INTRODUCTION Window receptor frame assemblies (Figures 1 and 2), also referred to as “subframes” or—in the context of the sill condition, “subsills” or “starter sills”—have had a relatively enduring history in the aluminum-framed fenestration industry. In 2007, RCI Interface published “Window Receptor Frames: What You Need to Know,”1 which examined the general advantages, disadvantages, and common challenges associated with receptor frames. In the 11 years since that publication, these authors have observed continued utilization of receptor frames in new commercial construction, particularly in high-rise multifamily buildings. Designers continue to specify receptor frames to benefit from their inherent features, including water management and accommodation of building structural deflection. Window installers often continue to exhibit a preference for receptor frames, given their ability to facilitate the window installation process—in particular, accommodation of construction tolerances. The range of outcomes experienced by project teams on window receptor frame projects remains relatively wide. Some projects proceed smoothly, delivering on performance expectations in a timely and cost-effective manner. Other projects experience setbacks related to air infiltration or water penetration resistance problems during or after construction. These occur particularly when the performance attributes of the receptor components are overlooked or not coordinated with the window product and surrounding construction, and the receptors are underestimated as merely accessories to the window units. MarcRCh 2019 RCI Interface • 23 Figure 2 – Window unit installed in sill receptor. Figure 1 – Window head receptor prior to installation of window unit. This article complements the 2007 article previously mentioned by providing the following: •An updated compilation of provisions in window standards andselect institutional specificationsrelating to receptor frames, including commentary by the authors; •A case study illustrating shortcomings in industry norms with regardto performance testing of windowreceptor frames; and •Recommendations for industryhousekeeping to bring receptor frame assemblies more in line with the fenestration units they retain. INDUSTRY STANDARDS UPDATE Outside of product-specific installation instructions, design and construction teams have limited published literature to guide the development and execution of window design when receptors are included. The industry resources that do exist are dispersed among several window standards and specifications. This section consolidates provisions pertinent to window receptor frames and provides related commentary from the authors. AAMA/WDMA/CSA101/I.S.2/A440-17 AAMA/WDMA/CSA101/I.S.2/A440-17, North American Fenestration Standard/Specification for Windows, Doors, and Skylights2 (AAMA 101), has, since 1985, been the building enclosure industry’s basis for establishing window product evaluation and certification standards. Specifically, AAMA 101 stipulates laboratory test procedures with which the performance rating and performance expectations for a window product are generated. A performance rating applies only to individual window units, not to a series of individual windows mulled together within a receptor frame.3 With regard to receptor frames, the current AAMA 101-17 includes the following: •Appendix A3: Under the WindowWall definition, AAMA 101 statesthat receptor systems “can bedesigned as part of drainage andmovement accommodation provisions.” This definition was addedin AAMA 101-11 (2011), subsequent to RCI Interface’s 2007“Window Receptor Frames.” •Para. 9.2.1 Test SpecimenRequirements – General: AAMA101 states that “Each specimento be tested shall be a completelyassembled, glazed, and functional product (including hardware).” Appendix A3 now acknowledges the performance features that design professionals have come to seek from receptor frames. In the authors’ opinion, Para. 9.2.1, with its use of “completely assembled” and “functional,” leaves room for interpretation that the air infiltration/water penetration testing methodology that establishes a performance rating should include the window receptor frame, where one is present. Based on the general scarcity of window manufacturers’ testing data that include receptor frames, we observe that few manufacturers interpret this provision in this manner. AAMA 450-10 AAMA 450-10, Voluntary Performance Rating Method for Mulled Fenestration Assemblies,4 describes procedures and requirements for determining the air infiltration, water penetration resistance, and 24 • RCI Interface MarcRCh 2019 structural performance of field-mulled fenestration assemblies. Field-mulled fenestration assemblies (Figure 3) are defined in AAMA 101 as formed by a combination of two or more separate fenestration products whose frames are mulled together, utilizing a combination mullion or reinforcing mullion. Products seeking qualification through AAMA 450 must first have satisfied the minimum