# Wall Insulation - Looking for Opinions



## Nelson (Sep 24, 2015)

Hi All-

We are in the middle of renovating two bathrooms in our house, one of which is in our walk-out basement. My question revolves around the basement. The bathroom in the basement sits between two bedrooms. We ended up building some new walls in this bathroom which resulted in ripping out 1/4 of the drywall in one of the bedrooms. The exterior wall for this bedroom is all above grade. Since I already have some drywall ripped out in that room, I am considering ripping out the drywall on the exterior wall and fixing the insulation behind it. Since this house was built in the 1970s, this wall has paper-face FG insulation with a vapor barrier (plastic) over top. We know now that this is bad. I haven't seen any evidence of bad mold but I still want to fix it.

Sooo, on to my question. I'm looking for opinions on the best way to insulate this wall. It's a standard 2x4 with aluminum siding on the exterior (not sure what the sheathing is). My inital instinct was to go the spray foam (closed cell) route at about 2 inches to get me to R10 or R11, which I think is about as good as I'm going to do with a 2x4 wall without doing foam board on the outside and, thus, having to redo siding - not something that's in the cards at the moment. I also considered foam board, using spray foam to seal around the board and the wood framing, though I don't know if I can get as good a R-level with a 2x4 wall - this would also be more work than spray foam.

At any rate, would love to hear some opinions...

Thanks!


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## semipro (Sep 25, 2015)

One option is to spray open cell foam in the stud bays and then install mold resistant drywall with a water permeable covering such as latex paint (not oil based paint or vinyl wallpaper).  There's no reason you can't fill the whole 3.5" depth to get an R value of about 12.

I suggest open cell foam rather than closed cell since you don't know what's under the aluminum siding.  The open cell foam will more readily allow any moisture trapped between the sheathing and insulation to dry inward.

Depending on how much needs to be done you'll probably find its cheaper to contract a foam sprayer rather than DIY.  The DIY foam kits are very expensive per volume and R-value. Edit: by material volume DIY spray foam is 2-3 times the cost of foam panel.  I recommend a hybrid application where panels are used to fill wide open spaces and spray foam is used in the more complex areas, usually side by side in the same wall assembly. 

Two other options: fill the stud bays with a foam board and seal with canned spray foam as you mentioned. Roxul, mineral wool is also a good option but won't provide as much air sealing. It is easy to work with though and will yield R14 in a 2x4 wall. The latest issue of Fine Home Building has a great article on mineral-wool insulation and I, personally, love working with the stuff. 

BTW, interior poly vapor retarders are still recommended in very cold regions.


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## Nelson (Sep 25, 2015)

Thanks much SemiPro. I've been looking at the DIY kits, mostly because I'm working with a tight schedule and I don't know if I can get someone out here before the drywall goes up. The tricky part is that I'm trying to manage this work into the two bathroom remodel, which is a pain all on it's own! As far as Open or Closed - what kind of shealting/underlayment would make you choose one over the other? Does it have to do with the vapor permability of said sheathing/underlayment?

I've thought about using foam to air seal the stud bays and then doing FG or Roxul - preferably roxul/mineral wool if I can find it. Anyone here gone this route?


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## semipro (Sep 25, 2015)

Nelson said:


> As far as Open or Closed - what kind of shealting/underlayment would make you choose one over the other? Does it have to do with the vapor permability of said sheathing/underlayment?


If the sheathing was relatively vapor tight (e.g. aluminum foil coated something) I'd be wary of using closed cell foam since it has a much lower permeability.  If tar paper or housewrap like Tyvek, which is vapor permeable, I would not be as concerned about trapping moisture.  Open cell foam tends to be more elastic and may adhere to sheathing/studs better for better air sealing.  One of the criticisms of sprayed foam is that it pulls away from what it's sprayed on and air sealing is lost.
Good reference here: http://www.greenbuildingadvisor.com/green-basics/spray-foam-insulation-open-and-closed-cell

Edit: BTW, when I compared the price of board foam vs. contractor applied spray vs. DIY spray, the DIY was much more expensive.  Look at the board-feet you get and the resultant R-value.


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## semipro (Sep 25, 2015)

Nelson said:


> I've thought about using foam to air seal the stud bays and then doing FG or Roxul - preferably roxul/mineral wool if I can find it. Anyone here gone this route?


