mineral wool floating floor construction and MSM calculation

Hi there everybody i'm just about to begin constructing my basement studio in Thessaloniki Greece (here is my design thread: http://www.johnlsayers.com/phpBB2/viewtopic.php?t=8898 ) I'm planning to float the floors in all the rooms. The problem is that i can't find products like Sylomer or Kinetics here in Greece and even worse there is probably no one with experience on these products and on the calculations needed to be done for them to work correctly as a MSM system. So i decided to build floating concrete floors on rigid mineral wool panels. I read all posts i found here and at studiotips regarding this kind of construction, and allthough i understand that this is not the best sollution regarding music spaces due to the higher MSM resonanse freq, i think it is the only way to do it proper over here. As i get it fiberglass is much better than rockwool because it allows more deflection under load. Mr. Desart wrote a lot of interesting things about that: http://forum.studiotips.com/viewtopic.p ... ting+floor http://forum.studiotips.com/viewtopic.p ... ting+floor http://forum.studiotips.com/viewtopic.p ... ting+floor So what i underastand is that deflection of 10 - 15% of the "spring" would lower the resonance frequency of the MSM system enough for musical aplications right? So my(one of 1000 ) question is: How can i calculate the deflection of the fiberglass panels? Can i use the technique that it was pointed on the drum riser post on this forum: put load on a fiberglass panel until it reaches the desired deflection? and if so, in what scale should i perform this experiment in order to get a practical result? would a 1 m2 panel work. On my floor i'm planning to use 10cm of 80-100 kg/m3 fiberglass and reinforced concrete upon it. please, i need your help on this Nikodemos

I honestly think that you're risking wasting your time and money on a floor that may cause the entire space to be isolated worse than if you don't attempt to float at all. Please study the "Is a Floating Floor Right For You? Answer: Probably NOT" sticky thread. --Keith :mrgreen:

Hi there Keith....believe me i've read this thread more than 10 times....but you see concrete buildings here in Greece and in EU in general are a very different thing from most US structures. The steel reinforced concrete foundation walls go all the way from bottom to top providing an excellent path for sound to travel through, from the basement right to the top floor of a 4 floor building.....so believe me floating the floor is a must in such a building......the problem is how to do it right :shock: I have read almost any info i could find on the net and on some great books regarding this matter but still.....there are several things to consider: how to do it, where to find the materials, can you find them?, what would be the cost etc etc....from all my research i found out that floating a concrete floor on minerall wool is probably not the best sollution.....actually the worst regarding resonanse frequencies of the MSM system to be build......but it is in my price range, i can easilly find the materials, and most important i can find experienced workers for the construction. Also from what i've read it is probably possible to build a m.wool - concrete floating floor with a more "musicall" - lower resonanse frequency......and that's where help is needed.......to find a way to calculate the MSM frequency of such a construction. On Newells and Everest books this kind of floating floors seem to be a "standard" but no one describes "how to do it" and "why to do it that way" or "what to expect from it". And i guess that since there is not enough data on certain aspects of mineral wool(over lots of different brands) like deflection specs, deflection over ageing etc, there is not a standard calculation form either. so it would be great if mr. Desart (since most of what i've found on the subject comes from him - mr.Desart please find the time to write a book it would be a great gift to all of us :) ) and mr.Sayers (who designed such a floating floor on the SAE website) could give a little guideline on this matter. I'm sure that this construction - thread would be very interesting for all the EU members of this forum. thanks in advance for all your help Nikodemos

Nikodemos, There are representatives of Sylomer in Greece as well: http://www.getzner.at/werkstoffe/print/ ... =en&id=133 Search the web or email them. The base producing company of Sylomer is Getzner in Austria. All these representatives (35 countries) have the necessary software to calculate this stuff for you. For glassfiber do you have Isover (or other brand) there? If they allow a 10 % deflection in function of material load, you can use it. Call them and ask for floating floor boards. (provide links). If you can provide a link (English, not Greek) I look into it. If you can find a distributor of "bonded foam", as I recently learned sometimes also called "chip foam" or agglomerated foam this works also and can used as substitute for fiberglass. That's this recycled grinded and bonded foam with these foam chips in them. In fact this foam has better acoustic properties (ratio deflection/MSM) than mineral wool, it's used a lot here for that purpose, but it hasn't the aging and moisture resistance properties of Sylomer.

