Rockwool rocks

[bluedog225]

I’ve never worked with rockwool batts before. I got a couple of bales from Restore super cheap and put them in this weekend.

The stuff is an absolute joy to work with. Dense, cuts easy, fits snug, no itch.

I know it cost more, but I’m never going back to fiberglass.

 

[WildBill]

Edit - never mind earlier comment. Its great for sound and fire resistance.

 

[bluedog225]

Well, now I’m curious.…

 

[finn]

I bought some for my new wood burning sauna last fall.

Easy to cut, no itch, and excellent sound deadening.

Cons are the dust is worse than fiberglass and I thought my exposed skin felt much dirtier than when working with fiberglass. I was using unfaced batts, and had trouble with the lack of structural integrity with a few batts that were friction fit in the ceiling. If the batts had to be removed for some reason, or fell down, they fell apart and had to be discarded

Also, it was difficult to source bats for 24” rafter spacing for the ceiling.

Then there’s cost, which didn’t matter much for a small structure like a sauna, but could add up.

Call it a mixed review from me. Not fully convinced yet…..

 

[Lassen Forge]

Rockwool is super old school, our house was insulated with the stuff in the 1960's. Back then, it was all blown in, and would pack down, and a common site was the "insulation truck" to blow in more as it wither packed down or people wanted better insulation. Doing it in batts is pretty awesome, means they have the whole pack down thing kinda figured out.

 

[mike93lx]

Rockwool is super old school, our house was insulated with the stuff in the 1960's. Back then, it was all blown in, and would pack down, and a common site was the "insulation truck" to blow in more as it wither packed down or people wanted better insulation. Doing it in batts is pretty awesome, means they have the whole pack down thing kinda figured out.

Blown in mineral wool? I've never heard of that. Interesting

 

[larry4406]

I recently installed R15 rockwool batts at an interior hall bath renovation for noise control. Really deadens the space. It actually feels odd walking in there with the sounded damped.

2x4 walls 16" o/c. Used a wet stone sharpened insulation knife to trim as needed. Some batts were very firm while others crumbled which was odd.

 

[NUTTSGT]

Edit - never mind earlier comment. Its great for sound and fire resistance.

Fire resistance.

It's not super common around here yet, available, not highly used. I'm curious as to how it will perform in a real world situation for structure fires.

 

[bluedog225]

My guess is guaranteed not to burn given what it is. And will not pass air to feed a fire as it’s so dense.

 

[bassJAM]

I put Rockwool batts in the ceiling and walls when I finished my basement. Like you said, easy to work with and it does a great job with sound. Like someone else mentioned, I found that I actually felt dirtier after installing though. And I've had to get back into the ceiling a few times to run speaker and CAT6 wires and it leaves a lot of mess when you pull out those batts and put them back in and they're relatively fragile.

 

[bluedog225]

Agreed “dirtier” but it‘s like dirt or ash. It washes right off.

 

[tworley]

Insulated my open stud garage last month with R15. It really absorbed any sound. Before I could hear the garage door open from anywhere in the house and could tell when my truck was running in the driveway. Now, not so much. Temp-wise, my garage is consistently 30+° above ambient which is a real nice change.

 

[Renegade1LI]

Fire resistance.

It's not super common around here yet, available, not highly used. I'm curious as to how it will perform in a real world situation for structure fires.

Hilti requires it in their firestopping details for filing voids.

 

[loganb]

Used it in my last house insulating the ceiling in our lower two levels (4 level split house so had a basement and sub-basement as they called it). We were replacing all the suspended ceiling tiles and updating lighting so gave it a try and wow....huge improvement in both comfort and sound. As mentioned above, it took a couple days to get used to the new "ambient" level after it was done as without the tv or music on it was very quiet and almost spooky. Big improvement in consistency of temp between the levels and helped reduce how much sounds carries. After that experience when I redid a shower I stuck it in the walls before the backerboard and tile went up, the main wall of the shower was common with the closet in my bedroom and it was hard to hear the shower running after we were done.

After those experiences, I don't plan on every "closing up" an interior wall or ceiling of a room I care about without putting mineral wool or similar insulation in. It's gone up a lot in price since I did the projects in 2017-ish...but for me the improvement in noise is well worth it for most spaces, reduction in fire risk and any temp/thermal gains are an added bonus.

 

[LopezBart]

Our house on Lopez has rock wool in walls, ceiling and floors. The house is quiet between rooms; the concrete floors did cause echos in a room before we put down rugs. Rockwool is really better.

 

[finn]

Agreed “dirtier” but it‘s like dirt or ash. It washes right off.

I suspect it’s sintered sand.

 

[loganb]

Video from ThermaFiber on how it's made:

 

[WisJim]

Rockwool is super old school, our house was insulated with the stuff in the 1960's. Back then, it was all blown in, and would pack down, and a common site was the "insulation truck" to blow in more as it wither packed down or people wanted better insulation. Doing it in batts is pretty awesome, means they have the whole pack down thing kinda figured out.

