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fiberglass insulation or denim insulation for walls

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Sep 06, 2013, 04:27 AM
vedo
fiberglass insulation or denim insulation for walls
I hear good and bad about both fiberglass insulation, and denim insulation, so im kinda lost. I live in michigan so its warm in the summer and cold in the winter. Our house was built in the 1950's and it gets pretty cold in the winter, so we are taking off all the old plaster, and putting new insulation,and drywall up. Now we been looking at insulation to put in the walls, and found the regular fiberglass, and then there is this blue denim insulation. What one would be a better insulation? We own the house, and plan on living in it for years, so we wanna make sure we buy a good brand that will hold up for years. So should i go with the fiberglass, or the denim??? ThanksI hear good and bad about both fiberglass insulation, and denim insula, so im kinda lost. I live in michigan so its warm in the summer and cold in the winter. Our house was built in the 1950's and it gets pretty cold in the winter, so we are taking off all the old plaster, and putting new insulation,and drywall up. Now we been looking at insulation to put in the walls, and found the regular fiberglass, and then there is this blue denim insulation. What one would be a better insulation? We own the house, and plan on living in it for years, so we wanna make sure we buy a good brand that will hold up for years. So should i go with the fiberglass, or the denim??? Thanksdenim?or fiberglass??
Sep 06, 2013, 08:50 AM
Jaybee
Stone wool (denim) type insulation is denser than fiberglass - meaning that it give better sound insulation and carries a slightly higher R-rating for the same thickness. Since it's stiffer, the denim installs by friction fitting - this makes it easier to install when put in standard spaced openings but it must be trimmed more precisely to fit in the odd sizes.

All the stone wool that I've seen doesn't have a vapor barrier, so if you need one there will be extra cost in time and materials to install a barrier.

No itching from stone wool.

So by a straight comparison, the stone wool product seems to have a slight advantage over fiberglass. In overall performance you will not see much difference between same thicknesses of the two different products.

However, fiberglass is about 2/3 the price of stone wool, which could be a significant amount if you are insulating an entire house.

The deciding factor could be rebates. It's very common for insulation to offer either seasonal rebates or bulk order rebates. This could tip the scales towards either wool or fiberglass depending on what is available.

This message has been edited. Last edited by: Jaybee,


Jaybee
Sep 06, 2013, 10:16 AM
vedo
So would the stone wool last longer then the fiberglass? The old fiberglass insulation that is in there now pretty much turned into dust and broke apart very easy...then agian it might be the original from the 1950's. Also what would be a good vapor barrior for stone wool? Im kinda leaning toward the stone wool, but i just wanna make sure it's worth spending the little extra money for a better quality product. Now if the fiberglass would do just as good i rather save the money and spend it on our next project..or drywall in my case. One more thing our studs are 2x4, so the stone wool i can get is a 3.5 in. thick R-13, but the fiberglass comes in the same size but a r-15. That is also another thing i forgot to mention earlyer.
Sep 07, 2013, 03:37 PM
SturdyNail
Vedo,

I just replaced the insulation in one of my walls with Roxul. What was in there was 1.5" economy, Kraft-faced, fiberglass held in place with a few drywall nails.
I installed 3.5" Roxul in my 2x4 wall. The 3.5 Roxul is rated at R-15 (I just checked the packaging to confirm). The 3.5" Kraft-faced fiberglass that I see advertised is R-13.
Installation of the Roxul was pretty much like Jaybee described. It does "feel" like a nice tight fit. It is a bit of a pain to fit around irregular areas because it doesn't compress as easily as fiberglass, but, we're advised not to compress the insulation anyway.

FWIW. I think that "Denim" insulation is different than Rock Wool (brand, Roxul). The ad I just saw for "Denim" insulation says it's made from recycled jeans.

This message has been edited. Last edited by: SturdyNail,
Sep 07, 2013, 08:13 PM
vedo
Sturdynail

I was also looking at that roxul, and i think thats what i am going to go with. That blue denim thats made of recycled jeans was my first choice , but i seen some pretty bad reviews about it, only being 2 inches thick when it should be 3.5, and people also said its very hard to cut. So i think im going with the roxul brand. Did you have to use a vapor barrior for your roxul, or does it have one already on it? Thanks for your guys advice. From the reviews i seen i made my mind up and im going with the roxul.
Sep 07, 2013, 11:32 PM
SturdyNail
Vedo,

The Roxul does not come with a vapor barrier.
I was insulating from the outside (i.e., I had removed the exterior siding and sheathing), so it would have been tricky (at best) to install a vapor barrier on the conditioned side of the wall.
I'm not convinced of the benefit of a vapor barrier. I think a wall needs to breathe, but, if your local building codes require one, then you'll need to decide if you're going to comply.
Someone described the consistency of Roxul as similar to a stale hot dog bun. I think that's fairly accurate.
Use a bread knife to easily cut the Roxul.

Good luck.
Sep 09, 2013, 09:45 PM
Jaybee
The 'lifetime' of fiberglass vs denim is a moot point. Both are going to still be there long after you are gone.

I would go with fiberglass as you will have the same insulation performance at a lower cost - plus the fiberglass has a paper barrier. The only real advantage over time that the denim has is more sound deadening qualities. That, and less itch during install.


Jaybee