SFPE Discussions

Insulation ratings

Hi, This is probably been discussed previously but need some feedback from the wider FE group. C/AS2- 2.3.13 states that Insulation ratings are not required to elements where sprinklers are installed throughout the building, in accordance with either NZS 4541 or NZS 4515.
My understanding is that this does not apply to elements that provide property separation or structural support, however in some projects sprinkler protection has been used for removing the insulating rating requirements of structural elements.

This allowance was introduced to the acceptable solutions in the 2014 re-write of the old (and in my opinion, unbroken) C/AS1 into the new C/AS1 to C/AS7 acceptable solutions.
It appears to remove an overlapping fire safety provision and place greater reliance on a fully operational sprinkler system. Not a good idea for storage buildings or certain retail buildings.
I would carefully consider the consequences of a sprinkler system failure (this does occasionally happen) - why do we have fire separations plus sprinklers? I dare say MBIE must have had a mountain of data to justify the new approach. For my money I would only consider the lack of an insulation in locations where no combustible material could be located within cooee of the uninsulated fire separation.
Floors with no insulation rating - wow!!! - I must be missing something.

By the words in C/AS2, I believe you are right Biswadeep. I do have issues with it in a couple of cases in particular, putting aside the risk assessment of sprinkler failure that Robert talks about.
For a wall on the boundary, a non insulated wall won’t protect against fire breaking in from outside, and nor will a sprinkler system necessarily protect against this. If it is large enough, then the sprinkler system can be overwhelmed. Similarly, the risk of fire spread in the case of a storage building may be significant, although I have never delved in to the numbers. Storage and bulk retail buildings have large fires and large radiating areas.
I have a real problem with uninsulated floors. An example I had was a carpark where they wanted to use welded steel plates as the floor, which would have achieved integrity but not insulation. If you look at the BRE test of sprinklered car fires, the temperatures above the fire at the ceiling were still around 700 degrees as I recall. The steel sheet will be thermally thin, and this is hot enough to be a hazard for fire fighters or occupants above, and also ignite car tyres, oil or combustibles on the floor above. This leads to fire spread beyond the floor of fire origin and also potentially a greater than allowed number of sprinklers operating.