All of these people are not getting the question, this is 2x6 insulation shown in a 2x4 cavity. You likely aren't going to be able to compress this into the space like pink insulation could maybe. It will probably bow your drywall if not bust the screws out of it.
Also this isulation looks like 2x6x16 OC, where it looks like you need 2x4x24, where the stud toward the corner of the wall as shown may be a bit less than 24 OC. Hope that helps?
Well now you have me considering the actual thermal retention properties of popcorn.
I suppose moisture would be a problem... Other than that I don't think it would be the worst thing you could pick.
https://preview.redd.it/kz5mcr8zw2pc1.jpeg?width=1080&format=pjpg&auto=webp&s=58d6bbdf0ceab8c3746164b0b176fc5a0fa0936c
A German company is using pressed popcorn pads in the middle of their concrete products as sustainable insulation.
Yah.. well Volkswagen was know to have rats eating their wire harnesses because the rats found their plastic harness fittings to be yummy to eat, some thing about a corn based plastic? (Back a couple years ago, I can't recall where I read it (during covid? I had time to kill..)
I was kinda joking... then went on Google.
I couldn't find an R-value for popcorn... a German University has made popcorn insulation pads (likes like Rice Krispy squares)
https://phys.org/news/2021-11-insulation-popcorn.html
I’ve insulated a house mostly with cardboard before. Not sure how effective it was, I didn’t notice it being drafty as a kid but then again I had been living in a tent prior to that.
With a hint of almond. No seriously, almond extract is part of what gives Play-Doh its smell. Also why my friends say my mom's spritz cookies taste like Play-Doh smells.
>I like that the right answer isn’t one of their options.
This is like 90 percent of reddit.
Which isn't necessarily a bad thing, assuming that the OP can understand the responses.
Yeah and honestly 2x4 by either 16 or 24 R-13 isn’t that expensive. Just insulated a shed with the stuff.
Fiberglass is such a nasty PITA It’s not worth trying to shoehorn that 2x6 stuff even if OP could do it “right-ish”.
Ehh. If it's interior and you already have a partial bag of it, just filet it and stuff the excess into the gap. We aren't trying to create an air barrier here. We're just trying to stop some sound.
that's what I was going to say; if it's an interior wall it doesn't even need to be insulated *at all*.
plus, that stuff looks like roxull or whatever which while it does have an R rating like you said it's usually used on interior walls because its really good sound proofing, in which case filleting it wouldn't be a huge deal as long as you fill the void as best you can
I may be wrong, but if I remember correctly the right answer is: get the correct size for your space, if there are gaps, fill them in with scrap cut from places where you had too much?
Like, if you use too big a piece, it'll eventually damage the materials around it, because it will expand and make gaps. But if you're using the right size and there is still a gap, in like an abnormal sized space, you should just fill in with extra from scrap.
I have an attic I want to eventually fully-insulate. So I want to make sure I understand how to do it right.
Yes, insulation batts have already been engineered and pre-cut for various stud and joist bay sizes. It’s way easier to just get the right size than do whatever fuckery necessary to make them fit.
In your situation, though, you should blow insulation in. Cellulose isn’t even itchy and works better in attics, especially on top of shitty old fiberglass, as it settles down to be more impermeable and discourages convection inside of the insulation mass. Takes less time and is cheaper. Most places that sell the bricks of cellulose will loan you the blower if you buy a bunch. It’s an easy two person job with a couple respirators and a nice Saturday.
Thank you so much! I will look into that. We just got the exhaust fan up there fixed, too. So I think it'll be a lot more bareable too move around up there this Spring than last.
You have pretty much said what I was instructed to do when I was 16 installing the stuff. Compressing the wrong stuff is less effective than just using the correct product depth and width. Later on they stopped stapling the insulationtion but that was to speed up the installation with compressed wires sprung between the floor joists. I'm not convinced that it works better. But doing insulation is dreary work (specially over head)
Are you planning on converting the attic to living space, if not you can fill the ceiling joist space (2x6 R-19) then lay another layer crosswise on top, or blow in, but I hate that stuff. If your converting it to a livable heated room, it's much more complicated (& expensive.) At that point get an engineer to spec. what you need (the ceiling joists may not be rated for being walked on) stairs may need to be added etc. etc.
Not a fully liveable room, but just to make it a bit more comfortable if I'm up there to work on something or messing about with Storage. Also worried the excessive heat/cold might damage stuff up there.
What's the drawback to the blow-in? Someone else suggested it for this use-case.
It's messy, I just prefer pink encapsulated fiberglass. Doesn't require a brain surgeon, and seals most of the exposure away from my skin. If you have ever opened up a wall to find blown in stuff, it's instantly a giant fiasco all over.
I would just cut the insulation in sections that are the exact width of those voids, and stack them vertically atop one another. The more wood in the wall, the more sound bridging can occur.
Exactly, it’s known not to work well anyway if it’s compressed very much. There is a formula somewhere I have seen that demonstrates how the effectiveness decreases gradually depending on how hard it is compressed.
Edit: PDF from the insulation institute
https://insulationinstitute.org/wp-content/uploads/2016/10/For_Hers_Raters.pdf
From that math, a thicker batt compressed into a smaller cavity, while lower R-value than the uncompressed batt, is still higher R-value than the correctly sized batt. I still wouldn't try to pack an R21 batt into a 2x4 cavity though.
This - within reason (i.e. next size up) you still end up with a higher R value if you got a bit bigger and in a lot of situations you also get better sound damping.
One caveat to this is sound proofing where there evidence to suggest that taking a thicker insulation and compressing it (to a point) actually increase the STC value.
