Blow In insulation only choice!

Hello, I have the unfortunate problem of needing to isolate the ceiling of a wood shop on the floor below to help with noise coming into the studio from the shop. The landlord is gracious enough to pay for half but is not willing to remove the existing ceiling. I posted details before here... viewtopic.php?f=1&t=14318&start=0 The only option is to blow in insulation, retaining the existing ceiling, the Green Glue, drywall, Green Glue, drywall. Being this is the case, what blow in insulation would be best? I know this isn't optimal, but it is what I am faced with. Any suggestions will be greatly appreciated. Sincerely, Ted Richardson Cedar Street Studios

Hi Ted, The best way to blow cellulose, I have many times used this with high results of sound insulation. Regards 808

The best way to blow cellulose, I have many times used this with high results of sound insulation.

So, "808", could you please explain how blown-in cellulose is going to decouple the ceiling below from the floor above? And how are you going to prevent it from bridging during the process of blowing it, which would cause flanking and make the isolation even worse?

The only option is to blow in insulation, retaining the existing ceiling, the Green Glue, drywall, Green Glue, drywall.

Whoaaaa!!! In your original post, you said that the ceiling below was "1.5 thick oak hardwood floor - 12"-14" tall joists - Slats - Plaster"! So how did that suddenly become "drywall, Green Glue, drywall"??? Did you REALLY go to all the trouble and expense of hanging two layers of 5/8" drywall plus green glue, without first bothering to decouple the ceiling? :shock: Are you saying that you did all that, didn't get any results, and now still have a big issue with sound getting through from below? Did you look at IR766 before you took that decision? It would have saved you a lot of trouble... It seems to me that your issue is not related to insulation: it is related to decoupling / flanking. If that's the case, then no amount of insulation in the cavity is going to solve the problem. It might help a bit more, but it will not be the magical solution that you seem to be hoping it will be. Just to make things clear: insulation is not isolation: Insulation is not very good at isolating. It can indeed be part of a system that isolates, but that system has to be designed correctly to do the job, and part of that design includes decoupling the two sides of the barrier. "Decoupling" means eliminating all mechanical connections between the two sides. EG, using something like resilient channel to disconnect the ceiling below from the joists. You have not done that, so no amount of insulation is going to solve your problem. All you did was add mass to the system, which probably didn't accomplish a lot. My guess is that you maybe gained 4 or 5 dB of isolation like that (theoretically, assuming you did it right and carefully sealed everything). Decoupling and proper treatment could have gained you 20 dB... My best guess (based on IR766) is that you had something like STC 43 to start with, and now you have perhaps STC 47. In other words, you barely noticed the difference. Blown-in cellulose MIGHT gain you another 2 or 3 dB, provided that you can figure out how to spray it in without it bridging anything. STC 50 is still not very good, for such a large investment. But here's the kicker: Quote from IR766 "Joist floors without resilient metal channels do not achieve STC 50 in any practical configuration, with or without sound absorbing material in the cavity.". Oops. In other words, what you have now is as good as its going to get. If you would have taken out the old ceiling, put in resilient channel, and THEN put on your two layers of drywall with GG, you would already have STC 53. Filling the cavity with rockwool at the same time would have taken you to STC 60 or better. Another layer of OSB on your own floor could have taken you to STC 63 or better. That's 20 dB above your original isolation level, instead of perhaps 4 or 5, and for roughly the same total cost... Another quote from IR766: "Putting sound absorbing material in the cavity of a joist floor with a ceiling that is not resiliently suspended provides no significant increase in sound insulation.". In other words, blowing in cellulose will do absolutely nothing for you at this stage. It would be throwing more wasted money after the money you already wasted. Sorry to sound harsh, but you already did ask about this on the forum, did get answers, and you ignored the advice you got from André, who is one of the leading experts here. Now you are stuck with a situation that cannot be improved much without undoing what you already did and doing it right this time. Blowing in cellulose is not going to help. One final question: Did you check with a structural engineer before you hung those extra nine thousand pounds of dead load from the joists? - Stuart -