I'm still not convinced though. Maybe you're right, but the facts you have identified don't make for an absolute unarguable case that you must float a floor for effective isolation. If you were going to build on an upper floor, then yes, I would tend to agree. If you are absolutely convinced that a floating floor is necessary, then I recomend the jack-up concrete slab system, by either Mason Industries or Kinetics Noise Control... Although even they will acknowledge that those systems are intended for impact noise control, not airborn. They can assist you with the calculations as well. I seriously considered the Mason system at one time... But a local acoustical engineer told me it wouldn't be necessary. I also had seismic issues to consider that would have made it challenging to get through buiding department approval without a structural engineer's certification. --Keith :mrgreen:

Thanx for your response mr. Desart i am aware of Greek sylomer dealers....the problem is that they never responded to my emails and calls for the past 2 months....and that's typical for Greece :cry: (That goes for Kinetics too... Anyway i'll keep trying to reach them but i certainly don't trust them... Regarding Isover fiberglass i found a few importers here in Greece, not plants. All info i found was some pdf in Italian :shock: it has this: dimension tolerance: lenght:+ - 10mm width: + - 5mm thickness: 3mm for a 85kg/m3 20mm board....is this deflection? if it is....then 3mm deflection on a 20mm board is 15%, right? should i look for something like this? and if so what is the optimum thickness for fiberglass panels in such a floating floor? I'll do some research on the foam now 8) thanks so much for your help :D Nikodemos

sharward wrote:

If you are absolutely convinced that a floating floor is necessary, then I recomend the jack-up concrete slab system, by either Mason Industries or Kinetics Noise Control... Although even they will acknowledge that those systems are intended for impact noise control, not airborn. They can assist you with the calculations as well.

This are certainly good companies as well. Nikodemus just info: Found this one, but don't know if it's the main dealer: http://www.ergoakoustiki.gr Keith, Have you compared systems that you are so absolute in your advice? Have you practical experience with them, and/or others?

sharward wrote:

If you are absolutely convinced that a floating floor is necessary, then I recomend the jack-up concrete slab system, by either Mason Industries or Kinetics Noise Control... Although even they will acknowledge that those systems are intended for impact noise control, not airborn. They can assist you with the calculations as well.

Keith, the mason industries jack up systems are designed and tested for air borne transmissions as well as impact noise - and are recommended specifically for sound studios....... I think you are confusing the Mason Industries literature on wood elevated decks with their jack up slabs............ BTW - you know what I love about Mason Industries?...... they don't patent anything they design for the market place - they actually encourage their competitors to use their designs.......... Sincerely, Rod

Nikodemus I see now that our post crossed. It's often a problem to get more industrial oriented companies interested in private persons (function of quantities, and not being organized as such). Try an email to Getzner itself, play dumb, tell that the studio people on the net advices their material and ask for a local supplier. If they give you a reference, you can tell that supplier you're directed by Getzner itself to them. They're often more sensitive not to harm there good name versus their supplier, than what they consider small turnover with a lot of blah-blah. About that wool I want to check myself what they write about it. Don't you have a type or code number (maybe easier to find on the net)? I haven't checked your plans now. But if you just use it underneath floating floors without walls being build on top of them, fiberglass and foam is maybe worth investigating further (cheapest manners to make floating floors). If you build your walls on them I should go for stuff like sylomer or the companies mentioned by Keith.