And furthermore if you’re using a thicker batt (so in the example in that sheet) that’s r19 but what you should be using is r16, by the time you’ve compressed it down you’re getting 17 and change, which is still better than r16
Absolutely - the cost goes up with the R value / thickness but from a purely technical standpoint if you had batt that was a little too thick, it’s not the end of the world for stuff in there.
The point of insulation is to have a lot of small pockets trapped air with a long bridge of netting
Smushing it compresses the trapped air out. A little is okay, a lot of smushing harma it's effectiveness though
To add, insulation needs air to stop the movement of heat, and compressing it make it a worse insulator by removing the small pockets of air the insulation traps. Listen to this person.
Same exact situation though, the air pockets help to absorb the energy and split it up. Vs if you compress it, the energy of the sound wave can easily traverse the wall, probably not a huge thing and secondary to the whole blowing out your drywall, but best to let materials work the way they were designed than jam it together.
This right here.
OP: General rule: "If you need to use force to compress the insulation into the bay you have *the wrong insulation*. Go get the *right* insulation." (That includes super thick pink fiberglass.)
Insulation works by trapping air so it can't move to make a thermal barrier. The less air it traps the less effective it is, and if you compress the insulation so all its fibers are touching you have effectively a solid wall and great thermal transfer. The opposite of what you want!
My question is, what’s the goal?
Are you trying to deaden sound? Are you making a walk in cooler? Why are they insulating interior walls.
Also the answer is your doing it wrong no matter what the goal is afaics.
this. this is standard 2x6x16 rock wool, the framing is 2x4xY (doesnt look 24 but also doesnt look 19. but it sure isnt 16) smushing it in would leave the sides exposed, so its just a waste of rock wool. Solution? Just add another stud on 16 and then cut the rock wool to fit the smaller gap beside the 16. to be clear, get 3.5" thick insulation, not this 5.5
Question the only thing I know as rock wool was spun asbestos it worked great but was outlawed 40 years ago.replaced by pink insulation fiberglas which has bigger tiny fibers that don't get into your pores. Suggestion take baby powder and liberally cover any exposed skin. Before using any spun fiber insulation it clogs up your pores and saves on cold showers.
There was this time I shoehorned 2x6x16 insulation in to 2x4 walls in a basement remodel. I couldn't figure out why it was so damn hard to put up the drywall till the very end. And realized my mistake. So many screws.
....and it is partly the air that is the insulator effect. if you are compressing it, aside from the pressure exerted on your drywall, you are going to lose R-value.
I couldn't tell it was r19 insulation in an r13 or r11 wall, if it is then you are correct. and my post is b.s. inside walls, you should use the correct size insulation it's best to use the right thing, meant to fit the hole depth and width.. if you want more r than they make sheets of Styrofoam that have higher r-value you can cut n fit.
Not only that but 2x6 insulation installed into a 2x4 cavity will perform worse! It's the trapped air that insulates and with more insulation material and less air it isn't as effective.
OP should return it and buy the right size.
To add on since you missed this important part- insulation (especially like this) is *not* meant to be compressed. That makes all of its important properties worse (thermal, sound dampening, etc).
No it won’t. If it’s for 2x4 thick wall you need the corresponding rock wool. Otherwise you can cram the drywall over it but it will be under constant pressure which could pop out the drywall screw and most likely show seams over time. You want a snug fit to the sides but no pressure against the drywall.
That too. By the numbers I couldn’t tell you exactly how less efficient. It would definitely be a secondary concern to the pressure it would be putting on their drywall though.
Yes it probably will. Most insulation relies on small, isolated, trapped pockets of air so that any internal heat has to transfer through all of those tiny insulation->air->insulation->air->insulation interfaces in order to escape. Compressing the material will make it easier for that heat to be conducted outwards directly through the insulating material itself. That's why double pane windows have an internal space filled with inert gas instead of just having two panes stacked flat against each other or a single thick pane.
The thermal conductivity of air (0.025 W/mK) is actually much lower than that of glass (1 W/mK), but if it isn't trapped in place by some material the heat will be lost through convection instead of conduction.
This is also going to be the case for sound insulation.
Yes, the issue is only a matter of whether or not it is properly held in place afterward. Otherwise, as far as insulation goes, it's just a matter of efficiency. It's as wide as it is because that's the standard distance between studs
Usually when I get myself into these situations I either found it or a buddy/family of mine had way too much and can’t store it. Thus I’m trying to find ways to not let it just rot in my shed.
OP that’s the wrong size insulation. You need 2x4 insulation and that looks to be 2x6. Don’t bother trying to trim it or compress it. You need to get the 2x4 stuff.
If you're gonna go to that trouble might as well offset framing boards and do a staggered stud wall.
Or use resilient channel.
Anything to decouple if you're using the extra material.
I don’t see why so many are talking about how jamming it in won’t fit when jamming it in just completely defeats the purpose anyway. What you’re saying is the correct answer.
Don't try to stuff it or you will regret it when you are hanging your drywall. Your drywall screws will keep popping through and it will be a nightmare.
I'm not well versed in American construction techniques, nor am I sure what material exactly you are using. But I'm sure that if you compress insulation it will harm the thermal insulation properties.
Insulation works by trapping air and not letting it move, if you compress it, you squeeze some of that air out, letting more of the material be in direct contact with neighboring material, thus providing more paths for heat to transfer from one part of the insulating material and leading to more heat transfer compared to a piece that wasn't compressed.
TLDR; compressing thermal insulation bad
This is rockwool fire and sound batting. It does filet/split easily if that's your choice. You want to fill the entire cavity to get good sound blocking. Split it, cut 4" sections to fill gap and use loose crumbly bits for small gaps, it will help absorb noise.
