[gacole2000]

I am working on my dedicated theater today. The insulation I got is wrapped in plastic. The R-38 for the floor joists has little holes in it but the R-13 for the walls does not. Should I remove the plastic for better absorbtion behind the drywall (double layer w/ green glue and ISO clips on a common wall and the ceiling)?

Thanks- Greg

 

[tonyvdb]

Removing the plastic will not improve the absorption of the insulation once it has been placed behind the drywall so just leave it particularly if the is an exterior wall as you must have a vapor barrier between it and the drywall.

 

[gacole2000]

Thanks!

 

[Ted White]

I agree with Tony. The absorption, especially with mid and lower frequencies will not be negatively affected with the plastic.

The ceiling would be fine with R19, also. If you have the R38 already installed, that's fine.

 

[Space]

A vapor barrier(plastic) should be one, not multiple layers as this will develop a dual barrier and essentially lock moisture inside the two.

 

[Ted White]

Curious if that would be the case if the plastic bag remained sealed?

 

[Space]

It is running a risk, in my experience.

But everything matters, and I know very little of the build perimeters as of this post.

Just throwing this out as there is often confusion on what a barrier is, do I REALLY need one, where it should go, do I need more then one, etc.

 

[Ted White]

Got it. Thanks

 

[gacole2000]

I have those same questions! This is a basement build. 2 new walls w/ ISOMAX clips, double drywall and greenglue (ceiling also). The exterior foundation wall I treated with heavy Drylock (wrapped corner). The other foundation wall has the garage above it. Never had any water issues. I plan on using the R13 left in the plastic, solid side facing the wall. Yes, it will be a tight fit, but I can make it work. Any advice is much appreciated. Thanks!

 

[Ted White]

Are your two new walls up next to foundation walls or shared walls with other rooms?

I assume the bagged insulation is rated for exterior walls, though I've never inquired.

 

[gacole2000]

New walls go to common areas. It is rated for exterior walls. It will not be sealed as it comes in a roll and I cut it to length so the top and bottom are open.

 

[Ted White]

Had you considered staggered or double stud walls? Great low frequency performance. Might save a few $. Or use the clips on the ceiling, maybe.

Just a thought

 

[gacole2000]

Considered it, but I needed to decouple the header from the floor joist, so I went with the clips and will be using them on the ceiling also.

 

[Ted White]

Obviously that's fine. You'll love it.

For others that may be reading, and have interest in a double wall, you can also decouple the top plate of the inner wall from the joists with a different type of clip.

 

[gacole2000]

I took out some beams so that wall became load bearing. I'm turning my riser into a bass trap and will put treatments on the walls. My weak link is probably my return air vent. The HVAC guys didn't catch my concept. I did line it with insulation and a layer of drywall (used flex ducts w/ 2 90 degree angles).

 

[Ted White]

Thanks for that clarification. So a fixed single load bearing wall. Installing a 2x4 wall in front of that would eat up too much room space at this point.

Clips decouple and are designed for such instances where you can't conveniently decouple with staggered or double stud.

 

[Ted White]

Curious, are the air ducts in a soffit or ceiling?

 

[gacole2000]

Ceiling.

 

[Ted White]

I see. Had you thought about placing the duct in a soffit? Better isolation is why I ask.

 

[gacole2000]

Too low of a ceiling and space constraints. I wish I had more room, but I am working with what I had.

Thanks- Greg