Glass curtain wall installation

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Curtain Wall. Traditional Assemble and glaze our stick fabricated, traditional curtain wall in the field with inside or outside glazing options. Unitized Proven products and systems that offer the advantage of speed, lower field installation costs and significantly improved quality control within a controlled shop environment.

The curtain wall should be designed for accessibility for maintenance. Low-rise buildings can generally be accessed from the ground using equipment with articulated arms. For high rise construction the building should be designed for swing stage access for window cleaning, general maintenance, and repair work, like glass replacement.

Davits and fall arrest safety tieback anchors should be provided on the roof and stabilization tie-offs provided on the face of the wall to comply with OSHA standards CFR Curtain wall leakage, both air and water, can contribute to IAQ problems by supplying liquid water and condensation moisture for mold growth.

This leakage can often remain concealed within the wall system and not become evident until concealed wall components experience significant deterioration and mold growth, requiring costly repairs. Glazing failures see Glazing. Repairs if feasible require significant disassembly of curtain wall. If restoration of internal seals is not physically possible or not economically feasible, installation of exterior surface wet sealing at all glazing and frame joints is often performed.

Failure of exposed gaskets and sealants , including perimeter sealants, from curtain wall movements thermal, structural , environmental degradation. Repairs require exterior access. Aluminum frames are inherently corrosion resistant in many environments if anodized and properly sealed or painted with baked-on fluoropolymer paint. Aluminum frames are subject to deterioration of the coating and corrosion of aluminum in severe industrial, coastal environments and galvanic corrosion from contact with dissimilar metals.

Frame corner seals constructed using sealant are prone to debonding from prolonged contact with moisture and from thermal, structural, and transportation movements. Curtain walls and perimeter sealants require maintenance to maximize the service life of the curtain walls. Perimeter sealants, properly designed and installed, have a typical service life of 10 to 15 years although breaches are likely from day one. Removal and replacement of perimeter sealants requires meticulous surface preparation and proper detailing.

Aluminum frames are generally painted or anodized. Factory applied fluoropolymer thermoset coatings have good resistance to environmental degradation and require only periodic cleaning. Recoating with an air-dry fluoropolymer coating is possible but requires special surface preparation and is not as durable as the baked-on original coating.

Anodized aluminum frames cannot be "re-anodized" in place, but can be cleaned and protected by proprietary clear coatings to improve appearance and durability. Exposed glazing seals and gaskets require inspection and maintenance to minimize water penetration, limit exposure of frame seals, and protect insulating glass seals from wetting. The best strategy for sustainability of curtain walls is to employ good design practices to ensure the durability maximum service life of the installation and to use systems that have a good thermal break and high R-value values as high as R-7 are possible with triple-glazed systems.

Also, the use of low-e and spectrally selective glass coatings can significantly reduce energy loads and improve comfort close to the wall. Aluminum and steel frames are typically recycled at the end of their service life. Recycling is less economical if the aluminum is contaminated with sealants, fractured glazing, etc.

There is a limited market for salvaged steel and wood frames. Select a curtain wall with a demonstrated track record in similar applications and exposures. Verifying track records may require significant research by the designer.

ASTM E provides guidance. Review laboratory test results of systems or similar custom systems for air, water, and structural resistance, heat transmission, condensation resistance, sound transmission, and operability.

Verify that tests pertain to the system under consideration and not a version of the system with the same product name but of different construction.

Curtain wall design should start with the assumption that external glazing seals, perimeter sealant joints and curtain wall sills will leak.

The following summarizes recommended features:. Pressure Plate Glazing: In this system the glass and infill panels are installed from the exterior, typically against dry gaskets. The outer layer of gaskets is installed and the gaskets are compressed against the glass by the torque applied to fasteners securing a continuous pressure plate. The plate is later typically covered with a snap-on mullion cover.

This system provides reasonable performance but is susceptible to leaks at corners or joints in dry gaskets. For improved performance four-sided gaskets can be fabricated at additional cost or wet sealants can be installed to provide a concealed interior toe bead or exposed interior cap beads.

Pressure plate glazing allows the easiest method to seal an air barrier from adjacent construction into the air barrier of curtain wall system. Interior Dry Glazing: In this system the glass and infill panels are installed from the interior of the building, eliminating the need for substantial scaffolding and saving money. The frame is fixed and exterior dry gaskets are installed.

Typically only the top interior mullion has a removable stop. The glass unit is slid into a deep glazing pocket on one jamb far enough to allow clearing the opposite jamb and is then slid back into the opposite glazing pocket and then dropped into the sill glazing pocket.

The removable interior stop is installed and finally an interior wedge gasket is forced in. Sometimes this method is called "jiggle" or "wiggle" glazing because of the manipulation necessary to get the glass into place. 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.

Wet sealant heel beads will improve performance and some systems include an extra gasket to form an air barrier seal. Installation of spandrel panels may need to be installed from the exterior. Structural Silicone Glazing: In this system the glass or infill unit is adhered to the frame with a bead of silicone. Outer silicone weather seals supplement the structural seal. Unitized systems are frequently structural silicone glazed, especially if four-side SSG is desired.