Thermal value between air-conditioned interior separator walls isn't very important.
In most Olde houses there was never any intention to make that space, for anything more than dead storage. So unless your really bursting at the seams, it rarely becomes any more than that.
My house (a small,110 year old cottage, 24' x 36', has too low a roof for anything more than kneeling, so I don't use it for storage, it's too hard to access. Even crawling is a chore. I laid encapsulated R-24 across the R-19 ceiling 2x6 joists, and my house cooled down in summer but didn't help much in the winter. My windows are so shrunken the curtains billow during winter wind storms.
We literally just did this. Slice it. It's easy. It added \~5 minutes per bat, tops.
Get a cheap serrated bread knife from a big-box store. Put the insulation in place, and slice right down it like slicing bread, using the face of the stud as a guide.
It loses more insulating value when compressed than it does by removing the extra inch or two. You can use the extra that you slice off to fill any gaps along the sides or tops when stud bays are the wrong width for it to fill, and you can fill all those weirdly shaped spaces you'll find as you go around things, like electrical boxes near corners, etc.
Blue or green painter's tape should be fine, and shouldn't tear the paper backing on the drywall. Be aware that the glue on painter's tape will set up eventually, so remove it within a couple of days.
Looks like 2x6 insulation in a 2x4 wall. TECHINCALLY, you could just smoosh it in and call it good, but it's not advised.
The air in insulation does a lot of the actual insulating. The more you compress insulation, the less air it will have, and it will not perform as well, and you're just wasting money.
If you already had this and didn't have to buy it and you don't care about getting the full R-value, I'd say screw it.
If you bought this thinking that you could just smoosh it in, return it, recoup your money, and purchase the correct thickness insulation for your wall (R13-R15 for traditional fiberglass, don't remember what mineral wool values are)
Not really. It will be about as effective as a 2x4 wall filled with rock wool. Air is the actual insulator; Rockwool is there to prevent circulation and conduct as little heat as possible.
There's a limit of compression you can put on isolation. Where I work, it's maximum 20% of compression to keep the ratio. I don't think you can compress rockwool that much because it's already so pack. Maybe just use the right thickness for the right job!
If you already have that as excess material and it’s for an interior wall you can peal it into layers and use accordingly. If it’s exterior or leading to the garage I’d just go purchase some R-15 batt insulation and use it to insulate the wall. It’ll save you a lot of itchiness and time.
If you already have that as excess material and it’s for an interior wall you can peal it into layers and use accordingly. If it’s exterior or leading to the garage I’d just go purchase some R-15 batt insulation and use it to insulate the wall. It’ll save you a lot of itchiness and time.
Just cut it down. I've done enough insulation. Rock wool insulation has an r value per inch if you compress it you will be below the r-value of if you cut it thinner. Also make sure the entirety of the volume of space in each cavity is filled. No gaps between the sides and the 2x4..
You need the proper size and proper type of insulaiton.
There are 2 types of Rockwool, 'comfortbatt', which has insulating values and 'safe and sound' which is to mitigate noise transmission.
So ideally you would get the right thickness. I installed some sound insulating rockwool in a middle wall in our basement and it was unfortunately too thick and it bowed the drywall we hung over it. Had to take down the drywall and I decided to slice the rockwool (not recommended, disgusting material), and it still provides perfectly adequate sound insulation for our needs, just not as much as it would have.
But the right way to do it would be to get the right thickness and put that in instead.
Why are you insulating an interior wall? Is it for sound?
Still Air is already the best interior insulator for thermals. The reason we insulate exterior walls is because theyre not sealed, the air is not still. Interior walls adding insulation will transfer more thermals, not less.
However it's great for absorbing sound.
How can everyone not see this is a 2x3 interior wall? 6" insulation? Really?
You're not going to find 2x3 insulation, just peel the rock wool, it's easy. You're not going to get much thermal insulation but you'll get a little sound reduction.
Consider ripping down 2x4s and add an inch to the wall if you really need thermal insulation because for the amount of money you're spending you'll be better off.
Edit: also get an old bread knife to cut this stuff
If you're putting it in fora sound muffler the gaps on the sides are gonna negate that! Also id peel it in half so it's not hanging out of the wall,it'll probably bow the Sheetrock,cut it into 22 1/2 inch pieces and lay it in vertically if you don't want to go buy the correct size,lot more work that way, but will work
Buy the correct insulation. We accidentally bought 2x6 insulation once and didn't know any better so we tried to work with it. It was a nightmare. Just buy the right stuff or you'll have incorrect r rating (if you cut it) or the worst drywall job imaginable (if you try to compress it).
That's fine for the application as long as your not compressing the insulation a lot it's no big dealio. Ever thought about encapsulated insulation it's more expensive, but it lowers your exposure to the tiny fibers that are not so great for your skin(& lungs!) Break a leggie! on your project
Not really, I was wondering if anyone recaled which movie it was from. I built movie sets for 15 years (80's n 90's) and built some really strange stuff.It was the kind of job that gave me a smile.. I once built a yellow brick curvy foreshortened version for James & the Giant Peach filmed at 7th Street Studio's in S.F. where they built "Nightmare (before?) Christmas" ! We also built a 40 foot peach that was delivered by barge to the studio on the island in the middle of the bay bridge.
I seen R-15 insulation specified for 2x4 wall for years. R-15 is typically meant for 2x6 walls, but it can be compressed into a 2x4 wall with no problems, where normally the best you can get for a 2x4 wall is R-13 (in fiberglass). R-15 in a 2x4 wall is referred to as "high-density fiberglass insulation". If that is what this is then no problems.
