Best practices for specifying windscreen systems

by sadia_badhon | August 22, 2019 12:24 pm

by Jon Chase

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With the rising popularity of the al fresco experience, windscreen systems are increasingly being incorporated in outdoor areas. These post-supported glass railings have been growing in popularity due to their ability to provide unobstructed views and wind protection, and as a visual complement to outdoor amenities such as rooftop decks, pools, and healing gardens. Windscreens are completely customizable, easy to install, and purposefully designed to make commercial exterior spaces more useful and also enjoyable.

Design elements

Windscreen systems can be customized and adapted to the specific needs of virtually any project or setting, taking into account terrain, building level, wind loads, line of sight, safety, and other environmental and performance factors. When it comes to aesthetics, the primary design elements include the following.

Height

Height is customizable based on individual project needs. For rooftop terraces, for instance, the height of the windscreen needs to be adjusted to comply with local building codes for maximum height and fall protection. A standard height for a windscreen system is 2 m (6 ft) above the walking surface, thus providing extensive coverage for furniture and patrons. A handrail is optional, but uncommon.

Airflow

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This is the degree to which a windscreen allows air to flow through a space. A system with a minimal footprint will allow for full airflow through the outdoor space, while minimizing wind exposure. While there are no vertical joints, there is often a 76-mm (3-in.) gap below the glass to allow airflow.

Glass selection

Specifiers can also customize glass selection based on the environment and wind load. Special coatings, interlayers, or films can be added to reduce glare, light transmittance, and provide ultraviolet (UV) protection. For example, glass panels can be frosted for privacy or kept clear for transparency. The size, thickness, and type of glass are designed to comply with building codes, industry standards, and safety requirements. The International Building Code (IBC) requires a minimum thickness of 6 mm (¹/₄ in.) for monolithic tempered glass, laminated tempered glass, or laminated heat-strengthened glass. At higher elevations, the wind load increases and thicker glass is needed to withstand the applied wind load. IBC also requires glass installed in exterior railing infill panels or balusters in wind-borne debris regions to be laminated and tempered to comply with safety glazing impact requirements of ASTM E1996, Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Windborne Debris in Hurricanes.

Finish

Windscreens are available in a variety of finishes to not only deliver a unique design, but also provide corrosion-resistance properties. The most common finishes include anodizing, paint, powder coating, or fluropolylmer.

Handrails

Handrails can be added to a windscreen system as an extra safety measure, but are not required. Further, light-emitting diode (LED) lighting can be incorporated into the handrails and/or posts to enhance safety and ambiance.

Windscreen benefits

As one of the most visible elements of any building project, windscreen glass railing systems serve an important aesthetic and structural role by adding support, safety, and style. The following are some of the key benefits of glass railing windscreens.

Visual appeal

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Windscreens made from glass can offer a modern, sleek look and provide unobstructed views. In cases when the system is installed on a rooftop, these glass walls can provide a 360-degree, panoramic view of an entire landscape. Depending on the manufacturer, windscreens can be designed with hidden fasteners to bring additional sleekness to the building. Common types of installation involve vertical posts with panels spanning between or a base metal U-channel or shoe with glass extending upward (no posts). Typically, glass is tempered and laminated. When acting as a guard, the windscreen must be 1067 mm (42 in.) from the walking surface, though, as previously mentioned, it is commonly detailed and provided at 2 m.

Noise reduction

The use of tall, thick glass—13 to 19-mm (¹/₂ to ³/₄-in.) laminated variety is common—provides a much higher sound transmission rating than conventional railing systems, meaning less noise is able to penetrate the surrounding area. Due to the solid (versus picket or cable) infill panels, the sound is reflected off the glass, reducing noise from adjacent roadways. This is especially beneficial for outdoor spaces alongside busy roads and noisy urban areas.

Design flexibility

Glass windscreens can be custom designed to meet the performance and safety requirements of any project. These requirements will be dictated by building codes and possibly by the design team or architect responsible for creating the performance specification. For instance, some windscreen products are designed to resist environmental loads including those from seismic events and wind loads, with the latter normally causing the highest demands.

Most commercial windscreen systems are capable of resisting wind loads of around 479 Pa (10 psf), while others are designed for up to eight times that amount, with a service-level wind load capacity of more than 3830 Pa (80 psf). This pressure typically corresponds to ultimate three-second gust wind speeds of 185 to 274 km/h (115 to 170 mph). An increased wind load allows for installation at much higher elevations. The wind pressure should be determined by a qualified professional engineer, as it is dependent on many factors, such as building geometry and height, geographic location of a project, type of building, and location of the railing on a building.

