question about layers of insulation in scotts (small) studio

hi.. this is my second post so please go easy on me.. i think i'm finally getting a handle on the principles of wall construction, slowly moving towards a point where i actually understand what all the different materials do and where it's possible to improvise a bit and where it's absolutely necessary to apply proven principles. i'm working in a small (9'x19'x9') detached garage (i posted some pretty , uh, delusional prelim. plans in the design forum under "9x19 ft garage studio" ) and per john's advice have decided to base my construction on the "small studio in 3d" (scotts i believe) that's been sticked on the forum... anyhow, i have a question about layers of insulation that i haven't been able to find a clear answer to (probably right in front of my nose, but believe me i've searched!).. in the sketchup plans for scotts it appears to me that there is basically a frame built inside the walls of an existing structure, that this frame is insulated with 2" 703 or whatever (though the insulation is set back into the stud cavities and not flush against the inside wall panels) and that a number of resonators and cloth panels are mounted along this interior frame. what i'm confused about is whether or not there's a leaf (of sheetrock? wood?) between the inside of the frame and the resonators/panels , whether or not the the resonators and panels pictured have their own insulation boards or are simply built against the insulation in the frame, and, if the frame is insulated separately, whether it would be advisable to pack the whole frame with 703 (as opposed to using the pink stuff and saving the nicer boards for the traps/panels/resonators).. i hope my questions make an ounce of sense... thanks loads in advance for any advice you all can provide! take care bryan

Can you provide a link to the design you're talking about? It sounds like an "inside out" wall to me but I'd have to look to be sure. If it's a "normal" wall (i.e., drywall facing the inside of the room), OC 703 is going to be a wast of money. The main purpose (as I understand it) of the insulation behind the drywall is to dampen it's resonance (like touching your finger to a cymbal). If, one the other hand, the insulation is covered with cloth of some sort and facing the inside of the room, you'd want the 703 (or mineral wool or something else dense) for it's acoustic properties. This "inside out" type of construction is mainly used when you don't have enough floor space to add acoustic treatments ON the drywall after the wall is built in the "normal" way. I hope that clears things up a little. len

hi len thanks for the reply! i think i understand what you're saying; 703 is useful for treatments on the innermost layer of the room (i.e. in absorbers mounted in the inside walls).. it's not economical as a frame filling insulation because this serves no acoustical purpose other than dampening sound as it resonates in the drywall.. that about right?? what i'm still confused about is whether or not, in these particular plans -- http://johnlsayers.com/phpBB2/viewtopic.php?t=5457 (it's the sketchup plan in the "design" forum eight or nine stickies down from the top under "small studio in 3d) there IS any drywall on the inside of the frame, or if the cloth panel aborbers and slat resonators are basically just mounted straight on the frame (which has its own insulation in between the studs).. in the pics john posted under "scott's studio" in the studios under construction part of the site, it appears that scott is packing the frame with fairly dense insulation , but i don't see any drywall going up over the frame before the treatment panels.. again, sorry if this seems semantic or something! i greatly appreciate your help thus far.. i'm trying to clarify this because in my case i don't have a lot of floor space (9x19ft) and it would be economical in that sense to build an inside wall frame with suitable geometry and then just mount all my treatment stuff onto that frame without building a wall against it first.. again, though, maybe i'm way off! thanks again for any help.. bryan

It appears to me that there is NO drywall on the wall at all. As long as the wall the frame is up against won't transmit sound (or allow noise in), this would work great. He has stuffed the cavities with mineral wool batts, a very economical and very effective solution. The only drawback I could see to this construction would be having exposed fabric all over the walls and cieling. Very tempting to pencils and small fingers. Any equipment or mic stands that fell over might just puncture all of your careful fabric stretching. You should note that if you build this way, you won't NEED to build any panel absorbers inside the room because it will be essentially completely dead. You might need a little in the corners to tame the LF but that should be about it. len

thanks len! two more quickies: i found 8# mineral wool batts for 39.00/48sqft is this too heavy (dense?) to use in the stud framing? i guess i'm confused as to whether pcf and the # marking i see attached to mineral wool are the same.. if so i imagine 8# would be way too dense..? if slat resonators/panel absorbers are unnecessary in a room insulated as youve described, why do you think scott's studio has so many? it appears that, in his plans, every wall of his rooms is covered in either slats or a cloth panel absorber.. i assume he wouldn't have put them there for no reason.. i dont mean to challenge what youve told me, i'm just trying (as usual) to understand his line of thought.. thanks for all your help; it's been fantastically useful to me! b

I wonder if it's pounds per square foot... :roll:

sharward sorry i am missin something? does 8#/sqft have a pcf equivalent? how do i factor in/out the extra dimension?