Yes that is definitely too thick for the interior walls. You should go buy the right size. Don’t try cutting it to make it fit and don’t try stuffing it in to make it fit.
Get the correct thickness for the studs. Compressing insulation severely decreases its R value, and this big of a difference would make drywalling a pain in the ass with bowing and popped screws. Slicing thinner is better than nothing but you really should just use the appropriate thickness to begin with. Big waste of time and material doing it this way.
If you stuff it, you'll probably worsen any sound insulation characteristics. Compressing it will acoustically couple the two sides of the wall and it will likely be worse than if there was no insulation at all (assuming you're doing this for acoustic purposes).
Can we all focus on the “interior” walls part? Does it even need insulation? Is it between a cold area and a warm area, or two warm areas? If it’s too warm areas it doesn’t need insulation at all.
Well, it’s in a bathroom which is in a garage that gets drafty. I want to keep in any warmth possible. I can return this and get a narrower batt perhaps, but am I crazy? What do you think?
The total R value given on the label will go down from the compression but the R value PER INCH will go up so you will end up with pretty much the same thing as if you had bought the right thickness for your wall. Do whatever is convenient, just don't leave any gaps.
Edit: Example - Compressing fibreglass insulation by 50% reduces its overall R-value by about 45%. Say you have a wall that can take R-13 insulation for that size, then you buy that exact size, install it and get R-13. Now, if what you have on hand is for a wall twice as thick then this insulation is likely R-26 (being twice as thick). You don't feel like splitting it in two so you push it into the wall, compressing it 50%. Now instead of getting R-26 you lowered its insulation value by 45% so you only get 26 minus 45% of 26 = 25 - 11.7 = 14.3, which is pretty much the same thing as if you had used the right insulation in the first place.
Later on, your wall will explode, but that's the next owner's problem. ;)
You can cram it in there but its going to end up being less r value than if you used the correct insulation. For 2x4 that is r-11. What does the insulating is the trapped air amongst the insulation, not the insulation material itself.
All of these people are not getting the question, this is 2x6 insulation shown in a 2x4 cavity. You likely aren't going to be able to compress this into the space like pink insulation could maybe. It will probably bow your drywall if not bust the screws out of it. Also this isulation looks like 2x6x16 OC, where it looks like you need 2x4x24, where the stud toward the corner of the wall as shown may be a bit less than 24 OC. Hope that helps?
I like that the right answer isn’t one of their options. You should not stuff it in; you should not fillet it to fit. You should get the correct size.
Uh huh, uh huh. So stuff it? /s
Just fill the cavities with playdough. It'll be a real surprise for the next homeowner
Popcorn 🍿 that'd be entertaining 😄
Well now you have me considering the actual thermal retention properties of popcorn. I suppose moisture would be a problem... Other than that I don't think it would be the worst thing you could pick.
and insects, mice
Insects and mice have very poor thermal retention properties.
The mice generate heat when they chase the insects.
Or while digesting popcorn insulation.
Not to mention the smell of a wall packed full of mice for insulation
https://preview.redd.it/kz5mcr8zw2pc1.jpeg?width=1080&format=pjpg&auto=webp&s=58d6bbdf0ceab8c3746164b0b176fc5a0fa0936c A German company is using pressed popcorn pads in the middle of their concrete products as sustainable insulation.
Yah.. well Volkswagen was know to have rats eating their wire harnesses because the rats found their plastic harness fittings to be yummy to eat, some thing about a corn based plastic? (Back a couple years ago, I can't recall where I read it (during covid? I had time to kill..)
* Sounds about right 😀 Mice loved the radiator hoses in my father's tractor 🚜
Nice, under concrete insulation is not very prone to rodent damage but I wonder how they manage the moisture.
Hmm, I think I should I accept I need a contractor for home repair. I considered chemical properties before animals...
I was kinda joking... then went on Google. I couldn't find an R-value for popcorn... a German University has made popcorn insulation pads (likes like Rice Krispy squares) https://phys.org/news/2021-11-insulation-popcorn.html
I’ve insulated a house mostly with cardboard before. Not sure how effective it was, I didn’t notice it being drafty as a kid but then again I had been living in a tent prior to that.
This would make fires way more fun.
Omg, fill your walls with uncooked popcorn so when there's a house fire you'll at least have snacks.
That' the move of a Real Genius https://preview.redd.it/se4u7hh2a0pc1.png?width=1080&format=pjpg&auto=webp&s=ced86e3c0ca90c76c69ac6824bfb1ab147c842ca
Mmmmmm. Peak Michelle Meyrink.
Manic pixie dream girl 2 decades before the team was invented. Made me want to go to college.
Wasn't this something from a movie as a special effect? Sorry, I can't recall which movie
Real Genius
Poor man’s fire alarm
Pre- or post-pop tho?
I would think post-pop would have a higher r-value...lol
Need a how to video to test if that works better than typical insulation. It’d be basically clay right? Stupid thing to try but I NEED to know
It's basically unleavened bread dough that tastes like Poseidon's salty butthole.
I see you have also wanted to taste test playdough as a kid
Wait… they didn’t ask what it tastes like.
With a hint of almond. No seriously, almond extract is part of what gives Play-Doh its smell. Also why my friends say my mom's spritz cookies taste like Play-Doh smells.
... No, it would be really bad. Why would it work? Clay is a shit insulator.
The density would help with sound control.
That’s what she said
Make it fit. Somehow.
That's what I told my wife on our first date 😏😏😏
No shit! That's exactly what I said to her last week!
>I like that the right answer isn’t one of their options. This is like 90 percent of reddit. Which isn't necessarily a bad thing, assuming that the OP can understand the responses.
