# Rolled batts in the plastic bag... any problems?



## monomer (Dec 3, 2006)

I will try to keep this simple and to the point... I am using compressed rolls of fiberglass batts, stacked one upon the other in a couple of corners in an attempt to create the "poor man's" (also the lazy man's) bass trap. The calcuated density of these compressed rolls is about 4.8 lbs/cu-ft and the rolls are unfaced, however I left them compressed (with the kraft paper banding still on) and in their plastic bags. What is the problem, if any, to leaving them in the sealed plastic bag as opposed to removing the bags and wrapping them in an old sheet?
Thanks to anyone who responds as I'm just trying to learn more about room acoustical treatments...


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## bpape (Sep 14, 2006)

No problem at all. If the batts already are paper faced and the paper is facing out in the rolled state, it's already upper mid and high frequency reflective just like the plastic.

There may be a TINY difference if the bag is sealed air tight and you're getting a tiny membrane effect from the sealed air cavity but I doubt you'd ever be able to measure it, much less hear it.

Bryan


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## patchesj (Jun 17, 2009)

Bryan, out of curiosity do you have any numbers on how this compares to tri-traps made out of 703?

As someone designing a room with an AT front wall and screen, this could be a very cost effective way to add some lower frequency absorbtion to the front wall.

Thanks..


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## bpape (Sep 14, 2006)

The difference is likely pretty trivial. The bags are a little thicker but also take up a lot more space. Hard to say really with the multiple layers of insulation and paper in the roll.

I don't think anyone has ever paid to have lab testing done on a roll of insulation 

Bryan


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## monomer (Dec 3, 2006)

bpape said:


> ...I don't think anyone has ever paid to have lab testing done on a roll of insulation
> 
> Bryan


Now that's funny...

Patchesj... Depending upon the R-rating the diameters will vary. I just buy whatever's on sale so the ones I'm using are from around 18" to 22" in diameter and the heights are either 15" or 23". It can be very cost effective IF you find them on sale and they remain hidden, trust me they are not attractive in the least. In my case, these are piled up in the front two corners behind a large projector screen with black breathable curtains hanging in the spaces on the ends. I expected the bass end to tighten up a bit with their addition but what came as a complete surprise was a noticable improvement in front stage imaging. I won't even attempt to try and explain why this happened but all I can say is it was a notable major improvement. BTW, I also added the long-style flat-pkg batts (also compressed in bags, however they are only 2.4 lbs/cu-ft) to the ceiling and flooring corners formed with the front wall. I will suggest that even if they were covered with an attractive material, it would still look like the "beverly hillbillies"'... these are only viable bass traps if they will never be seen.


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## lsiberian (Mar 24, 2009)

I'd suggest some sort of aesthetic cover at the very least.


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## Lonely Raven (Aug 27, 2008)

bpape said:


> No problem at all. If the batts already are paper faced and the paper is facing out in the rolled state, it's already upper mid and high frequency reflective just like the plastic.
> 
> There may be a TINY difference if the bag is sealed air tight and you're getting a tiny membrane effect from the sealed air cavity but I doubt you'd ever be able to measure it, much less hear it.
> 
> Bryan


So Bryan, 

If I could find some insulation batts that are unfaced (no paper etc), and keep them in their original bags, would they possibly be effective behind a couch that's up against a wall? I have a couch with a big lean angle to it, and I could probably fit 8" thick by 18" tall behind there and nobody would know but the mice. I won't bother if it's not effective being behind a couch though.


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## bpape (Sep 14, 2006)

If your couch is that close to the wall, it will definitely help with controlling boom in the corner behind the couch. You'll still have bass buildup off the wall behind your head but it's certainly a big improvement over nothing.

Bryan


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