SSG. Fundamentals of Structural Sealant Glazing. Introduction

Transcription

1 SSG Fundamentals of Structural Sealant Glazing Photos Courtesy of SmithGroup Introduction This presentation is about the use of silicone sealants for structural sealant glazing (SSG) Information on sealants for weatherproofing applications is described in a separate presentation This presentation is general in nature For in-depth information on SSG refer to ASTM International publication C1401 Guide for Structural Sealant Glazing

2 What SSG is and is Not It is: Adhering glass and panels to a metal framing system Using a structural quality silicone sealant Typically two- and four-side adhesion for rectilinear panels Other shapes round, polygonal, triangular, etc. It is not: Mechanical attachment of glass and panels to a metal framing system Butt glazing: Has no vertical mullions and is not SSG SSG and Conventional Mullions Mechanically Attached Curtain Wall Photo courtesy Momentive Performance Materials Typical Roles of Participants Architect Building and SSG system aesthetic design concept SSG Consultant System technical design expertise Can assist throughout the project SSG System Fabricator Develops a quality control system Designs and fabricates system Keeps quality control information SSG System Installer Develops a quality control system Installs system Keeps quality control information Photo Courtesy of Dow Corning Typical Applications Glazing glass into windows, curtain walls, and skylights Insulating and laminated insulating glass (IG), monolithic and laminated glass, spandrel glass, specialty glass, etc. Sloped glazing and skylights Laminated IG units typically Glazing other materials onto metal framing systems Stone and stone clad composite panels Metal panels Coated Metal, Aluminum, Stainless Steel, etc. Other miscellaneous applications Photo Courtesy of Dow Corning Photo Courtesy SmithGroup

3 SSG System Potential Risk Fundamentally SSG relies on: Structural sealant adhesion no mechanical fasteners A typical adhesion chain Glass to structural sealant Structural sealant to aluminum finish Aluminum finish to aluminum Design, fabrication, and installation requires: More technical knowledge and workmanship skill Has more inherent risk Pay attention to the details A quality control program is required Illustration Courtesy of Dow Corning History of SSG Systems Development 1965 PPG TVS all glass system Monolithic glass mullions 1970: Two-side SSG with monolithic glass 1971: Multi-story four-side SSG with monolithic glass Smith Hinchman and Grylls Headquarters building, Detroit, MI 1976: Two-side SSG with insulating glass 1978: Four-side SSG with insulating glass 1980 s: Attachment of panels other than glass For example: metal, stone, and composite panels Smith Hinchman and Grylls Building Photos Courtesy of SmithGroup How Durable Are SSG Systems? No capability to predict SSG service life 50+ year history of successful installations. There have been material and workmanship problems Attaining and maintaining adhesion Fundamental for success and longevity Use proven materials and techniques Require prefabrication adhesion and compatibility testing Must have a quality control program. From predesign to installation Architect, Consultant, Fabricator, and Installer Inspection and maintenance Performed periodically Mullion Glass Structural Silicone Spacer Weather Seal Illustration Courtesy of Dow Corning

4 Structural Sealant Definitions Bite The effective structural contact dimension of a structural sealant (ASTM C717) Sometimes referred to as Glueline Thickness The minimum structural sealant dimension between structurally bonded surfaces. (ASTM C717) Dead load A panel s weight that can create shearing stress on an SSG joint Spacer Structural Sealant Bite Thickness Glue line Dead load Shearing Stress Illustrations Courtesy of Dow Corning Architectural Design Questions Will the SSG system be standard or custom? Will it have two- or four-side adhesion? Four-side SSG typically factory glazed Two-side SSG typically site glazed Is an SSG consultant required? Standard or custom system? Will it be a unique or ground breaking system? What is its complexity, size, and potential liability? Is there buy-in for the system from all stakeholders? Architect, Building Owner, Contractors, Code Authority, etc. pressure plate (mechanical fixation) gasket structural silicone at verticals Two-side SSG System Four-side SSG System Photos courtesy Momentive Performance Materials SSG System Design Issues Coordinate structural sealant(s) selection Fabrication structural sealant Multicomponent or single-component sealant Remedial work structural sealant Single-component sealant SSG joint characteristics Structural bite a minimum of ¼-inch. Glueline thickness a minimum of ¼-inch. Bite to thickness ratio should fall between 1:1 and 3:1. Install structural sealant using standard application procedures. Adequate installation access required Illustration Courtesy of Dow Corning