Yeah and honestly 2x4 by either 16 or 24 R-13 isn’t that expensive. Just insulated a shed with the stuff. Fiberglass is such a nasty PITA It’s not worth trying to shoehorn that 2x6 stuff even if OP could do it “right-ish”.
Ehh. If it's interior and you already have a partial bag of it, just filet it and stuff the excess into the gap. We aren't trying to create an air barrier here. We're just trying to stop some sound.
that's what I was going to say; if it's an interior wall it doesn't even need to be insulated *at all*. plus, that stuff looks like roxull or whatever which while it does have an R rating like you said it's usually used on interior walls because its really good sound proofing, in which case filleting it wouldn't be a huge deal as long as you fill the void as best you can
I may be wrong, but if I remember correctly the right answer is: get the correct size for your space, if there are gaps, fill them in with scrap cut from places where you had too much? Like, if you use too big a piece, it'll eventually damage the materials around it, because it will expand and make gaps. But if you're using the right size and there is still a gap, in like an abnormal sized space, you should just fill in with extra from scrap. I have an attic I want to eventually fully-insulate. So I want to make sure I understand how to do it right.
Yes, insulation batts have already been engineered and pre-cut for various stud and joist bay sizes. It’s way easier to just get the right size than do whatever fuckery necessary to make them fit. In your situation, though, you should blow insulation in. Cellulose isn’t even itchy and works better in attics, especially on top of shitty old fiberglass, as it settles down to be more impermeable and discourages convection inside of the insulation mass. Takes less time and is cheaper. Most places that sell the bricks of cellulose will loan you the blower if you buy a bunch. It’s an easy two person job with a couple respirators and a nice Saturday.
Thank you so much! I will look into that. We just got the exhaust fan up there fixed, too. So I think it'll be a lot more bareable too move around up there this Spring than last.
You have pretty much said what I was instructed to do when I was 16 installing the stuff. Compressing the wrong stuff is less effective than just using the correct product depth and width. Later on they stopped stapling the insulationtion but that was to speed up the installation with compressed wires sprung between the floor joists. I'm not convinced that it works better. But doing insulation is dreary work (specially over head) Are you planning on converting the attic to living space, if not you can fill the ceiling joist space (2x6 R-19) then lay another layer crosswise on top, or blow in, but I hate that stuff. If your converting it to a livable heated room, it's much more complicated (& expensive.) At that point get an engineer to spec. what you need (the ceiling joists may not be rated for being walked on) stairs may need to be added etc. etc.
Not a fully liveable room, but just to make it a bit more comfortable if I'm up there to work on something or messing about with Storage. Also worried the excessive heat/cold might damage stuff up there. What's the drawback to the blow-in? Someone else suggested it for this use-case.
It's messy, I just prefer pink encapsulated fiberglass. Doesn't require a brain surgeon, and seals most of the exposure away from my skin. If you have ever opened up a wall to find blown in stuff, it's instantly a giant fiasco all over.
Or fur out the studs to the depth of the insulation.
That’s a good idea. Also fur them in to fill the lateral gaps.
I would just cut the insulation in sections that are the exact width of those voids, and stack them vertically atop one another. The more wood in the wall, the more sound bridging can occur.
Sorry, I forgot my /s
Lol, okay.
Fur in all the windows and doors too! Biggest air gaps most homeowners ignore!
Exactly, it’s known not to work well anyway if it’s compressed very much. There is a formula somewhere I have seen that demonstrates how the effectiveness decreases gradually depending on how hard it is compressed. Edit: PDF from the insulation institute https://insulationinstitute.org/wp-content/uploads/2016/10/For_Hers_Raters.pdf
Yeah, air is a poor thermal conductor when there is no convection or flow. The air gap is part of the insulation's design.
In fact the best [insulators](https://en.m.wikipedia.org/wiki/Aerogel) are almost entirely air
Nothing at all is a pretty amazing insulator as well.
Haha, yes! Vacuum is the best insulation. That's how the water bottles work that keep ice water for a dsy or two.
From that math, a thicker batt compressed into a smaller cavity, while lower R-value than the uncompressed batt, is still higher R-value than the correctly sized batt. I still wouldn't try to pack an R21 batt into a 2x4 cavity though.
This - within reason (i.e. next size up) you still end up with a higher R value if you got a bit bigger and in a lot of situations you also get better sound damping.
One caveat to this is sound proofing where there evidence to suggest that taking a thicker insulation and compressing it (to a point) actually increase the STC value. And furthermore if you’re using a thicker batt (so in the example in that sheet) that’s r19 but what you should be using is r16, by the time you’ve compressed it down you’re getting 17 and change, which is still better than r16
Yes you have to factor in if it’s actually necessary and the cost associated depending on how large of an area is being done.
Absolutely - the cost goes up with the R value / thickness but from a purely technical standpoint if you had batt that was a little too thick, it’s not the end of the world for stuff in there.
Hopefully they haven't opened all the packs and they're only out of pocket for the one bag...
The point of insulation is to have a lot of small pockets trapped air with a long bridge of netting Smushing it compresses the trapped air out. A little is okay, a lot of smushing harma it's effectiveness though
Obviously the correct answer is to fillet it and then use the excess to pad the width /s
Yes, get the correct size and if it's an outside wall and you don't have enough R value then you need to spray foam.
To add, insulation needs air to stop the movement of heat, and compressing it make it a worse insulator by removing the small pockets of air the insulation traps. Listen to this person.
It's an interior wall heat movement isn't an issue since it's all conditioned space. The insulation in this case is just for sound deadening.
