Limitations Matter When it Comes to Fire Rated Glazing

It is a fact that all fire rated glazing products have limitations. So when coming across advertisements urging designers to “be unlimited” when it comes to using glass ceramics, or any other fire protective glazing, they are misleading. Especially when they tout fire ratings up to 3 hours.

While the advertiser’s message of asking designers to think outside the box and use glass where it hasn’t been used before is understandable, it is still important for designers to realize that fire rated glass – especially glass ceramic – does have its limits under the International Building Code (IBC). One only has to look at the Chapter 7 tables (see below) to know that glass ceramics and other fire protective glazing such as specialty tempered and wired products have specific size and application limitations. The reason being that fire protective glazing only blocks smoke and flames, and not radiant heat. This inability to block radiant heat is the reason why all fire protective glazing products have the following imposed limitations:

• Overall sizes are limited to the maximum size tested.
• For interior separations 20-45 minute fire-protection-rated glazing is only permitted in 1 hour rated fire barriers for incidental use area or mixed occupancy separations, or in fire partitions and is limited to 25% of the wall area.
• Sidelights and transoms in fire door assemblies are limited to a maximum of 45minute rating
• Exterior walls permit 20-90 minute fire protective glazing for fire windows depending on fire separation distance and occupancy type in the section 705 of the 2012 IBC.
• 60 minute, 90 minute, and 180 minute fire-protection-rated vision lites in fire doors are limited to 100 sq. inches.

There is a problem with the unqualified statement ‘fire ratings up to 3 hours’, and here’s why: while it is true that ceramics, a fire protective glazing product, are listed up to 3 hours, it is purposely misleading. What the advertisement doesn’t tell you – but should have, if code compliance is important to this advertiser – is that where 60/90/120/180 minute ratings are prescribed; the code limits the use of ceramics to 100. sq. inches in 60/90/180 minute doors and ceramics cannot be used at all in 60/120 minute interior windows, sidelites and transoms regardless of whether sprinklers are employed or not.

The good news is that fire resistive glazing does not have the size and application limitations that the IBC imposes on fire protective glazing. In addition to blocking smoke and flames, fire resistive glazing tested to ASTM E-119 also blocks the passage of radiant heat. Because of this, fire resistive glazing can be used up to the maximum size tested in all 60 to 120 minute applications. Here’s a side by side comparison of fire protective vs. fire resistive glazing used in a 1-hour stairwell application:

Part of the confusion is in the way fire rated glass products are asked to be tested by the manufacturer and listed by testing agencies. It is important for design professionals and code enforcement officials to understand that the listing agencies do not list fire rated glass products in accordance with the codes or limitations on their use, but rather, by what the manufacturer tested. Test agencies simply report the sizes and types of assemblies in which a product was tested. For example, test agencies often list ceramic glazing products in 60 and 90-minute sidelite and transom assemblies. These products that are not permitted in opening protectives specified to have 60 minute or 90 minutes under any building code in the United States. Accordingly, listings cannot be relied on for size or determining accepted code applications of fire rated glass products. So when in doubt, refer to the IBC requirements – not a product’s listing and or paid advertising – to ensure code compliance.

Hopefully, this starts a dialogue between other fire rated glass suppliers, testing agencies and building officials regarding this issue. The fact is, ceramic is not a fire-resistance-rated glazing product under the code because it does not meet ASTM E-119. Every day, fire rated glazing providers are asked to quote or provide materials that are not usable or that could be rejected in the field. This is happening because listings do not state the limitations to the listings given. As seen in the following chart (based upon the 2012 and 2015 editions of the IBC), the tested sizes and applications given to ceramics are not code compliant per the IBC. It’s time to make it easier for designers, building officials and end-users to select the correct and code approved product for their application by having the limitations of the listings qualified in those listings.