5 Structural Glazing Sealants Multicomponent Requires mixing of two components Cures by chemical reaction between components Factory installed Fast cure rate, which is adjustable Single-Component One-part material, no mixing Cures by chemical reaction with atmospheric moisture Factory or construction site installation Full cure can take as long as 2 to 3 weeks Dependent on relative humidity level SSG joint access to humidity Photo courtesy Momentive Performance Materials Humidity Access Illustration Courtesy of Dow Corning Other Sealants Metal framing system sealants Compatible with structural and weatherproofing sealants Weatherproofing sealants Use silicone sealants Meet ASTM C920 with Joint design by ASTM C1193 and C1472 Single-component Will require adhesion testing Other wall system(s) sealants Abutting systems Use silicone sealants, discourage use of other polymer types Must adhere one to the other Compatible one to the other Photos Courtesy SmithGroup Role of SSG Material Suppliers Sealant, glass and other manufacturers technical staff Provide design and installation information Require correct use of their products, such as: Adhesion and compatibility testing Cleaning, priming and sealant application Assist with development of system details SSG Sealant reviews can include: Appropriate sealant stress level Proper joint configuration Glazing reviews can include: Proper drainage of IG unit glazing pocket Proper support of glazing Illustration Courtesy of Dow Corning

6 Specifying SSG Systems Basic System Criteria Establish appropriate criteria Properly specify various components Require submission of a quality control program Questions to answer: How will maintenance access be provided? How will maintenance activities be accommodated? Window washing Broken or failed component replacement Scaffolding tie-backs or tracks? Is attic stock needed? Which items? Quantity? Where stored? Complicated design more attic stock Specifying SSG Systems Basic Performance Criteria Specify appropriate testing for: Air Infiltration ASTM E283 Water Infiltration ASTM E330 Structural ASTM E331, AAMA Sound Control Thermal Properties R-Value, SHGC, Condensation resistance Day lighting Visible light to solar heat gain (LSG) (Visible Light)/SHGC Greater than 1 Specifying SSG Systems Structural Joint Criteria Structural sealant Meet ASTM Specification C1184 Structural sealant design issues 20 PSI max. structural sealant stress 2.5 min. structural sealant design factor Structural loads Movements Framing effects Wind, dead, snow, live, seismic Building motion, differential thermal, live load, dead load Elastic frame deformation, creep, shrinkage, seismic Force protection Blast and missile impact resistance

7 Specifying SSG Systems Adhesion Testing Substrate sealant adhesion testing Do not rely on previous test data from another project Changes can occur in formulation and manufacturing process Require adhesion testing for every project Test substrates manufactured for the project - not off the shelf samples When to perform adhesion testing During design Verification of new materials Preconstruction verification of adhesion For production run materials Periodic testing during fabrication or installation To monitor for any detrimental changes Painted Finishes Anodized aluminum Granite Structural Sealant Adhesion Test Performed by SSG sealant manufacturer Test performed using ASTM C794 Typical substrates: Glass (uncoated usually not tested) Coated glass may require deletion of coating Metals such as anodized, stainless steel, etc. Factory coated metals - adhesion can vary By coating type, color, and manufacturer Stone usually granite Inherently a variable material Criteria for rejection Loss of adhesion - must fail cohesively Adhesion In-Peel Test Samples Photo Courtesy of Dow Corning Specifying SSG Systems Compatibility Testing Component compatibility testing System components must be compatible Test it if touches or is in close proximity to a structural sealant No detrimental interaction required Typical materials: Glazing gaskets for two-side SSG systems Structural sealant spacers Glass or panel setting blocks Weep system drainage tubes Joint fillers back-up rod Other miscellaneous organic materials Illustration Courtesy of Tremco

8 Structural Sealant Compatibility Test Performed by SSG sealant manufacturer Test performed using ASTM C1087 Ultraviolet and heat exposure for 21 days Criteria for rejection of component Color change of structural sealant Could indicate future loss of adhesion Sealant manufacturer evaluation Loss of adhesion of structural sealant Automatic rejection Compatibility Test Samples Photo Courtesy of Dow Corning Specifying SSG Systems Quality Control Quality control document required Material quality verification Sealants, solvents, primers, and other components Fabrication monitoring, for example Frame fabrication milestones Substrate cleaning procedures Substrate priming Two-part sealant mixing ratio and cure rate Installation requirements Factory or construction site glazing? Panelized or stick-built system? Photos Courtesy of Dow Corning Specifying SSG Systems Visual Mock-Ups Predesign visual mock-up(s) Usually small scale samples Evaluate: Different finishes and glass types Does it achieve the aesthetic goals? Prefabrication visual mock-up(s) Usually large scale Evaluate finishes and glass types Does it achieve the aesthetic goals? Can be performed at the factory or construction site The sooner the better Visual Mock-Up at the Construction Site Photo Courtesy SmithGroup

