"sandwiched" 703 or 8# rockwool for panel absorber

Brian Middleton · Post by **Brian Middleton** » Sat Jul 02, 2005 8:55 am

I've found a local outlet of the spi chain that carries 703 and rockwool; they don't have 4" 703, though, just 2". They do have 4" rockwool, but it's 8 pcf, which I understand is not ideal because of the grazing-incidence issue.

How big a pain is it to glue or otherwise attach two sheets of 2" 703 together to make one 4" absorber? Conversely, how big a factor is the grazing-incidence thing in practice? Bottom line: if you HAD to choose between sandwiching the 703 and using the 8 pcf rockwool for making plain fabric-covered panels, which would you choose?

(The rep I talked to said he thought he could get 4" 703 on special order, but the way he said it gave me the feeling that the pricing would not make me happy, and I'm already overspending here.)

AVare · Post by **AVare** » Sat Jul 02, 2005 11:03 pm

Bottom line: if you HAD to choose between sandwiching the 703 and using the 8 pcf rockwool for making plain fabric-covered panels, which would you choose?

Easy, the 2" doubled up and not glue it unless needed for mounting purposes.

Andre

bpape · Post by **bpape** » Tue Jul 05, 2005 1:19 am

Yes. The 703 4" is an expensive option on special order.

As was said earlier, 2 layers of 2" back to back with no bonding will work exactly the same.

AVare · Post by **AVare** » Tue Jul 05, 2005 5:28 am

The 703 4" is an expensive option on special order.

Quick comemnt. IT all depends on the area, region, business size, building industry and phase of the moon.

Here you can get, deoending oin the dealer, 703 for about a constant price per poungd, regardless of thickness. Oher dealers it is all over the palce. The best bang for the buck is Roxul Safe n sound. Other parts fo the country/continent/world have different prcies.

Andre

bpape · Post by **bpape** » Tue Jul 05, 2005 2:56 pm

It really depends on if the 4"is part of their regular stock. If so, then it can be pretty reasonable. If not, Owens wants such ridiculous order sizes that it gets pretty silly sometimes.

AVare · Post by **AVare** » Wed Jul 06, 2005 12:14 am

For posterity (future readers of theis thread) note what Bpape and I wrorte about. CALL AROUND to get the best price. Rememeber to call commercial/HVAC type places. Home Depot etc do not carry this stuff!

Andre