Although the building code doesn't specifically look for flammability within a house for a class 1 building, through some more testing today we found that when you apply a 'blow torch' which would be around 800degC for a short time the sandwich ignites.
The polyurethane core wants to burn, but is filled with carbon-dioxide 'bubbles' from the foaming process so is continuously starved for oxygen so stops burning. However a continued flame source will keep igniting this foam core.
We next removed the foam and applied the blow torch to the fibreglass / resin matrix and found that there is some flame here also (being the resin).
Please note that what I am mentioning above has nothing to do with the fire-rated system which is completely fire-resistant. This is a standard internal wall. Having said this, its not acceptable in our view. So it needs to be fixed...
We then reached out to our supplier and also the supplier of the fire retardant for the external walls and in very quick responses we have modified the system to now include the following:
An additive to the PU core to become B1 level fire resistance
An additive to the resin to be fire resistant
The customisation of a new fibreglass fabric (upon our request) so that the chemical additive for our awesome performing fire rated walls is now added to our custom fibreglass material to be completely fire-resistant.
This will now be used for all of our walls which is brilliant and should be very comforting to clients who purchase these state of the art houses. Being that we have requested a custom product, this has eliminated the need for an additional process so in turn has kept the price increase to an absolute minimum.