Yeh I know the stuff.. I thought that was called sisalation? It definitely works anyway cos the use it up in port Hedland in a lot of houses and it's frequently 45+ Celsius there.. I noticed it while crawling through roof spaces as an apprentice haha. Much nicer than crawling through insulation batts. Just curious as to the noise difference because when I bought my house there was no insulation on the ceiling and it was noisy as f*ck then I chucked in all the r4 batts and it killed all the noisey reverbyness of the house