Best insulation?EPS or Rockwool

awishawash

Hi all, was just wondering what they reckoned would be best for soundproofing a wall, rigid expanded polystyrene aerobord, or rockwool. The rockwool seems to be loosely packed.For sound, maybe the tightly packed aerobord would be better?
also on the topic of sound, another wall that is freshly built(cavity with aerobord) will need plasterboard on it and i am wondering whether or not to put 2x1 battens on first then put on the slabs, or put some skinny insulation between the 2x1, or wet plaster it. Which would be the best for sound, without going overboard!
any help much appreciated!!

patrido

is this just for sound proofing or is there a thermal requirement also?

most standard thermal insulation materials do not tend to have acoustic performance ratings in their product specs. you could guess from the density of the board, but i don't think that would be a reliable guide.

you might be best looking at dedicated sound products (which also give thermal insulation) like moy acoustic or some of the rockwool acoustic products. they are made from heavier material for better sound absorbtion.

the glass wool and rock wool products are available in semi rigid batts, as well as rolls. the batts can be better, as the rolls can settle over time and leave small gaps at the top.

awishawash

Thanks for the reply Patrido, its purely for sound. I think I will chance the rockwool fluff as I have it bought. Hope it works! What you think about the 2x1 batts with plasterboard for the other wall?or would a thick coat of wet plaster be alright..again soundly speaking..

Victor

Rockwool is probably better for sound insulation as there is less mass to carry the sound.

Sound insulation needs two factors, mass and lack of connectivity.

Of course if this is critical soundproofing (recording studio, music room, S&M dungeon ....) then it might be worthwhile getting an specialist engineer to design it.

For your other wall, consider cranking up the insulation substantially. The advantage of using plasterboard over wet plaster is a quicker drying time and you only need to do a skim funish (some jobs get away with just taping, filling & sanding the joints).

awishawash

Thanks for the post Victor, regarding that cavity wall which is just bare block at the moment, I'm basically asking if I use 2x1 batts behind plasterboard, would it offer better sound insulation than just wet plastering the blocks.
This would mean a 1" gap between wall and board ie. lack of connectivity - better? or is it too little to matter. And wouldnt the battens bridge the sound from the wall anyway?
I have a gas pipe to run up the wall aswell but I better make a new post for that...!

Victor

awishawash wrote:

Thanks for the post Victor, regarding that cavity wall which is just bare block at the moment, I'm basically asking if I use 2x1 batts behind plasterboard, would it offer better sound insulation than just wet plastering the blocks.

Probably slightly better using the plasterboard - its less "hard".

awishawash wrote:

I have a gas pipe to run up the wall aswell but I better make a new post for that...!

People like to keep these really short internally and paint them yellow.

awishawash

People like to keep these really short internally and paint them yellow

Sorry Victor its late, what do you mean really short internally.

Victor

awishawash wrote:

Sorry Victor its late, what do you mean really short internally.

Keep the minimum amount of pipe (thats pratical) inside, with most of the pipe outside. That way if the pipe is damaged, it vents into the open air and doesn't build up internally.

patrido

Victor wrote:

Rockwool is probably better for sound insulation as there is less mass to carry the sound.

Sound insulation needs two factors, mass and lack of connectivity.

Of course if this is critical soundproofing (recording studio, music room, S&M dungeon ....) then it might be worthwhile getting an specialist engineer to design it.

For your other wall, consider cranking up the insulation substantially. The advantage of using plasterboard over wet plaster is a quicker drying time and you only need to do a skim funish (some jobs get away with just taping, filling & sanding the joints).

you need more mass, not less. mass absorbs the sound, as in a concrete wall.

to reduce the connectivity, look at resilient bars or robust details.

patrido

awishawash wrote:

Thanks for the post Victor, regarding that cavity wall which is just bare block at the moment, I'm basically asking if I use 2x1 batts behind plasterboard, would it offer better sound insulation than just wet plastering the blocks.
This would mean a 1" gap between wall and board ie. lack of connectivity - better? or is it too little to matter. And wouldnt the battens bridge the sound from the wall anyway?
I have a gas pipe to run up the wall aswell but I better make a new post for that...!

on a concrete wall, this might not make a very big difference. google for robust details by gypsum and other companies, and you will get some ideas for seperation. if you did go with this idea, you could use resilient bars on the verticals to achieve more seperation.

one option would be to construct a stud partition wall just (say an inch) inside the concrete wall, using 4x2s. Fill the gap between the studs with rockwool or similar. Then use a single or double layer of plasterboard, which you can tape and fill, or skim. You will lose about 6 inches out of your room though, and it really depends on the direction your floor joists are running.

If the partition is running perpendicular to the joists, it should be fine (though you could always consult an engineer). If the partition is running parallel with the joists, you need to be very careful. It needs to be built directly on a joist (or preferable a double joist) with bridging to the next joists. You would need to be consulting the building regs (i think it's the structure section), and probably an engineer.

awishawash

Thanks for all the input lads, i think going to so much trouble is pointless for the decibel reduction. I have loads of 2x1, and 2 extra boards so I reckon as Victor was saying in creating an airspace before the sound hits the next barrier would be slightly better than the 15 mm of wet finish, I dont mind losing the extra 22.5mm. Havent got the space to go all out with a stud partition though but a good idea for isolating a room.

Whilst on the subject of insulation - is there anything wrong with mixing insulation type?I have a few bits left over that would do a small bit of studwork for around a shower.

Victor

Victor wrote:

Rockwool is probably better for sound insulation as there is less mass to carry the sound.

This should read "Rockwool is probably better for sound insulation as there is less connectivity to carry the sound." I was being too simple in my statement.

Slabbing and skimming is not only drier work, but because the slabs are softer than sand-cement the sound reflection within the room is slightly reduced. For increased effect, use soft furnishings, hanging drapes and even acoustic panels.

It doesn't hugely reduce sound transmission, but a litltle.

awishawash

I know that was what you meant. Cheers again.