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Roxul rock wool insulation


1sthouseSLC's Avatar
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01-12-13, 06:24 PM   #1  
Roxul rock wool insulation

Just found out that soon local Lowe's will be carrying this product. I know there is no exterior insulation in our house walls except the two rooms I have done myself. I am wondering if Roxul would be worth the expense considering we do not plan on staying in this house for more than 5 years (it's only 900 sq ft, one child and another on the way)? Would the fire proofing properties of the insulation lower home owners insurance? Since it has no face, do you have to put up a vapor barrier (ie. plastic) or just drywall over it?

 
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01-12-13, 07:38 PM   #2  
The expense as compared to... fiberglass? IDK, but, if I were you, I would consider both the potential utility savings and the probable increased value at resale.

I would also use the ZIP-Code Insulation Program, or some similar calculator, to determine both the optimum R-value for each installation area in the house and the savings in utility costs predicted to come from each improvement.

Would the fire proofing properties of the insulation lower home owners insurance?
That's a question for your insurance company - and maybe for a couple of their competitors. BTW, to the best of my knowledge, the fire-resistant properties of rock wool only apply to it, not to the house it's installed in. But your insurer may see that as important, or have a different interpretation. It shouldn't hurt to ask.

Since it has no face, do you have to put up a vapor barrier (ie. plastic) or just drywall over it?
Unfaced rock wool needs a separate vapor barrier applied between it and the heated space, just as any unfaced insulation does.

 
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01-13-13, 06:07 AM   #3  
Personally, I would stick with fiberglass. AFAIK, you don't get much more (if any) additional R-value with Roxul. You do get better fire-resistance and sound absorbtion, nether of which really matter that much in a sealed exterior wall.

Especially if this isn't your 'forever' home, I would spend the extra money on something that will get you more resale value in a few years.


Good luck... what's the worst that can happen?

 
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01-13-13, 08:26 AM   #4  
Nashkat, thanks for the info. I will look at that calculator and see what it says. Part of the reason I want to use Roxul is the sound absorbing properties. We live on a semi busy street so less street noise would be nice. Maybe better to install it just on one side of the house rather than everywhere.

I checked the cost and it really isn't triple fiberglass as some have said, it's roughly double. I know I can get a .25$ rebate from the gas utility per sq ft installed. Granted, fiberglass is still cheaper, but I want to make the home as "green" as possible.

 
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01-13-13, 01:47 PM   #5  
I haven't worked with Roxul myself, but I think it is generally nicer to handle. It is denser than fiberglass and will resist air flow. Roxul would be my choice for a batt insulation.

 
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01-13-13, 06:00 PM   #6  
Mineral wool batts, in my understanding, are, relative to fiberglass:
  • easier to install - they just press into place;
  • more fire retardant;
  • more resistant to wind scour, which can bee important in attics;
  • more resistant to dust and dirt lodging;
  • less irritating to handle;
  • provide greater sound attenuation; and
  • provide greater R-value per inch, which can be important if you need to add R-19 in a 2 X 4 framed wall, for example.
The downsides are the higher cost per ft.[SUP]2[/SUP] and the need to install a separate vapor barrier.

 
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01-14-13, 06:17 AM   #7  
Fiberglass needs a separate vapor barrier, that would not be a downside to Roxul.

 
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01-14-13, 07:27 AM   #8  
Those are all reasons that make me think it is at least worth a try. We have a 2 year old and a baby on the way so the least irritating material would be best. I don't mind fiberglass, but wife and daughter find it extremely irritating. A couple puppies managed to pull out fiberglass and spread it on the bed. They laid down for a nap, but started itching almost instantly.

Less sound is always good, our house is small so insulating inside (ie bedroom and bathroom walls) to keep sound down would be a benefit. I will probably use Styrofoam for that purpose.

Additional r value is a benefit as right now it is 2 degrees outside. Our furnace is working full time and we have additional heat for our bedroom to keep it mid 60s.

Even with the additional cost, I think it might be beneficial for me to use. Thanks for all the info.

 
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01-14-13, 12:12 PM   #9  
Fiberglass does need a separate vapor barrier if it is unfaced or faced with plain kraft paper, and the space, the moisture and the temperature differences warrant the installation of a vapor barrier. If conditions warrant a vapor barrier and fiberglass batts faced with asphalt-coated kraft paper or foil are installed, no separate barrier is needed. Installing one would create a double-vapor-barrier condition, which can trap moisture and lead to damage.

 
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01-14-13, 12:19 PM   #10  
Yeah, good point - the fiberglass needs a vapor barrier but you can buy it with that attached; I didn't think about it that way.

 
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01-14-13, 09:05 PM   #11  
The insulation I used in the past was completely plastic wrapped except the cut ends. I don't mind having to cover the Roxul in plastic, a sheet is much easier to staple up than batts of insulation. Any specific mil I should use for the vapor barrier?

 
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01-14-13, 11:11 PM   #12  
I use 6 mil clear. I like to buy it wide enough to go above the top plate - maybe out onto the ceiling joists and maybe up between them - and out onto the floor. I trim off the excess and cut the windows open after the wallboard is hung and taped and the trim is installed - just before the shoe mold goes on, IOW, and just before taping the ceiling/wall joint.

 
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01-04-14, 02:09 PM   #13  
Project outcome

Hi, OP.

Did you complete the project? What did you install? How do you like the results of Roxul?

Keith

 
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02-17-14, 05:15 PM   #14  
Outcome, results, Roxul rock wool insulation

I know this is an old thread, but I too am wondering how it all came out. As it is, I am wondering the very same thing about a small area in my house. I am using roxul, I have used it in other places and love it! It cuts with a simple kitchen serrated knife, slips into place, (almost) no muss, little fuss! Very little itch factor as well.

 
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