I've done this with a pro foam applicator gun for just the seams, then installed Roxul.  It seemed to work well but its challenging to seal at all seams, including those between framing elements, I generally do those with caulk rather than foam.  (e.g., the gap between stud and sill plate or top plate, that faces the room interior).


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## Nelson (Sep 25, 2015)

Cool - unfortnately, looks like that link is for Prime members only.

I've done a fair amount of air sealing so I'm not afraid of taking that challange on. I've only used the Great Stuff in the cans with the plastic applicator - may have to invest in the pro gun if I go the seal and batt route. The challange I'm seeing with Roxul is that I can't find it around here expect for a pallet of 12  bags, which is more than I need at the moment. I see that Owens has their version called ThermaFiber which it looks like I might be able to get by the bag. My assumption is that the differences between Roxul and ThermaFiber would be minimal, if any but haven't used either product.


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## semipro (Sep 25, 2015)

Nelson said:


> Cool - unfortnately, looks like that link is for Prime members only.


Sorry about that.  It was working for me now I'm being told I can't view it either.


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## Nelson (Sep 25, 2015)

So, another question. If I go the seal/batt route, what have others done for the seal portion? I was thinking spary can foam, but I'm wondering if it might be easier/more economical to caulk. If caulk, what type of caulk?


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## Wisneaky (Sep 26, 2015)

Since you live in Wisconsin I'd recommend going to your closest Menards store and buying a big froth pak. Spray foam the cavities an inch or two thick and any outside walls put up a poly vapor barrier before installing the drywall. I used this is my crawl space and it's amazing. If I could do it all over again I would have done all my walls with it.


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## Wildo (Sep 26, 2015)

If you're looking to do the bays as well a contractor is the way to go.  Your state may offer a rebate as well.  Closed cell will get you over R-20 if you fill the 2x4.  You can find out what kind of sheathing in under 10 minutes total  by unhooking the bottom row of siding to take a peek.  I love my sprayfoam.


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## semipro (Sep 26, 2015)

Nelson said:


> So, another question. If I go the seal/batt route, what have others done for the seal portion? I was thinking spary can foam, but I'm wondering if it might be easier/more economical to caulk. If caulk, what type of caulk?


There was an interesting evaluation done by the Journal of LIght Construction on air sealing materials including caulks, tapes, etc.  One finding that surprised me was that Liquid Nails did a really good job of sealing between different boards and a wiring penetrations.  I can attest to how well liquid nails works after tearing out our basement walls for remodeling.  The stuff is tough! 
That said, there are many good caulks for air sealing out there. I think that main thing to keep in mind is that they do not work well in larger gaps unless you use foam backer. 
The JLC article is here (I hope): *http://tinyurl.com/ova3mwf*


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## johneh (Sep 26, 2015)

I'm a fan of closed cell spray foam
not only can you get  great R value
but closed cell gives you a thermal break
is water proof and no air infiltration .
It keeps you nice and warm and draft free
in one application


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## semipro (Sep 26, 2015)

Nelson said:


> I've only used the Great Stuff in the cans with the plastic applicator - may have to invest in the pro gun if I go the seal and batt route.


This may interest you: https://www.hearth.com/talk/threads/multi-use-foam-applicator-gun-follow-up.107613/


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## velvetfoot (Sep 26, 2015)

I have something similar.  It's a lot less messy than the cans.  You can use it a little, put it down, and use it again months later. 
I wonder if you can buy 3.5" thick foam boards?  I know there are 2" boards and I think 1.5".


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## Wisneaky (Sep 26, 2015)

velvetfoot said:


> I have something similar.  It's a lot less messy than the cans.  You can use it a little, put it down, and use it again months later.
> I wonder if you can buy 3.5" thick foam boards?  I know there are 2" boards and I think 1.5".


Rigid foam is expensive and you still need to seal around the edges.


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## velvetfoot (Sep 26, 2015)

Wisneaky said:


> Rigid foam is expensive and you still need to seal around the edges.


True.  But sealing won't be as bad with the gun.  And you can do it all yourself without relying on someone else.  It'd be good to get estimates.


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## Wisneaky (Sep 26, 2015)

I wouldn't use cans of foam at all. That stuff is messy and real crap to work with. Better off going spray foam.


