At the intersection of fire safety and daylighting

by sadia_badhon | March 27, 2019 12:50 pm

by David Vermeulen 

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An interesting dynamic in commercial building design is the dual need for compartmentation and transparency to help promote occupant well-being. Far too often, these demands conflict in areas with fire- and life-safety criteria.

On one hand, compartmentation, or the division of spaces through fire-rated building materials, is critical to slowing or stopping the spread of flames and smoke in a fire event. On the other, the opaque forms of standard fire-rated building materials, like concrete and gypsum, limit light transfer and views. This is problematic in modern building design as numerous studies underscore the positive link[2] between access to natural light and improved occupant well-being[3].

To help resolve this dilemma, project teams are increasingly turning to fire-rated glazing in commercial building design. Combining a transparent form with the ability to withstand temperatures up to 870 C (1600 F) or greater, it is uniquely positioned to bring fire safety in line with the daylighting design intent.

Depending on the selected product, building design teams can use fire-rated glazing to comply with codes and standards and maintain fire ratings from 20 to 180 minutes. As such, it is possible to employ the material to bring daylight deep into interior spaces formerly restricted by concrete or gypsum. Common applications include those in and around evacuation pathways, including stairwells, doors, entrances, corridors, atriums, and lobby walls—all of which benefit greatly from enhanced light transfer.

Why fire-rated glazing?

Today’s fire-rated glazing products are virtually clear, wireless, and able to provide the same defence against fire as traditional fire-rated materials. Current offerings provide fire protection (defence against flames and smoke) or fire resistance (defence against flames, smoke, and radiant and conductive heat transfer).

In Canada, glass with a fire-protective designation is tested to:

• CAN4/Underwriters Laboratories of Canada (ULC) S104, Standard Methods for Fire Tests of Door Assemblies;
• 10c/CAN4-S104/ Underwriters Laboratories (UL) 9, Fire Tests of Window Assemblies; and
• CAN/ULC S106,Standard Method for Fire Tests of Window and Glass Block Assemblies.

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Such glass is suitable for use in opening-protective applications, including transoms, borrowed lites, and doors. Fire-protective glass can also enhance safety and security as it offers greater visibility for people entering and exiting rooms.

Glass with a fire-resistance designation is tested to stringent Canadian and U.S. standards for walls, such as:

• CAN/ULC S101, Fire Endurance Tests of Building Construction and Materials;
• ASTM E119, Standard Methods for Fire Tests of Building Construction and Materials; and
• UL 263, Fire Tests of Building Construction and Materials.

Glass products meeting these criteria keep radiant and conductive heat transfer at bay for the duration of their fire rating. Therefore, they can exceed the traditional size parameters of fire-protective openings, making them suitable for use in locations where the total glazing area exceeds 25 per cent of the wall. This greatly enhances daylighting design freedom. For example, instead of being limited to smaller windows, borrowed lites, and small view panes in doors, building teams can now have large expanses of glass meeting some of the most stringent fire-rated building codes.

Additionally, manufacturers now offer integrated fire-resistive glass and framing systems.

A look at fire-rated glazing systems 

The term ‘fire-rated glazing systems’ refers to the fire-rated glass and frames designed and tested to work together as a cohesive unit, rather than individual components. They not only simplify specification, but also are suited to meet daylighting needs.

Fire-rated glass curtain walls are one of today’s more common system solutions, providing a substantial area of glazing for interior or exterior applications with fire-rated criteria. One system achieves its multifunctionality by using fire-resistive frames (steel is usually the primary framing material) that are anchored to the structure of the building using common means such as clips, angles, or plates. The fire-resistive glass in the curtain wall system is then typically held in place with a pressure plate. The plate creates the necessary pressure between individual lites of glass, the framing, and glazing gaskets. This is critical to maximize air and water penetration resistance through the wall. It is also important to note the pressure plate fasteners are hidden under a finished cover to suit the desired appearance.

Given the success of fire-rated glass curtain wall systems, a growing number of manufacturers are now adding to their system solution lineup. Here is a look at three recent market introductions and the daylighting benefits they provide.

Silicone-glazed, fire-rated curtain wall systems

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These systems go a step beyond standard curtain wall offerings, making it possible to create dramatic spans of fire-rated glass with clean sightlines and produce the popular frame-free look. One available assembly achieves this functionality by using fire-resistive-rated glass that is attached to narrow, fire-rated, steel frames with a toggle retention system becoming completely hidden once installed.

