# Insulating wall between garage and living area



## omgdiddy (Feb 13, 2015)

I recently found out that the wall between my garage and living area does not have insulation in it. The geniuses who built the home several years ago accidentally(?) insulated the next interior wall (which is closet space) instead. I was going to tear off the unfinished sheetrock in the garage and add insulation to the cavities. The only thing is, I won't be able to staple the paper to the other face side of the studs. Will it be ok to staple it as far in on the side of the stud as I can reach? Or is this going to cause issues? I don't want to rip out the finished sheetrock in the closets because there is a lot of shelfing attached and in the way. Thanks for any advice. Diddy.


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## SeniorSitizen (Sep 10, 2012)

Being this isn't an exterior wall consider insulation batts and don't be concerned with the vapor barrier.


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## Bud9051 (Nov 11, 2015)

Hi omg,
Where are you? In the far north they may still need a vapor barrier but as SS says, being a wall facing the garage there is less concern. I would consider Roxul and it does not have a facing.

Being a garage wall air sealing has double importance, prevent air infiltration and protect from deadly fumes. Seal around all electrical boxes and penetrations. Check current code requirements for drywall thickness.

As far as having a VB the paint on the inside serves as a vapor retarder.

Bud


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## SeniorSitizen (Sep 10, 2012)

If in a cold climate Rosin Paper would make a decent vapor barrier and could be installed much easier than screwing around with a vapor backed insulation. Then insulate.

I like the paint idea being my wife is the painter and loves to do it.


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## Crazyjake8493 (Sep 26, 2014)

I would use Roxul if you wouldn't be able to staple the batts of fiberglass from the other side. The Roxul will friction fit well in place, and will add more sound dampening between the garage and living space as well.


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## Daniel Holzman (Mar 10, 2009)

I had an identical issue with my garage. I tore off the sheetrock, and installed styrofoam blocks cut to fit the cavities. I used expanding foam in the areas where the styrofoam did not fit perfectly. Styrofoam (and the numerous other similar products) has an R value of about 4 - 5 per inch, better than any other product I am familar with, and the styrofoam is not damaged by moisture.


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## Gary in WA (Mar 11, 2009)

No, you don't want to staple it to the side of the stud, called "inset" stapling, allows convective loops around the FG. The faced FG is over-sized to friction fit the cavity, if worried, staple a short length to the top plate, folding it there to press fit the cavity, sounds as if local Code requires it. Our State Code requires a vapor retarder (Type 2 VB) paper (in direct contact with the FG insulation on ALL areas with an unconditioned (garages included) space on the other side, rather than just standard paint (Type 3 VB), check locally. Red rosin paper would not meet our Code with 50+ perms (similar to drywall) compared to kraft faced (1 perm) and won't drip red dye when wet.

Your FG is fine as it meets, actually exceeds mineral wool in an application with wood studs 16"OC, 5/8" Type X on garage side. If in a really cold climate, add foam board (or strips) to the face of the studs to stop thermal bridging, ADA drywall (and fire tape as existing) as mentioned already. This would change the door jamb depth/elect. boxes, requiring extra work... 

Gary


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## Windows on Wash (Aug 30, 2011)

Which FG exceeds the performance of mineral wool? I didn't see the poster specify a type (i.e. density). 

It is often thought that mineral wool is superior for reason other than its moisture insensitivity. What study did you read that shows otherwise?


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## Gary in WA (Mar 11, 2009)

Rockwool; http://www.roxul.com/files/RX-NA_EN...d/Residential/SAFEnSOUND_TECHDATASHEET_EN.pdf

FG; http://www.certainteed.com/resources/Guide for Residential Sound Control.pdf

Granted, the brand of FG may be different and using 1/2" on both (house side) would reduce the STC slightly- on both. They are so close not to worry - within STC 5.

Do you have a link showing otherwise, always open to new info... thanks.

Gary


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## Windows on Wash (Aug 30, 2011)

When did sound enter into the discussion from the original poster? 

Also, you look at assembly #10 on page 7 of the Certainteed link you supplied, they quote and STC of 50 vs. and STC of 52 for Roxul when comparing identical assemblies. 

System Description
Sound Transmission Class (STC)
5/8" gypsum boards (type x)
52
3 5/8" steel studs spaced 24" OC
ROXUL SAFE'n'SOUND Steel Stud


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## Gary in WA (Mar 11, 2009)

So, you didn't read 'steel studs" at the bottom of your quote? The OP and I were both talking about wood studs, apples to apples, with FG having a slightly higher rating. Less material leaves room for more insulation. I'm surprised you would think Roxul is better at sound than FG after "thanking" Ted White for answering otherwise here; http://www.diychatroom.com/f19/roxul-insulation-58518/index2/#post2875593


Did you read new info that proves your point to change your mind 180* since last January... I'm always open to learn more, leave a link? Thanks, Gary


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## Windows on Wash (Aug 30, 2011)

No...I did see the steel studs reference at the bottom. 

There is only one wall construction detail that is listed in both of your pdfs that is definitively comparable as equal. That is the steel construction that is reference above. 

The wood construction details may be the exact same, but there are some missing details from the Roxul data sheet (i.e. whether or not they 1/2" filler) that are listed on the Certainteed data sheet. Again, they may be the same, but we want to stay within the facts as they are detailed and verified. 

That being said, when the walls are constructed of the exact same materials, the Roxul (from your data sheets) outperforms the fiberglass by 2 STC points when using the exact same wall construction details. 

If that is the case (from your data sheets), one might rationalize that the difference in STC is due to the insulation in this case. 

It is not a difference of significance, but I still think the Roxul is the better selection here for insulation performance to be honest.


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