thanks for your response mr.Desart well, contacting the Getzner directly is probably the best way, i'll send an email right now.....i hope i won't get ignored there too.....after all i just want to spend some money :D :D Actually my plan is to build the inner walls on the floating floor.....do you think fiber glass is a bad idea in such a case because of ageing etc or in generall cannot support a heavier structure?I mean i read in a lot of posts at studiotips that if someone makes the concrete thick enough, lets say 15 cm - 300 - 320kg/m2 then he shouldn't really worry about the walls,people and equipment load on top....do i have it completely wrong? Anyway i'll try to post the link of the isover pdf or the pdf itself Keith, thanks for your interest....you are very helpfull :D thanks Nikodemos

Nikodemus, Have you calculated the weight of your walls already? That becomes a line load at the perimeter of the concrete. That means that you have to use either higher densities there or if cut in pieces, a higher number of pieces per surface unit. What I mean is the resilient material must be adjusted to the load. Cheaper solutions as fiberglass aren't really documented very well for such more technical applications. For simple floors where you can count on the load distribution by the topfloor, you can use more stylized cheaper stuff. If it becomes more technical, I should resort to the more technical solutions designed for such purpose. You won't easily find people selling you fiberglass, willing to investigate and guarantee this for you.

i was under the impression that if there is a continious underlayment under the concrete the load would spread equally on all surface...no? anyway i was under the impersion that with a reinforced concrete slab of 15cm the load of the walls would be insignificent..... i am not a "fiberglass maniac" :D i just want to have an alternative sollution ready in case my quest for syllomer fails...... i found some info on minerall wool form greek supliers but guess what...it's all in greek :? so i'll try to contact them and get this info in english...for you to check them when you find some time i search for this aglofoam but what i seem to find is some thin(3-8mm) rolls for vibration control under wooden or tile floors...is this what we're talking about?(ethafoam,fibran are some brands).....can you point a specific brand to search for in Greece....i mean aglofoam does not provide any return searches in the greek google :oops: Nikodemos

This is (different names I encountered for the same stuff), Rebonded foam, Bonded foam, Chip foam, Agglomerated foam http://www.ulgens.com/sponge01/id7.htm In Belgium it's produced by Agglorex (name related to process) and Recticel. But that must exist anywhere. It are the scrap parts of the production of standard open cell polyester and mainly polyether. Unlike mentioned on the above page they can produce this in higher densities. I've seen them close to 300 kg/m3. Most of the scrap parts from foam manufacturers (and maybe other sources) will become this kind of foam. This is produced in blocks and afterwards cut in any thickness. For very thin foam (underlayer), they sometimes glue the ends together to deliver it in rolls. While it starts which all kind of colors from these scrap parts the production process allows to give the final foam a dominant color, which is often used just to distinguish between produced densities. Personally I don't know any other typical brand name than Agglorex (not on the net) making agglofoam, since for lots of producers it's just another type of foam, giving it one of the above names (and maybe others), and major dealers can distribute it under whatever own nice sounding name. It once just started as reclycling for foam in packing. Agglorex got even payed to help other producers getting rid of their scrap. But since one can give this foam properties one can't get with the original foam it's made off, it got numerous technical applications, making these scrap parts a relative expensive commercial item. I can't help you finding local suppliers, and have no idea which name you should look for. You must ask a foam guy there. But be careful. You can look for such stuff, and maybe designing a cheaper floor, IF you know how to handle all this. I don't think you can count on groups to do this kind of work, which normally costs a multiple of the money you save by not using the stuff which is designed AND documented for this purpose. If you build walls which are heavy enough to relate to the isolation of your floating floor, you should take that perimeter line load into account.