requirements of AAMA 101. AAMA 450 does not explicitly mention receptor frames. Despite the lack of a direct window receptor reference, AAMA 450 includes fundamental parallels that make it relevant to receptor frames. Primarily, AAMA 450, as the name implies, is a voluntary standard. Since receptor frames (particularly head receptors and sill receptors) are frequently used in mulled window assemblies, the voluntary nature of AAMA 450 implicitly authorizes the foregoing testing and rating of the complete mulled fenestration assembly, including applications where the mulled assembly is captured in a receptor frame. AAMA 502-12 AAMA 502-12, Voluntary Specification for Field Testing of Newly Installed Fenestration Products,5 establishes a method to evaluate the installed performance of fenestration products for air leakage resistance and water penetration resistance under reproducible conditions (Figure 4). This standard is a routine construction-phase requirement in contemporary project specifications for windows on commercial projects. With regard to receptor systems, the current AAMA 502-12 has changed since AAMA 502-02,6 which was contemporaneous withRCI Interface’s 2007 “Window ReceptorFrames” publication. AAMA 502-12 includes the following: •Para. 3.2 – Test ChamberArrangement: AAMA 502-12mandates that the test specimen include window receptors,stating, “The test chamber shallbe attached and sealed to thewall/roof construction in sucha manner as to create a pressure differential across the entirespecimen (including subframe/receptor and/or panning) andthe perimeter seals.” Contrasting with AAMA 502-12, AAMA 502-02 included the following: •Para 2.0 – Test Methods: Thissection provided two test methods, Method A and Method B,that differed in their location ofthe test specimen perimeter andconsequently whether the specimen captured the window receptor, when present. Method A wasa test of the window productalone; the receptor frame wasnot tested under pressure. AAMA502-02 noted that the receptor frame limitation of MethodA should be clearly understoodby the project stakeholders. Topartially compensate for this limitation, Method A featured anOptional Sill Dam Test, in whichthe testing party applied (by plugging the receptor weeps) a static water head height in inches(0.192 multiplied by the specified test pressure in psf) intothe sill receptor while monitoringthe specimen for water penetration through the receptor frame.Method B configured the testchamber to include the receptorframe and perimeter seals of thefenestration assembly, similar tothe mandate in AAMA 502-12. The development between AAMA 502-02 and 502-12 that now mandates inclusion of the sill receptor in field performance testing is an improvement with regard to limiting risks to project stakeholders. There remains a disparity between the fact that AAMA 101, YOU CALL ME RAINHYDROTECH CALLS ME OPPORTUNITY MarcRCh 2019 RCI Interface • 25 Figure 3 – Field-mulled window assembly. 26 • RCI Interface MarcRCh 2019 Figure 4 – AAMA 502 test in progress. which establishes a window performance rating, does not clearly require the inclusion of receptors in laboratory testing, but the field testing standard AAMA 502-12 now does. ASTM E2112-18 ASTM E2112-18, Standard Practice for Installation of Exterior Windows, Doors, and Skylights,7 provides technical guidance related to the installation of fenestration units on low-rise residential and light commercial structures. With regard to receptor systems, the standard notes the following: •Para. 3.2.130: ASTM E2112defines a “subsill” as “a separate framing member that, wheninstalled on the underside of asill, becomes an integral part ofthe sill.” •Para. 5.16 – Pan FlashingSystems and Subsills forWeatherability: ASTM E2112notes, “The height of the panshall be appropriate for thefenestration product beinginstalled, according to manufacturer’s instructions or the adviceof the design professional. Todetermine the minimum heightrequirements for the interiorheight of the pan flashing, referto Annex 3.” •Annex A3.1 – DeterminingInterior Leg Heights: The annexincludes Table A3.1, which provides a water height and corresponding minimum leg heightfor the pan flashing/subsill forseveral water test pressures anddesign pressures. The annexstates, “The pan flashing heightrepresents the known rise of avertical column of water withan unsealed pressure differential(plus 1/8 in. for a frame-levelingallowance).” •Para. 5.16.3 – Use of PanFlashings, Note 16: ASTME2112 states, “Pan flashingsmay not be applicable for certaininstallations, for example…window receptors…” ASTM E2112 implicitly acknowledges the relationship between the receptor and the window assembly as “integral.” Additionally, the standard notes that the height of the receptor’s vertical back leg should be coordinated with the window product. Also, despite the standard’s statement that pan flashings “may not be applicable” to receptor frame systems, our experience is that since receptor frames rely heavily on sealants, they have inherent