9 Specifying SSG Systems Technical Laboratory Mock-ups Laboratory mock-up(s) of system Verify aesthetic intent Verify fit of materials and components Fine tune and debug assembly techniques Verify replacement and repair techniques. Conduct performance tests Air, water, structural, movements, thermal, sound, etc. Using industry standard test methods ASTM, AAMA, etc. Best opportunity to correct problems Full-Scale Curtain Wall Mock-ups Photos Courtesy SmithGroup Specifying SSG Systems Technical On-Site Mock-ups Construction Site Mock-Up(s) Can be used as a quality reference during system installation Verify workmanship Verify performance Typically air and water infiltration tests Disposed of when construction completed Or can be come permanent part of construction Not the best opportunity to correct problems ASTM E330 Water Infiltration Test Photo Courtesy SmithGroup Specifying SSG Systems Construction Workmanship Testing Verification of workmanship Periodically during installation Typically for: Air infiltration - ASTM E783 Water infiltration - AAMA Or ASTM E1105 How many tests? One test for every 5,000 SF? More? Less? Base on project size and complexity Multiple systems = multiple tests How often to test? Initial installation then randomly and periodically AAMA Water Infiltration Testing Photo Courtesy SmithGroup

10 The SSG Construction Process Typical Stages Submittals and shop drawings Material verification and approval System detail review Fabrication monitoring Quality control program Material and component testing Installation monitoring Quality control program Material and component testing Photo Courtesy SmithGroup The SSG Construction Process Submittals and Shop Drawings Review of SSG quality control program Are all material quality, fabrication, and erection aspects adequately described? Has test data for components been submitted before fabrication? Structural sealant(s) for adhesion Gaskets, spacers, setting blocks, etc. for compatibility Last chance for SSG system drawing detail review This is not the time to consider material or other substitutions Photo Courtesy SmithGroup The Construction Process Fabrication Monitoring Monitor quality of components Sealants, glass, primers, gaskets, spacers, etc. Periodic quality testing Metal framing joints, seals, and tolerances Document with check lists Structural sealant Cleaning, priming, and application Curing time before frame movement Milestone testing Periodically test a completed frame Typically for simulated wind load Photos Courtesy SmithGroup

11 The Construction Process Installation Monitoring Monitor quality of components Sealants, primers, gaskets, spacers, cleaners, etc. Periodic quality testing Metal framing joints, seals, and tolerances Documented with check lists Structural sealant Cleaning, priming, and application Curing time before frame movement Workmanship testing ASTM and AAMA test methods Initially and periodically Panelized Curtain Wall Stick Built Curtain Wall Photos Courtesy SmithGroup SSG Systems Maintenance Post Construction Plan for during system design Not later! Capable of being economically maintained Why? Replacement of failed or broken components Weather sealant replacement Periodic cleaning Periodic inspections Local law requirement usually at 5 year intervals Verify system continuing performance Photo Courtesy SmithGroup Remedial Work Considerations Plan for during system design Not later! System design must permit easy access Failed IG unit replacement They have a life time, replacement must be anticipated Broken glass replacement Replace SSG sealant or other components Attic stock facilitates rapid replacement Especially if heat treated glass is required Photos courtesy Momentive Performance Materials

12 General Sealant Resources Web site includes fundamental information on sealant chemistries, application equipment, and ASTM standards Features Sealant TechSelect Tool with links to vendors and contacts SSG Resources Industry Standards ASTM ( C717 Standard Terminology for Building Seals and Sealants C794 Standard test Method for Adhesion-in-Peel of Elastomeric Joint Sealants C920 Standard Specification for Elastomeric Joint Sealants C1087 Standard Test Method for Determining Compatibility of liquid-applied Sealants with Accessories Used in Structural Glazing Systems C1184 Standard Specification for Structural Silicone Sealants C1193 Standard Guide for Use of Joint Sealants C1401 Standard Guide for Structural Sealant Glazing C1472 Standard Guide for Calculating Movement and Other Effects When Establishing Sealant Joint Width ASTM SSG Standards Compilation ASTM Standards and Technical Articles Relating to Structural Sealant Glazing SSG Resources Industry Standards ASTM ( E283 Standard Test Method for Determining the Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen E330 Standard Test Method for Structural Performance of Exterior Windows, Curtain Walls, and Doors by Uniform Static Air Pressure Difference E331 Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference E783 Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors E1105 Standard Test Method for Field Determination of Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform or Cyclic Static Air Pressure Difference

13 SSG Resources Industry Standards WBDG WHOLE BUILDING DESIGN GUIDE AAMA ( Standard Test Method for Water Penetration of Windows, Curtain Walls, and Doors using Dynamic Pressure Quality Assurance and Diagnostic Water Leakage Field Check of Installed Storefronts, Curtain Walls, and Sloped Glazing Systems WBDG ( Joint Sealants, by The Adhesive and Sealant Council, Inc. Journal of Building Enclosure Design Organizations ASTM Committee C24 on Building Seals and Sealants ( Member companies of the Adhesive and Sealant Council ( American Architectural Manufacturers Association ( National Institute of Building Sciences (NIST) The Whole Building Design Guide web site ( WBDG WHOLE BUILDING DESIGN GUIDE Acknowledgement The ASC graciously acknowledges the following member companies and other organizations for contributing to this presentation Dow Corning Corporation ( Momentive Performance Materials ( Tremco ( SmithGroup (

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