thanks for all the info mr.Desart....i really apreciate it :D i search for bonded foam here in Greece (well on the web) but didn't find anything...so i guess it's not widely used over here... i'll try to get these sylomer people since as i get it this is the best sollution ...on the other hand i want to get more in to the fiberglass - concrete thing as an allternative sollution Here is the link for the isover products http://www.metaxiotis.gr/en_catalog/2/B ... ospect.pdf as i allready told it is written in Italian :shock: but i couldn't find anything in english with these specs.....and i did search!! i've attached a plan of my structure...the inner walls should waight about 35kg/m2 In a hypothetical case where i've found a fiberglass panel with the proper specs regarding deflection, thickness, density etc do you think that i should use a more dense panel around the perimeter of the room because of the greater load? My intence is to build the whole thing as good as possible regardless the cost....so i'm not searching for a cheaper sollution but for the best one regarding the fact that i am in Greece.... Nikodemos

I come back to this later. http://www.isover.com/SiteContent/view.do?navId=72 What is Piano GB. I assume that piano stands for silent, hence some special type (:) or special name) for Gypsum Board?

Nikodemos, you stated the folowing:

i was under the impression that if there is a continious underlayment under the concrete the load would spread equally on all surface...no? anyway i was under the impression that with a reinforced concrete slab of 15cm the load of the walls would be insignificent.....

Your impressions are incorrect on both counts. Concrete will flex under load - there is no way for you to take an edge load out of the equation with a 15cm slab. Although that gives you enough mass to lower the center frequency of the slab to a range suitable for music - it is not going to be rigid enough to do what you suggest - not unless it is a very small slab in area - and then still only if your wall loads are fairly balanced in weight (which is not suggested by your sketches). a thicker slab could perhaps (with the right reinforcing design) be designed to do what you suggest - but the engineering and construction costs would not make it worth the while....... On another note- your details introduce a perfect flanking path back into structure....... While hanging the ceiling is acceptable (I would rathr see the inner walls carry the load and comlpetely decouple them from the structure) the walls should stop at the ceiling........... Connecting them to the floor above is your weak point - this from 2 perspectives - one the connection to the outside structure you're tring to isolate yourself from - and the other being the possible lowering of TL values due to the 3rd leaf you introduce into the equation. Let them end at the top of the inner ceiling framing - and then you can use either isolating lateral braces tied to the structure above for seismic bracing - or do the same off of the adjacent walls that do tie to the structure. Diagonal bracing consisting of (either) an iso-spring or neoprene iso hanger can serve as a very effective bace for the inner structure - as can the WIC clips manufactured by Mason Industries that would attach to the adjacent wall assembly. Either way - this is your best construction method to acheive maximum isolation with your assembly. Please describe in more depth your wall assembly - it would be a shame to have walls that did not equal the isolating capabilities inherant in your slab when all was said and done. Sincerely, Rod

mr.Desart Piano is gypsumboard from Knauf with higher density (10,7kg/m2 for the 12,5mm board instead 9kg/m2 of their average boards) mr.Gervais first of all thanks for checking this thread :D i was afraid that most of my conclusions were wrong :oops: however my question is: if i must go for a mineral wool - concrete floating floor(that is if i don't make it with the syllomer and equals) what should i do regarding the walls load matter? should i put on the perimeter of the room more dense wool? and how could calculate how dense and how wide? I'm not trying to get advices for free here, believe me, but i've talked to some "profesionall acousticians" here in Greece and they didn't have a clue what we were talking about.....so i feel a bit lost :shock: Regarding my wall plan and especially the inner wall - inner ceiling joint i've been asking this very same question(with a drawning) in this forum http://www.johnlsayers.com/phpBB2/viewt ... c&start=30 but unfortunatelly i didn't come up with an answer.....i do think that this is not the best approach to do it regarding TL but: i talked to quite a few drywall technicians and nobody had experience on such a structure....that's not a good thing!! Also i found this aproach on Everest's books....and i was really concerned about the liability of such a structure regarding it's stability...you see i don't have your knowledge and experience and as far as i can say greek drywall technicians don't have a clue neither.... Of course i'll take your word on it....i have your book, but i couldn't find something on this(or i've missed it :oops: ) because i think your book aims mostly to full drywall assemblies and not to concrete buildings...and i, probably due to lack of knowledge, couldn't transcribe things to match my situation. I would be greatfull if you could get in some details on "how to do it" Now some info on my wall plan: on the outter side of the studio 25cm reinforced concrete - 10cm of cavity filled with 30kg/m3 glass wool - 3 layers of 12,5mm drywall(knauf piano 10,7kg/m2) on 100mm steel studs filled again with glass wool. on the inner side(between rooms): 3 layers of 12,5mm drywall(knauf piano 10,7kg/m2) on 100mm steel studs filled with glass wool - 10cm cavity filled with 30kg/m3 glass wool - 3 layers of 12,5mm drywall(knauf piano 10,7kg/m2) on 100mm steel studs filled again with glass wool. I'm also thinking of putting a layer of grrenglue between 1st and 2nd layer of drywall everywhere and probably to add another layer of gypsumboard in the main recording room's inner wall in order to get different masses on walls and smooth out the resonanse freqencies between walls. Finally on the inner wall of the practice room i plan to add a 3mm layer of lead between 2nd and 3rd layer of gypsum board to add even more mass with minimum space loss. I attached my initial wall plan Nikodemos

