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wall insulation - more or less glass wool
Old 17th May 2013
  #1
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wall insulation - more or less glass wool

I'm in the wall building stage of my project - MAM, wooden studs with 30mm Gyproc on each leaf. Wall studs on both sides are being stuffed with Isover Energylite glass wool Batts (600x1200mm density = 47.5 m/2)

The air gap is on average 300mm between the walls

I have just read many posts saying that when it comes to wall insulation "The pink fluffy stuff is best" We have a fluffy pink glass wool product available locally called Aerolite - its 100mm thick and has density of 12kg/m2. Would this in fact be better than the 47.5 batts I am using despite the lower density ?

Or perhaps because of the ample space available between the leafs I could add another layer of Aerolite over the stiffer glasswool to improve overall performance ?

Any thoughts?

Thanks!
Old 18th May 2013
  #2
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Rod Gervais's Avatar
 

Installing rigid/dense insulating materials in walls makes no sense - the best "bang for the buck" is standard residential insulation.

What is going to provide you with the greatest increase in isolation (besides decoupled structure) is mass - as you add mass you increase low frequency isolation levels - if you can get a handle on the low frequencies - higher and mid frequencies will take care of themselves. Spending money on more expensive insulation (in wall cavities) is simply throwing money away.

By the way - just for the record here - this is not an opinion - it is fact. Simple opinions are pretty much useless in anything having to do with isolation. Engineering however has value.......

Rod
Old 18th May 2013
  #3
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Thanks Rod

So you feel that 12kg density would be ok then? The Aerolite "Think Pink" product is floppy, comes in rolls and presents more of a challenge to set between the studs though I guess it could be held in place by tape/mesh or similar . .

Interesting as most local studio builders I have met use the more expensive "IM475" product . . I wonder if I can return mine!
Old 18th May 2013
  #4
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No challenge whatsoever - the unfaced fluffy insulation should be what is known as "friction fit" - however for a comfort level you can always use a couple of stick pins to keep them in place.......

Google Image Result for https://www.kamcoboston.com/Store/customer-images/products/images/27201215390ihpbar.jpg

Rod
Old 18th May 2013
  #5
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+1

For wall cavity absorption, use 12 to 16 kg/m3 density 'regular' building insulation. This is a fact and not our 'feeling'.

UNLESS you are building a concrete block MAM partition and need something to prevent mortar from falling into the air gap; enter the rock wool or rigid product.

BUT it is NOT necessary for improved STL performance.

Remember that 'better' is a SUBJECTIVE description. -Find out the facts.

Cheers,
John

PS. It will usually 'hold' itself in between studs. Fill it full. See attached phtoto.
Attached Thumbnails
wall insulation - more or less glass wool-4955746991_0cb99f6f69_b.jpg  
Old 18th May 2013
  #6
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Thanks John (once again) for your input . . Great illustrative pic by the way .. As a final point of clarification do you think there would be improved STL performance by installing an additional layer of the pink fluffy stuff over the already installed 47.5 batts?

I am reading all I can to "find the (many) facts" but meanwhile thank goodness for this forum where very specific topics/applications can be discussed! Thanks again to all posters .
Old 18th May 2013
  #7
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Well, I'll put it this way; Fill the stud frames with regular building insulation and it's very good... fill the air gap as well (not tight!) and it's a 'little' better.

Depends on your budget and how much you are willing to spend on small increases in quality. As in Audio Gear, quality increases of 10% usually require a logarithmic increase in budget.

Cheers,
John
Old 18th May 2013
  #8
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I agree with John (no big surprise) however would caution you that over-packing is counter productive - no gains with the potential for some losses.......

The pink fluffy is just that - pink and fluffy - it is compressed in packaging and when removed from that packaging it expands pretty drastically - typically, with a 1" space between framing members, you would expect the entire void to be filled using standard materials (correctly sized for the walls) without the need to stuff additional insulation in the bays.

If the inside framing is staggered from the framing in the exterior walls then the framing itself helps to brace the insulation, locking it into place.

