Combining 1" and 2" 703 in place of 3"???

jthomas1 · Post by **jthomas1** » Wed Sep 29, 2004 4:33 am

I just visited a local insulation company, they carry OC 703 but only in 2 inch and 1 inch. I see 3 inches being used all over the forum. So I guess have two questions really. Is 3 inches of insulation necessary in a wall? This company can probably order 3" for me but, if 3" is not avaliable, can I just glue a 1" and a 2" piece together.

Now that I'm thinking about it what keeps the insluation in the wall from falling into the cavity in double wall construction? I tried searching the forum for this, but I couldn't turn anything up. I was thinking something like metal channel attached horizontally.

Thanks, take it easy.

-Josh

dymaxian · Post by **dymaxian** » Wed Sep 29, 2004 6:08 am

can I just glue a 1" and a 2" piece together.

Sure. It's the thickness of insulation that is important, not how many pieces you put together to get there. Unless the pieces are faced with foil or vinyl or something, in which case I'd recommend you pull off any pieces that would be buried inside the 3" total thickness.

I have the same situation you do- local insulation guys can order 3", but stock 1" and 2". I'm just going to get a box of 1" panels and put them 3 or 4 or 5 thick wherever I need 'em. You'll get the same effect.

what keeps the insluation in the wall from falling into the cavity in double wall construction?

Rigid fiberglass insulation won't bend and flop over on it's own, if that's what you mean. If you're talking about fiberglass batt insulation (the blanket stuff used in most residential construction) that stuff is made in rolls just wide enough that the friction on the studs on either side holds the insulation up. If you're worried about it falling, you can get metal straps that will hold the stuff up. Look for the stuff they use for cross-bracing and you'll be all set.

jthomas1 · Post by **jthomas1** » Wed Sep 29, 2004 8:53 am

Right on Kase thanks for the info. Now, I wonder if it is less expensive to use multiple peices of 703 versus buying the 3" kind.

-Josh

AVare · Post by **AVare** » Thu Sep 30, 2004 8:37 am

Now, I wonder if it is less expensive to use multiple peices of 703 versus buying the 3" kind.

Don't forget to ask about competeing compnies' products and rockwool type (eg from Roxul and Thermafiber) insulation. In walls 703 has no magical combination of properties.
Teh thicker the better, up to compresing the insualtion with the leaves, and the denser the better.

Good luck!
Andre

jthomas1 · Post by **jthomas1** » Thu Sep 30, 2004 12:18 pm

AVare wrote:In walls 703 has no magical combination of properties.

What is this magical combination of properties you speak of? =P

I did infact ask about the Roxul product while I was there. They made it sound like it was no good, at least not as good as the OC. Although, I've seen it used by many posting on the forum.

z60611 · Post by **z60611** » Thu Sep 30, 2004 1:33 pm

jthomas1:

They made it sound like it was no good, at least not as good as the OC.

To compare them you can look at http://www.bobgolds.com/AbsorptionCoefficients.htm
Then you'll know.

AVare · Post by **AVare** » Thu Sep 30, 2004 2:22 pm

What is this magical combination of properties you speak of?

There is nothing special about 703. Bob gave a link to his excellent page to compare products..

Have Fun!
Andre

jthomas1 · Post by **jthomas1** » Fri Oct 01, 2004 3:43 am

Yes I looked over that site. I noticed something strange about the comparison tables though, why is it that OC procucts have the mounting column yet the others do not.

OK... I compared 703 3lb/cuft at 3" in an air space to Roxul's ABF 2.5lb/cuft at 3"(Hope i picked the right two to compare). And, according to the source(that website) "Differences in coefficients of less than 0.15 are not significant." The two look almost identical. Overall NRC is 1.05 for both procudts. I'm not putting the ABF down, it appears just as good. From what I've read on the forum, it looks less expensive. Assuming money isn't the deceiding factor though, what properties make the Roxul product a better choice?

z60611 · Post by **z60611** » Fri Oct 01, 2004 5:16 am

jthomas1

From what I've read on the forum, it looks less expensive. Assuming money isn't the deceiding factor though, what properties make the Roxul product a better choice?

The best choice is the one that is
a) available in your area
b) offers the best absorbtion for the dollar.

Those are the rules, not manufacturers.

Sometimes there's heat issues too, in which case rockwool is better than others.

In my area Roxul RHF is about half the cost of 703, and Roxul Safe N Sound is much cheaper.

If the Owens Corning stuff is cheaper in your area, then that's the way to go.