I would attack the design like this: Rod

Mr.Gervais First of all thanks for your help and interest i'm going to meet with an engineer friend of mine who's helping me with the project and show him your approach. I have some initial questions: would it be possible to use this way of decoupling you describe fot the wall - floor joint, for the wall - ceiling joint? In my basement the height is 3,45 m but there are some points (i think it's joists the right word? :oops: ) where the height is 2,90m. I f i get it right from your plan with this way the height of the inner ceiling is defined by the minimum outter ceiling height (3,45m)right? I was wonderng if there is a way to build the walls all the way to the concrete ceiling and decouple them from it the way you describe the decoupling from the floor. Can these decoupling braces be used in a ceiling - wall joint or they work only under load? I underastand that your approach is the correct one and why this happens but i am concerned about the height. With your design is there a way for the inner ceiling to follow the concrete ceiling height? and another question: when you say 3 leaf in my plan you mean the inner ceiling and the 2 walls? if theoritically i could perfectly decouple the walls from the ceiling in my plan would that 3 leaf effect be important? thanks again for your help and your advices :D Mr.Desart I've spent the last 3 days researching mineral wool in Greece regarding properties, availability, brands etc. and i REALLY understood what you describe in your studiotips "thoughts on minerall wool" post.....In every country the same brand has completely different products with different specs making the research for a suitable product probably impossible....Here in Greece glass wool is not the first choice in building insullation so there are not too much choices in brands and types in the market plus tha availability is questionable. Also for such a small project as mine (compared to the construction industry) the supliers seem to be quite unwilling to provide info and specs(even unfriendly sometimes!!!) On the other hand i there is lots of rock wool products manufactered here in Greece with their specs available. I looked in the isover link and compared the info on impact and airborne noise reduction regarding thickness, dynamic stiffnes etc to Geollan 100kg/m3 rock wool panels and it looks as it could be a product that could fitt in....what do you think about that? i mean rock wool in general Also could you tell me what you think about my inner wall plan..... thanks A LOT!!! Nikodemos