Rod
Old 18th May 2013
  #9
Gear Guru
Test

I had a link for a British Gypsum test, but the link is dead now unfortunately.
They compared low density floppy vs the semi rigid dense expensive boards. They included the fill amount. There were no advantages to using the rigid in terms of Transmission loss. In fact performance was worse at some frequencies. Interestingly a half filled void, with the semi rigid not fully filling, had poor performance. So a full fill of light fluffy, supported by cross pieces or mesh or whatever. No harm to say it again, do not stuff/compress it. This would couple the two leaves at LF.
DD
Old 18th May 2013
  #10
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Take out the heavier stuff and use that inside the room for treatments
(of course, the 'pink fluffy' can be used to great effect for treatment inside the room when thick enough application are used... sometimes even better than denser insulations depending on usage)
Old 18th May 2013
  #11
Audio X
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Quote:
Originally Posted by AwwDeOhh View Post
Take out the heavier stuff
I don't think there's a need to go that far. It's not like thicker/denser stuff is evil or anything. I mean, if a guy like Tom Jouanjean doesn't have a problem using denser fiber in his designs it can't be nearly as bad as it's being made out to be.
Attached Thumbnails
wall insulation - more or less glass wool-side-walls-rw.jpg   wall insulation - more or less glass wool-bass-trap-rear-wall-90-.jpg   wall insulation - more or less glass wool-rear_wall.jpg  
Old 18th May 2013
  #12
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Sure, but if he's going to 'buy it twice' for treatment inside the room, better to use what he has already and save the coin.> > was Basically my point.
Old 18th May 2013
  #13
Audio X
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Quote:
Originally Posted by jhbrandt View Post
Depends on your budget and how much you are willing to spend on small increases in quality. As in Audio Gear, quality increases of 10% usually require a logarithmic increase in budget.
Definitely worth noting, but it's also the attention and accumulation of those increases in quality that add up to high performance all around.
Old 18th May 2013
  #14
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I can't speak for Thomas, as he may very well have 'other' purposes for the denser stuff. And you may be misunderstanding what is going on there.
(another reason why I say to never copy what something looks like)

But if you are using this to increase the isolation of a partition with 'damping' or absorption in the Cavity of a MAM system...

It IS a waste of money.. bottom line. It does not perform 'better'.

Cheers,
John
Old 18th May 2013
  #15
Audio X
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Quote:
Originally Posted by jhbrandt View Post

if you are using this to increase the isolation of a partition with 'damping' or absorption in the Cavity of a MAM system...

It IS a waste of money.. bottom line. It does not perform 'better'.

Cheers,
John
My inclination is to believe you, because logically I can almost see this making sense, but do you have any links or studies that show what you guy's are saying is true.. just for my own curiosity?
Old 18th May 2013
  #16
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Yes, I do. It is very late here in Indonesia ( I should be sleeping)

I promise to dig up that data for you tomorrow morning (your evening today)
-- and THANK YOU for 'Questioning Everything'.

Cheers,
John
Old 18th May 2013
  #17
Audio X
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Ok. Thx. No rush.
Old 18th May 2013
  #18
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Rod Gervais's Avatar
 

Quote:
Originally Posted by Audio X View Post
My inclination is to believe you, because logically I can almost see this making sense, but do you have any links or studies that show what you guy's are saying is true.. just for my own curiosity?
Audio,

Go look at some of the Canadian studies - they are very extensive.... IR-761 is a good beginning:

http://archive.nrc-cnrc.gc.ca/obj/ir...r761/ir761.pdf

Rod
Old 18th May 2013
  #19
Gear Guru
Drum head

Semi Rigid insulation batts can have a sort of drum head effect. This is particularly obvious with corner straddling fibreglass panels of 100KG/m^3 or more. It seems likely that a whole wall of such fibre might exhibit a similar partially resonant effect.

DD
Old 18th May 2013
  #20
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boggy's Avatar
Quote:
Originally Posted by Audio X View Post
I don't think there's a need to go that far. It's not like thicker/denser stuff is evil or anything. I mean, if a guy like Tom Jouanjean doesn't have a problem using denser fiber in his designs it can't be nearly as bad as it's being made out to be.
I agree

IMHO:
Thomas designs aren't simple, and someone must be aware of level of professional support on this forum, where, from one side, most people doesn't have too much education about physics and acoustics.... so, gs forum problem discussion need to go in much simpler way, sometimes possibly even trivial, if we want to have it... simply because there are some (good) easier methods to solve some of acoustical problems without too much chance to make mistake, and without too much calculations (I personally feel that nobody wants to do any calculations before posting on gs ), and we can share it, I also expect that people is aware that this hardly can be everything one can do in acoustics...

Denser absorbing material may be used but its use is limited to many specific factors which must be included in calculations (very specific to particular material), it is hardly can be expected that level of details or type of solutions on public forum discussion...




Old 19th May 2013
  #21
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Hello everyone,

Here is the data requested. See attached. (ctu-n1.pdf)

Page 4, under the Bold heading of 'Sound-Absorbing Materials' is pertinent. I will quote a few parts here for those who do not wish to sort through the document:

"Sound-absorbing materials are only effective when used in assemblies with the faces correctly isolated..." meaning decoupled. "adding sound-absorbing material to the cavity increases the STC by about 10 points. ...Sound reduction continuously improves as the thickness of sound-absorbing material covering the whole face of the specimen is increased. ...However, in terms of the STC, no important acoustical differences were found among the sound-absorbing materials used. ...Overfilling a cavity with a material that is fairly dense and rigid, for example, introduces the risk of sound transmission through the sound-absorbing material itself. The stiffer the material, the greater the reduction in the STC." (Emphasis Added)

Don't forget to read the summary at the end of the document.

