Post by alexandermakhlouf on Jul 3, 2019 0:37:45 GMT
Let me explain my set up before I dive into questions. I’m beggining construction on my basement home studio and I’ve gotten all my dimensions and logistics planned out, but I reached one last decision. How to insulate the ceiling. My basement is unfinished so the joists are exposed all the way up to the sub floor “10ft high from sub floor to basement floor”. I have one foot of depth to stuff insulation between the joists. My goal is to have the best balance of an acoustically sound room AND a room that doesn’t leak loud sound to the house above it. Originally I was going to stuff a full foot of Owens Corning 703 “705 faced in corners”. But after some research and budget constraints, I think the full foot may be overkill. I am now thinking to fill the joists with 6 inches of the 703/705 and the remaining 6 inches up to the sub floor with just R-15 pink fiberglass insulation. I know a vapor barrier is necnessary with the R-15.
Will the vapor barrier be considered a reflective surface and ruin my calculated room dimensions even if it’s above 6 inches of 703/705?
Would roxul/rockwool be a better option instead of the R-15 pink stuff?
Would it be a better option to have an airgap after the 6 inches of 703 and then just another 2 inches of 703 touching the subfloor?
Or was the original plan for the full foot of 703 the best option and I’m just overthinking and should just pay the extra money haha?
Hopefully you guys can help with some advice. Thanks!
You only want to go 8" max thickness of rigid like 703. You can go as thick as you like with fluffy - the upper practical limits being around 3'. No one can say what putting FRK between layers of fluffy and rigid would do. I'm not entirely convinced that the fluffy needs a vapor barrier.
First, it is my understanding that a vapor barrier in walls/ceilings between living spaces should be avoided. Check with a competent builder for the correct answer.
Now to add to the confusion, we talk about using foil or kraft paper with bass traps to enhance LF performance, but we don't try to block water vapor from traveling between rooms.
About sound transmission between rooms, that is a different subject and requires different techniques than acoustic treatment. The main idea is that you need M. A. M. configuration (mass - air - mass) the two mass components are typically drywall of 2 to 3 layers thick and should be vibrationally isolated (not touching each other). The "air" layer is where the insulation goes but this insulation will not treat the room acoustics, you'll still need treatment on the inside of your room.
So...you can fill your joist space with fluffy and cover with fabric but that will do only a little bit for transmission. For better transmission isolation, add mass to the underside of floor between joists (if the upstairs is open and can be worked on, just add mass to the floor above, but that is usually impossible). Fill between joists with fluffy, then either build a room within a room OR easier, use RC (resilient channel) to isolate the ceiling layers of drywall from the joists. Check with your builder to see if the existing structure will carry the additional load.