What is Structural Glazing?
Need a brilliant and cost-effective solution for contemporary glass design? Structural Glazing is your answer, systems that W&W Glass specialize in!
Structural glazing systems, in their simplest form, are types of curtain wall systems consisting of glass that is bonded or anchored back to a structure without the use of continuously gasketed aluminum pressure plates or caps. The glass can be comprised of monolithic, laminated, dual-glazed or even triple-glazed insulating glass units (IGUs). The back-up structure may use horizontal and/or vertical aluminum mullions or be a glass mullion, steel blade, cable or stainless steel rod. The interior and exterior may use extruded silicone/EPDM gaskets, or a wet sealed silicone depending on the system. This system creates a completely clean, flush exterior appearance while the interior members have many different options depending on design and budget.
So why would you want to go with a structural glazing system? Structurally glazed systems create a greater transparency than traditional captured systems. There are less visual interruptions due to the lack of metal on the exterior (and potentially the interior), creating a seamless, continuous glass look. Traditional captured curtain wall systems have pressure plates and caps that can conduct large amounts of heat in or out of the façade depending on the season. Since there is little to no exposed exterior metal, there is also less thermal bridging with structural glazing, saving on energy consumption costs. Now, let’s take a look at some of the different types of structural glazing systems in the market today.
A stick-built structural glazing system is one of the oldest and most conventional curtain wall types. It is assembled from similar components to that of a captured system, with the exception of an exterior aluminum pressure plate and cap with gaskets to hold the glass in place. It is either siliconed or toggle fastened in place on site depending on the manufacturer’s system. The toggled system glazing is predominantly shop fabricated to have either a channel bonded to the back of the glass with silicone, or to have the insulating glass spacer frame with a reveal to fasten to internally. These methods allow for dry fixing of the units on site to eliminate curing time. Otherwise, the systems that are wet sealed on site must have the glass temporarily clamped in place for 1-2 weeks to assure the silicone is fully cured before the exterior silicone weather seal is applied. Besides an exterior wet silicone/gasket seal, air and moisture control is achieved through what is called pressure equalization. Pressure equalization is a means by which air within the system located between the glass and aluminum mullions helps to drain water at each lite of glass (zone drainage) or at the base of the system (overall system drainage). These systems are often used for low-rise projects less than 15,000 sq. ft. of area, projects where the labor is less expensive, and projects with low repetition.
A unitized structural glazing system is a pre-assembled glazing system. Multiple glazing types and materials can be combined into one “unit” in a quality controlled shop environment. The glazing materials are siliconed in place and allowed to fully cure to give a similar flush exterior appearance to that of the stick-built system, without the concerns for weather conditions on site (as you should not silicone below 40 degrees Fahrenheit) and quality of sealant application on site by the tradesmen. These units can be installed one panel tall and one panel wide or at times, two panels tall or two panels wide. After the glass, spandrel materials, and anchors are glazed into unit frames within the shop, they are loaded onto flatbed trucks to be installed “just in time” at the job site. The units receive additional silicone/EPDM gaskets after they are set by crane from the outside, or from each floor to create the “stack joint”. The stack joint acts as the complete air and moisture barrier of the system allowing a weep at each floor. Unitized systems handle movement much better than most others because each panel is gasketed together to be able to move independently with the structure, and the additional movement capacity of the anchors. Generally, these systems are used on mid-rise to high-rise structures that are 20,000 sq. ft. and up where there is high repetition, tight job site access, and high installation labor costs.
Point supported glass systems are the most transparent structurally glazed systems available on the market today. They can be custom engineered to fit any opening. From the exterior, they have silicone sealants between the joints like other structurally glazed systems, but have far less obstructed views looking from the inside out and vice versa due to the elimination of vertical and/or horizontal aluminum mullions. When using glass fins as a vertical back-up structure, the whole façade can appear to be virtually transparent! Glass is held in at specific points using stainless steel fittings to transfer deadload and wind loads back to the structure. Most glass types are available for point supported glazing, including: insulating glass units, low-e coated glass, laminated glass, monolithic, etc. These glasses can be paired with a host of back-up structures to create vertical walls, roofs and skylights, canopies, elevator enclosures, or windscreens. There are many options available depending on design aesthetics, structure and budget constraints.
Vertical cable tension walls (sometimes also known as cable nets) are the thinnest point supported glass system structures that can make the tallest unsupported spans, but require the largest amount of load on the boundary structure and are usually the most expensive. There are also stainless steel tension structure systems that are deeper, but put less loads on the boundary structure; however, these systems have similar costs to that of vertical cable walls. There can even be hybrid combinations of horizontal steel and cables/tension rods as well. Glass fin walls and glass on steel systems (steel tubes, plate beams, or pipes) are usually the least expensive option and put far less loading on the boundary structure. They do, however, require greater depth of the vertical members to resist loads. The depths can range from around one to four feet on average depending on spans and module widths. These custom designed systems allow for a lot of artistic creativity and flexibility from the design aspect. They are a great fit for an all glass entrance, lobby, atrium, cafeteria, or any other feature area of a building.
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W&W Glass, LLC is a family owned business with a 70-year history in the metal and glass industry, one of the largest metal and glass companies in the New York metropolitan area and the largest supplier of structural glass systems in the country. We have over two decades of experience in the design and installation of various building enclosure systems, including stick-built curtain walls, pre-glazed unitized curtain walls, Pilkington Planar structural glass facades, and custom metal and glass enclosure systems. We install all of our work with our own dedicated union labor force. W&W is consistently the largest employer of glaziers in the NY metropolitan area.
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