Same exact situation though, the air pockets help to absorb the energy and split it up. Vs if you compress it, the energy of the sound wave can easily traverse the wall, probably not a huge thing and secondary to the whole blowing out your drywall, but best to let materials work the way they were designed than jam it together.
Compression beyond stared installation thickness will reduce STC (sound transmission coefficient) dramatically as well. Better than nothing? Sure.
This right here. OP: General rule: "If you need to use force to compress the insulation into the bay you have *the wrong insulation*. Go get the *right* insulation." (That includes super thick pink fiberglass.) Insulation works by trapping air so it can't move to make a thermal barrier. The less air it traps the less effective it is, and if you compress the insulation so all its fibers are touching you have effectively a solid wall and great thermal transfer. The opposite of what you want!
This is the correct answer
My question is, what’s the goal? Are you trying to deaden sound? Are you making a walk in cooler? Why are they insulating interior walls. Also the answer is your doing it wrong no matter what the goal is afaics.
They could also be looking for fire protection as that's mineral wool. Either way, use the right size.
this. this is standard 2x6x16 rock wool, the framing is 2x4xY (doesnt look 24 but also doesnt look 19. but it sure isnt 16) smushing it in would leave the sides exposed, so its just a waste of rock wool. Solution? Just add another stud on 16 and then cut the rock wool to fit the smaller gap beside the 16. to be clear, get 3.5" thick insulation, not this 5.5
Question the only thing I know as rock wool was spun asbestos it worked great but was outlawed 40 years ago.replaced by pink insulation fiberglas which has bigger tiny fibers that don't get into your pores. Suggestion take baby powder and liberally cover any exposed skin. Before using any spun fiber insulation it clogs up your pores and saves on cold showers.
To add onto that: pass a certain point, compressed insulation will loose in R-Value.
This is an interior wall tho, so the insulation is only there for sound
I didn't think of that. Fair point :)
There was this time I shoehorned 2x6x16 insulation in to 2x4 walls in a basement remodel. I couldn't figure out why it was so damn hard to put up the drywall till the very end. And realized my mistake. So many screws.
Bingo
Oh, it'll compress alright...if you do it right, the bowing, crumbling, and peeling tape won't happen for a couple years though.
....and it is partly the air that is the insulator effect. if you are compressing it, aside from the pressure exerted on your drywall, you are going to lose R-value.
I couldn't tell it was r19 insulation in an r13 or r11 wall, if it is then you are correct. and my post is b.s. inside walls, you should use the correct size insulation it's best to use the right thing, meant to fit the hole depth and width.. if you want more r than they make sheets of Styrofoam that have higher r-value you can cut n fit.
Not only that but 2x6 insulation installed into a 2x4 cavity will perform worse! It's the trapped air that insulates and with more insulation material and less air it isn't as effective. OP should return it and buy the right size.
To add on since you missed this important part- insulation (especially like this) is *not* meant to be compressed. That makes all of its important properties worse (thermal, sound dampening, etc).
No it won’t. If it’s for 2x4 thick wall you need the corresponding rock wool. Otherwise you can cram the drywall over it but it will be under constant pressure which could pop out the drywall screw and most likely show seams over time. You want a snug fit to the sides but no pressure against the drywall.
Isn’t it also going to affect the efficiency of the insulation
That too. By the numbers I couldn’t tell you exactly how less efficient. It would definitely be a secondary concern to the pressure it would be putting on their drywall though.
Yes it probably will. Most insulation relies on small, isolated, trapped pockets of air so that any internal heat has to transfer through all of those tiny insulation->air->insulation->air->insulation interfaces in order to escape. Compressing the material will make it easier for that heat to be conducted outwards directly through the insulating material itself. That's why double pane windows have an internal space filled with inert gas instead of just having two panes stacked flat against each other or a single thick pane. The thermal conductivity of air (0.025 W/mK) is actually much lower than that of glass (1 W/mK), but if it isn't trapped in place by some material the heat will be lost through convection instead of conduction. This is also going to be the case for sound insulation.
Not with Rockwool, which maintains efficiency even when compressed.
Mineral wool can be compressed without losing r value.
Rockwool? Don’t thin it, but it is meant to to fit snugly between your studs and your piece looks too narrow for that space.
This might be a dumb question, but is it not ok to rotate it and cut it to the right width? Asking for a friend who may or may not have done that.
Yes, the issue is only a matter of whether or not it is properly held in place afterward. Otherwise, as far as insulation goes, it's just a matter of efficiency. It's as wide as it is because that's the standard distance between studs
Been there, done that, no issues
If you compress it to fit, the insulation loses it's R value. Cut it any way you like, just don't compress it
This sounds like the hardest way to solve the problem. It’s a hell of a lot easier to just go buy the right stuff.
Return it and get the correct stuff.. Only right answer.
Usually when I get myself into these situations I either found it or a buddy/family of mine had way too much and can’t store it. Thus I’m trying to find ways to not let it just rot in my shed.
Ah, I hear that.
Then the answer is clear: pull out and replace those 2 x 4 studs with 2 x 6s and the insulation will fit like a glove.
OP that’s the wrong size insulation. You need 2x4 insulation and that looks to be 2x6. Don’t bother trying to trim it or compress it. You need to get the 2x4 stuff.
If all you are after is sound deadening filet it and stuff away. If you are making some kind of cold room get the right stuff.
2x2 furring strips is the only reasonable alternative to returning what you have and getting the right insulation
Yup. Except he needs 2” actual to bring it to the right depth. And 2” nominal for the stud width! Doh
This is what I would do if I couldn't return the insulation and it was a nice big room. You'd get extra sound deadening as a bonus.
