2 differend kinds of insulation, or just more of the same?

Hello all! i am looking to do some soundproofing in my warehouse / loft. i have a studio on the second floor, with plywood floors and 1" boards (old school) under those. these sit atop 16" deep joists, and at the moment they are completely bare - so no insulation btw the two floors i have someone moving in downstairs, and am trying to spearhead the 'insulation operation' (if i don't do it, it won't get done) we both rent, but are trying to make this workable for both of us, before they move in. the place is being remodelled as we speak. the warehouse under me is 10k sq ft but my studio is only aprox 1600 sq ft - so there is a bit of a 'reverb chamber' going on below me. there will be some sort of a personal trainer business there, so SOME music, and SOME talking.. but not any classes or aerobics or that stuff.. and ceilings are high (probably btw 16 and 20ft) so i've got some distance (hopefully helpful - esp if there are speakers on the floor, as opposed to up under my floor) my goal is to reduce as much as possible the noise from the downstairs area.. on the lowest budget (of course). is it unreasonable to assume R30 fiberglass, resilient channel and drywall will do the trick? the questions are (for starters) 1 - do i fill ALL of that 16" gap btw us with fiberglass, or only some of it - e.g. using 9" fiberglass and then leaving 7" air?? or do 9+4 and leave 3" air??? does the airgap help?? 2 - is it unreasonable to use 5/8 drywall with resilient channel isolators on the underside of the joists (the ceiling)? Should i go with two layers? thank you!!! Husky

Husky, What you are suggesting will do the trick only in reference to directly beneath your area. Air borne sound will make it back into your space via the rest of the open ceiling as it searches for the path of least resistance. It might help if you did as you are suggesting, and then make certain that you get this past the framed wall boundaries of your room above and mass up the cavity, floor to attempt to mitigate the sound from moving in between the panels. At the very least use acoustical caulk where your sheetrock ends to seal the perimeter.

Thank you, Brien.. yes, the plan is to try to add generous "overage" on the underside - in other words not just insulate directly under me hopefully i'll be able to add about 4 feet in each direction, past the perimeter of my place, to minimize leakage. re. the insulation though: should i fill the whole thing with R30 fiberglass?? or some other kind?? two different kinds?? husky

Conventional insulation would be 9 inch. Do not mix the insulation it gains you nothing that can be proven.

ok great.. thanks! i'll fill 'er up with two layers of 9" the gap is 16" - that's not too compressed, is it? Husky

The one layer of insulation will work. If you want higher isolation then add another layer of mass...or decouple with RC or clips and hat track AND add another layer of mass.

thanks again!!! ok, so your take is that 18" of fiberglass (in a 16" cavity) will not be an improvement over a single layer of 9" insulation? i'd imagine 'more is more' in most cases here, right? or is it better to leave a 7" airgap here?? not sure i can get away with two layers of drywall with gaps.. might have to go for a dual layer drywall situation with no gaps - since this is not in my space, but below me, and i'm essentially making a deal with the tenant downstairs to let me in there to insulate before he moves his business in there. two layers with airgap might be too time consuming. if i can get away with a single layer of 9" insulation and 7" of air, that'd certainly help me in the $$ dept :-) please advise... H

ok, so your take is that 18" of fiberglass (in a 16" cavity) will not be an improvement over a single layer of 9" insulation?

Exactly. There might be a slight increase, but not much. You would be getting into the area of "diminishing returns". The insulation does nothing to stop the sound getting through: it is merely there to damp the resonance inside the wall, and that will be taken care of by the 9". This is a very important function (damping resonance), but 9" will do the job. Adding the other 9" would only help a little extra, and probably isn't worth it.

i'd imagine 'more is more' in most cases here, right?

Yes, but it gets to the point where adding one extra inch does not have anywhere near the same effect as adding the first inch. With each additional inch, the added effect is lower and lower. I mean, you sure CAN fill the entire space, if fire code allows you to do that, but there isn't a lot of justification, acoustically, for doing so.

not sure i can get away with two layers of drywall with gaps.. might have to go for a dual layer drywall situation with no gaps - since this is not in my space, but below me, and i'm essentially making a deal with the tenant downstairs to let me in there to insulate before he moves his business in there. two layers with airgap might be too time consuming.

I'm not sure what you mean by "with air gaps". The space where you will be adding insulation IS the air gap! That is the one and only air gap that you need. Adding additional air gaps between the layers of drywall below will make things WORSE, not better. I think you misunderstood what Brien was saying. The two layers of drywall go directly on top of each other, no air gaps. And if you will have access to the room below, then do yourself a huge favor (and your neighbor too); Like Brien said, put resilient channel across the joists, and hang the two layers of drywall from that. Or even better, use RSIC clips and hat channel. Either of those options will decouple the drywall from the joists, which greatly increases the isolation. That is probably the single best thing you can do here: decouple with resilient mountings. - Stuart -

Thank you, thank you!! this is fantastic news. cuts my fiberglass budget in half!! this was recomended for decoupling http://www.homedepot.com/p/Clark-Wester ... Toe_bbOLea is it a good choice? is there something else that's cheaper / better / easier? you'd mentioned 'hat channel'?? Husky

is it a good choice?

Yes, that will work fine.

is there something else that's cheaper / better / easier? you'd mentioned 'hat channel'??

Hat channel, but NOT by itself! Hat channel looks very similar to resilient channel, and is probably cheaper, but it is NOT the same, and will not do the job... by itself, You can us hat channel (also called "furring channel") PROVIDED THAT you attach it using RSIC clips. Like this: http://www.acousticalsurfaces.com/rsic_ ... _clips.htm http://www.soundproofingcompany.com/ins ... -overview/ So if you use hat channel, you MUST also use the RSIC clips to get the decoupling. So, you can either use resilient channel by itself, or you can use hat channel plus RSIC clips. - Stuart -

If you use RC, it has a load requirement of 5 PSF, as best as I can tell and the insulation should not rest on the sheetrock. Also, read the instructions and do some research on RC installation. You can very well short circuit this material with one ill placed screw...screw since nails are not recommended at all. The material runs perpendicular to the joists, that means at a 90 degree right angle and there are spacing specifications based on the existing layout of your joists and the thickness of sheetrock you are wanting to add.

Thanks for that! Yes, i got the perpendicular part.. makes total sense, of course. re. the insulation weight.. are there any thoughts on how to secure it in between the joists, so it doesn't sag / lean on the ceiling? perhaps stretching some string across the joists? H

There are what we used to call lighten rods, I think the industry calls them this as well as "tigers teeth". This is a thin piece of wire that stretches from member to member, but is just long enough that it forces the rod to dig into the framing and supports the insulation.