Thanks for the response, Fei. I arrived at PE insulation board as the best option too, but am not fully comfortable using it as a proxy without knowing if is really representative even when adjusting for density.
On another note – we are also looking at mineral fibre ceiling tiles, which are quite common for their acoustic performance. Unfortunately I don’t see this material as an option in the database either. There is the template -https://etoollcd.com/Library/Template/Index/44771 – which uses mineral fibre insulation as a proxy, similar to what you’ve suggested for the PET board.
In both these cases I’m wondering how closesly this could match, whether it’s in the ballpark. I imagine manufacturing process and energy could vary significantly. If you have any further thoughts on this it would be much appreciated. Also wondering if there AusLCI could comment or if there is chance these materials could be added to the database. Or if there are other databases we could check as a comparison.