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Why no rockwool insulation?

Modern Jess

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Jan 2, 2011
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Bay Area, California
In Washington we started to rock wool the walls R21, then we put up the vapor barrier and our framer told us that they stopped putting up vapor barrier. We called the building department, and the also said the same. They were seeing more mold issue with the vapor barrier.

Yeah, vapor barrier is tricky. It is contra-indicated in some parts of the country, and there are many installers who don't even know when it should be or shouldn't be used and where.
 
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DC73

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Dec 27, 2014
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Lubbock TX
Yeah, vapor barrier is tricky. It is contra-indicated in some parts of the country, and there are many installers who don't even know when it should be or shouldn't be used and where.

Agreed. Most building scientists don't even use the term vapor barrier any more. They use "vapor retarder". The location of and whether or not a vapor retarder is even needed is highly climate specific. And, as you allude to and to further complicate matters, many installers are living in the past.

DC
 

Astro-t

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Jan 5, 2010
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Pennsylvania
First, please quote so we know who you are responding to.

Second, I don't give a **** what the fiberglass reps call it. Their opinion is driven by their paycheck, not what's right.

Third, you have no freaking idea what you're talking about. Rock wool is NOT fiberglass. You are entitled to your own opinions, but you aren't entitled to your own facts.
What is in it? I'm 100 percent sure it's fiberglass mixed ! It's not batts of fiberglass! You better research it before you open your mouth��
 
Last edited:

Modern Jess

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What is in it? I'm 100 percent sure it's fiberglass mixed ! It's not batts of fiberglass! You better research it before you open your mouth��

Ten seconds of googling would have given you the answer that I already knew.

From Roxul's FAQ page:

WHAT IS STONE WOOL?
ROXUL insulation is a rock-based mineral fiber insulation comprised of Basalt rock and Recycled Slag. Basalt is a volcanic rock(abundant in the earth), and slag is a by-product of the steel and copper industry. The minerals are melted and spun into fibers.
 
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MDSPHOTO

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Nov 10, 2011
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Oz
I've used the product for some acoustic room improvements in my home. Lowes can special order it, but an online acoustic site had a better price. Came in 2'x4' sheets and I used 1x2s to build a frame and then cut the rock wool to fit and covered with an acoustic fabric. I believe it is indeed a combination of US customers not aware of the product and the cost compared to other insulation products that prevent builders from using it in construction.

 

Tim The Tool Man

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Mar 1, 2012
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Location
Lehigh Valley, PA
There is a lot of confusion in terminology going on in this thread. Wow!

1. Roxul makes a product in the industry know as rock wool it does not, and never has had, asbestos in it.

2. There were many different products produced here in the U.S. prior to about 1978 that were also know as rock wool or similar but were manufactured through a different process and with different raw materials. Depending on which mine these raw materials came from, asbestos was present.

3. Depending on where it was mined, Vermiculite insulation also contained asbestos and it was silver in color somewhat resembling rock wool.

4. Fiberglass is not used in anyway in the manufacture of modern rock wool.

5. Rock wool is expensive.

6. Comparatively speaking fiberglass is far more affordable.

7. Both products, if installed correctly, function as advertised.

8. Vapor barrier is not the be all end all panacea that Canadian builders and code writer believe it is. In colder climates it is great and a wise move. For us folks in more Southern and humid climates, not so much. Our buildings need to breath in order to avoid mold problems.

9. If you find yourself doing any type of remodel on an older home and come across very brittle fiberglass looking pipe insulation, or a black, grey, or silver wall or attic insulation material, STOP! Have it tested before you do anything more...


That said, I recommend Roxul to all my customers...
 

Abeo

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Oct 22, 2009
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784
Location
Calgary, Ab
I used roxul in my garage walls. Was super easy, even for a first timer like me. It was a little more expensive than fibreglass, but I was using it for it's noise abatement properties as well. I put a few sections above my compressor so the noise wouldn't transfer to the attic and annoy the neighbors, but went with blown in fibreglass for the rest of the attic. Vapour barrier is used here regardless, and I can't buy backed batts if I tried, so that wasn't in consideration.

For DIY, the ease of installation is hard to beat.
 
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