Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Insulation

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 10-03-2011, 08:49 PM   #1
Member
 
Join Date: Oct 2011
Location: Twin Cities, MN
Posts: 99
Share |
Default

Exterior Bathroom Wall Insulating


Long-time lurker, but a new member as of today. I've been looking around quite a bit for this info, but wanted to ask about my specific situation to be sure I'm on the right track.

Remodeling a bathroom with one exterior wall (about 7 feet). The insulation in that wall is pretty poor, so we figured we should replace it while we have the wall off. The tub/shower is up against that wall, and I've been doing a bunch of research trying to figure out what my best option is for insulation that will be less likely to have mold issues and problems with dew points/inside-outside temperature and humidity differences/moisture. We live in Minnesota, so there's quite a temperature swing throughout the year.

As it stands, I'm leaning towards using Dow Super Tuff R sheets, and a couple questions on those....

-Are they stackable? Is it kosher to fill in the full 3 1/2" with insulation?
-Do I need any sort of vapor barrier in place as well?

Once the insulation is installed, I'll of course be putting up concrete board and some Redguard. Anything I'm missing?

dvaupel is offline   Reply With Quote
Old 10-03-2011, 10:13 PM   #2
Member
 
Join Date: Oct 2011
Location: Twin Cities, MN
Posts: 99
Default

Exterior Bathroom Wall Insulating


and just to clarify, I'm talking about cutting the sheets into strips that fit between the studs. I've been somewhat confused by install instructions I've seen for this type of insulation, so needing clarification.

dvaupel is offline   Reply With Quote
Old 10-03-2011, 11:12 PM   #3
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Exterior Bathroom Wall Insulating


Quote:
Originally Posted by dvaupel View Post
and just to clarify, I'm talking about cutting the sheets into strips that fit between the studs. I've been somewhat confused by install instructions I've seen for this type of insulation, so needing clarification.
This isn't a very good option as it is near impossible to cut the foam so that it fits in tight enough to be effective to its full potential. It would be ideal to leave a gap on all side and spray foam fill the perimeter to seal it in. But then that begs the question of just spray foaming the walls all together.

Unless you are using Polyiso or closed cell foam (2.0 lbs), XPS is relatively comparable in R-value to most batt. applications. (example: XPS is R-5 per inch, so a 2x4 wall will give R-17.5, while a 3-1/2" batt can give R-15. A minimal R gain for the cost difference.) The true benefits of spray foam is the air sealing capabilities. The true benefit of rigid foam is the thermal bridging capabilities.
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 10-04-2011, 07:57 AM   #4
Member
 
Join Date: Oct 2011
Location: Twin Cities, MN
Posts: 99
Default

Exterior Bathroom Wall Insulating


I've been back and forth with the spray foam idea as well, but from what I've seen it would be more cost-effective to go with the sheets and then foam around the edges. And I've definitely considered batting but have mostly shied away because of potential for moisture problems....am I over thinking this?
dvaupel is offline   Reply With Quote
Old 10-04-2011, 09:15 AM   #5
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Exterior Bathroom Wall Insulating


You should be treating the moisture drive at the wall's surface with some kind of vapor barrier. The insulation is secondary.
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 10-04-2011, 09:28 AM   #6
Member
 
Join Date: Oct 2011
Location: Twin Cities, MN
Posts: 99
Default

Exterior Bathroom Wall Insulating


Quote:
Originally Posted by AGWhitehouse View Post
You should be treating the moisture drive at the wall's surface with some kind of vapor barrier. The insulation is secondary.
That's why I've been having so many questions about this...between the concrete board, Redguard, and the different insulation materials, I'm getting lost in understanding what will be a sufficient vapor barrier. It sounds like some batting insulations have the barrier on them and the same with foam....am I wrong on this?
dvaupel is offline   Reply With Quote
Old 10-04-2011, 09:31 AM   #7
DIY staff
 
Join Date: Sep 2009
Location: Kane county,Illinois
Posts: 21,403
Default

Exterior Bathroom Wall Insulating


If you are going to waterproof the face of the backer board in that area no additional vapor barrier should be used.
__________________
New members: Adding your location to your profile helps in many ways.--M--
oh'mike is offline   Reply With Quote
Old 10-04-2011, 11:09 AM   #8
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Exterior Bathroom Wall Insulating


Quote:
Originally Posted by oh'mike View Post
If you are going to waterproof the face of the backer board in that area no additional vapor barrier should be used.
I agree...

The redguard is considered a class II vapor retarder. Therefore the insulation doesn't need or want to handle vapor retarding. Un-faced batt type insulation with caulked joints for air sealing would allow for any moisture within the wall cavity to dry to the exterior. It will be cheaper on the wallet too.
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
The Following 2 Users Say Thank You to AGWhitehouse For This Useful Post:
Canucker (10-05-2011), oh'mike (10-04-2011)
Old 10-04-2011, 11:49 AM   #9
DIY staff
 
Join Date: Sep 2009
Location: Kane county,Illinois
Posts: 21,403
Default

Exterior Bathroom Wall Insulating


AG--You do know your stuff---and can put to into words so much better than I do.
__________________
New members: Adding your location to your profile helps in many ways.--M--
oh'mike is offline   Reply With Quote
The Following User Says Thank You to oh'mike For This Useful Post:
AGWhitehouse (10-04-2011)
Old 10-04-2011, 04:42 PM   #10
Member
 
bubbler's Avatar
 
Join Date: Oct 2010
Location: North Shore MA
Posts: 481
Default

Exterior Bathroom Wall Insulating


Quote:
Originally Posted by dvaupel View Post
That's why I've been having so many questions about this...between the concrete board, Redguard, and the different insulation materials, I'm getting lost in understanding what will be a sufficient vapor barrier. It sounds like some batting insulations have the barrier on them and the same with foam....am I wrong on this?
My bathroom exterior wall--it's about 6' wide, 2' of that is tile and 4' is painted (with a window in the middle of the 4').