NOTE: cellulose spray or blown-in is inferior to all other insulation materials, producing a much lower transmission loss compared to standard insulating glass fiber.

Furthermore, if you have a look at Chris Whealy's Porous Absorber Calculator and plug the numbers for the frequency range of absorption for regular fiberglass batt insulation (R-13) @ about 8000 rayls/m compared to 60kg rock wool @ about 22000 rayls/m. --Draw a line horizonally on the charts at 0.8 & you will see the LF absorption characteristics of the lighter (cheaper) stuff is actually better.

Now don't go changing your absorption panels! There is a reason why we use the denser stuff for that...

Also, remember that we (studio builders and designers) use this material that was originally DESIGNED for use in buildings and homes for thermal insulation. Noise insulation is a 'new thing' and is just catching on in the large manufacturing companies that make these products. We are a very small market for them.

Cheers,
John
Attached Thumbnails
wall insulation - more or less glass wool-pa-r-13.jpg   wall insulation - more or less glass wool-pa-60kg-rockwool.jpg  
Attached Files
File Type: pdf ctu-n1_eng.pdf (93.9 KB, 501 views)
Old 19th May 2013
  #22
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Hey John the CTU doc is an interesting read . .

I had read elsewhere that thickness of wall insulation material was not a factor as the key was density not thickness . . but here it states that sound reduction improves as the thickness of material is increased .. hmm

It is often stated that isolation improves as the air gap size is increased but I have not found any hard data that describes at what point that increasing the size further becomes negligible. Or if in fact there is such a thing as an air gap that becomes too large for correct isolation wall performance ? A stated earlier in my thread I had to build walls with a 300mm air gap due to supporting columns being in the way . .

Regards
Matt . .
Old 19th May 2013
  #23
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Rod Gervais's Avatar
 

Quote:
Originally Posted by audiotreat View Post
Hey John the CTU doc is an interesting read . .

I had read elsewhere that thickness of wall insulation material was not a factor as the key was density not thickness . . but here it states that sound reduction improves as the thickness of material is increased .. hmm

It is often stated that isolation improves as the air gap size is increased but I have not found any hard data that describes at what point that increasing the size further becomes negligible. Or if in fact there is such a thing as an air gap that becomes too large for correct isolation wall performance ? A stated earlier in my thread I had to build walls with a 300mm air gap due to supporting columns being in the way . .

Regards
Matt . .
If you are talking a 2 panel insulated cavity it really becomes a question of "how much real estate do I want to give up".... this because you will get increases in isolation as you give up room space for increases in cavity depth and greater depth of insulation.

In the case of uninsulated spaces we generally view the width of a corridor as effectively becoming a room for all practical purposes - but this is not the case if the inside wall surfaces were removed and the corridor was to then be filled with insulation.

In theory you would never reach a point where this ceased to work for an increase in isolation - you would just reach a point where it made no sense from a practical point of view...... giving up huge areas within a building to isolation makes no practical sense when you can keep the real estate as usable property and achieve the same results through other manners... for example constructing walls that are not only separate frames - but that are also decoupled from the structure they rest on - adding mass to the surfaces... just 2 examples of many options.

It would also not make any sense to isolate beyond the limits of the volume within the room you are trying to isolate from the remainder of the world.

So when we design we weigh the end results against the cost of the gains...

Rod
Old 19th May 2013
  #24
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Quote:
Originally Posted by jhbrandt View Post
Noise insulation is a 'new thing' and is just catching on in the large manufacturing companies that make these products. We are a very small market for them.
I don't often catch anything not quite right in your posts.....

This is not quite correct though....

"Sound Batt" insulation has been in use since at least the 1980's...... which was my first use of the product - it may well have existed before then - a lot of things existed before my involvement with them......

It is a lighter density insulation than standard thermal fiberglass insulation - and we used it pretty extensively for both office and residential construction over the years. It was developed primarily for an increase of isolation in the frequency range of speech.

I gave up using it back in the mid to late 90's however because (again) any small gain that might be realized through it's use was not worth the premium paid due to the fact that it was a specialty product.

We could always realize the best return on our investment simply by using standard insulation and taking care to make certain that the remainder of the construction was properly installed.

Rod
Old 19th May 2013
  #25
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Quote:
Originally Posted by Rod Gervais View Post
I don't often catch anything not quite right in your posts.....