Low maintenance

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Glass windscreens are designed to resist the elements. Concept designs or systems are typically detailed by the project architect or a system from a particular vendor is specified. Quality finishes, such as anodized or powder coated, can provide an aesthetic color and enhance the durability of the windscreen surface, making them more resistant to corrosion. Exposed edges of the glass are typically polished smooth.

Improved safety

Not only do windscreens serve as protective barriers against strong winds, but also guard railings providing fall protection. Additionally, windscreen systems should be designed with ease of assembly in mind, enhancing safety for installers as well.

Specification considerations

While glass windscreens may be one of the last products to be installed, their specification should
be considered early in the design process—ideally at concept—as the structure must be designed to support the system. There are four critical aspects to consider when specifying a glass railing windscreen system.

Materials and components

An understanding of typical glass windscreen material properties will help when evaluating conditions and designing new systems. Windscreen systems are designed and constructed using laminated glass infill. Polyvinyl butyral (PVB) or a more advanced and high-performing architectural safety glass interlayer is commonly used with 1.5 to 2.5 mm (59 to 98 mils) thickness, both tempered and laminated, as well as aluminum, steel, or stainless steel framing. Using these types of structural components allows for corrosion resistance. These components are lightweight and offer a selection of protective finishes.

Structural compliance

In addition to applicable local codes, architects, engineers, and contractors must comply with the structural and load requirements of the IBC to provide a quality, tested, and proven safe product. In most areas, glass railing windscreens must be able to withstand at least 91 kg (200 lb) of concentrated force at all times, including the force of high winds, especially atop multistory buildings. For instance, some glass windscreens systems are capable of resisting wind speeds up to 249 km/h (155 mph). Systems can be engineered and tested to meet the requirements of Miami Dade County and other wind borne debris regions. Windscreens are often considered guards, and must withstand 23 kg (50 lb) per linear foot of load.

Weatherproofing

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Weather and waterproofing are important considerations during the specification process. Serious issues can develop when different metals are in contact with one another and nature. Thus, it is important to separate incompatible materials to prevent galvanic corrosion. Movement occurring with changes in temperature must also be considered during the design process. Glass windscreens should be designed to allow for movements resulting from expected temperature changes in the geography of the project. Taking thermal stress into consideration will maintain the structural continuity along the entire windscreen system. Thermal breaks and tolerance gaps within fittings are reviewed per project based on specifications and local code. In areas of high annual rainfall, waterproofing is necessary to safeguard the building’s structural integrity. For regions impacted by hurricanes, or areas prone to high winds, modifications may be required to meet local codes.

Installation

When it comes to installation, traditional glass windscreens involve vertical posts with integrated vertical channels, and often require installers to lift large panes of glass and slide them in from above the post system. Size limitations on the glass of a windscreen become dependent on engineering and the glass fabricator’s capabilities, in general, it would be rare to see a panel larger than 2 m (8 ft) in height or width.

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However, as windscreen systems continue to advance, so do installation methods. Some manufacturers offer snap-fit aluminum posts making for quick, safe, and easy assembly. Snap fittings are designed to meet the maximum wind pressures, wind speeds, and wind-borne debris requirements. With one side of the post in place, the glass is positioned in front of the system and held in by double-sided foam tape. The tape holds in the first pane of glass while the next piece is installed. The cover is then snapped in from the front, safely securing the glass panel in place. This simple design reduces the installation time, thereby, lowering labor costs and helping keep a project within budget.

Liability

It is crucial to work closely with the windscreen manufacturer at the onset of the design process. In the author’s experience, it is always beneficial when architects and glaziers enlist the help and expertise of the manufacturer to best understand their options and capabilities. Design is typically delegated with sealed drawings and calculations, especially when determining capacity, structural requirements, and code compliance. Misunderstanding of regulations and a lack of building code knowledge can result in costly rework.

A knowledgeable partner will be able to provide valuable insight regarding regulations and how they might impact the project scope, logistics, and cost.

Conclusion

As interest in functional, comfortable, and visually appealing outdoor spaces continues to rise, so too will demand for commercial glass windscreen systems. Keeping building codes, proper installation, and material selection in mind is critical for designing efficient windscreens that will withstand the test of time and the environment. Fortunately, today’s systems offer an abundance of options that are not only code compliant, but also aesthetically designed to complement and elevate the look and experience of any outdoor space.

Jon Chase is the vice-president of Trex Commercial Products, overseeing projects such as the U.S. Bank Stadium, the Los Angeles Rams Stadium, and Audi Field. Chase is responsible for a team of 45 engineers focused on product innovation and project execution in the ornamental railing and glazing industry. He can be reached at jchase@trexcommercial.com[7].

Source URL: https://www.constructionspecifier.com/best-practices-for-specifying-windscreen-systems/

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