Daylighting benefit

Allows for large spans of fire-rated glazing with minimal frame profiles and clean sightlines, resulting in unobstructed daylight transfer.

Butt-glazed fire-rated systems

These interior-only glazing systems get their visual continuity from using fire-resistive-rated glass wall panels that are butt-glazed using silicone sealant. The panels are then secured in place with a heat-resistive perimeter frame.

Daylighting benefit

Allows design professionals to create continuous fire-rated glazed walls with nearly colourless transitions between glass panels for greater vision, transparency, and light transfer through hallways.

Fire-rated glass floor systems

Further, fire-rated glass floor systems have the ability to provide a code-approved barrier between the various building levels and can support structural loads while defending against the spread of fire.

Daylighting benefit

Allows daylight to be shared between floors while providing critical compartmentation in open, lofty interiors in commercial buildings.

Making the most of fire-rated glass

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There are numerous ways design professionals can use fire-rated glazing to support occupant well-being while providing protection from the threat of fire. To maximize the material’s full potential in commercial applications, one should consider the following tips.

Create transparent compartmentation

Fire-rated glazing products can offer transparent compartmentation. They can provide the necessary sub-division of space and reduce an area’s overall volume while creating an open, light-filled esthetic (see “KMK Place, St. John’s”).  This is true in modern design as the absence of compartmentation in large, shared spaces provides an opportunity for faster fire growth due to greater air volumes[7].

Orient for light transfer

According to the Daylighting Guide[8] for Canadian Commercial Buildings, the majority of Canada’s population lives near latitude 46 degrees. At this latitude, it is possible for interior spaces to receive 15 times more illumination than required to perform indoor tasks—even under overcast skies.

Fire-rated glazing is well-suited to take advantage of the region’s available sunlight and maximize its transfer throughout buildings. More specifically, due to the increase in fire-resistive glazing systems with the ability to meet the temperature-rise criteria, project teams can now align expansive fire-rated glazing assemblies in a range of settings to draw light into a building’s core.

Since it is up to the building team to ensure the product is oriented in such a way as to maximize light penetration, considerations include whether or not it is possible to:

• use floor-to-ceiling, fire-rated transparent wall panels with narrow fire-rated framing to improve sightlines and increase daylight transfer;
• incorporate full-lite, fire-rated glass in doors;
• install fire-rated curtain walls in spaces that are hard-to-illuminate such as stairwells;
• install non-slip, fire-rated glazed floor systems beneath skylights, allowing natural light to pass down into rooms that are otherwise cut off from sunlight; and
• incorporate exterior fire-rated glazing systems to provide lot-line defence and improve light transfer along the perimeter.

Fire-rated glazing can also help restore light transfer in renovations. Many existing structures rely on traditional, opaque building materials to provide fire protection. While functional, these materials often create dark and poorly lit interiors. By employing fire-rated glass to change these solid walls into clear ones, design teams can open up light-restricted areas while maintaining code compliance.

As with any project, daylighting needs vary by building type, occupancy, and owner goals. Lighting levels can be modelled through simulation methods to test and help predict all requirements are met.

Promote views

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Modern fire-rated glazing can also be employed to enhance visual connectivity and preserve views to the outside in areas where there is a code requirement to provide fire protection. These benefits are proving to be increasingly valuable to occupant well-being as a growing number of reports state Canadians now spend more time indoors than out. Consider a recent Nature Conservancy of Canada[10] report that noted three-quarters of its survey respondents “found it much easier to stay inside.” Many participants pointed to Canada’s rain, snow, and extreme weather conditions as deterrents to spending time outside.

While the transparent form of fire-rated glass supports visual connectivity, its benefits are further realized in products with a nearly distortion-free viewing surface. For example, fire-protective glazing products, such as fire-rated glass ceramic, can be ground and polished on both sides. This process results in glass with a smooth surface finish and high visible light transmission. Fire-resistive glass products are also available with exceptional clarity. One product on the market is comprised of layers of nearly colourless, wireless, low-iron float glass and clear intumescent interlayers. It emulates the look of ordinary float glass and allows for large, clear viewing areas in locations subject to strict fire-rated criteria by code. New product offerings, such as butt-glazed fire-rated systems, are also available to better promote views between spaces. The aforementioned system achieves a frameless look by using fire-resistive-rated glass wall panels that are butt-glazed using silicone sealant. The panels are then secured in place with a heat-resistive perimeter frame. With narrow butt-glazed joints and a predominant glass presence, it allows for exceptional transparency, clean sightlines, and purity of view.

