Initial findings came back this morning with the first system. Early findings are just what we hoped for 3 areas:
1 - Thermal - the wall system without any additional external cladding should achieve approx R4.3 which is MASSIVE. Add this with the fact that this construction method is monocoque (or fully sealed) the end result will be a house that is crazy insulated. Getting closer to 8 Stars without trying could be possible.
2 - Acoustic - the response here is the only way to truly tell is by a physical test. However from their estimations based on similar sandwich systems it seems we will get very close to Rw 50 for normal walls, and when doubled up for party wall we should able to SMASH the Rw + Ctr 50 which is great.
3 - Structure - Only the walls have been calculated so far based on a 2 storey house with load rating provided by our structural engineer. Currently the system is 1.8 times stronger than the building code is requiring! (wow). The calculations also didnt factor in the outer skins (becomes very complex to compute as a few things going on at once), so when we get physical testing done we expect the strength will be much higher.
ISSUE # 1
The first issue we are needing to resolve is heat to composites. The materials (carbon fibre, fibre glass, etc) are fine with extreme heat, its the resin which is the issue. Research into the BCA for fire resistance has indicated we need to get gradual heat up to 1,100 degrees Celsius to achieve 180/180/180 (which is only used on non-sprinkler apartment buildings - far higher than what is needed for residential construction).
Most resins will 'melt' or lose stability at around 150deg. So this created alarm bells.
Engineer has suggested a different core material (cant go into the specific details here) which will stay stable under these extreme heats. We have a fire-rated 'film' as part of our system, however this will stop the burn, but only reduce the heat a little - fire isnt our issue - extreme heat is (only our issue for 180/180/180 which it is unlikely we will ever do).
A potential solution for this also exposed a flaw in the brief to ACS-A being that they were asked to fire rate the structure, where as I didnt tell them that there would be an additional cladding system fixed to the outside (same as normal construction) that will block most the heat - in most cases are fire-rated in their own right. So there are 2 things to be done here to satisfy Issue # 1:
1 - Improve the current system to better insulate the core to reduce the direct heat - 2 scenarios have been discussed today to achieve this.
2 - Get samples (based on point 1 above) and do physical testing on 10 or so wall systems that include an outer cladding. This is the only way we will truly know the extend of heat the system can achieve.