Nikodemos, I had no time yet going more in-depth. You got a nice suggestion from Rod already. About the differences in rockwool and fibreglass. You read right. There is the difference in geographical raw materials (minerals), the different things they mix it with to make these melted minerals optimal spinnable, binding additives, production method, etc. But: when using the stuff for absorption, it all doesn't matter that much (taking into account that rockwool by thicker fibre is mostly denser/heavier for same functionality), but when using the dynamic stiffness, elasticity and compressibility it becomes more important. I had a discussion with Rockwool here, and have measurement data in function of dynamic stiffness from WTCB (national Building research institute). In theory it works as good as fibreglass, but since the fiber of rockwool (as I know it) is more brittle, the producer does not allow the same deflection under load than fibreglass with the same dynamic stiffness. I think in general fiberglass is more elastic, which in in favour for floating floor principles in function of higher allowed deflection. Hence my experience and research tells me that rockwool while used a lot for floating floors and resilient skins (floating walls), they are applied within standard building frequency ranges. They do not allow enough deflection in % of the material thickness in function of degeneration of the fibers. Hence as I know it here, Rockwool floating floors are not ideal for very low resonance floating floors (studio applications). Fiberglass is more elastic and seems to allow higher deflection rates and still guarantee long-time behavior. That makes fiberglass a better material for this type of studio applications. I'm rather sure (my belly), that your idea of fiberglass calculated on the normal load, with high denser fiberglass at the edges to compensate for the wall weight IS possible. But this stuff is badly documented for these purposes, and even if I should calculate this for Isover boards here, in how far can this be translated to whatever boards you buy there, EVEN WHEN THEY ARE FROM THE SAME BRAND? In order to make standard building stuff commercially attractive they produce in different factories to cover local regions. They even buy existing (former competing) factories with there own raw material sources and production methods to expand their teritory. Rockwool boards in Belgium are somewhat different from these in Germany, as well in code as well in how they look and feel. To summarize: for floating floors with studio-low MSM frequencies I should NOT resourt to Rockwool as I know rockwool. I think with fiberglas it should be worth investigating, even for an application with walls at the edges as you drafted it (adjusting densities). But that cost time, cooperation with the producers to get data, they likely have but don't publish, etc., and I certainly should not guarantee one could copy this exactly for boards from other factories. Density and stiffness are not always nicely related, but are a combination of fibers, the added chemicals, and the binding process. There are rockwool and fiberglass blankets +/- 90 to 120 kg/m3 feeling really soft as a blanket. That's because there (almost) aren't binders in it, therefore the wool is even stitched with metal wire on chicken wire to keep it in place. A 70 kg/m3 base rockwool board used as base for ceiling tiles (self carrying) feels/looks quite different (more stable/tight) than a standard 70 kg/m3 board used for thermal applications. I have a couple of OC 703 and OC 705 here, and they feel different from the corresponding Isover boards I know. The safest manner is still to use material as intended and guaranteed by the producer. Therefore all these more technical vibration brands exist.

well, i still haven't been able to contact the sylomer dealers here in Greece and that's probably normal since the last 7 days the whole country has beev on fire with dozens of people killed and whole villages burnt to the ground :cry: :x :cry: .....at the same time we are 2 weeks before the national ellections and so nothings seems to work in these country.....The problem is that time is running......so the minerall wool scenario seems to be the leading one in my case.... Mr.Desart my next question is probably stupid and tottaly anti-scientific (and it couldn't be different since i'm the one who's asking :D ): How dissfunctional would be in my "real world" situation (my studio is based in the basement of a building with an unused parking space above on ground level and with no other buildings attached to it) a minerall wool - concrete floating floor built as calculated as possible but certainly not reaching the low MSM frequency of a proper acoustical floating floor? I mean my concerns are sound travelling through rooms and mainly impact noise and vibrations(i guess) reaching the appartments on the first floor 7m above my floor.....can the sound passing through this MSM system even at these lower resonance frequences trigger such a big mass as the existing concrete structure to vibrate and transmit the sound to that distance? even if they are decoupled (with the minerall wool) from the sound source?...and if so the tranmitted to the 1st floor would be loud enough to be annoying? (i mean to the usuall rood, anti-musician old couple that lives on the first floor above every basement studio :D ) Nine years ago we built a practice room in this same basement and i see it now we did everything wrong :oops: 3 leaf walls, terrible doors etc plus a minerall wool concrete floor....as i can remember it was 7cm of reinforced concrete on top of 10cm mineral wool(i don't remember if it was fiberglass or rockwool or even th dencity...i just remember it was hard :D ) we didn't know anything about calculations or MSM freq or anything.....just some friend told us "do that" :oops: The thing is that even right outside the room door the TL was not high enough (mainly through the door) the TL between rooms was acceptable and most important there was no sound on the first floor....an there was lots of noise there before the floor!!!I know that this floor is not working correctly and that it probably won't last but.....my point is this: could a floting floor of this kind (kind of "domestic") but calculated as much as possible to fit the current acoustical and structural needs(walls load etc) be a wiining scenario for my situation? I hope i don't sound stupid or rude :D Nikodemos