vulnerabilities that warrant complementing the sill receptor with a durable sill pan flashing system in most applications. Additionally, regardless of whether the window design includes a pan flashing system below the sill receptor, we note that the air/water barrier of the surrounding opaque wall assembly must be flashed into the rough opening and integrated with the window product with accessory materials (e.g., flexible sheet membranes and sealants). UNIFIED FACILITIES CRITERIA (UFC) Unified Facilities Criteria (UFC) documents provide planning, design, and construction criteria required for all United States Department of Defense (DOD) facilities (e.g., U.S. military departments and the defense agencies). The DOD portfolio of facilities consists of several hundred thousand buildings and structures. The UFC documents include technical specifications referred to as Unified Facilities Guide Specifications (UFGS). UFGS Section 08-51-13 (dated May 2011)8 relates to aluminum windows and includes the following related to receptor frames: •Section 2.3.8 Accessories: Thissection is the only location within the UFGS aluminum window document that referencesreceptor frames: “Provide windows complete with necessaryhardware, fastenings, clips, fins,anchors, glazing beads and otherappurtenances necessary forcomplete installation and properoperation. [If applicable], furnishextruded aluminum subframereceptors and subsill with eachwindow unit.” We note that the only place UFGS Section 08-51-13 mentions receptor frames is in the accessories provision, alongside other appurtenances. We suggest that this and similar methods of specifying receptor frames promote an unintended association of the receptors as an appendage, rather than an element with a direct relationship to performance of the overall window assembly. ORDINARY ROOFS WASTE MEHYDROTECH ROOFS LEVERAGE MY POTENTIAL MarcRCh 2019 RCI Interface • 27 CASE STUDY The following case study illustrates the relatively common occurrence of a project team learning of a receptor-related performance shortcoming only after construction had begun. The authors provided building enclosure consulting services on a mixed-use development that included a multifamily high-rise component. The design for fenestration systems typically included window products in a window wall application. The window wall assemblies were designed to be retained in head, jamb, and sill receptor frames. The project specifications defined the performance criteria for the window to resist water penetration at 12 psf differential pressure. The submitted window product was rated under AAMA-101 to meet those performance criteria. However, as of the commencement of window installation, the sill receptor had not been demonstrably tested in conjunction with the window product at a differential pressure that met or exceeded the specified performance criteria. After the windows had been ordered and shipped, and approximately one-fifth of the window units had been installed, the team learned the sill receptor would require field modifications to achieve the window system rating required by the project specifications. The upturned back leg of the installed sill receptor was not tall enough to resist the rise of a vertical column of water produced by the design pressure in the absence of a continuous air seal between the receptor and window frame that extended to the jamb of the rough opening. Such air seal continuity is notoriously challenging to achieve, especially in the context of mulled windows; and in this case, the continuity was unknown, given the “blind” (i.e., concealed by window components) response of the sealant during the setting of the window frame extrusion into the receptor raceway. The contractor therefore made a remedial modification to the sill receptor on every window on the building to increase the vertical back leg of the sill receptor height at the sill-to-jamb corners and corner mullions with a discrete aluminum extension. The extensions were sealed in place with gun-grade sealant applied from the interior (Figure 5). This project setback had the following consequences: •The performance of the windowson the overall project is now moredependent on workmanship-sensitive details, given the field-installedremedial nature of the work. If theperformance incompatibility between the window product and the receptor had been identified before theconstruction phase, a factory component (e.g., receptor with a continuous, taller back dam) could havebeen provided, making the ability forthe window installation to meet thespecified performance criteria readily reproducible and without undue reliance on field-applied sealants. •The sequence of the window installation was such that an interior trimpiece covered the remedial extensionimmediately following installation,making it difficult for the projectteam to perform quality assurancemeasures related to the remedialwork. •Subsequent windows required additional validation testing and theassociated effort from the entireteam