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## semipro (Sep 26, 2015)

Wisneaky said:


> Rigid foam is expensive and you still need to seal around the edges


Rigid panel foam is 1/3 to 1/2 the price of DIY spray foam like Dow Froth-Pak by end-product volume.
The advertised R-value of the Froth-Pak is 6.1 (per inch thickness) as compared to 5 for XPS foam board though.







As I noted above: 


semipro said:


> Edit: by material volume DIY spray foam is 2-3 times the cost of foam panel. I recommend a hybrid application where panels are used to fill wide open spaces and spray foam is used in the more complex areas, usually side by side in the same wall assembly.


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## velvetfoot (Sep 26, 2015)

Perhaps a first time user might not do as well as advertised, lol.


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## Wisneaky (Sep 26, 2015)

semipro said:


> Rigid panel foam is 1/3 to 1/2 the price of DIY spray foam like Dow Froth-Pak by end-product volume.
> The advertised R-value of the Froth-Pak is 6.1 (per inch thickness) as compared to 5 for XPS foam board though.
> 
> View attachment 162409
> ...


Your rights. Wasn't thinking correctly when I posted that comment. You still need to seal around the edges with rigid foam or you'll have air intrusion.


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## semipro (Sep 26, 2015)

My go-to method for insulating exterior stud bays lately for remodeling has been:

Using a commercial canned spray foam applicator or caulk to seal the seams/cracks
Installing a 1" layer of XPS board installed against the sheathing
Use canned foam to seal in the foam panel

Installing rock wool batt insulation (e.g. Roxul) against the foam board.
I may use thicker foam if the studs are larger than 3.5" deep. 

That said, if I was doing new construction and everything was opened up I'd just have a contractor spray it all.


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## Nelson (Sep 26, 2015)

semipro said:


> My go-to method for insulating exterior stud bays lately for remodeling has been:
> 
> Using a commercial canned spray foam applicator or caulk to seal the seams/cracks
> Installing a 1" layer of XPS board installed against the sheathing
> ...



I believe the Roxul I'm looking at is 3.5" thick - does it compress easily enough to fit a 1" XPS board behind it? Also, what is the thought process behind the 1" XPS board? Extra R-value, vapor issues?

Thanks for all the replies so far!


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## johneh (Sep 26, 2015)

If you compress bat insulation you are defeating its purpose
you loss insulating value if it is compressed


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## semipro (Sep 26, 2015)

The Roxul I've purchased at Lowes was 3" thick so not an issue for me.
The foam was added to help with air sealing while adding some thermal insulation.
Most of our exterior walls are built with 2x6s and I've only round Roxul in 3 and 3.5 in. thickness so I tend to add the foam board to fill the space.
Fiberglass is relatively easy to compress and resulting R values are affected as johneh mentions: http://www2.owenscorning.com/literature/pdfs/10017857 Building Insul Compressed R-Value Chart Tech Bulletin.pdf
I would not try to compress Roxul much.  It is much more "solid" than fiberglass.  This makes it great to work with though.  It fills cavities more tightly and is great to cut.  I compare it to cutting bread.  In fact, a serrated bread knife works on it very well.


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## Nelson (Sep 26, 2015)

Ah, ok. I think the stuff I'm looking at around here is 3.5" so I I would have to skip the XPS, though I believe the XPS would act as thermal retarder which may be good or bad.


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## jeanw (Sep 30, 2015)

Yeah we bought quite a bit of that Roxul.. nice to work with. they had it in stock at Lowes .expensive but nice. putting it in basement ceiling cavities.. to insulate and it  cut down on sounds... just got to finish it. LOL


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## Nelson (Oct 1, 2015)

semipro said:


> There was an interesting evaluation done by the Journal of LIght Construction on air sealing materials including caulks, tapes, etc.  One finding that surprised me was that Liquid Nails did a really good job of sealing between different boards and a wiring penetrations.  I can attest to how well liquid nails works after tearing out our basement walls for remodeling.  The stuff is tough!
> That said, there are many good caulks for air sealing out there. I think that main thing to keep in mind is that they do not work well in larger gaps unless you use foam backer.
> The JLC article is here (I hope): *http://tinyurl.com/ova3mwf*



this was a cool article. I'm glad to see that DynaFlex 320 was a good performer. I've been using that stuff for years and love it. Flexible, easy to work with and easy to clean up.


