[mccabem]

In my new construction basement theater, I plan on having the stud walls about 3/4" to 1" away from the bare concrete foundation walls.


Should I place some of the rigid insulation sheets on the back side of the stud wall between the studs and the concrete? I am placing R-13 insulation in the stud wall and thought this would help keep the r-13 insulation from getting moisture from the foundation walls. (It's a new home and we haven't had any moisture issues but thought a little prevention might help).


This is a "room within a room" construction designed theater. Will it be ok if the rigid insulation sheet is in contact with the stud wall and the concrete foundation? I wouldn't think it would transfer any measurable amount of low frequency to the foundation wall, but would hate to diminish all my other efforts of sound isolation.


Any thoughts?


Thanks,

Matt

 

[foolsandkings]

I am in the same situation. My builder (and another guy in the building trades in my neighborhood) have both advised to used construction adhesive to attach rigid foam board directly to the concrete, and then leave a 2-3" gap between the foam and the 2x4 walls.


This is based on heat insulation and mold risk more than acoustics.

 

[ShaunM]

I used rigid foam and built the stud walls tight against it. I used it for warmth and moisture issues and I don't know what kind of acoustic value(if any) there is in it's use.


Here is a link that has a lot of information on why rigid insulation is a good idea.

http://www.buildingscience.com/resou...ns/default.htm

 

[Craigo87]

I also used rigid foam board on my basement walls before putting in studs, insulation and sheetrock. But before I glued the foam board to the walls, I painted them with some of that white Drylok paint specially designed to seal against moisture leaks. Although we don't have any cracks or water infiltration now, it was pointed out to me that things change, and what was dry one year may become wet another. Didn't want to be accused of being penny wise and pound foolish.


Craigo

 

[Andy238]

Ditto here. I put 1" pink rigid foam up with glue and have my 2x4 studs tight up against the foam board. I'm planning on putting in some R-13 batts as well. I looked at the BSC website and they recommend non-faced batts between the foam and sheetrock. Trouble is I can't find R-13 unfaced insulation! They (HD Lowes) do have like R-19 or higher in unfaced though. I guess I'll have to squish it in a bit.

 

[foolsandkings]



Quote:
Originally Posted by Andy238 /forum/post/0


Ditto here. I put 1" pink rigid foam up with glue and have my 2x4 studs tight up against the foam board. I'm planning on putting in some R-13 batts as well. I looked at the BSC website and they recommend non-faced batts between the foam and sheetrock. Trouble is I can't find R-13 unfaced insulation! They (HD Lowes) do have like R-19 or higher in unfaced though. I guess I'll have to squish it in a bit.

It's a nuisance, but you can easily peel the paper backing off the insulation rolls or batts.

 

[Andy238]

Now why didn't I think of that

Thanks for the idea. I may do that if there is a huge price dif between the faced and thinnest unfaced insulation.

 

[Randy D]

I've seen it suggested a number of times on this forum to score the paper with a utility knife to allow moisture to escape.

 

[SatelliteGuy]

At first, I was going to leave an 1" air gap between the concrete block and the new framing. Then after discovering several bee hives and mice dropping within my walls and ceiling, I turned away from this idea. Imagine having a small mouse and / or bees trapped between your walls.


After reading about this subject on several sites, I have decided to use 3/4" rigid foam between the concrete block and the framing after applying two coats of Drylock. Some sites recommended not using a vapor barrier. I believe this is only when you use the 3/4" rigid foam board. However, I am unsure about this.


For insulation I am going to use this UltraTouch product made out of recycled blue jeans. http://www.natureneutral.com/php-bin...v_id=&next_id=


Not only is it flame retardant and mildew and mold resistant, it is applied needing no googles, gloves or face mask.

 

[SatelliteGuy]

I believe the insulation needs to be un-faced batts when using 3/4" rigid foam, because a dual vapor barrier would then exist? Is this correct?

 

[ecrabb]

Technically, the XPS is a vapor retarder, not a barrier... But, yes, you should use unfaced batts when using XPS foam - assuming you subscribe to the Building Science Corp methodology. Don't forget guys - the Building Science methods may be at odds with your local building codes so consider that if you're pulling permits or you're sensitive about doing things the legal way, rather than what potentially may be the best way.


SC

 

[Wilds]

Squishing insulation down makes it loose a lot if its insulating properties. I don't know to what extent, but I know it shouldn't be done. It would be better to strip or cut the paper from R13.

 

[Brian Ravnaas]

mccabem,


if the foam is touching the concrete, the results won't be bad. If (as an example) you had the studs spaced out from the concrete and put the insulation on the back of the studs so you had


concrete

air

insulation

studs/R13

drywall


that would create a triple leaf and have some potential for causing trouble. You would then have a low-freq resonance situation of studs+drywall+foam resonatiing on that small air cavity.



But if it was


concrete

insulation

studs/R13

drywall


That won't be a problematic, as it won't create a situation where a mass-spring resonance is occuring on a tiny air cavity.


I would recommend the cheap, typically white, granular styrofoam over the more expensive, more rigid, blue or pink kind in this case.


double drywall ont he studs will also go a way towards alleviating any concern.

 

[mccabem]

Brian,


Thanks for the reply. There is no air space and I am double drywalling. Good thing your response agrees, I've already glued these to the wall.

Matt

 

[Andy238]



Quote:
Originally Posted by Brian Ravnaas /forum/post/0


double drywall on the studs will also go a way towards alleviating any concern.

I'm using the latter of the two examples from Brian. I know DD is best for walls between interior spaces and ceilings. But is double drywall on the wall against the concrete a big benefit?


Andy

 

[Winkelmann]

Getting the landscape drainage and the drain tile right is the best assurance for a dry basement. I live in Atlanta and I can tell you, there is no such thing as waterproof. Water resistant would be more fitting. When we get gully washers, after a dry spell, even the best made roof can leak; basements are no exception. Foam sheets will not stop water. It is my understanding that rigid foam is meant to help keep vulnerable building materials (such as untreated lumber and sheetrock) from contact moisture - which will feed mold.


Based on the public profiles of those who've posted, what do the codes in your area require?

 

[Andy238]

I'm not sure specifically what the code requirements are but I did submit my plans to get a permit and did spell out what the wall construction would be (ie, rigid foam, unfaced fiberglass batts, & drywall). They didn't kick it back or say anything about not being able to do it that way. Hopefully they aren't going to wait until my inspection to tell me that!

 

[SatelliteGuy]

I read XEPS 3/4" rigid foam board should be used along with unfaced insulation or an 1" gap between the block wall and framing with faced insulation. I believe I have choosen to go the XEPS 3/4" rigid foam board route, because it lets me use the new cotton UltraTouch insulation. Also, I feared mice and / or bees and such becoming trapped between the wall if I went with the 1" air gap.

 

[Thomas Willard]

If you are going to use double drywall, one inexpensive way of adding a little (R-1) insulation, but good noise control is to sandwich a layer of the rigid pink insulation that comes fan folded and is used for backing under aluminum or vinyl siding. I did not use double dry wall but did use this rigid insulation on a common concrete wall between my unit and an adjoining unit before adding the studs and fur stripping to which a fastened the single sheet of drywall. This helps in controling the sound transmission.

 

[mfino]

This thread has some good information, but I'm stuck with a quesiton.


How far do you go up the wall with the Rigid Insulation boards? Do you go as high as the foundation wall itself, or do you extend past it and go up to the top plate of the stud wall, leaving a cavity behind?


thanks.