# Quiet Walk acoustical underlay as treatment



## MatrixDweller (Jul 24, 2007)

I just finished laying down some laminate floor. I purchased the best underlay I could find, which was the Quiet Walk brand. It consists of a thin recycled cotton fiber pad and a vapor barrier. 

I have about 2/3 of a roll left. I was wondering if I could use this to build panel absorbers and how well they would work. I can peel the vapor barrier off fairly easily and would layer them to form 2" or 3" thick panels. If it does work well I can always buy more on sale at $35/100 sqft regularly $55/100 sqft.


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## bpape (Sep 14, 2006)

I'd have to know the thickness and density of the cotton.

Bryan


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## MatrixDweller (Jul 24, 2007)

It says 13.8lbs per 100sqft (or per roll not cubic feet). It seems to be about 1/8 of an inch. I'm not exactly sure how to do the lbs per cubic foot conversion.

I think that it is calculated as: 13.8 / 100 x 8 x 12 = ~13.2 lbs/cuft 
(this would be like sandwiching 96 1ftx1ftx1/8" layers together)


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## Jason_Nolan (Jul 4, 2008)

.138lb per cubic foot?


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## MatrixDweller (Jul 24, 2007)

I think I have it calculated correctly in my post above as 13.2lbs/cuft. That doesn't take into acount small voids in the sandwich. It seems pretty dense to me. Maybe my calculation is off. A roll is 100 sqft by 1/8" thick and weights 13.8 lbs. It would take almost a whole roll sandwiched together in 1 ft squares to make 2" thickness. It's probably not too cost effective but since I have some laying around it might do. If it is so dense then maybe a 1" panel would do the trick.


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## Jarrod (Sep 29, 2009)

I get 4.4lb per cu ft. Edit: no, 13.2lb.

Edit: No fair, you changed the input data for the calc from 300sq ft per 13lb to 100!  I think you have the correct calc though. 13.2 should be correct. But that means you can only make a single 1'x1' panel out of an entire $35 roll? Not too cost effective...


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## MatrixDweller (Jul 24, 2007)

I misread the spec a couple times thinking the roll was 100ft long (it's actually 33.3ft long). the specs are listed in the PDF on the corporate web site that I linked to.

http://www.quickstyle.com/products_underlayment-accessories_brands.php?brand=quietwalk

A whole roll would make a little over a cubic foot or one 2" thick 3'x3' panel (or 4'x2').


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## Jarrod (Sep 29, 2009)

Right the 96 layers would make a 1'x1' a foot thick, not 2". Makes sense.


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## MatrixDweller (Jul 24, 2007)

I forgot to subtract the weight of the plastic vapor barrier. The cuft density is probably more likely between 7 and 8 lbs/cuft or so assuming the vapor barrier is around 1/3 of the total weight. It's not 6 mil poly, more like 4 mil.


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## bpape (Sep 14, 2006)

Realistcally, it's more like 1/8 lb per cubic foot. WAY too expensive


Bryan


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## bpape (Sep 14, 2006)

13.8 lb/cu ft. 1/8 INCH/cu ft. So, take 13.8/8/12 and that's the density

Bryan


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## MatrixDweller (Jul 24, 2007)

Now I'm confused. Would that be the density at 1/8 of an inch?

Maybe I can just use that stuff to line the front and back of a panel instead of using polyester blanket filler. Then again it might be too reflective.


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## bpape (Sep 14, 2006)

Density doesn't change with thickness - only weight/mass changes. OC703 is 3lb/cu ft whether it's 1" thick or 6" thick.

Bryan


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