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## Nelson (Oct 1, 2015)

Ok, so after days of racking my brain and reading as much as I could, I am being paralyzed by too much analysis. I'm pulling the trigger on this approach. Quick context - we are in climate zone 6. The wall I'm working on is an exterior wall, fully exposed to the outside but is part of a walk-out basement (this is the wall on the walk out side). Objective is to achieve better thermal efficiency in the wall.

1. Remove existing vapor barrier, drwall and existing insulation (standard fiberglass, best I can tell)
2. Seal all framing edges (where framing meets sheathing on exterior), framing pentrations and top and bottom plates - use DynaFlex 230 for most sealing. Will have spray foam on hand for larger gaps and holes
3. Install Roxul ComfortBatts 
4. New drywall - may even seal new drywall to framing if time allows

Hope to start work within a week or two. Will let you know how it goes!

Suggestions, comments or concerns are always welcome so speak up!


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## kennyp2339 (Oct 2, 2015)

Nelson said:


> Ok, so after days of racking my brain and reading as much as I could, I am being paralyzed by too much analysis. I'm pulling the trigger on this approach. Quick context - we are in climate zone 6. The wall I'm working on is an exterior wall, fully exposed to the outside but is part of a walk-out basement (this is the wall on the walk out side). Objective is to achieve better thermal efficiency in the wall.
> 
> 1. Remove existing vapor barrier, drwall and existing insulation (standard fiberglass, best I can tell)
> 2. Seal all framing edges (where framing meets sheathing on exterior), framing pentrations and top and bottom plates - use DynaFlex 230 for most sealing. Will have spray foam on hand for larger gaps and holes
> ...


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## Nelson (Oct 4, 2015)

The other part of this project was to lay down foam board/plywood over the concrete floor. I went with 3/4" XPS and 5/8" plywood. Foam board glued to the concrete and plywood glued to the foam board and everything screwed down with tapcons.

Took about as long as I thought it would - didn't run into any major surprises either. Temp'd a bare spot of concrete (in adjacent bathroom that is being remodeled) and also temp'd the new floor. New floor is 3-4 degrees warmer which is pretty much what I was hoping for. Room is also running 2-3 degrees warmer. Still early, but those results have me very pleased!

Will be working on the walls next weekend with drywall work the follwing week. Will post more pics when I start on the walls.


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## velvetfoot (Oct 4, 2015)

Nice!  Did you really need all that glue with the tapcons?  What are you going to put on top?


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## Nelson (Oct 4, 2015)

velvetfoot said:


> Nice!  Did you really need all that glue with the tapcons?  What are you going to put on top?



Good question. I don't know - I'm guessing I could have got away without it but I get a little obsessive about having a sturdy subfloor.  Putting in tapcons is a little labor intensive so I opted to go with a glue and screw mix to cut down on the number of tapcons.

We will be putting carpet on top..


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## mtrel (Oct 5, 2015)

Nelson said:


> Ok, so after days of racking my brain and reading as much as I could, I am being paralyzed by too much analysis. I'm pulling the trigger on this approach. Quick context - we are in climate zone 6. The wall I'm working on is an exterior wall, fully exposed to the outside but is part of a walk-out basement (this is the wall on the walk out side). Objective is to achieve better thermal efficiency in the wall.
> 
> 1. Remove existing vapor barrier, drwall and existing insulation (standard fiberglass, best I can tell)
> 2. Seal all framing edges (where framing meets sheathing on exterior), framing pentrations and top and bottom plates - use DynaFlex 230 for most sealing. Will have spray foam on hand for larger gaps and holes
> ...



Don't you need some kind of vapor barrier on the inside?


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## Nelson (Oct 5, 2015)

mtrel said:


> Don't you need some kind of vapor barrier on the inside?



I'm electing to forgo the vapor retarder/barrier on the inside after doing tons of reading (green building advisor and building science corp) on the subject. 

The general consensus is that a vapor barrier is not required on the warm side of the enclosure except for some pretty specific circumstances.


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## Nelson (Oct 5, 2015)

I enjoyed reading this arcticle and the ensuing comments/conversation. Very insightful.

http://www.greenbuildingadvisor.com/blogs/dept/musings/do-i-need-vapor-retarder


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## Nelson (Oct 14, 2015)

The insulation part of the project is finished! 

Air-sealing....











Roxul in...











