Not all fire rated glass is created equal. In this blog post, I will discuss the two types of fire rated glass products, when and where they can be used, and provide some background on where the requirements come from.

Types of Fire Rated Glass

There are two types of fire rated glazing products:

• Fire-resistive glazing
• Fire-protective glazing

These two terms are related to defined terms in the Canadian Building Codes:

Fire-resistance ratings are assigned to assemblies (walls, floors, columns, roofs, etc.) to limit the spread of fire. Fire-protection ratings are assigned to closures (doors, fire shutters, dampers, wired glass, etc.), which are generally installed to protect openings in fire separations; they do not achieve the same level of protection as assemblies with a fire-resistance rating, so there are some restrictions on their use.

Difference Between Fire Rated Glass Types

Fire-resistive glazing is a barrier to radiant heat, fire-protective glazing is not.

The biggest difference between the two types of fire rated glass can be seen by the text in bold in the defined terms above:

• Fire-resistive glazing – barrier to flame/smoke and radiant heat
• Fire-protective glazing – barrier to flame/smoke only

Fire-resistive glazing can be considered as a transparent wall since it is a barrier to flame and radiant heat. Many of these products will turn opaque when exposed to heat to block radiation from passing.

Fire-protective glazing is a closure and has more restrictions on where it can be used. These products are similar to wired glass. They are tested to remain in place under fire exposure for the tested duration, as opposed to tempered glass which can fail in as little as 5 minutes under similar test conditions.

Where Do These Requirements Come From?

Fire-resistive glazing needs to be tested to CAN/ULC-S101, “Fire Endurance Tests of Building Construction and Materials,” based on Sentence 3.1.7.1.(1) of the Canadian Building Codes. This is the same standard that any listed wall assembly is tested to for use in Canada. For non-loadbearing partitions, the standard includes a number of passing criteria:

• Integrity – limit passage of hot gases and flames
• Insulation – average temperature rise on unexposed side cannot exceed 140°C, or 180°C at a single location
• Hose stream test – assembly subjected to fire hose stream after the fire test period without allowing passage of water, flame, or hot gasses

An assembly that passes the above criteria is assigned a fire-resistance rating based on the duration of the test (45 min, 1 h, 2 h, etc.).

Fire-protective glazing needs to be tested to CAN4-S106-M, “Fire Tests of Window and Glass Block Assemblies”. You may also see rated glass that has been tested to CAN/ULC-S104, “Fire Tests of Door Assemblies,” for use in fire doors. Both tests evaluate components for use as closures to protect openings in a fire separation.

CAN4-S106-M uses the same temperature curve as CAN/ULC-S101, but it has different passing criteria. Here is a rough summary of the major requirements:

• No through openings in the glazing or around the frame
• No flaming on unexposed side of the glazing
• Hose stream test – majority of glazing must remain within the stops, minimal openings allowed to develop

The biggest difference between the two standards, is that CAN/ULC-S101 limits the allowable temperature rise on the unexposed side of the assembly, while CAN4-S106-M does not.

Where Can Fire Rated Glass be Used?

Fire-resistive glazing can be used in place of any fire rated wall. Consider it as a transparent fire rated wall, so the Canadian Building Codes do not place any special restrictions on their use . However, they need to be installed based on a listing or tested assembly, which may have some size restrictions.

Fire-protective glazing is a closure, so its use is limited by restrictions on closures. The National Building Code of Canada, BC Building Code, and Vancouver Building By-law, have the following requirements:

• Maximum size requirements for closures – Article 3.1.8.6
  • Sprinklered building – max. 22 m2 with no dimension more than 6 m
  • Unsprinklered building – max. 11 m2 with no dimension more than 3.7 m
• Area limits for wired glass and glass block in dead-end corridors, exit enclosures, and firewalls – Articles 3.1.8.17 to 3.1.8.19
  • Exit enclosures
    • Building up to 3 storeys – max. 0.8 m2 aggregate area
    • Building over 3 storeys – max. 0.0645 m2 (100 in2) aggregate area
  • Not allowed in firewalls
• Limiting distance <1.2m – not allowed – Sentence 3.2.3.5.(2)

Although the area limit requirements and restrictions on use where the limiting distance is under 1.2m are specific to wired glass and glass block, in my opinion, these requirements should also be applied to any transparent closure conforming to CAN4-S106-M. Fire-protection rated glazing products provide a similar level of protection to wired glass, since they do not limit the temperature rise; therefore, similar restrictions on their use in exits and firewalls is warranted. A code change may be necessary to better address these products as their use becomes more widespread.

What About Fire Rated Frames?

Frames for both types of fire rated glass need to match the rating of the glazing. So fire-resistive glazing will need an associated fire-resistive framing assembly.

The glazing-framing system needs to be installed according to the manufacturers requirements and listing to ensure if meets the fire rating requirements.

Thought Provoking Questions

Sentence 3.1.8.6.(2) of the BC Building Code states the following:

The size of an opening in an interior fire separation required to be protected with a closure shall be not more than 22 m2, with no dimension more than 6 m, provided the fire compartments on both sides of the fire separation are sprinklered.

This restricts the size of a single opening or closure, but can you exceed those limits if you have multiple openings protected by many closures? Can you have unlimited fire-protective glazing in a fire separation, as long as it is not an exit or a firewall?

Let me know what you think in the comments.