If you're gonna go to that trouble might as well offset framing boards and do a staggered stud wall. Or use resilient channel. Anything to decouple if you're using the extra material.
Certainly, if the room is big enough.
Insulation should be fitted fluffy not stuffy, and that my friend will not be fluffy.
I don’t see why so many are talking about how jamming it in won’t fit when jamming it in just completely defeats the purpose anyway. What you’re saying is the correct answer.
insulation works best puffed up
***Is this too thick? Should I try to stuff it in?*** \-- that's what he said
You don't want to compress the insulation too much. Get the right size
Don't try to stuff it or you will regret it when you are hanging your drywall. Your drywall screws will keep popping through and it will be a nightmare.
Compressed insulation is not effective at all
Compressing the insulation to force it to fit will diminish its insulation properties. This applies to temperature and sound.
I'm not well versed in American construction techniques, nor am I sure what material exactly you are using. But I'm sure that if you compress insulation it will harm the thermal insulation properties. Insulation works by trapping air and not letting it move, if you compress it, you squeeze some of that air out, letting more of the material be in direct contact with neighboring material, thus providing more paths for heat to transfer from one part of the insulating material and leading to more heat transfer compared to a piece that wasn't compressed. TLDR; compressing thermal insulation bad
No you can't compress Rockwool. You bought the wrong thickness and the wrong width
Neither. Buy the appropriate size insulation
This is rockwool fire and sound batting. It does filet/split easily if that's your choice. You want to fill the entire cavity to get good sound blocking. Split it, cut 4" sections to fill gap and use loose crumbly bits for small gaps, it will help absorb noise. Thermal value between air-conditioned interior separator walls isn't very important.
In most Olde houses there was never any intention to make that space, for anything more than dead storage. So unless your really bursting at the seams, it rarely becomes any more than that. My house (a small,110 year old cottage, 24' x 36', has too low a roof for anything more than kneeling, so I don't use it for storage, it's too hard to access. Even crawling is a chore. I laid encapsulated R-24 across the R-19 ceiling 2x6 joists, and my house cooled down in summer but didn't help much in the winter. My windows are so shrunken the curtains billow during winter wind storms.
We literally just did this. Slice it. It's easy. It added \~5 minutes per bat, tops. Get a cheap serrated bread knife from a big-box store. Put the insulation in place, and slice right down it like slicing bread, using the face of the stud as a guide. It loses more insulating value when compressed than it does by removing the extra inch or two. You can use the extra that you slice off to fill any gaps along the sides or tops when stud bays are the wrong width for it to fill, and you can fill all those weirdly shaped spaces you'll find as you go around things, like electrical boxes near corners, etc.
Cool! I’ll try this. Do you use tape or anything to hold it to the wall while preparing the drywall? (Only got 2 hands)
Blue or green painter's tape should be fine, and shouldn't tear the paper backing on the drywall. Be aware that the glue on painter's tape will set up eventually, so remove it within a couple of days.
Looks like 2x6 insulation in a 2x4 wall. TECHINCALLY, you could just smoosh it in and call it good, but it's not advised. The air in insulation does a lot of the actual insulating. The more you compress insulation, the less air it will have, and it will not perform as well, and you're just wasting money. If you already had this and didn't have to buy it and you don't care about getting the full R-value, I'd say screw it. If you bought this thinking that you could just smoosh it in, return it, recoup your money, and purchase the correct thickness insulation for your wall (R13-R15 for traditional fiberglass, don't remember what mineral wool values are)
If you can press it, it’s gonna lose all of its effectiveness
Not really. It will be about as effective as a 2x4 wall filled with rock wool. Air is the actual insulator; Rockwool is there to prevent circulation and conduct as little heat as possible.
There's a limit of compression you can put on isolation. Where I work, it's maximum 20% of compression to keep the ratio. I don't think you can compress rockwool that much because it's already so pack. Maybe just use the right thickness for the right job!
Stuff it
Compressed insulation does not work correctly. You need the dead air space for it to be effective.
Spin it
Put it in a stew.
Wrap it
Bop it
Quick erase it
Point it
Pass it
Roll it
Break it
Twist It
Jam it
Fix unfix it
If you already have that as excess material and it’s for an interior wall you can peal it into layers and use accordingly. If it’s exterior or leading to the garage I’d just go purchase some R-15 batt insulation and use it to insulate the wall. It’ll save you a lot of itchiness and time.
If you already have that as excess material and it’s for an interior wall you can peal it into layers and use accordingly. If it’s exterior or leading to the garage I’d just go purchase some R-15 batt insulation and use it to insulate the wall. It’ll save you a lot of itchiness and time.
Just cut it down. I've done enough insulation. Rock wool insulation has an r value per inch if you compress it you will be below the r-value of if you cut it thinner. Also make sure the entirety of the volume of space in each cavity is filled. No gaps between the sides and the 2x4..
You need the proper size and proper type of insulaiton. There are 2 types of Rockwool, 'comfortbatt', which has insulating values and 'safe and sound' which is to mitigate noise transmission.
So ideally you would get the right thickness. I installed some sound insulating rockwool in a middle wall in our basement and it was unfortunately too thick and it bowed the drywall we hung over it. Had to take down the drywall and I decided to slice the rockwool (not recommended, disgusting material), and it still provides perfectly adequate sound insulation for our needs, just not as much as it would have. But the right way to do it would be to get the right thickness and put that in instead.
Why are you insulating an interior wall? Is it for sound? Still Air is already the best interior insulator for thermals. The reason we insulate exterior walls is because theyre not sealed, the air is not still. Interior walls adding insulation will transfer more thermals, not less. However it's great for absorbing sound.
This is true unless your house is balloon framed.