Balance occupant comfort

As Chris Meek, director of the University of Washington’s (UW’s) Integrated Design Lab (IDL), explains it, the occupant experience is actually about comfort.

“Buildings either do the work of providing comfort or discomfort for the people inside them,” he explained, “which is why it is so important to create buildings that are centred on the needs of their occupants.”

Fire-rated glazing is no different than any other glazing material in that it must transfer light in the occupant-centred manner Meek addresses. Unbalanced natural light distribution can diminish workplace productivity, lead to excessive heat gain or loss, and increase electrical lighting loads.

While many facets of daylighting design affect occupant comfort, the following fire-rated glazing strategies can help teams achieve success:

• use fire-rated insulated glass units (IGUs) incorporating tinted or low-emissivity (low-e) glass for more efficient solar energy management;
• lightly sandblast fire-rated glass to diffuse light if privacy and light transfer are both desirable;
• employ fire-rated steel frames with a thermal conductivity of approximately 31 Btu per hour (about 74 per cent less than aluminum) and help reduce the potential for heat gain and loss between the glass and frames; and
• simulate the actual construction to give the designer insight on how the fire-rated glazing system will affect the sizing of the building’s HVAC systems.

KMK Place, St. John’s

When developer KMK Capital was tasked with planning the four-storey, 7342-m2 (80,000-sf) office building in St. John’s, it had the following design goals: create a unique look to stand out from nearby traditional buildings; and design an open floor plan to provide daylighting and a smooth flow through the building structure. To satisfy these design demands, Gibbons + Snow Architects desired a glass-filled atrium providing a focal point both inside and outside the building. It would also allow for light to be carried through multiple interior spaces. In accordance with the National Building Code of Canada (NBC) and local regulations, the atrium needed to incorporate fire-resistive materials to provide safe passage for people exiting in the event of an emergency. To preserve the open floor plan and help bring daylight deep into the building, the firm turned to a two-hour fire-rated glass and framing system. The selected system’s narrow frame profiles and large spans of fire-rated glazing separate the main building from the glass atrium across all four floors, preserving daylight and views for occupants. The Underwriters Laboratories Canada (ULC)- and Underwriters Laboratories (UL)-classified system provides a barrier to radiant and conductive heat transfer and incorporates fire-rated doors for a complete entrance solution. Additionally, smoke baffles were required and installed for fire and life safety. “It is not too often you will see an atrium of this calibre in office buildings,” said Sandy Gibbons, the project’s architect. “We needed a specialty product meeting certain needs like replacing solid walls and creating an open space, while not forcing us to compromise on esthetic.” From floors to curtain walls, building and design teams can employ  fire-rated glass in a number of configurations to marry form with function and create interiors occupants can enjoy.

Moving forward

Before capitalizing on the daylighting and design benefits of fire-rated glass, questions about cost may arise. The specialty material does have a higher price point when compared to opaque fire-rated building assemblies. However, the good news is, today’s wide range of fire-rated glazing materials often makes it possible to find a solution in line with architectural construction costs.

It is also important to keep in mind the amount of fire-rated glazing used in many projects is relatively small. Further, with many commercial buildings designed to last 30 years or more, there is adequate time to amortize its cost and reap the product’s full benefits.

If cost concerns remain, manufacturers and suppliers can assist in helping the design professionals and building owner understand what life safety and performance benefits they are purchasing.

Conclusion

According to the 2016 Census, there are approximately 35.1 million people living in Canada. Providing fire- and life-safety protection for these individuals is critical. So too is daylight. With proper use, fire-rated glazing can help bridge the gap between these two important needs.

[11]David Vermeulen is the national sales manager for Technical Glass Products (TGP), a supplier of fire-rated glass and framing systems and other specialty architectural glazing. TGP works closely with architects, designers, and other building professionals, providing them with state-of-the-art products, service, and support to maximize design esthetics and safety in commercial and institutional buildings around the world. Vermeulen can be reached at davidv@fireglass.com[12].

Source URL: https://www.constructioncanada.net/at-the-intersection-of-fire-safety-and-daylighting/

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