R-Values of Safe’n’Sound vs. Comfortbatt Rockwool Insulation
PatriciaCranberry
| 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 Comfortbatt..it was easy enough to install…
Any opinions? (wink wink)….Thanks in advance.
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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.
Inger,
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?
The interesting thing is R-15 Rockwool is often cheaper than Safe'n'Sound. So if the R-15 does sound just as well, why not use it? For me the question is not R-value but sound rating. If the R-15 is just as good for sound, and it's cheaper, I'd go with it.
Comfortbatt R-15 doesn't perform the same as Safe n Sound for sound control. It's not miles apart, but there is a difference due to the air gap in a 2x4 wall with the 3" SnS and its density.
Once you look at the whole wall assembly, the difference between the two, and even between the two and just using fiberglass batts is dwarfed by the other variables, like good sealing of penetrations, what drywall is used, etc.
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.
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!
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.
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"
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.
It has been tested, it's about R-15. It's not appropriate for exterior applications because it's not faced (no moisture barrier.) As such it's used for interior walls and/or ceiling/floor applications, but anyway, it's about R-15. You do NOT want the last 1/2" filled for a variety of reasons. One is that the installation may not be perfectly smooth, as romex or pipes may make it a bit lumpy here or there; you don't want that pressure against sheetrock especially if you're using thinner stock (1/4" or 3/8"). Likewise you don't want pure transmission from one side of the wall to the other, you want a space - like a thermal break is for window installations. Just think of it was a not very well sealed double-pane glass: the 1/2" is the "break" that stops transmission from one wall to the other, while the Roxul helps absorb most of the vibration and sound.
"It's not appropriate for exterior applications because it's not faced (no moisture barrier.)"
Rockwool Comfortbatt isn't faced either. There's lots of (better) ways to get a vapor retarder into the wall assembly that doesn't rely on the batts being faced.
Can you share the ways to get green vapor barrier into the wall assembly? Building a tiny house now. Researching. Ty!!
I'm not an expert, but there are articles here on the subject. Smart membranes and OSB sheathing are options off the top of my head. In most cases a retarder is preferable to a barrier.
Go to 475.supplies and study their details and products. They also offer detailed advice. Be careful though, your head might explode.
Trevor Lambert what are the other ways to make a good vapor barrier ? Would love to know ! Building a tiny house.
Best for tiny house is a Huber ZIP System Sheathing. Its a vapor barrier already applied to your exterior sheathing. Then Tape seams with Huber vapor tape and your done. Insulate interior wall with Rockwool. Use 5/8" interior drywall for more exterior sound attenuation. And 3 pane windows .
Zip is between 2 and 3 perms, which a pretty effective vapour-retarder. However not all all assemblies benefit from an exterior VR, which means you get next to no drying to the outside.
So two layers of 3" (6.0")Safe N Sound at 2.5lbs/cuft density seems to come out equal to 1 layer of 7.25" Comfortbatt R30 at 2.0lbs/ cuft right? 2.5/2.0=1.25. .... 1.25*6.0"=7.25". My guess is R30 is cut in half and compressed to get the higher density since the math works out. Right? Seems like either way it would be an identical install/quality of sound attenuation
The reason Safe n' Sound is a bit htinner is so that it leaves an air gap at once side and doesn't contact both sides of the wall. That air gap helps with sound isolation. If you maintain the air gap, then you're probably close with your math in terms of sound attenuation, but I'd test it first before doing a large scale build with an untested assembly.
Bill
Zephyr7 Yes I agree Bill but you don't want the insulation to touch the wall assembly, but I was kind of thinking basement ceiling cavities that are much deeper. I hear they have 6-in safe and sound now,yet none of the big box stores carry it
In that case you should be fine just layering up what you can find until you get to the thickness you want.
In my own experience, the "regular" and sound control versions of mineral wool batts seem pretty much the same in terms of density, so I doubt there is much real difference between the two aside from their thickness.
Bill
I just want to leave this comment for the sake of saving someone else a headache. Safe-n-sound is not thermally rated although it is probably around R-11 - R-13. My understanding is that it is a denser material to absorb sound and therefore has less air in the space, reducing it's thermal insulating properties. It is for use in interior walls only. It will not pass inspection on an exterior wall. My contractor was adamant that it was R-15 but indeed, it is not. I believe he thought it was the same as Rockwool's ComfortBatt which actually is rated with an R-value.
Kerrymf. Good point to the original poster. Its not thermally rated and will not pass inspection for exterior walls or exterior ceilings. Interior use only. Comfortbatt for that purpose.
You can write to the manufacturer and they will send you a letter stating an R value to make inspectors happy if required.. The material IS thermal insulation too by it's nature, it's just not rated as such on the package. The safe'n'sound stuff is a bit more than R12 (for 3" thickness). I wouldn't recommend using it in exterior walls or other areas needing thermal insulation though, since you should be using the full thickness batts for that.
BTW, having worked with both materials myself, I don't notice any difference in density or product feel between regular batts and the safe'n'sound version.
Bill
If you look at comparable products from Johns Manville, their Sound and Fire Block Batts have a similar 2.5 pcf. I believe the Safe and Sound is labeled as >2.4 pcf. I believe the regular ComfortBatts by Rockwool are labeled >2.0 pcf. Johns Mansville, at least in the link, doesn't provide that number for their "TempControl" batts. In any case, unlike Rockwool, JM actually gives the R-Value for their sound-deadening batts of 3.7 per inch. Both the Rockwool ComfortBatt and JM TempControl have an R-Value of approximately 4.285 per inch (15/3.5). So, assuming the similarly higher density Rockwool Safe and Sound and JM Sound and Fire perform relatively the same, the 3" batts likely have an R-Value of 11.1.
https://www.jm.com/content/dam/jm/global/en/building-insulation/Files/BI%20Toolbox/MineralWoolProductComparisonChart.pdf