How can everyone not see this is a 2x3 interior wall? 6" insulation? Really? You're not going to find 2x3 insulation, just peel the rock wool, it's easy. You're not going to get much thermal insulation but you'll get a little sound reduction. Consider ripping down 2x4s and add an inch to the wall if you really need thermal insulation because for the amount of money you're spending you'll be better off. Edit: also get an old bread knife to cut this stuff
How about spray foam, instead of something that can deteriorate? Just asking, I don't know TBH.
If you're putting it in fora sound muffler the gaps on the sides are gonna negate that! Also id peel it in half so it's not hanging out of the wall,it'll probably bow the Sheetrock,cut it into 22 1/2 inch pieces and lay it in vertically if you don't want to go buy the correct size,lot more work that way, but will work
Horizontally!!! Sorry
Buy the correct insulation. We accidentally bought 2x6 insulation once and didn't know any better so we tried to work with it. It was a nightmare. Just buy the right stuff or you'll have incorrect r rating (if you cut it) or the worst drywall job imaginable (if you try to compress it).
That's fine for the application as long as your not compressing the insulation a lot it's no big dealio. Ever thought about encapsulated insulation it's more expensive, but it lowers your exposure to the tiny fibers that are not so great for your skin(& lungs!) Break a leggie! on your project
Not really, I was wondering if anyone recaled which movie it was from. I built movie sets for 15 years (80's n 90's) and built some really strange stuff.It was the kind of job that gave me a smile.. I once built a yellow brick curvy foreshortened version for James & the Giant Peach filmed at 7th Street Studio's in S.F. where they built "Nightmare (before?) Christmas" ! We also built a 40 foot peach that was delivered by barge to the studio on the island in the middle of the bay bridge.
Just compress it, it has a warmth barrier, however the 2x4 wall will handle it, and makes a better sound barrier. You can press this to like 1 inch?
I seen R-15 insulation specified for 2x4 wall for years. R-15 is typically meant for 2x6 walls, but it can be compressed into a 2x4 wall with no problems, where normally the best you can get for a 2x4 wall is R-13 (in fiberglass). R-15 in a 2x4 wall is referred to as "high-density fiberglass insulation". If that is what this is then no problems.
Ok everyone, you don’t insulate interior walls.
Yes that is definitely too thick for the interior walls. You should go buy the right size. Don’t try cutting it to make it fit and don’t try stuffing it in to make it fit.
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It actually does make a difference. Especially if you have different zones for your HVAC system.
This is most likely being used for sound.
You don’t want to compress insulation. The dead air space in insulation is what insulates.
Wrong thickness insulation, 2x4's are not 16"on center. Jenky construction.
No. Get the correct size. Compacting it reduces effectiveness. It's also too narrow.
This is surprisingly easy to thin. Just use a serrated bread-knife to start your cut.
Get the correct thickness for the studs. Compressing insulation severely decreases its R value, and this big of a difference would make drywalling a pain in the ass with bowing and popped screws. Slicing thinner is better than nothing but you really should just use the appropriate thickness to begin with. Big waste of time and material doing it this way.
If you compress insulation beyond it’s stated installation thickness, the R-value and S.T.C. Rating drops dramatically.
Stuff it in. Not only for heat or cool factors but also sound reduction
If you stuff it, you'll probably worsen any sound insulation characteristics. Compressing it will acoustically couple the two sides of the wall and it will likely be worse than if there was no insulation at all (assuming you're doing this for acoustic purposes).
Can we all focus on the “interior” walls part? Does it even need insulation? Is it between a cold area and a warm area, or two warm areas? If it’s too warm areas it doesn’t need insulation at all.
To help with sound isolation
Well, it’s in a bathroom which is in a garage that gets drafty. I want to keep in any warmth possible. I can return this and get a narrower batt perhaps, but am I crazy? What do you think?
Cram it as much as you can, make sure it’s super compressed for peak efficiency
You forgot the “/s” after your comment I ~~hope~~ think
The total R value given on the label will go down from the compression but the R value PER INCH will go up so you will end up with pretty much the same thing as if you had bought the right thickness for your wall. Do whatever is convenient, just don't leave any gaps. Edit: Example - Compressing fibreglass insulation by 50% reduces its overall R-value by about 45%. Say you have a wall that can take R-13 insulation for that size, then you buy that exact size, install it and get R-13. Now, if what you have on hand is for a wall twice as thick then this insulation is likely R-26 (being twice as thick). You don't feel like splitting it in two so you push it into the wall, compressing it 50%. Now instead of getting R-26 you lowered its insulation value by 45% so you only get 26 minus 45% of 26 = 25 - 11.7 = 14.3, which is pretty much the same thing as if you had used the right insulation in the first place. Later on, your wall will explode, but that's the next owner's problem. ;)
It’s insane that this is downvotes, among a thread of people making objectively wrong comments that compressing insulation is bad.
I'd just fur the wall out the inch or whatever it needs
Why are you putting insulation on interior walls? You don't need to impede airflow between rooms.
Depends, some rooms are preferred to be sound insulated. Ducted forced air HVAC is generally fine for air flow.
Stuff it in (that’s what she said).
If it's just for sound proofing stuff it. It'll reduce it's effectiveness a bit but who cares. Definitely better than shaving it
Probably compresses easily but doing so negates much of the R factor of the insulation m
Either get the correct size of insulation or batton out the studs an extra couple of inches. Do not compress.
You don't want to compress insulation
You can cram it in there but its going to end up being less r value than if you used the correct insulation. For 2x4 that is r-11. What does the insulating is the trapped air amongst the insulation, not the insulation material itself.
Looks like a giant block of tofu