When is a window a wall?

Interested in the views of my most learned colleagues. In an argument with my client regarding a fire wall they’ve decided to fully glaze. This fire wall is protecting a single means of escape safe path, they’ve put in --/60/30sm glazing and I’m arguing it should be --/60/60sm glazing. They’ve pointed to C/AS2 4.16.1 and table 4.2 which permits ‘closures’ …“e.g for passage of …light” to only have --/60/30sm rating.

My argument is that this is missing the intent of C/AS2 and NZBC and an approx 4m long by 3m high fire wall protecting a safe path needs to have a --/60/60sm rating!

C/AS2 4.2.1 is the definitive answer for me (“glazing in fire separations shall be fixed fire resisting glazing having the same FRR values for integrity and insulation as the fire separation”) but seems to contradict 4.16.1?!

Yes you are correct.

4.16. has the requirements for closures (these are elements that CLOSE a hole in a fire separation i.e. doors and access panels/hatches) .
The fully glazed wall is The fire separation and therefore has to have the fire resistance rating required of the wall.
The lesser insulation rating required of a closure recognises the fact that as it is a closure it is unlikely to have room contents close to it or at least not directly in front of it and therefore a radiating object wont be close to the closure.

Hope this helps



Brilliant, cheers Nick. I always wondered why this allowance for a lowering of the insulation was permitted for a fire door, your comment regarding the burning items not likely to be in front makes perfect sense.

I would agree with the people above that using C/AS2 the insulation rating is required.
However if the design is undertaken using C/VM2 the reason for the fire separation would need to be looked at and a lower insulation rating maybe justified (or no insulation rating). If it is for means of escape then C/VM2 would permit egress past a glass screen with the 30 minute insulation rating (refer 3.6.1 g) which address egress past a window or glazed panel, analysis is not required where the insulated glazing has an FRR of not less than -/30/30. (you can also do a calculation if no insulation).

Might want to check out the definition of an external wall and split out the primary from the secondary elements. Regardless of the extent of the glazing it will always be secondary to the elements requiring structural adequacy. Fire separations need both.