Vapor Barrier (ie plastic sheet) over insulation... - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 8 Old 02-10-2015, 10:34 AM - Thread Starter
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Vapor Barrier (ie plastic sheet) over insulation...

Have the drywall off now and the exterior walls have vapor barrier sheets (plastic) covering the pink stuff. For soundproofing is this good or bad?

I know there is nothing I can do as I think the VB is a required thing, so curious what it means for any soundproofing I am doing. I am inclined to just leave the pink and then do my DW over the clips/channels.

I can't imagine the plastic sheets are acoustical transparent so curious what effect they have.

Thanks!!!
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post #2 of 8 Old 02-10-2015, 11:56 AM
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Vapor barriers are sort of an oxymoron in how they work. The idea is to keep exterior moisture/vapor from coming into the living space , but if there is any moisture present, it will trap it in the wall studs and insulation if there is a vapor barrier over the studs. This is where all of the bad mold and mildew comes from. So, if your basement is not sealed from the outside, putting plastic on top of studs and fiberglass is really not a good thing to do -- Even if required by code.

A better remedy is to coat the interior cement/block with a water-tight coating. I use a 2 part polyimide epoxy on concrete for this and many other coating work my company does. It's cheap and not hard to do, but it is very messy and very smelly. In fact it is deadly if used in a confined space without proper safeguards, clothing, and breathing equipment. So, not something I would ever recommend a home owner/handyman do, but it is the best answer for existing basement vapor protection.

I am currently doing my own HT. One of the very first things I did was coat all the floor and walls this way. I had a dry basement, so there wasn't any need to any water abatement/mitigation, just the coating system itself. With a properly waterproofed basement, there isn't any need for any vapor barrier, except in showers/sauna's/baths and such.

-Rodger
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post #3 of 8 Old 02-10-2015, 12:21 PM
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Quote:
Originally Posted by manfrog View Post
Have the drywall off now and the exterior walls have vapor barrier sheets (plastic) covering the pink stuff. For soundproofing is this good or bad?

I know there is nothing I can do as I think the VB is a required thing, so curious what it means for any soundproofing I am doing. I am inclined to just leave the pink and then do my DW over the clips/channels.

I can't imagine the plastic sheets are acoustical transparent so curious what effect they have.

Thanks!!!
I will tell you this...I had a vapor barrier in my basement on all of my cement walls. The other half of my basement was a walkout and was not cement. This vapor barrier was a BAD idea for us. It caused a diaper effect of some sort and trapped moisture in between the cement and the plastic. I ended up having to rip all the top row of drywall down and pull all the plastic out. Every single bay was very wet...tons of moisture built up after only a week. It was literally soaked in there. I had heard from several contractors that they use vapor barriers, but after my experience i could never recommend this to anyone.
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post #4 of 8 Old 02-10-2015, 12:52 PM
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Quote:
Originally Posted by marjamar View Post
Vapor barriers are sort of an oxymoron in how they work. The idea is to keep exterior moisture/vapor from coming into the living space , but if there is any moisture present, it will trap it in the wall studs and insulation if there is a vapor barrier over the studs. This is where all of the bad mold and mildew comes from. So, if your basement is not sealed from the outside, putting plastic on top of studs and fiberglass is really not a good thing to do -- Even if required by code.

A better remedy is to coat the interior cement/block with a water-tight coating. I use a 2 part polyimide epoxy on concrete for this and many other coating work my company does. It's cheap and not hard to do, but it is very messy and very smelly. In fact it is deadly if used in a confined space without proper safeguards, clothing, and breathing equipment. So, not something I would ever recommend a home owner/handyman do, but it is the best answer for existing basement vapor protection.

I am currently doing my own HT. One of the very first things I did was coat all the floor and walls this way. I had a dry basement, so there wasn't any need to any water abatement/mitigation, just the coating system itself. With a properly waterproofed basement, there isn't any need for any vapor barrier, except in showers/sauna's/baths and such.

-Rodger
Totally agree !!

My basement had water seeping during a major storm here in NE. I did a perimeter drain system and didn't put the plastic for vapor barrier. I am using a dehumidifier, runs usually every 15 days just to get any moisture out of the area.
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post #5 of 8 Old 02-10-2015, 01:49 PM
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Does not matter for soundproofing.

Go to the User CP and fill out your location. I can tell you if it's required based on your location. I try to avoid sheet plastic if I can; in a lot of climates it creates more problems then it solves.

Tim
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post #6 of 8 Old 02-11-2015, 07:44 AM - Thread Starter
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thanks for the help!


A follow-on question though...


Doers the sound go through the vapor barrier? My question related to the insulation behind it now.


If I spend some extra on some "acoustic" Roxual Safe and Sound insulation (I know the feeling on this stuff being a waste of money), but regardless of feeling for the cost/value ratio of the stuff, is the vapor barrier putting up a block (i.e. the plastic sheet) that the sound would not pass through anyways and thus the Roxul is not even hit with the sound?


Thanks again!
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post #7 of 8 Old 02-11-2015, 07:44 AM - Thread Starter
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Originally Posted by Mr.Tim View Post
Does not matter for soundproofing.

Go to the User CP and fill out your location. I can tell you if it's required based on your location. I try to avoid sheet plastic if I can; in a lot of climates it creates more problems then it solves.

Tim

Sent you a PM
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post #8 of 8 Old 02-11-2015, 07:47 AM
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No, for all intents and purposes it does not effect it any more than the drywall in front of it.

If there was nothing else in front of it (eg you had fabric frames with no drywall), then yes it does have some acoustic properties (reflects higher frequencies). Sometimes those are good properties.

Regardless of any sound properties, Safe'n'Sound is great stuff to work with.. worth the extra $$ just for that, IMHO.

Tim
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