We pulled everything back to the studs & tore out the old R-1 fiberglass from 1950.

I installed "faced" R15 FG batts w/ the face "out" (toward the room), the paper ear-flaps stapled to the studs and then taped the seams between batts w/ Tyvek tape. I used the window&door can of spray foam around the window and on a few particularly large gaps in the exterior sheathing where the felt was exposed.

I put up "half inch" hardi board for the 2' where tile would be and put up blueboard + skim coat of plaster for the other 4' (which was later primed and painted). Siliconed all seams of the hardi-backer on hardi-backer or hardi-backer on tub. Typical porcelain tile went up on the hardi-backer.

I also installed a generously sized bath vent directly above the shower with a ~2' duct run to the exterior, and put it on a motion activated switch w/ 30-min delay--someone goes in the bathroom, the fan starts and doesn't stop until 30 mins after they leave. Whatever energy cost penalty I have from over ventilating I feel I make up for in the moisture and negative-olfactory departments.
bubbler is offline   Reply With Quote
Old 10-06-2011, 10:25 AM   #11
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Default

Exterior Bathroom Wall Insulating


Fiberglass batts give the least “bang for the buck” – the reason why they are the cheapest. The "biggest loser" in fiberglass insulation....

I would use some 2” rigid foam board on the face of the studs, if enough clearances for other bathroom fixtures, then add d.p. cellulose or rock wool cavity insulation. At the very least, ” f.b. or sill sealer on the studs. F.g. batt can lose up to 70% R-value when wet and more R-value because of non-lab installation (air-sealed on all six sides) due to convective air leaks from outside behind and around the batt, especially if you have older wood board sheathing? Minimum IRC (code) for your area requires R-19 wall insulation, anything less is like getting a ‘D’ grade on a school test; R-15 wouldn’t even be passing… http://findarticles.com/p/articles/m...6/ai_n8582994/
The R-15 is high density so interior c.loop. would not be there, though outside batt c.loops may, depends on installation. The cellulose would stop cavity air movement and redistribute any moisture from exterior leaks.

Is there any foam board outside- under the siding? (The optimum solution- keeps the dew point on the sheathing high enough not to condense and thermally breaks the R-3 studs from the drywall as a heat sink). Could you describe the wall assembly?

Air-seal the plywood/OSB/boards at the exterior joint to studs, also the plates to the ceiling drywall, and plate to floor; with caulk or canned foam. Also any wiring/plumbing holes through either plate and the studs. Add rigid f.b. on the exterior wall top plate leaving room for your ventilation baffles.

You could stack the f.b.- with canned foam to air-seal, depends on the wall assembly…….

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 10-06-2011, 11:12 AM   #12
Member
 
Join Date: Oct 2011
Location: Twin Cities, MN
Posts: 99
Default

Exterior Bathroom Wall Insulating


Quote:
Originally Posted by GBR in WA View Post
Fiberglass batts give the least “bang for the buck” – the reason why they are the cheapest. The "biggest loser" in fiberglass insulation....
Could you describe the wall assembly?
Here's the rundown....

House was built in the mid-50's, previous owner had siding done in the last 5ish years. There's 1/2" Green Guard foam underneath the siding, then I imagine the OSB/Ply. 2x4 studs for interior. I hesitate to put anything on top of the studs because of necessary fixture locations.

Last edited by dvaupel; 10-06-2011 at 12:43 PM.
dvaupel is offline   Reply With Quote
Old 10-06-2011, 11:15 AM   #13
Member
 
Join Date: Oct 2011
Location: Twin Cities, MN
Posts: 99
Default

Exterior Bathroom Wall Insulating


Quote:
Originally Posted by AGWhitehouse View Post
Un-faced batt type insulation with caulked joints for air sealing would allow for any moisture within the wall cavity to dry to the exterior.
Am I correct in assuming you're talking about the joints between sheets of concrete board, ceiling, tub, etc?
dvaupel is offline   Reply With Quote
Old 10-06-2011, 12:28 PM   #14
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Exterior Bathroom Wall Insulating


The caulking was for air-sealing the wall cavity to ensure the best performance of the batt. insulation. Caulking at the stud and plate edges help to eliminate the air movements within the wall cavity that reduce the effectiveness of the insulation.

http://www.energystar.gov/ia/partner...d_Insulate.pdf
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 10-06-2011, 02:06 PM   #15
Member
 
Join Date: Oct 2011
Location: Twin Cities, MN
Posts: 99
Default

Exterior Bathroom Wall Insulating


what about a stone wool batt for this? With what I'm understanding so far, it seems like that (plus caulking, etc) is a happy medium in it all.

dvaupel is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Trouble with staggered wall rightit Building & Construction 2 03-09-2011 06:23 PM
Insulating existing basement wall tigereye Remodeling 1 12-28-2009 06:24 AM
Insulating wall when running Copper Tube lines to an exposed wall face scubber Carpentry 5 04-13-2009 10:23 PM
Insulating above block wall that is above sheetrock klein General DIY Discussions 6 12-11-2008 09:37 PM
Atlantic-need your opinion on markd's comments about my vapor barrier? yummy mummy Building & Construction 11 03-07-2007 09:47 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.