# Cellulose vs. Fiberglass for sound control



## shreiber (Jun 6, 2010)

I read some posts decrying the use of cellulose as to dense to properly control sound. I don't know about lab tests but on the field I have installed many walls/ceilings with insulation and Green Glue and I find that the cellulose does a better job then the fiberglass batts. I would be curious to hear from other installers what their experience from actual installed jobs have been.


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## SlimPickins (Aug 10, 2010)

I can only guess that you're referring to Ted White talking about this over in the 'soundproofing a basement' thread, and I don't think he said that cellulose is bad, just that you can screw it up if you put too much in.


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## Ted White (Jul 14, 2009)

Exactly. 

The value of a lab is that you can isolate all sorts of variables, then use calibrated microphones to measure the results. In the foeld, our ears aren't all that accurate or specific, and we never know if we're hearing sound from the ceiling, side walls, ducts, etc.

Lab data from many sources, including the esteemend NRC in Canada, show that cellulose, fiberglass, mineral fiber, polyester and cotton all perform about the same if they are similar density. So pick your poison.

We know that if the insulation is too compacted, it will simply act as a conductor.

We know that insulation in a coupled partition doesn't add much isolation in the best of circumstances, and that the same insulation in a decoupled partition provides much more benefit.

We know that a ~1/2 full cavity provides most of the isolation, and that completely filling the cavity doesn't bring much more benefit.


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