Whoaaaa!!! In your original post, you said that the ceiling below was "1.5 thick oak hardwood floor - 12"-14" tall joists - Slats - Plaster"! So how did that suddenly become "drywall, Green Glue, drywall"??? Did you REALLY go to all the trouble and expense of hanging two layers of 5/8" drywall plus green glue, without first bothering to decouple the ceiling? :shock:

The ceiling, which is under the 1.5" Oak floor (our floor in the studio), and then the joists, is comprised of the slat and plaster, all of which is still there. We have not made any decisions as to how we are going to accomplish this. My problem is that the landlord does not want to rip out the existing ceiling, which is the slat/plaster. Which only leaves the choice of this combination, top (our floor) to bottom (2nd floors ceiling)... 1.5 thick oak hardwood floor 12"-14" tall joists (filled with blown in insulation) Slats Plaster Green Glue 1/2" drywall Green Glue 1/2" drywall Another problem is the existing sprinkler system on the 2nd floor, which needs a specific amount of space between it and the ceiling, which is currently only 8". This doesn't leave enough space for resilient channel and new drywall ceiling, even if i could remove the existing slat/plaster ceiling. After calling the Green Glue Company and speaking with them today, they said it would help even with adding directly to the existing ceiling as described above, and of course blown in insulation. If I am going to use blow in insulation, since I cannot insulate any other way, which type should I use? This is all I am asking.

Sorry to sound harsh, but you already did ask about this on the forum, did get answers, and you ignored the advice you got from André, who is one of the leading experts here. Now you are stuck with a situation that cannot be improved much without undoing what you already did and doing it right this time. Blowing in cellulose is not going to help.

No advice has been ignored, and I appreciate André's, which I advised my landlord of, but I am limited as to what I can do. I am just trying to achieve the greatest results. Again I have not moved forward with any construction.

One final question: Did you check with a structural engineer before you hung those extra nine thousand pounds of dead load from the joists?

As for the ceiling, the building is an old casket factory, and they hung heavy machines from the ceiling joists. Our landlord has no doubt it will support what we are looking to do. Just a side note, the walls surrounding the rooms, on all floors, are 2.5 foot thick brick and mortar. Again, I really don't have the option of ripping out the existing ceiling, and it looks like I will just be able to add mass via GG/Drywall/GG/Drywall, and am looking to find out what type of blown in insulation would be best. I wish I could decouple the ceiling, but it's not possible. Thanks again for any ones input, Ted Richardson

Once again, I'd strongly suggest that you read IR766 before you do anything further. Especially the two parts that I quoted above: "Joist floors without resilient metal channels do not achieve STC 50 in any practical configuration, with or without sound absorbing material in the cavity." "Putting sound absorbing material in the cavity of a joist floor with a ceiling that is not resiliently suspended provides no significant increase in sound insulation." In other words, based on a pretty extensive set of thorough laboratory tests done on a large number of different floor configurations by a very reputable organization, you simply CANNOT do what you think you can do, without either decoupling, or add ridiculous amounts of mass to the floor. It just will not work. You cannot beat the laws of physics by hoping that if you can just find some formula of blown-in cellulose that has miraculously magical properties, it will somehow warp the space-time continuum enough to send your offending sound waves through a worm-hole to the other end of the galaxy! It ain't gonna happen. Pipe dream. GG is right in that adding two layers of drywall with GG in between will improve on what you had originally. But as IR766 points out, the practical limit with this plan is about STC-50. So you have to answer the question: is STC-50 good enough for what you want? Seeing that you already have something like STC-43, at most you are going to get a 7 dB improvement (and that would only be achieveable if you used 5/8 drywall, instead of the thin 1/2" stuff that you propose). To put that in perspective, subjectively it won't even reduce the current level by half. The result will be more than half as loud as what it is now. Is that good enough? Because that is your theoretical limit. Without decoupling, you just cannot do any better, realistically.

If I am going to use blow in insulation, since I cannot insulate any other way, which type should I use? This is all I am asking.

