunities for installers to get certified.

While the designers and owners incur added costs and responsibilities, only the contractors are accountable for maintaining certified personnel to perform the installations. If construction activity is to move forward without expensive delays, these contractors must be able to find certified installers.

Until alternatives—such as moratoriums on enforcement, and permitting other qualified entities to conduct the certification training—are in place to address this looming problem, designers should be alert to the potential for added costs and delay when specifying adhesive anchors for installations requiring special inspection.

GaryHigbeeAIAGary Higbee, CSI, AIA, is the director of industry development for the Steel Institute of New York (SINY) and the Ornamental Metal Institute of New York (OMINY). Formerly the assistant director for technical services with New York State’s Building Codes Division and in architectural practice for three decades, he served in various capacities throughout this period on NYS, HUD, and ICC code drafting and development committees. Higbee is a member of the American Institute of Architects (AIA), American Institute of Steel Construction (AISC), American Society of Civil Engineers (ASCE), along with other national associations. He can be reached at higbee@siny.org.

Standards and Terminologies

In the May 2014 issue of The Construction Specifier, we published the article, “Passive Fire Protection and Interior Wall Assemblies,” by Gregg Stahl. Soon after, a reader contacted us regarding what he considered inaccuracies. We reached out to the author and, in the interest of continuing the discourse about this important topic, excerpts from both sides are included below.

Reader: The first issue is the reference to ASTM E603. The author mentions this is one of two standards that rates assemblies. Actually, ASTM E603 is a “guide” standard, and is used to explain the various types of fire tests, whether they are ASTM, NFPA, UL, or FM, and how they can be compared and contrasted. This standard is not a test method.
Author: The reader brings up several good points in regard to the article on passive fire protection. It should be noted, however, this piece was intended to provide a general overview on the basic principles of passive fire protection. As to the first point, the reader is technically correct. E603 is in fact an ASTM “Guide,” not an ASTM “Standard.” In the “Scope” section of this guide, it does state one of the purposes is to “allow(s) users to obtain fire-test-response characteristics of materials, products, or assemblies, which are useful data for describing or appraising their fire performance under actual fire conditions.” In the subsequent paragraphs, I go on to describe how A603 is used as well as differentiating it from the E119 fire test, which is testing the effectiveness of a particular assembly.

Reader: The second issue is the article states ASTM E119 tests the effectiveness of an assembly as a “fire barrier.” Although not untrue, the use of “fire barrier” seems to limit the type of fire-rated assembly that is tested, since a “fire barrier” is a specific type of fire-rated assembly used by the IBC and NFPA. ASTM E119 is used to test any type of assembly for fire-resistance, whether it is a wall, roof system, floor system, column, beam, etc.
Author: I should have been more precise in the selection of the terminology used. The intent of the term was to use a dictionary meaning, not a fire test assembly meaning. A Google search for the term will produce numerous definitions, such as the one below:

fire barrier: a continuous vertical or horizontal assembly, such as a wall or floor, that is designed and constructed with a specified fire resistance rating to limit the spread of fire and that also will restrict the movement of smoke. Such barriers might have protected openings.

Reader: The third issue is mentioning the hose stream test is used to “measure an assembly’s resistance to water pressure.” This is misleading. The hose stream test is not really a measure of an assembly’s resistance to water pressure, but to test the system’s integrity. As the commentary to the standard states, the hose stream tests the “ability of the construction to resist disintegration under adverse conditions.” In other words, it is a way of testing, from a distance (it is very hot) the assembly’s integrity from falling debris.
Author: The reader references “the standard,” but I do not know to which standard he is referring. ASTM E2226, Standard Practice for Application of Hose Stream, states:

1.3 – The result derived from this practice is one factor in assessing the integrity of building elements after fire exposure. The practice prescribes a standard hose stream exposure for comparing performance of building elements after fire exposure and evaluates various materials and construction techniques under common conditions.

The application of the hose stream does exert pressure on the assembly after it has completed either the full cycle of an E119 fire test or 50 percent of the time of the rated wall assembly. I agree the single word “pressure” does not go far enough to explain—the intent was to determine the integrity of the remaining assembly.

Reader: The fourth and final issue is the use of “area separation firewalls” in the article, and its associated endnote. The use of “area separation” walls was dropped when the IBC was published in 2000, and is not a term used by NFPA’s standards. The correct term used by both the IBC and NFPA is “fire wall” (not a single word). The endnote (no. 3) gives the impression these “area separation firewalls” are used to separate residential units or commercial tenants. This is incorrect. A fire wall divides a building—residential or commercial—into separate buildings so they can be considered independently when applying the code. “Fire partitions” are used for residential unit and commercial tenant separations within a single building and do not require the type of requirements described in the article.
Author: I respectfully disagree with the reader, who seems to be making the reference to area separation walls fit his use without recognizing the term can have more than one use or intent. It was employed here with no reference to NFPA or IBC, and was not intended as the reader interpreted it.
The term “area separation wall”—or “ASW” as it is commonly abbreviated—is used for a particular type of fire-rated wall assembly with a two-hour fire resistance rating, which is typically intended to permit controlled collapse of one unit in a multifamily residence, while still remaining intact and able to protect the adjacent unit in a fire situation. This is a common term in the construction industry. The reader can check the literature of various manufacturers and find this type of assembly. There are also various UL assemblies for this type of construction.

Clarification on wall systems article

The April 2013 issue of The Construction Specifier included a technical feature by J.W. Mollohan, CSI, CCPR, CEP, LEED GA, entitled, “Exterior Wall Assemblies: Are You Getting What You Specified?”  We received the following letter from Cliff Black, a CSI member and a building envelope product manager for Firestone Building Products.

I am writing in regard to the article on exterior wall assemblies. I agree with the author the issue is certainly a challenging one for the design and specifying community. I would like to cite the bracketed statement at the top of page 57, which states, “buildings of two stories or more.” This appears to be taken in the context of the design of National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components, addressing multi-story fire propagation.

However, the International Building Code (IBC) 2603.5 states NFPA 285 is required for buildings of any height for Types I through IV construction incorporating combustible plastic insulation in the exterior wall assembly. IBC Chapter 14 (“Exterior Walls”) calls for differing requirements for water-resistant barriers (WRBs) and various combustible claddings, qualified by height.

In this case, I believe the statement should read “buildings of any height,” rather than “buildings of two stories or more.”

 

Mr. Mollohan replied to Mr. Black, and has allowed us to share it with other readers of the magazine:

 

Good catch, Clint! You are absolutely correct that one must be familiar with multiple chapters of the IBC to determine whether an NFPA 285 test is required. My error, and your correction, illustrates the difficulty of this provision. I am attaching an adaptation of a flow chart originally created by Barbara Horwitz-Bennett of DuPont Building Innovations for guidance to interested readers:

Diagram_edited-1

Sprayed Fire-resistive Materials, Bond Strength, and the IBC

by John Dalton

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Photo © BigStockPhoto/Tim Markley

Sprayed fire-resistive materials (SFRMs) are passive fire-protection materials intended for direct application to structural building members. They are predominantly cementitious or mineral-fiber-based, with the fire-resistive qualities and physical characteristics varying widely between the respective types. A recent code change pertaining to these materials is important for design/construction professionals to understand. Continue reading