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Community and Q&A

Safe’n’Sound R-0 (?) vs Comfortbatt R-15 for Interior 2×4 Walls only

Inger Peters | Posted in Green Products and Materials on

Safe’n’sound vs Comfortbatt
R-? (Not rated) vs R-15
3″ thick vs 3.5″ thick
estimated cost per sq ft: $0.80 vs $0.77

I read somewhere that Safe’n’Sound is denser and better at sound insulating.Which I like the sound of. 🙂 But my mind says “What about that last 1/2” that Safe’n’Sound doesn’t fill? I think it ought to be filled. And why can’t someone (or has someone) tested the R-value of the Safe’n’Sound? I should just go with the was easy enough to install…

Any opinions? (wink wink)….Thanks in advance.

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  1. Yupster | | #1

    According to Rockwool's website "Interior insulation products do not require an R-value and as such, we do not brand our interior insulation with this information. " If it's strictly being used for sound control, it makes sense to use the product designed specifically for that application. My guess would be the additional 1/2" didn't provide enough of a benefit to be worth the additional material, so they saved on material costs instead. Or perhaps the batt is the same as a ComfortBatt just compressed denser, leading to a thinner batt out of the same material. But I'm just pulling this out of thin air, so take it with a McDonalds-worthy amount of salt.

  2. User avatar GBA Editor
    Martin Holladay | | #2

    It would certainly be possible for a lab to determine the R-value of Safe'n'Sound. It hasn't happened because the manufacturer (Rockwool, formerly Roxul) doesn't want to pay for the testing.

    If you are installing this product in a partition for soundproofing, why do you care about R-value?

  3. User avatar
    Dana Dorsett | | #3

    If it's being used for soundproofing you do NOT want the extra 0.5" filled.

    That is because when the fiber is in direct contact with the wallboard on both sides it increases the mechanical coupling between the sides, transferring the sound vibration picked up by one sheet of wallboard and transferring some of that energy to the other wallboard. With even a tiny air gap that path goes away- the sound has to travel through the air gap first.

    At comparable density it's R value will have about the same R/inch. For rock wool that is about R4.3/inch, so at 3" you'd get ~R13 or maybe a bit less compared to R15 @ 3.5". But if there is an air gap the potential convective bypass around the batt can cut into thermal performance, which is why you DO want the cavity completely filled if it's for insulation rather than sound abatement.

  4. Inger Peters | | #4

    I would like to install a product that does both well. I will have mini-split heads in several rooms so the insulation value was in part to help control temps and secondly to control sound. Thanks!

  5. User avatar
    Dana Dorsett | | #5

    Even with some amount of thermal bypass channel the R13-ish batts will be providing quite a bit of temperature zone isolation. It would be difficult to accurately measure the difference in thermal performance between R13 and R15 even at room to room temperature differences of 40F or greater.

  6. PJ Clem | | #6

    From Rockwool/Roxul tech support: "ROCKWOOL SAFE’n’SOUND® is available in a 3” thick batt for both wood and steel stud sizing.

    This product is generally designed for an interior acoustic insulation, but will give you a thermal value of R11.7 for the 3” batt"

  7. David Williams | | #7

    We just used Roxul batt in the joists and walls to isolate the bedroom from the floor above and adjacent bath at our cabin. Our insulation guy said the Safe n' Sound is essentially the same stuff and both products would work equally well in providing sound dampening as well as thermally isolating the room. We also have mini-split heads in the bedroom and the upper kitchen/living room, which means I can keep the bedroom like a meat locker in the summer for better sleeping.

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