You are asking the wrong question here. The answer to that question is "No type at all, since none of them will accomplish what you dream they might". By the way, IR766 does mention blown in insulation, and will give you a partial answer, but not one you are going to like. Anyway, the questions you should be asking are: What do your current measurements say? What do you see on your SPL meter when you check how loud the sound is that is getting through to your room? Will reducing that by an absolute maximum of roughly 7 dB be good enough? Is it worthwhile spending all that money for just a 7 dB reduction? That's the question you should be asking. Personally, I doubt that it is worthwhile, but only you can answer that question, (if you dare to admit to yourself that is is the right question). - Stuart -

Cedar Street Studios wrote:

Hello, I have the unfortunate problem of needing to isolate the ceiling of a wood shop on the floor below to help with noise coming into the studio from the shop. The landlord is gracious enough to pay for half but is not willing to remove the existing ceiling. I posted details before here... viewtopic.php?f=1&t=14318&start=0 The only option is to blow in insulation, retaining the existing ceiling, the Green Glue, drywall, Green Glue, drywall. Being this is the case, what blow in insulation would be best? I know this isn't optimal, but it is what I am faced with. Any suggestions will be greatly appreciated. Sincerely, Ted Richardson Cedar Street Studios

Ted, Several concerns arise from attempting to blow insulation into an overhead cavity. One is not knowing how this floor/ceiling was framed. An educated guess, and I am an educated guesser, would lead me to think that you will encounter blocking or bridging in between the joists. Effectively this will create a dam which will not allow the material to flow entirely into the void. The second concern is that cellulose insulation, which is most likely what your contractor will recommend, does not play well with electrical areas or devices that produce heat. Which is not to say that if you blow it in, it will catch fire, but that a professional should be involved. A professional contractor will know what to use and if it can be done properly or not. There is not a specific acoustical benefit gained except for the possible damping of the cavity and the floor itself and there is also no specific insulation choice since cellulose is about all you can >blow< into a cavity. Good luck

Adding insulation will not give adequate isolation. Look at pdf pages 70-72 in IR 811. Even the most effective improved floor has poor isolation at 50Hz. The changes that you are suggesting are somewhat less effective than the construction in method 1, This improved the STC by 4 points, from 34 to 38. IT IS NOT EFFECTIVE. Andre

Seeing as you refuse to listen to any of the GOOD advice being given to you here - and seeing as you are bound and determined to throw your money away doing this, why don't you just go to an insulation contractor and ask them what they want to blow in and how much they are going to charge you. When everyone explains that there is no recommendation because it isn't going to help - please don't waste their valuable time by asking the same question over and over again - it is quite frustrating............ take the 5 minutes and read IR-766 (here's a link in case you can't find it) and then stop pestering............ http://www.nrc-cnrc.gc.ca/eng/ibp/irc/c ... s-n25.html Rod

OK, I really REALLY appreciate everyone's attention to my post, and I have read, and understand, why it is necessary to decouple the ceiling from the joists to be able to have any sort of decent isolation. Just to be clear, I DO want to take the old ceiling down, fill with Rockwool, and use resilient channels and all, but my landlord is trying to not do this because of the time it will will take away from the tenant on the 2nd floor. The reason for this post was to see if filling the existing ceiling with blow in and applying GG/DW/GG/DW directly, as per Green Glue company suggestion, would be at all adequate, which I understand that it will only be negligible. A couple of you feel strongly that I am ignoring your suggestions, and again, I am not. I have sent the link of this post to my landlord in hopes that he can see what we are up against.