It sounds to me like 8 pcf mineral wool but that would be just a guess. It would be best if you confirmed it with the supplier. Try SPI in the references. I was told by Knightfly 8 pcf would be a little too dense so I got 4 pcf. You should be able to get mineral wool a little cheaper than that. I think I ended up paying about .60/sq ft for mine (4" thickness). As to Scotts reasoning, it may be that what he did was make separate removable cloth covers for his walls instead of additional absorbers to go over the mineral wool. The slotted resonators can be used to bring back a little life into a room that was made a little too dead by all the absorbtion since they will reflect the highs back. You would also have to seal the area behind the slats for them to be effective. It is in your best interest to ask questions until you understand and to question, especially advice from me, if it doesn't quite sound right (no pun intended) to you. len

len, thanks again! i'm glad you dont mind my prodding for advice too much... it's great to finally engage in a little bit of dialogue? conversation? as opposed to just reading and reading and reading (though they clearly both have their benefits!) if i were to build cloth panels that fit onto the wall frame to cover the insulation , would i want the rockwool in between the studs to be flush against that cloth/frame, or would it not really matter? also, if the slat resonators need a sealed cavity to work,it seems like i would basically have to build them as standalone absorbers even if they're just mounted against the studs.. is this correct? otherwise i'm not sure how i'd seal off the area behind the slats..(maybe with tons of special caulk or something?) moreover, in that case i'd have to put new insulation behind the slats inside the sealed cavity, right? everything becomes clearer and clearer and more complicted all at once! b

rasdestroyer wrote:

sharward sorry i am missin something? does 8#/sqft have a pcf equivalent? how do i factor in/out the extra dimension?

All I saw was "8#" which is ambiguous. I was just wondering if the measurement you were getting from the supplier was per square foot. After all, they price it by the square foot... :roll: It's probably cubic (should be), but it wouldn't hurt to confirm that. --Keith :mrgreen:

rasdestroyer wrote:

f i were to build cloth panels that fit onto the wall frame to cover the insulation , would i want the rockwool in between the studs to be flush against that cloth/frame, or would it not really matter?

Only for how good it looks. If the insulation sticks out too far, you're going to see it "poking" through the insulation (like a baddly stuffed pillow). You would have to pay close attention to how you attach the cloth frames though so that they wouldn't rattle against the studs. Also, if you chose this construction technique, you couldn't use pink fluffy insulation - it's not nearly dense enough to work. The mineral wool (or similar product) would be best. As far as your slat resonators go, considering this construction method, yes you'd want stand alone absorbers. Not a bad thing really. I just want to emphasize that your are no where near the point of taking hammer to nail yet. You're going to want to have a design drawn up (use SketchUp from Google), and then have everybody here kick it around before you start unless you want to risk doing a lot of work and spending a lot of money that you'll have to lose later. Believe me, the more time you spend planning and redesigning, and "building in your head", the faster and better your end result will be. I know the smell of sawdust is a strong pull but resist the urge until you are ready. len

len, sharward, thanks for your tips! don't worry, i'm not itching too hard to erect an ill-fated design; i think if there's anything i've gathered from the forums thus far it's that it's easy to build and build and build and still not accomplish acoustic/isolation goals if basic principles/procedures are ignored.. i think i'm getting a handle on my insulation needs (at least for this stage in the design process).. next i need to figure out the actual floorplan.. i'm very fond of scott's design, as the dimensions of his room and mine are very similar (minus the ceiling - i have a slightly graded roof that is 9 feet at its high end and 8' 6" at its low end) .. i'm not sure if i should relocate my posts to the design section or just continue to expand this thread? in any case, i guess i have to back up for a minute and draw some stuff out to submit to you all before i move forward.. thanks loads for your help up until this point.. i shall return asap! b

At this stage, you're probably better off moving over to the design forum since it appears you've got your insulation questions answered. It can be difficult for newbies here (and the 'ol timers for that matter) because it could go either way. Insulation is a construction material but you aren't building anything (yet) but you can't really finish your design until you have some of these material questions answered. My suggestion: Start a thread in "studio design" and keep it there until you are ready to start building at which point you can move back to "studio construction" unless at the design stage you run into some trouble figuring out wiring and need to ask in the "wiring" forum. Use your best judgement. len