Please Help - problem installing Mineral Wool in Ceiling

[corleyd]

I have been lurking/reading for a year+. I am about 1/2 way into construction of a one room practice/recording facility. I need help.

I have a 16'x23' room with 10' ceiling. Right now I have a standard construction box shell- 2x4 stud walls on slab with 1/2" osb and 1/8" hardiboard siding. To beef up the "outer leaf" of my two leaf wall/ceiling design, I have added a layer of 1/2" MDF in between the walls studs and ceiling joists - glued and nailed and acoustic caulked all edges. Of course this makes my ceiling's outer leaf only the 1/2" MDF with the attic area above.

PROBLEM - I bought locally my 3" acoustic insulation batts called Thermafiber. They are 2'x4' batts but have no backing or facing - just the mineral wool in a slab. Trying to get the batts into the ceiling has been a major headache. First I tried them with the wire supports used for normal type insulation but the acoustic batts were too heavy for the wire. Then I tried mounting my RC to the ceiling joists so that the RC would act as a slat. But the 3" opening between the MDF and the RC is tight and the acoustic batt just falls apart as I try to force it into the space. I tried using a 1/2" piece of plywood as a platter to hold the batt, then push up against the MDF to compress the batt, and hope to slide it in. But the batt clings to the MDF and crumbles.

How can I get it in there? Could I enclosed the batts with a cover of thin plastic to keep it together or would that destroy their acoustic role?

Could I enclose the batts with butcher paper?

My only other thought is to place the batts on the drywall that will go up onto the joists (using a drywall jack). But this would be tedious because I would have to cut slots in the batts where the RC crosses as well as it would be difficult getting the batts/drywall exactly lined up with the ceiling joists so that the batts fit in between the joists.

Help. Ideas?

Thanks,
Dennis

[knightfly]

Using either plastic or paper over the batts won't be noticeable at all when they are behind drywall, so if that works for you I'd go for it.

If not, I would remove the RC temporarily (it is screwed and not nailed, right?) place the batts one at a time between the joists, and retain them with 1/2" wide fiberglas strapping and staples (long ones) into the joists. Then re-install the RC and CLIP the fiberglas strapping so that the batts sag against the RC - That way, once the drywall is up, the batts will bear down lightly on the inside of the drywall panels and give a degree of damping to the drywall panels. This helps transmission loss noticeably.

Either way, covering the batts with plastic (even garbage bags) isn't a bad plan... Steve

[corleyd]

Steve,
Thanks for the feedback and your trash bags suggestion. I tried it last night and it worked. Thank you. I was really frustrated. It is tough enough to deal with the sheer amount of work it takes to build this room. It was just over the top when I couldn't figure out how it was going to proceed past this bump.

thanks again,
Dennis