Seeing as you refuse to listen to any of the GOOD advice being given to you here - and seeing as you are bound and determined to throw your money away doing this, why don't you just go to an insulation contractor and ask them what they want to blow in and how much they are going to charge you. When everyone explains that there is no recommendation because it isn't going to help - please don't waste their valuable time by asking the same question over and over again - it is quite frustrating............ take the 5 minutes and read IR-766 (here's a link in case you can't find it) and then stop pestering............ http://www.nrc-cnrc.gc.ca/eng/ibp/irc/c ... s-n25.html Rod

Again, I am not refusing to listen. I have in no way started any of the project. I am now gathering information to give to my landlord in hopes that he will understand what it takes to accomplish the task. In no way am I trying to pester anyone. And Rod, thanks for the link. All of this information is very helpful, and believe me, I am handing it to my landlord, as I don't have money to waste. It's great to see that you guys care and are passionate about this. It helps us that are less knowledgeable, but want to do it right. Thanks again, Ted Richardson

Given your limited parameters, about all you can do is what you've already described. Blowing in cellulose is a sketchy proposition, as has already been discussed. If you can't create a low density fill, you risk making thinks worse by compacting in spots and therefore coupling the ceiling and floor surfaces. I think an insulation contractor might simply tell you what you want to hear, and so you might very well be better off to pass on the insulation. If you substituted the 1/2" for 5/8" drywall that would be a larger delta for mass. As mentioned, a coupled system will only ever get you so far, but if that's all you can do, then that's all you can do.

As opposed to starting a whole new thread - I thought I would ask in this one - so I hope nobody lynches me for doing so! :cry: Anyhoo - I am in a position where I am being evicted from the inside of our house. My wife is "encouraging" me to move my stuff outside into our Utility room. The room has drywall, which I have mostly tore down (at this point). There is no insulation in the wall. So I called around - and nobody wants to do a blow-job for such a small unit. :lol: that didn't sound right, eh? So now I am faced with using regular type of insulation. I am considering some RockWool type insulation; some Owens Corning insulation (QuiteZone stuff); or Johns Manville insulation. My question is this: is there any particular type of insulation y'all would recommend at this point? I have already purchased some acoustic treatment (after I'm finished with the new sheetrock, insulation, etc) from Real Traps (BareTraps x 4), and PrimAcoustic (the London room thingy). Thanks for any advice. Take care! Scott

Scott, the best bang for the buck is always regular fluffy fiberglass insulation - it is better for low frequency isolation than more dense materials....... decoupling from the structure is also very important is you wantot acheive any real isolation values when it comes to music........

Excellent input, Mr Gervais. Thanks for taking the time to reply. I guess I'm gonna get my brother to run by Home Depot or Lowes to get something pink & fluffy. I appreciate it. Take care! Scott

rod gervais wrote:

Scott, the best bang for the buck is always regular fluffy fiberglass insulation - it is better for low frequency isolation than more dense materials....... decoupling from the structure is also very important is you wantot acheive any real isolation values when it comes to music........

Back up the bus! (Sorry, "hick" term I use for when I missed something) Did I misread on other threads? I, for some reason, was under the impression that between your two leaves you wanted to use 3 pcf rockwool or the like - was I wrong with this?

bwilkinson wrote:

Did I misread on other threads? I, for some reason, was under the impression that between your two leaves you wanted to use 3 pcf rockwool or the like - was I wrong with this?

Yes, you were wrong. Andre

Well, that just saved me a few grand! Back to update the design again!

Did I misread on other threads? I, for some reason, was under the impression that between your two leaves you wanted to use 3 pcf rockwool or the like - was I wrong with this?

What you want in your air gap is some form of insulation. Fiberglass and rockwool are two good ones 48 kg/m3 (3 pcf) is a good choice for rockwool, but isn't the only choice, by any means. Like lots of advice here, it's a trade off. 48kg/m3 rockwool is usually recommended since it is easy to find in most places around the world, reasonably cheap, and has reasonably known acoustic properties. But it isn't the only thing that works by any means, nor necessarily the "best". It's actually not even easy to decide what "best" even means here! Best price? Best performance? Best fire rating? Best installation? Best duration? Best whatever? It's all a trade off.... - Stuart -

Soundman2020 wrote:

Did I misread on other threads? I, for some reason, was under the impression that between your two leaves you wanted to use 3 pcf rockwool or the like - was I wrong with this?

