Replies

1. Expert Member
   BILL WICHERS | Jun 07, 2019 10:02pm | #1

   It’s easy to cut with a bread knife, but that’s for normal stuff like cutting out pieces to clear electrical boxes and the like. I haven’t tried splitting a batt in half the way you’re thinking, but it’s probably doable. The mineral wool I’ve worked with the most is the Owens Corning stuff, and it’s sort of like a bunch of layers like a breakfast biscuit. You may well be able to split a batt without too much trouble.

   I’d do a few test splits before ordering a large quantity of material though, just to be on the safe side. If you are successful splitting a few batts, then you should be ok. The material itself is pretty consistent lot to lot.

   Bill

2. 
   jerryc81 | Jun 07, 2019 10:18pm | #2

   Thanks for the heads up, ideally I would have got some 3.5” but it was 7-10 day order everywhere around me and I needed it by this coming Monday due to reasons out of my control. Thanks for the info. It’s for a home theatre room and I love the sound deadening applications it gives

3. Expert Member
   Akos | Jun 07, 2019 10:35pm | #3

   For sound, any type of insulation works. You don't have to go with mineral wool, fiberglass is just as effective.

   For best results, make sure the insulation doesn't touch both sides, so for a 3.5" wall, you want 3" insulation.

4. 
   Peter Yost | Jun 10, 2019 09:39am | #4

   Sound transmission--like heat transmission--is a combination of conduction and convection. Air leaks create "flanking" pathways for sound to travel.

   I am not so sure that the greater density of rockwool does not provide greater conductive sound protection. In any event, look for opportunities to reduce both conductive and convective sound transmission.

   Peter

1. Expert Member
   Akos | Jun 10, 2019 09:52am | #5

   This is my goto for STC values:
   http://publications.gc.ca/collections/collection_2018/schl-cmhc/nh17/NH17-198-1994-eng.pdf

   2x6 wall with RC and 5/8"

   Mineral wool STC 45
   Fiberglass STC 46
   Cellulose STC 41

   Cellulose is worse as it was packed, so you get a lot of sound transmission through the fibers as it is touching both sides.

   Pretty much any insulation works, best if not quite fills the space. From what I understand, the effect of the insulation is to make the wall cavity seem deeper, it is not "insulating" sound.

5. 
   Jon_R | Jun 10, 2019 10:56am | #6

   Much greater effect on sound is achieved by using steel studs and double drywall.