Roxul Rockboard 60 vs Comfortboard for exterior insulation – availability
I am in Upstate SC, zone 3 mixed-humid climate in other words – termite and carpenter ant heaven, hence the desire to use Roxul. The plan is 2 inches of exterior insulation with a rainscreen created by 1″ furring strips, plywood sheathing and 2 x 6 interior walls insulated with dense pack cellulose.
I am getting ready to order the exterior insulation for the house. I actually wanted Roxul Comfortboard, but haven’t been able to find it locally.
I can special order from the big home improvement stores but it will be very expensive and they said something about needing an entire truck load before they would order.
I have found Roxul Rockboard online at an acoustic supply house that should be similar. The Rockboard 60 would cost less than the Comfortboard. Shipping is high, but not horrible and they can get it here in about 3 days.
Do you think the Rockboard 60 would be a good replacement for the Comfortboard? Do I need to go to Rockboard 80? Obviously that would cost more.
Thank you as always for your help. (The house is coming along really well. The carpenters are getting the hang of air sealing though it is an alien concept for them. I’m posting updates on my blog Green in Greenville (greenvillegreen.blogspot.com).
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Replies
Lucy,
The only differances between the two Roxul products is compression resistance. The Comfoboard is the highest compression resistance board that they offer. If you can find Rockboard 80 it's got a higher resistance than Rockbard 60.
This all has to do with when you screw it on to the wall. The higher resistance, the less deformity you will have to straighten out. Since there are not good screws like the Heco Topix Therm that will work for 2" thick board (they only work at 4" and thicker), I'd seriously consider spending the extra cost of getting Comofoboard or Rockboard 80. It will cut down a lot of labor.
I checked the specs on the Roxul website. The compression resistance at 10% of Comfoboard is 743 psi vs Rockboard 60 at 353 psi. The Rockboatd 80 is back up there at 743psi. That's twice the compression resistance. Take a look here: http://www.roxul.com/products/building+envelope/roxul+rockboard
Albert,
Thank you for that information. It sounds like Rockboard 80 is what I need to order.
Lucy,
I was wondering how your project went and how you felt about the roxul Rockboard 80 product. I too am interested in using roxul but cannot find where to purchase the comfortboard.
Jim
Jim,
I wrote a big long answer yesterday, but got caught up in the GBA glitch and when I hit the "post" button my answer went away. Grrrr! Now I copy my anything I type here before I post it.
I do think Rockboard 80 and Comfortboard are about the same thing. If they have the some compression resistance, how can they be different? I should have emailed the Roxul people but I didn't.
We did end up ordering the Rockboard 80 from ATS Acoustics. They delivered in less than a week. The shipping was substantial, but I didn't have 6 weeks to wait to get it from Home Depot or Lowe's. I've got to order some more regular Roxul (my carpenter calls it "Roxie") to insulate under the floor. I will ask for quotes on the Comfortboard and compare it to what I paid for the Rockboard and let you know the price difference.
My carpenters didn't have any trouble installing it. They would butt it up to the sheet next to it, hammer in a couple of nails to hold it until the rainscreen furring was put up. Carlton, the head carpenter, was the one who put the screws in the furring. He said you could go by feel and tell keep the furring strips even. He did a remarkable job. I can't see any wavy areas in the siding. It looks great.
The stuff itches like crazy in my opinion. I always wear gloves just to touch it. One of the carpenters practically put on a hazmat suit because it bothered him so much, but the 2 others didn't think it was too bad.
I posted a brief note on my blog about the "mineral wool sweater" over the house. http://greenvillegreen.blogspot.com/2013/10/cozy-mineral-wool-sweater-on-house.html
Albert,
The rigidity of the MW boards is quoted in psf not psi. Dividing by 144 results in a psi capability that requires attention to setting the battens or furring just right, and not over driving. JHC TB19 calls for 15 psi for walls with more than 1" of non-nailable substrate.
Is there a way to get the benefit of the MW permeability without compressing it?
· Externally mounted studs and R15 batt MW tucked in, then WBR , furring and cladding;
Oh.. I guess that defeats the CI idea...
· Are the studs wood?
What if they are 3 1/2-in. Type 9 EPS, 4-in. Wide,
The WRB pull across the foam studs and batts, and
Capped with 1x4 furring (wood or metal).
I am sure this has been tried and found impossible to build or it didn't or couldn't work.