This is not quite correct though....
........
I agree with John that manufacturers whose products we use for porous absorbers, are still primarily oriented to thermal insulation, probably because thermal insulation can be, more than anything, translated to direct money savings... in contrast to this, acoustic insulation primarily has only health impact, and we live in the world where primary rule (even religion) is money. So if we have some acoustic impact or "feel" when we read about this product, this is relatively minor regards to main industry target - thermal insulation. IMHO, it is fortunate that rockwool/glasswool thermal insulation are good acoustic absorber in the same time... so people get good sound insulation with thermal insulation even if it is not main manufacturer "desire"... it is only confusing for non-educated folks (who get correlation between thermal insulation and sound absorbing instinctively) and styrofoam is used very often for radio vocal booth "acoustic treatment" here (in my country)...

AFAIK, even today, we still have problems to find gas flow resistance constants for all porous products in standard specifications... so here is even thread with only this parameters... to be easier to find.

To be clear, nobody ever forbid to use anything for acoustical treatment, even rockwool and glasswool .... but this still doesn't mean that all of this are produced primarily for acoustical absorption needs... I think that this is the main point of John writings...

EDIT: following this proportions (money savings - health benefits) studio building business virtually doesn't even exist, so we cannot expect to much effort for our needs...
Old 19th May 2013
  #26
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Quote:
Originally Posted by boggy View Post
I agree with John that manufacturers whose products we use for porous absorbers, are still primarily oriented to thermal insulation,

To be clear, nobody ever forbid to use anything for acoustical treatment, even rockwool and glasswool .... but this still doesn't mean that all of this are produced primarily for acoustical absorption needs... I think that this is the main point of John writings...
Boggy,

We weren't discussing thermal products for absorbers - we were discussing thermal products for isolation within wall assemblies........ acoustic room treatments had nothing to do with this particular discussion. I'm slightly confused by the response you made.

Having said that - sure the manufacturers are geared towards thermal insulation primarily - and i do not see that changing........ the market for acoustic products is a tiny piece of their sales - the largest market (real money) is in building envelopes, the 2nd largest market is HVAC - room acoustics is a fringe market that just sort of "happened".... that they are spending any money on marketing for this at all is actually pretty surprising to me.

This because people like us are out there supporting sales of these products in that particular market for free......

Rod
Old 19th May 2013
  #27
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Quote:
Originally Posted by Rod Gervais View Post
Boggy,

We weren't discussing thermal products for absorbers - we were discussing thermal products for isolation within wall assemblies........ acoustic room treatments had nothing to do with this particular discussion. I'm slightly confused by the response you made.
.........
This is because I accept glasswool in sound insulation wall constructions as porous absorption material primarily, a damping added to two parallel, dense and relatively easy vibrating surfaces... I don't use some other absorbing material for room treatment, different from one used for sound insulation... If gas flow resistance is acceptable (it is only relevant for me)... I will use same material in both cases... but I'm really off topic here ... with global industrial business interests... I'm aware of that... sorry.
Old 19th May 2013
  #28
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Boggy,

Nothing to apologize for, I was just a little confused there for a minute...... all is good......

Rod
Old 19th May 2013
  #29
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Northward's Avatar
Quote:
Originally Posted by jhbrandt View Post
I can't speak for Thomas, as he may very well have 'other' purposes for the denser stuff. And you may be misunderstanding what is going on there.
(another reason why I say to never copy what something looks like)

But if you are using this to increase the isolation of a partition with 'damping' or absorption in the Cavity of a MAM system...

It IS a waste of money.. bottom line. It does not perform 'better'.

Cheers,
John
Indeed.

Using denser Rockwool than 45kg/m3 (2.8 to 3.0 lbs Ft3 I think) is useless. 45kg being pretty much optimal.

We only use denser Rockwool (60kg) and Homatherm (65 to 70kg/m3) for inner shell acoustic treatment, within a very specific scheme.
The denser materials covers the gap between purely resistance to flow treatment (>100Hz, rockwool) and purely membranes type treatment that takes care of the very low frequencies.

Although Homatherm FLEX CL100 has an Alpha coeff of 1 @ 100Hz, it feeds back a wee bit in the higher mid range with an alpha of .7 or .8 IIRC.

Which is balanced by the layer of Dacron and the fabric and... distance.

But its mechanical behaviour (not seen if you look at resistance to flow based tests or calculations) makes it very efficient way under 100Hz. Hence a good tool to "fill the gap" until the membranes kick in.

Hope this helps Audiotreat.
Old 19th May 2013
  #30
Audio X
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Thanks for the links and for Thomas weighing in..
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