Two-sided SSG, with pressure plate glazing or wiggle glazing on the other two sides is acceptable to be field installed. Butt-Glazing: SSG is frequently mistakenly referred to as butt-glazing. True butt-glazing has no mullion or other back-up member behind the joint and relies solely on a sealant, typically silicone, between the glass units to provide a perfect barrier seal.

Establish the required Condensation Resistance Factor CRF based on anticipated interior humidity and local climate data and select a curtain wall with an appropriate CRF. Designers should be aware that the CRF is a weighted average number for a curtain wall assembly.

The CRF does not give information about cold spots that could result in local condensation. Projects for which condensation control is a critical concern, such as high interior humidity buildings, require project-specific finite element analysis thermal modeling using software such as THERM. Careful analysis and modeling of interior conditions is required to accurately estimate the interior temperature of the air at the inside surfaces of the glass and frame.

Curtain walls that are set well outboard of perimeter heating elements will have air temperatures along their interior surface that are significantly lower than the design wintertime interior temperatures. Thermal modeling of the building interior using Computational Fluid Dynamics CFD software can help establish a reasonable estimate for air temperatures at the inside surfaces of the glass and frame.

These interior air temperatures are inputs for the thermal modeling software. Include lab mock-up thermal testing in addition to CFD modeling for analysis of project-specific conditions.

Unusual or custom details, such as copings, deep sills, projected windows, spandrel areas and shadow box can dramatically alter performance.

Use thermally broken or thermally improved aluminum frames for best performance. Special insulation provisions may be required where curtain walls project beyond adjacent cladding systems e. Consider frame geometry for thermally conductive aluminum frame materials. Minimize the proportion of framing exposed to the outdoors. 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.

Occasionally, there are concerns relating to having too much uncontrolled daylight, sometimes referred to as glare. The challenge is to strive for the highest visible light transmittance VT and the lowest solar heat gain coefficient SHGC while not preventing the glass from being too reflective when viewed from both the exterior and the interior, while controlling glare.

Unitized systems are typically custom designed. There isa wide range of systems on the market from manufacturers that provide varying levels of reliability. Unitized systems range in performance ability from industry standard to high performance walls. It is thus recommended that projects specifying unitized curtain wall systems incorporate a team member who has a breadth of experience in designing and working with unitized systems.

Unitized systems are typically pressure equalized rain screen systems. The units should be completely assembled in a factory and shipped to the site for installation on the building.

The units are placed on the floors, bundled in crates, using the tower crane and lowered into place using a smaller crane or hoist owned by the glazing contractor. The mullion dimensions tend to be slightly larger than a stick system due to their open section as compared to the tube shape of a standard stick curtain wall section.

The advantages of the unitized system derive from the more reliable seals achievable from factory construction and the reduced cost of labor in the factory versus that of high rise field labor. Units can be assembled in a factory while the structural frame of the building is being constructed. Where stick systems require multiple steps to erect and seal the wall, unitized walls arrive on the site completely assembled allowing the floors to be closed in more quickly.

Unitized systems also require less space on site for layout thus providing an advantage for urban sites with space limitations. The interlocking vertical mullions will typically have two interlocking legs. One leg will be in the plane just behind the glazing pocket and the other at the interior face of the mullions. The interlocking leg in the plane of the glazing pocket will be sealed by gaskets and is the primary line of defense against water and air infiltration.

More robust systems will also include a gasket at the interior interlock. Systems whose connecting legs lock also compromise the ability of the system to accommodate movement. The installation of a curtain wall system begins long before the glazier ever gets to the job site.

The general contractor has selected your company to install the wall. The arrangements have been made for the materials to be delivered to the job site and the wall components have been shipped. What follows is a generalization of the procedures involved with erecting a curtain wall system.

By no means is this the only technique of assembling a wall, but this section covers the steps necessary to install a stick wall and a unitized wall.

Establish control lines. Find out from the contractor exactly where the stick wall should go. Bench marks may be painted on the floor and over the edge of the floors.

They must be visible on all floors before, during and after the construction of the curtain wall to be used by all the trades. Bench marks are used as reference points for measuring the location of most everything on each floor.

The layout determines the exact wall placement by the use of offset lines and finished floor levels developed from the control lines established earlier. This procedure should be checked and double-checked by more than one person. The curtain wall must be one continuous plane up and around the building. Each floor must have the proper amount of room for attaching anchors.

Even though the floors are not perfectly level or plumb, the wall must be. Anchor plates. Anchor plates are bolted, welded or cast into the structure of the building. The type of anchors used depends on the type of wall design, the building design and the load considerations of the wall.

Most steel beam construction has the anchors bolted or welded on to the structural beams. In concrete construction impediments or weld plates are cast into the concrete floor. This allows the anchors to be welded or bolted to a steel anchor, instead of being separately anchored into the concrete at each location.