Nikodemos wrote:

....... here in Greece and that's probably normal since the last 7 days the whole country has beev on fire with dozens of people killed and whole villages burnt to the ground :cry: :x :cry: .....at the same time we are 2 weeks before the national ellections and so nothings seems to work in these country.....The problem is that time is running......so the minerall wool scenario seems to be the leading one in my case.... ........... I hope i don't sound stupid or rude :D

:mrgreen: No you don't sound stupid or rude, just very stubborn in a fun manner. Nikodemus, I don't feel safe with rockwool in that situation. Hence I'm not going to advice it, and no I'm not going to guess. You can go to rockwool with 10 cm and follow Rods advice building your walls not on the floating floor. Otherwise don't use rockwool for that floor. The thickness here of 100 mm will make up for the lower deflection rate. :) Now you can rephrase your question in another manner, but this is as far as I go. :( I know about these fires, and it's disastrous. I really do feel with you and these people. And if it's true that these fires are somehow or partly related with guys wanting to use that land for development stuff, they should hang them all on the highest trees (that related land development law of yours). :twisted: And about elections: We had them 6 to 7 weeks back. Belgium was never so divided between our regions. After 6/7 weeks of intense discussions (day/night) on all levels we are as far as the first hour after the election. And at this moment nobody has any idea how to overcome or compromise related real in-depth principle differences. (different cultures related to different languages and economical strength).

Mr.Desart i promise i will not ask another question on the "floor" subject.....until i'll have something usefull to say or show anyway :D thanks for everything Nikodemos

Nikodemos wrote:

Mr.Desart i promise i will not ask another question on the "floor" subject.....until i'll have something usefull to say or show anyway :D

Nikodemos, one of the real problems with using eithe rthe fiberglass or rockwool for the walls is that the loadings can vary tremendously along the wall. For example - a wall 8' in height constructed with 2x4 framing and 2 layers of 5/8" drywall will weight about 6 psf - or about 48 plf (per linear foot). So you caclulate the required density of fiberglass you need to carry that load while meeting the required compression ratios and then you suddenly come to a place where you have a door opening - and you have a point load on the hinge side of about 300 pounds (if you build my super door) and then 1/2 of the header weight - and you can't makre it from A to B with the material you are using............ but you also can't start using small pieces here and there. That's why you really need to look at this very caefully. I actually develop wall elevations with all openings and showing individual studs and calculate for each and every load point individually - especially with rooms that are not rectangular in shape - thus the ceiling load is ever changing,,,,,,,,,,,,,,, I hope this helps you to understand Rod

I remember going through this type of exercise when coming up with my first few floating floor designs, using EPDM rubber pucks as the proposed elastomer. I even purchased a sheet of 1/2" thick EPDM for the purpose and paid a machine shop to conduct some tests on a sample puck to determine its deflection under varying loads. I probably spent months going back and forth with various ideas before finally coming to a conclusion that it wasn't going to work for me, especially in my state where the propensity of earthquakes in some areas (not really mine, thankfully) have had a significant impact on building code strictness. Even if I had come up with a method of calculating all my point loads perfectly, I'm convinced it would not have passed my local building department's initial plan check process. I'm not trying to hijack the thread here, as I've "moved on" and am quite pleased with having done so -- my point is that the process is, as you're finding, very complicated. You seem to have an appreciation for that. :-)