as a response to the in-situremediation. Most of the project windows will never be tested to validatethe performance of the in-situ remediation. RECOMMENDATIONS AND INDUSTRY HOUSEKEEPING Some window standards have begun to acknowledge window receptor frames and their relationship to water penetration resistance of the window assembly, but overall, the building enclosure industry has developed only minimally since 2007 in the context of understanding and avoiding receptor-related performance pitfalls. Though receptor frames are not a new technology, many project teams do not learn that a receptor frame assembly does not meet the specified performance standards until the construction phase is underway, when remedial options are costly and time consuming, and options for technical adjustments to the window system are limited. At the same time, although it is reasonable for a building owner to expect that their investment in a window assembly is buying them a level of factory-manufactured performance that meets or exceeds specified performance requirements, we find that project stakeholders are often surprised—unfortunately late in the construction process and especially when project teams forego project-specific mock-up testing—that the windows they purchased need to receive relatively impromptu applications of sealant in the field to enable the window assemblies to pass performance tests. With that said, we recommend the following to bring receptor frame assemblies more in line with the fenestration units they retain: •Designers should carefully specifyand enforce a competent fenestration performance testing program.9 •Like the AAMA-502 field tests,AAMA-101 should be updated to 28 • RCI Interface MarcRCh 2019 Figure 5 – Remedial sill receptor with upturned back leg extension. require that window receptor frames are laboratory tested/rated with the window products retained by the receptor. If window manufacturers determine that it is not feasible to test every possible combination of window products with and without receptors, at a minimum, AAMA 101 should be updated to clarify that where receptors are utilized, their performance attributes (e.g., height of the vertical back leg of the sill receptor) shall be coordinated with the window product. Additionally, lacking laboratory testing with the receptors, designers should specify project-specific laboratory validation testing that includes the receptors as part of the submittal phase. •AAMA 450 should be updated torequire that window receptor framesare laboratory tested with the mulledwindow products retained by thereceptor. Window manufacturersshould design their receptor systemsto meet the stated performance levelof the window product retained, asit is not the consumer’s expectationthat the overall window assemblywould have varied performance criteria between the window and receptor frame. •Designers should specify, and building owners should enforce the implementation of project-specific mock-up testing (on site or in an appropriate fabrication shop/laboratory)that includes the surrounding window conditions (rough opening, air/water/vapor barriers, flashings,and sealants) well before wholesaleinstallation of fenestration systemsbegins on the building. •Given the unpredictability of continuous air seals between windowsill/jamb receptors and the windowproduct when the sealant is installedin a blind manner, we recommendthat designers specify a gasketedor positively installed (i.e., from theinterior side of the window after thewindow product is set into the receptor) continuous air seal that is ableto be subjected to quality assurancereview. With the same logic, receptorframes at the windowsill should bedesigned with a height that is calculated to exceed the rise of a verticalcolumn of water produced by thedesign-level wind pressure. •Since receptor frames include inherent vulnerabilities, given their reliance on gun-grade sealants and theassociated workmanship sensitivity, projects seeking a very low-riskprofile should include a durablewatertight sill pan flashing systemto complement the sill receptor. Caremust be taken to coordinate attachment provisions of the sill receptorwith the sill pan flashing to avoidcompromising the watertight integrity and performance of the sill panflashing system (e.g., avoid fastenersthat extend down directly throughthe horizontal leg of the sill panflashing). •The Optional Sill Dam test includedin AAMA 502-02 was a valuable andeasy-to-perform quality control measure and should be reincorporatedas an option in future versions ofAAMA 502. •UFGS specification developers(and similar entities that produceinstitutional specifications regarding commercial window requirements) should consider rephrasingthe receptor-related text in UFGSSection 08-51-13 to clarify that window sill receptors, given their directrelationship to water penetrationresistance of the window assembly,shall be tested in the same manneras the window product. The authors anticipate that if the steps above are adopted more rigorously by the building enclosure industry, and if window receptor frames are given the respect they deserve, the industry will see a reduction in the frequency of unnecessary project setbacks related to window assemblies with receptors. REFERENCES 1.Derek B. McCowan, Michael J. Louis.