Question 1

What is fire rated glass?

Accepted Answer

Fire rated glass is glazing that has been tested to maintain its performance in a fire for a specified period, providing a fire-resistant barrier that also allows visibility and light transmission. Standard float glass has no fire resistance - it will crack and fall out of its frame within minutes of fire exposure, providing no barrier to flames, hot gases, or smoke. Fire rated glass is manufactured using different technologies depending on the required performance: wired glass (the traditional fire glass, with a steel wire mesh embedded in the glass that holds it together when it cracks, providing integrity but not insulation - now largely superseded); toughened glass (borosilicate or specially toughened soda-lime glass that can provide integrity performance); and intumescent interlayer glass (laminated glass with intumescent layers between the glass plies that expand in a fire to form an opaque insulating barrier, providing both integrity and insulation). The choice of fire glass type determines whether the product achieves E (integrity only) or EI (integrity and insulation) classification.

Question 2

What is the difference between E and EI fire glass ratings?

Accepted Answer

E (integrity) rating means the glass maintains a complete barrier to flames and hot gases for the rated period, but does not control the amount of heat radiated through the glass to the unexposed side. An E30 glass in a fire door or screen will prevent flames passing for 30 minutes, but the glass surface facing away from the fire can become very hot - hot enough to ignite combustible materials placed near it or cause burns on contact. EI (integrity and insulation) rating means the glass both maintains the barrier and limits the temperature rise on the unexposed face. An EI30 glass limits the average unexposed face temperature rise to no more than 140 degrees C above ambient for 30 minutes. EI glass is required where people may be in close contact with the glazing during evacuation (corridors and stairwells where people brush past the glass) or where the heat radiation from integrity-only glass would be sufficient to impede evacuation. Building Regulations Approved Document B specifies which locations require E or EI rated glazing.

Question 3

What sizes can fire rated glass vision panels be in fire doors?

Accepted Answer

Fire door vision panels (the glazed openings in fire doors allowing visibility through the door) must use fire rated glass appropriate to the door's fire rating. For FD30 fire doors (30 minutes integrity), vision panels must use glass achieving at least E30 integrity. For FD30S doors (30 minutes integrity plus smoke control), vision panels must use glass achieving at least E30 with integrity against smoke. For FD60 doors, E60 or EI60 glass is required. The maximum area of vision panel glazing in a fire door leaf is typically limited by the door's tested and certified configuration - a fire door is tested as a complete assembly including any vision panel, and the certification specifies the maximum glazed area that was included in the test. Using glass panels larger than those in the certified test configuration invalidates the door's fire rating. Standard FD30 door vision panels are typically 150x200mm or up to 300x300mm depending on the door's test evidence. Larger vision panels in fire-rated screens and partitions (rather than doors) can be achieved with appropriate fire glass systems tested as complete systems.

Question 4

Can standard double glazing be used in fire rated applications?

Accepted Answer

Standard double glazing (insulated glass units - IGUs - using standard float glass) has no fire resistance rating and cannot be used in fire-rated applications. Standard float glass fails very quickly in fire - the thermal shock from uneven heating causes it to crack and fall out of its frame within 3-5 minutes, providing no useful fire barrier. Fire rated insulated glass units are available, using fire-rated glass as one or both of the outer panes with appropriate interlayer and edge seal systems, but these are specialist products tested as complete systems and must be used within the tested configuration (including the specified frame and bead system). It is not acceptable to substitute standard glass for fire-rated glass in fire door vision panels or fire-rated screens, even if the frame itself is rated. The complete glazing system (glass, interlayer, frame, bead, and fixing method) must all have been tested together.

Fire Rated Glass

Just so you know...