Thu, 15 Oct 2026 16:45:45 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106524#Comment_106524 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106524#Comment_106524 Tue, 29 Mar 2011 09:13:53 +0100 Peter_S https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106557#Comment_106557 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106557#Comment_106557 Tue, 29 Mar 2011 15:51:15 +0100 dstart
Do you think Flexi Rockwool in the main cavity too? Or leave the main caivty empty for the full 'separation'. One acoustic engineer told me leave it empty, but seems counter intuitive.

Obviously it would add some thermal and fire proofing, but sounds is the big issue

best

Daniel]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106582#Comment_106582 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106582#Comment_106582 Tue, 29 Mar 2011 23:10:31 +0100 Peter_S I am not an acoustician so cannot give specifics for your situation, but as a rule of thumb, adding mineral wool insulation within the cavity will definitely increase thermal/fire performance whilst possibly not adding anything further to the acoustic properties of the wall. Rockwool batts are unlikely to make it worse however so the acoustic engineer you spoke to may have been approaching the issue purely from sound transfer relative to wall build up.
I wouldnt bother too much with the Rockwool Flexi in a standard masonary cavity though, your paying extra for it to be able to squeeze into framed construction which you won't need sandwiched between two leaves of blockwork, standard batts will do. As mentioned before, make sure there is a tight joint at the abutment with existing or all the hard work could be undone.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106587#Comment_106587 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106587#Comment_106587 Wed, 30 Mar 2011 06:58:18 +0100 tony