“Window Receptor Frames: WhatYou Need to Know.” RCI Interface.RCI, Inc. June 2007. pp. 7-13. 2.AAMA/WDMA/CSA 101/I.S.2/A440-17, North American Fenes-tration Standard/Specification forWindows, Doors, and Skylights.American Architectural Man-ufacturers Association, Window &Door Manufacturers Association,CSA Group. 2017. THE GARDEN ROOF® ASSEMBLY INTRODUCED OVER 20 YEARS AGO, PROVIDING:stormwater management solutionsreduceretaindelayextended roof longevityadditional usable spacefull assembly warranty Learn more today at hydrotechusa.rainhydrotechusa.com/power-of-rainHELPING YOU HARNESS THE POWER OF RAIN™© 2019 Garden Roof is a registered trademark of American Hydrotech, Inc.Harness the Power of Rain is a trademark of American Hydrotech, Inc. MarcRCh 2019 RCI Interface • 29 3. Brian S. Rose, Philip K. Frederick, and Bradford S. Carpenter. “Window Walls: Blurring the Line Between Glazing Products.” The Construction Specifier. CSI. November 2017. pp. 24-34. 4. AAMA 450-10, Voluntary Performance Rating Method for Mulled Fenestration Assemblies. American Architectural Manufacturers Association. 2010. 5. AAMA 502-12, Voluntary Specification for Field Testing of Newly Installed Fenestration Products. American Architectural Manufacturers Association. 2012. 6. AAMA 502-02, Voluntary Specification for Field Testing of Newly Installed Fenestration Products. American Architectural Manufacturers Association. 2002. 7. ASTM E2112-18, Standard Practice for Installation of Exterior Windows, Doors, and Skylights. American Standards for Testing and Materials. 2018. 8. “Unified Facilities Guide Specifications.” Naval Facilities Engineering Command. May 2011. 9. Evan J. Landis, Chrystal Chern, and Anthony J. Nicastro. “Referencing and Specifying Fenestration Fieldtesting.” The Construction Specifier. CSI. June 2017. pp. 26-36. 3 0 • RC I I n t e r f a c e Ma rc h 2 0 1 9 Jin Rui Yap is a staff member of SGH’s Building Technology group in Washington, DC. Jin consults on building enclosure design and rehabilitation assignments for a variety of clients. Jin’s expertise includes building science-related risk assessments of the building enclosure, including hygrothermal modeling of opaque wall assemblies and thermal modeling of fenestration systems. Jin Rui Yap John Karras is a Senior Project Manager at Simpson Gumpertz & Heger (SGH). He is a professional civil engineer with more than 16 years of combined design and construction management experience on commercial projects. He is a member of RCI Inc. and is the Education Committee chair for the Mid Atlantic Chapter of RCI. John Karras Megan Toumanios is a senior staff member of SGH’s Building Technology group in Washington, DC. Since 2013, Megan has consulted on building enclosure design, rehabilitation, and investigation assignments for owners, architects, and general contractors. Megan’s expertise includes roofing, below-grade waterproofing, and fenestration systems. Megan Toumanios The Occupational Safety and Health Administration (OSHA) has authorized its inspectors to use camera-equipped unmanned aircraft systems (UAS or drones) to collect evidence during inspections—with the consent of the employer. OSHA guidance states that inspectors must “obtain express consent from the employer” before operating a drone for inspection purposes over a workplace. OSHA says that if it is notified of an objection by the employer, it will not fly the drone. During 2018, OSHA used drones on at least nine inspections—most frequently following accidents at worksites that were considered too dangerous for OSHA inspectors to enter. Some employers have expressed fear that OSHA’s use of drones has the potential to expand its violation-finding capabilities during such inspections. OSHA can cite employers for violations that are in plain sight. OSHA has also revealed that it is exploring the option of obtaining a Blanket Public Certificate of Waiver or Authorization (COA) from the Federal Aviation Administration (FAA) to operate drones nationwide. If it is granted such permission, it is unclear whether the agency’s policy requiring employer permission will survive. Attorneys have advised that if an employer decides to consent to OSHA’s request to employ a drone, they should consider reaching an agreement with the agency to include the specific flight plan and agree that all photos will be promptly shared and to have an authorized representative observe the drone’s operation. Another concern is an employee’s Fourth Amendment right to object to the expansion of an overbroad inspection. The Fourth Amendment prohibits unreasonable searches and seizures. – EHS Today and National Law Review OSHA’s Use of Drones for Building Inspections Raises Concerns Photo credit: © Can Stock Photo / kadmy
