I'm considering using 4" thick Thermafiber insulation. If I pack it too tight between inner and outer wall, will I loose my isolation? i.e. how much can I compress insulation before it starts to conduct structureborn sound?
Creature82
Can insulation conduct structureborne sound?
Originally posted at johnlsayers.com, topic 7456.
I'll take a stab at this before more knowledgeable folks can be more specific.
The catchphrase around here (from Steve most of the time) is that slight compression is what you're aiming for -- basically, enough to apply a little pressure on the drywall or sheathing for the purpose of dampening, but not so much that it becomes a structure-borne flanking path.
How wide is your air gap?
--Keith :mrgreen:
Hi Keith -
the air gap varies... see illustration. I guess it doesn't make any sense to try to weave thru a 1/2-inch space.
What about laying in the traditional way? just put it between the studs?
So I guess the bottom line is, you can compress it a little, say 20% for arguement sake. Comments?
Creatch
20% is probably pretty good... Although compressing 4" batt in a 3 1/2" stud cavity is probably fine.
Why don't you just remove the staggered studs you will no longer need? Then it would be a non-issue........Hi Keith - the air gap varies... see illustration. I guess it doesn't make any sense to try to weave thru a 1/2-inch space. What about laying in the traditional way? just put it between the studs? So I guess the bottom line is, you can compress it a little, say 20% for arguement sake. Comments? Creatch
Hmmm... I'll have to think about that. I like that no-nonsense solution. I'm a little worried that my ceiling joists are perched near the inner edge of the 2x6 top plate... don't want cross-grain bending. I suppose if they bear far enough back it might be okay. I'll sleep on it.
Thanks,
Nervous Nellie (aka Creatch)
BTW - to answer the original question - unless you fill the entire cavity (from the front wall to the real wall) with material - this isn't going to be an issue.
If the 2 walls are not connected - compressing insulation within the individual bays will never created a source for flanking tansmissions.
It could very well give you a slight decrease in isolation - but unless the 2 individual frames connect - and are thus "bridged" - flanking will not occur.
Sincerely,
Rod