Weep holes in a water-managed system function largely to drain water that enters the glazing pocket while weep holes in a pressure-equalized system function primarily as vents to allow air movement between the exterior and glazing pocket. Glazing problems specific to curtain wall construction include visual obstruction from condensation or dirt, damage to opacifier films from material degradation, condensation and/or heat build-up, and IGU issues/laminated glass issues. Units are hung from the top or face of the adjacent floor or building structure using mated brackets and field applied bolts with a minimum of clearance for access and assembly. The long-term reliability of such seals is extremely suspect and such systems should be avoided. The units should be completely assembled in a factory and shipped to the site for installation on the building. AAMA and IGMA, two industry leaders, have unified to form an exponentially stronger alliance. Curtain wall perimeters should have flashings (sill, jambs and head) that are sealed to the air and water barrier at adjacent walls. Double-skin systems, which employ a ventilated space between the inner and outer walls are rare in the U.S., but have been constructed in Europe and Asia where energy costs are much higher. Includes bibliographical references. Refer to AAMA 1503 for descriptions of test method, parameters and equipment for determining U factors and CRF's for window products. This section incorporates comments about standard and custom systems. Shadow box construction creates a perception of depth behind the spandrel glass that is sometimes desired. Details are not provided for interior glazed systems because air infiltration is a concern with interior glazed systems. Curtain wall design should start with the assumption that external glazing seals, perimeter sealant joints and curtain wall sills will leak. Unitized systems generally rely on rain screen design principles and gaskets and/or the interlock of mating frames for moisture protection at joints between adjacent modules. Performance is slightly reduced because dry metal to metal joints occur at the ends of the removable stop at a point that should properly be air and watertight. Architectural, FGIA Virtual Conference Panels to Focus on Financial Aid, Recovery in Wake of COVID-19, FGIA Updates Selection and Application Guide for Plastic Glazed Skylights and Sloped Glazing, FGIA Releases 2019/2020 Market Studies, Offers Forecast of Fenestration Industry Trends. The sightlines are a function of both the width and depth of the curtain wall frame. Thin stone panels are most commonly granite. There is usually a gap in the gasket at the corners after shrinkage occurs. Unit dimension of mating head and sill extruded profiles allows for specified floor to floor deflection at the stack joint. A through-wall metal flashing at the base of the brick cladding above the curtain wall protects the curtain wall from leakage through the wall above— (see. Individual units of glass must accommodate the movement of the surrounding aluminum frame by sliding along glazing gaskets, distorting the gaskets or a combination of both. Steel can be added to a unitized system to increase its spanning capability. Failure of exposed gaskets and sealants, including perimeter sealants, from curtain wall movements (thermal, structural), environmental degradation. Curtain wall frame conductance is a function of the frame material, geometry and fabrication (e.g. Isometric of Open Stack Joint Unitized Curtain Wall System (Figure U–2)   PDF, Isometric of Completed Stack Joint Unitized Curtain Wall System (Figure U–3)   PDF, Vision Glass Jamb Unitized Curtain Wall (Figure U–4)   PDF, Unit Stack Joint Unitized Curtain Wall (Figure U–5)   PDF, Intermediate Horizontal Unitized Curtain Wall (Figure U–6)   PDF, Jamb at Spandrel Area with Anchorage to Slab Unitized Curtain Wall (Figure U–7)    PDF, Unit Anchor to Slab Edge Section Unitized Curtain Wall (Figure U–8)   PDF. Field testing of curtain walls: Require the field testing of curtain walls for air infiltration and water penetration resistance, for quality assurance of curtain wall fabrication and installation. Aluminum has a very high thermal conductivity. In the vision area the interior heat helps to mitigate the cold and prevents condensation. The plate is later typically covered with a snap-on mullion cover. Detailing of spandrels, shadow boxes and interface with adjacent construction must maintain the continuity of the air barrier and rainscreen to function properly with a pressure-equalized rainscreen curtain wall framing system. Refer to the Resource Page on Considerations for Building Design in Cold Climates. Lateral load resistance requirements (wind loads, spans) generally dictate frame depth. “Formatted to include mandatory language, optional language and detailed technical commentary, guide specifications in Section 5 allow architects and specifiers to address project-specific performance and testing requirements consistently.”. Design the drainage system to handle condensation as well as rain. The splice between the vertical mullions will also be designed to allow vertical movement while providing lateral resistance. Functional / Operational—Ensure Appropriate Product/Systems Integration, Building Envelope Design Guide—Glazing, Building Envelope Design Guide—Windows, See appropriate sections under applicable guide specifications: Unified Facility Guide Specifications (UFGS), VA Guide Specifications (UFGS), Federal Guide for Green Construction Specifications, MasterSpec®. Select frames with wept glazing and pocket sills sloped to the exterior to collect water that penetrates the glazing and drain it to the exterior. Vision glass is predominantly insulating glass and may have one or both lites laminated (see Glazing), usually fixed but sometimes glazed into operable window frames that are incorporated into the curtain wall framing. Floor and ceiling closure is provided for fire and acoustical separation using code approved assemblies. For this reason, do not insulate between the interior portion of mullions and adjacent wall construction either. The use of glazed curtain walls can present challenges in balancing the desire for more natural daylight versus addressing the heat gain typically associated with such systems. Metal panels can take various forms including aluminum plate, stainless steel or other non-corrosive metal, thin composite panels consisting of two thin aluminum sheets sandwiching a thin plastic interlayer, or panels consisting of metal sheets bonded to rigid insulation, with or without an inner metal sheet to create a sandwich panel. Proper placement of insulation at the curtain wall perimeter reduces energy loss and potential condensation issues. Wet sealant heel beads will improve performance and some systems include an extra gasket to form an air barrier seal. “New curtain wall guide specifications are expected to be of particular interest,” said Steve Fronek (Wausau Window and Wall Systems), a leader within the AAMA Curtain Wall Manual Update Task Group. Curtain wall systems, especially unitized systems, require expertise on the part of the building designer, the manufacturer, the fabricator, and the installer.