My dad had our house insulated with blown in rockwool back in the 1950s. Had to be before 1957 because of when we moved from that house. I had boxes of the wooden discs that had been cut out of the sheathing so they could blow in the insulation. Those discs were a fun addition to my wooden blocks that were 2x6 cutoffs of a big lake dock that my grandfather had built. (I think that the house and 3 or more empty lots, in town, in central Wisconsin, cost my folks $1,500 in the early 1950s.)

 

[Kaizen]

I'll never use fiberglass again. I used it in my garage walls to keep the sound down from my late night antics. Can barely hear my 7.5 hp running from outside.
I also ripped off the sheathing of my old house and firred out the old 2x and got more in all the walls. Sound deadening, doesnt absorb moisture, and no tool install for the win. I do mask up just because it seems to squirt out the dust

 

[RPH]

According to manufacturers.
“ ROCKWOOL insulation is fire resistant and can withstand temperatures above 1,000°C. It's made from stone wool, which is non-combustible and has minimal organic content.ROCKWOOL insulation can help limit the spread of fire in a building and prevent toxic smoke from being released. “

 

[russ455]

Also non wicking of moisture. Wish it was not so expensive

 

[ToolsRCool]

Was studying up on this just today. For my 26x24 garage, it would be an additional $1,000 exactly in cost to insulate the 3 primary ground floor 10' tall 2x6 walls in RockWool R-23 batts as compared to R-21 Pink Panther fiberglass batts. Not sure the R-2 gain for $1,000 would be worth it in additional natural gas cost savings. I'd think that ROI would be pushed out pretty far. I'm likely not doing it due to that. No sound or fire resistance concerns in this application.

$200 jump to go from R-19 Pink Panther rolls to R-21 Pinky batts, that's fine for an R-2 jump, but I'm not going to pay 5x that for the next R-2 jump.

 

[loganb]

Was studying up on this just today. For my 26x24 garage, it would be an additional $1,000 exactly in cost to insulate the 3 primary ground floor 2x6 walls in RockWool R-23 batts as compared to R-21 Pink Panther fiberglass batts. Not sure the R-2 gain for $1,000 would be worth it in additional natural gas cost savings. I'd think that ROI would be pushed out pretty far. I'm likely not doing it due to that.

The payoff on thermal is likely poor....but it also provides superior acoustic performance and fire resistance then standard fiberglass batt. Depending on garage usage, location, adjacent items the fire or noise benefits may be worthwhile for some

 

[mepstein]

I used it in my workshop. I'll never use fiberglass again even though it went up almost 50% post pandemic and stayed there. There are many advantages to RW besides just a small increase in R value. It's better at blocking air movement than fiberglass, Water resistant, pest resistant, Acoustic performance is amazing and it won't catch on fire. It's also easier and quicker to install than fiberglass.

 

[ToolsRCool]

The payoff on thermal is likely poor....but it also provides superior acoustic performance and fire resistance then standard fiberglass batt. Depending on garage usage, location, adjacent items the fire or noise benefits may be worthwhile for some

Understood and agree, just thermal in my use case.

 

[mike93lx]

Understood and agree, just thermal in my use case.

Rockwool is great but for your use case, the cost savings for fiberglass make it the way to go

 

[russ455]

is the pest/rodent blocking a real thing? Or marketing hype

 

[loganb]

Understood and agree, just thermal in my use case.

Yup, agree completely then. Likely get far better thermal/air leakage improvements from a case of caulk and an afternoon sealing joints prior to insulating then you'll ever see on an R2 improvement.

 

[ToolsRCool]

Yup, agree completely then. Likely get far better thermal/air leakage improvements from a case of caulk and an afternoon sealing joints prior to insulating then you'll ever see on an R2 improvement.

10-4. New build in my situation, so quoting options. Will still seal everything well, use house wrap, tape, vapor barrier, etc.....

 

[csp]

R value alone isn't the only thermal benefit. It's also much more resistant to air infiltration and basically air blowing through it. R-value doesn't really tell the whole story when it comes to energy efficiency. Air moving through the walls will strip conditioned air way more than just passive radiation.

 

[carlaisle]

The purpose of insulation is not to stop air infiltration. If you have air whistling through your walls you have other problems that need to be addressed.

 

[karoc]

Wow, this post makes me feel good about my purchase of Rockwell for 6” walls. I have bags of it waiting for me, after reading these comments I feel I made right choice.

 

[bluedog225]

I can see how it would be tough for a fire to draw oxygen through this stuff. Not really going to happen.

For some reason, I’m more interested in anything that will give me better fire resistance these days. I may even change my mind about using sheetrock. Much as I hate the stuff, the fire resistance is unbeatable.

 

[tworley]

is the pest/rodent blocking a real thing? Or marketing hype

When I was researching rockwool, their FAQ stated this...

 

[duneslider]

I have used rockwool to plug holes in an effort to prevent rodents from entering, it seems to have worked for me. None has been pulled out as far as I can tell.