What you want in your air gap is some form of insulation. Fiberglass and rockwool are two good ones 48 kg/m3 (3 pcf) is a good choice for rockwool, but isn't the only choice, by any means. Like lots of advice here, it's a trade off. 48kg/m3 rockwool is usually recommended since it is easy to find in most places around the world, reasonably cheap, and has reasonably known acoustic properties. But it isn't the only thing that works by any means, nor necessarily the "best". It's actually not even easy to decide what "best" even means here! Best price? Best performance? Best fire rating? Best installation? Best duration? Best whatever? It's all a trade off.... - Stuart -

You begin with whether or nor fire rating is a factor or not........... if it is - you seek out a design (UL, FM, whatever) that allows the use of insulation. NOT ALL ASSEMBLIES ALLOW THIS - IF IT IS NOT SPECIFICALLY NOTED IN THE DESIGN THEN IT IS SPECIFICALLY NOT ALLOWED. This is very important to remember - the placement of insulation (of any type) in a cavity will actually raise the temperature in that cavity - and thus hasten structural failure - so it is critical that they test to be certain that the failure times being tested for will remain with that assembly if insulation is in place. They will also specify the exact maximum thickness allowed in the cavity. You would expect to see something similar to the (taken from ANSI/UL Design No L547):

5. Batts and Blankets* — (Optional) — When truss depth is 18 in. or greater, insulation is optional. Insulation may alternately be secured to plywood subfloor with staples spaced 12 in. OC or to the trusses with 0.090 in. diam galv steel wires spaced 12 in. OC. Insulation may be draped over the resilient channels and gypsum board ceiling membrane and the resilient channels and gypsum board attachment shall be modified as specified in Items 6 and 7. Any glass fiber insulation bearing the UL Classification Marking for Surface Burning Characteristics and/or Fire Resistance, and having a min density of 0.5 pcf may be used. The Finish Rating is 24 min. when the insulation is draped over the resilient channels and gypsum board ceiling membrane and 25 min. when it is installed on underside of the plywood subfloor or when it is omitted. 5A. Batts and Blankets* — When truss depth is less than 18 in., Max 3-1/2 in. thickness of glass fiber insulation shall be draped over the resilient channels and gypsum board ceiling membrane and the resilient channels and gypsum board attachment shall be modified as specified in Items 6 and 7. Any glass fiber insulation bearing the UL Classification Marking for Surface Burning Characteristics and/or Fire Resistance, and having a min density of 0.5 pcf may be used. The Finish Rating is 24 min. when the insulation is draped over the resilient channels and gypsum board ceiling membrane. 5B. Loose Fill Material* — Loose fill material may be used as an alternate to batt insulation (Items 5A and 5B). When used, the resilient channel and gypsum board attachment is modified as specified in Items 6 and 7. Any loose fill material bearing the UL Classification Marking for Surface Burning Characteristics, having a min density of 0.5 pcf and installed at a max thickness of 3-1/2 in. may be used. The finished rating when loose fill material is used has not been determined.

Remember one thing - you cannot modify anything about a rated assembly - so search carefully for one that provides exactly what you need from both a fire separation and acoustic isolation point of view. And if this ceiling you discuss is separating you and a separate tenant below - then it is a fire rated assembly - at which time you would have to research the exact construction to determine what assembly it is and would it even allow the installation of insulation in the cavity. Next - if it is NOT a fire separation - then it becomes a question of price point versus performance....... With the insulation part of this it's pretty simple - fluffy fiberglass insulation (standard thermal insulation) outperforms (slightly) insulations of greater density in the lower frequency range- if you are dealing with STC (hence frequencies in the range of the human voice) then it is just the opposite - greater density materials have a slight edge over normal insulation. For music the least expensive alternative always has the slight advantage................. as far as longevity goes - as long as we speak of fiberglass or rockwool - longevity is not an issue.......... we'll be long dead and gone before either material began to change significantly - I cannot speak for the fabric based recycled products.......... I hope this helped...... Rod

Thank you (all three, Andre, Rod, and Stuart) for the explanations... and thank you to Ted for allowing the hijack.