Wired Glass vs. Fire-Rated Glass
Wired glass is rated up to 45 minutes of fire protection, but is NOT safety glass. Embedded wire weakens the glass and increases the likelihood of breakage. Breakage occurs under the minimal impact of 100 ft/lbs, which is the force of a small child. The impact of a child’s hand or leg through easily broken wired glass can be snared by the wire, resulting in even more severe injury. In 2003, Wired glazing was forced to comply with CPSC impact-safety standards. In 2006, wired glass was banned, though can still be made available with surface applied safety film in limited applications.
Available in 20 minute and 45 minute fire ratings, fire-rated glass like PYROSWISS prevents the passage of smoke and flames. It can symmetrically withstand high thermal stress, is free of UV-sensitive interlayers or embedded wires, and is optically clear, providing very high light transmission values of up to 89%. This makes it ideal for use in high impact safety rated locations such as 20-minute fire-rated doors and 45-minute fire-rated sidelites.
Intumescent Fire-Rated Glazing
Available from ¾” up to 4” thickness, Vetrotech’s CONTRAFLAM intumescent fire-resistant glazing is rated for between 45 and 180 minute applications and is the most advanced in design by compartmentalizing smoke, flames, and the dangerous transfer of radiant heat. These multi-layer products have heat absorbing polymer gel between two layers of tempered glass or thin layers of transparent intumescent material sandwiched between layers of either tempered or annealed glass.
When fire-resistant glass is heated, a series of reactions occur. First, the exposed layer of glass cracks and the first layer of intumescent material is activated. The panel becomes opaque, reducing heat transmission. Eventually, the heat degrades the intumescence and the second layer of glass cracks. This process repeats through all layers, depending on the fire rating. The glass on the unexposed surface, however, remains cool and does not slump.
Below is a visual representation of the structure of an intumescent glazing system and how it would react in the event of a fire.
- Thermally broken steel profile systems used in conjunction with fire and safety-rated glazing products provide a barrier to radiant and conducted heat transfer
- Interlayer absorbs energy from fire and limits transmission of radiant heat to non-fire side.
Fire-Protective vs. Fire-Resistive: What does this mean
Fire rated glazing can either be defined as fire-protective or fire-resistive. The lesser Fire Protective glazing defends against smoke and Flames whereas Fire Resistive glazing is more advanced in design and restricts the dangerous transmission of radiant heat.
Fire-protective glass does not provide protection from the dangers of radiant heat transfer. It is simply designed to protect against the spread of smoke and flames with an ability to achieve such protections that range from 20 to 180 minutes. As a result of its limitations, fire protective rated glazing is restricted by code to specific building application, area, and sizing limits.
Fire-resistive glass not only blocks smoke and flames but also provides a barrier to the dangers of heat. Tested similar to fire protective in terms of fire, hose stream, & impact - however it also must meet ASTM E119 - which is the standard method for fire rated wall construction. Because these products are tested to the same standard as a fire rated wall assemblies they are defined by the IBC as “transparent walls”.
While these products are strenuously tested and designed to slow or stop a fire under a range of conditions, just like “bullet resistant glass” and “Bulletproof glass” are different, so is “fireproof glass” and “fire resistant glass”. In both cases, we use the term resistant, referring to the fire-rated glazing code requirements and testing standards included in regulations around the world to ensure we produce fire-rated glass to keep our customers on the safe side.
Understanding the effects of Heat Transfer of Fire-Rated Glass
Fire-protective glass products are intended to contain smoke and flames, but do not protect against heat. As such, they cannot exceed 25% of the total wall area. Fire-resistive glass products, however, contain smoke and flames as well as protect against radiant heat. Their “Transparent Wall” Assembly is not limited in size or application, but must include heat resistant framing
In any building, there will be defined compartments that are in place to keep a fire contained in the event of a fire. These are defined in Chapter 7 of the IBC as: Fire walls, fire barriers, and fire partitions. These compartments are recognized by NFPA 257 as an effective method of restricting fires to their area of origin or limiting their spread.
Fire-Rated Glass Code Requirements and Testing Standards
ASTM E119: Standard test methods for fire test of building construction and materials
NFPA 80: Standard for regulating the installation and maintenance of fire protective openings in walls, floors, and ceilings.
NFPS 252: The standard for fire door systems
NFPA 257: The standard for fire-rated window assemblies, glass block, and other light-transmitting assemblies.
In accordance with the IBC, both fire-protection-rated glazing and fire-resistance-rated glazing are required to be permanently labeled with a multitude of information. These labels specifically identify the product name, basic characteristics and compliance with impact safety requirements. The letters now replace the test standard numbers - The IBC made these revisions to help in better matching product with application. If a product has been tested to more than one standard, it will show multiple letter markings. Refer to the markings listed here to indicate the type of assembly the glazing has been tested for as well as the number of minutes of fire resistance or fire protecti