Interesting part of this was that I discovered that there is an inch of foam board on the outside (you can see the blue boards in the first two pics). I wasn't expecting any insulation on the outside as this home was built in the mid-late 70s. I'm guessing they resided at some point and that was when it was added.  - foam was right up against the studs so I assume there is sheathing on top of that, on the exterior. A little extra r-value.


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## velvetfoot (Oct 14, 2015)

Did you fill the edges of the foam with great stuff or caulk?


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## Nelson (Oct 14, 2015)

velvetfoot said:


> Did you fill the edges of the foam with great stuff or caulk?



I used caulk to seal the edges between the 2xs and the exterior foam. I'm glad I did because it's tough to get a flat edge on the foam which would have prevented the roxul from laying flat against the foam.


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## Nelson (Oct 14, 2015)

btw, for any of you reading this and planning on insulating the floor like I did - pay close attention to the direction lever on your hammer drill. On mine, the direction lever is right above the trigger. I went through at least 3 bits before I realized I had the direction lever in reverse! ugh!


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## velvetfoot (Oct 14, 2015)

You would've probably had to wait a while til it cured and then trim it with a knife-more work.


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## Nelson (Oct 14, 2015)

velvetfoot said:


> You would've probably had to wait a while til it cured and then trim it with a knife-more work.



Exactly - which isn't impossible but surely a pain and more work. Plus, I like the fact that I was able to tool the caulk and make sure I got a nice seal. It can be more difficult to seal up really small gaps with the spary foam in a can as it's hard to control. Probably not as much of an issue with a pro applicator where you can get a nice even bead.


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## velvetfoot (Oct 14, 2015)

Yeah.  I felt the same.  The trick for the foam would probably is to not have such a narrow gap, but I have an obsessive need to get it to fit as tight as possible which doesn't work well with that concept.  Then it expands while it cures.


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## Isaac Carlson (Oct 15, 2015)

I have never been a fan of fiberglass.  It is messy, itchy, expensive for what you get and it is very drafty.  Anything else is better.


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## semipro (Oct 15, 2015)

Nelson said:


> Interesting part of this was that I discovered that there is an inch of foam board on the outside (you can see the blue boards in the first two pics). I wasn't expecting any insulation on the outside as this home was built in the mid-late 70s. I'm guessing they resided at some point and that was when it was added. - foam was right up against the studs so I assume there is sheathing on top of that, on the exterior.


There may be no sheathing outside the foam.  Sheathing is only needed for attachment of siding and a water/wind barrier, and for prevention of racking.  Siding can be attached to the studs, or better yet furring strips attached to the studs, to create a drainage plane.  Foam may serve as water/wind barrier though house wrap may be installed under the siding or furring strips.  Using foam this way, wood sheathing is primarily needed only in the corners to prevent racking.

Edit: foam installed this way helps prevent thermal bridging through the studs.


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## Nelson (Oct 15, 2015)

semipro said:


> There may be no sheathing outside the foam.  Sheathing is only needed for attachment of siding and a water/wind barrier, and for prevention of racking.  Siding can be attached to the studs, or better yet furring strips attached to the studs, to create a drainage plane.  Foam may serve as water/wind barrier though house wrap may be installed under the siding or furring strips.  Using foam this way, wood sheathing is primarily needed only in the corners to prevent racking.
> 
> Edit: foam installed this way helps prevent thermal bridging through the studs.



cool, thanks for the info. I didn't have time to thoroughly poke around to see what was on the outside of the foam. Not sure it matters a whole lot from a thermal perspective - the sheathing certainly provides very minimal r-value and is vapor permeable.

Looking forward to some cold weather to see how things work out!


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## iron (Oct 30, 2015)

sorry i'm late to the thread, but i am also thinking of doing something very similar to nelson. for my spray foam, i was planning to use this: https://www.sprayfoamkit.com/   basically, a CCF. you can buy propane-sized tanks and it comes with the applicator gun. install should be easy enough, minus the keeping the wall temps at a certain level (65?)

does anyone have thoughts on that product?

nelson, for your floor, have you noticed "potato chipping" resulting from only a single layer of plywood? i read threads that talked about using (2) layers of 1/2" plywood and staggering the seams. this would theoretically stop the edges from popping up. 

a quick response would be appreciated. i am planning to install new stair stringers this weekend and had planned to allot 2" for the thickness of the basement floor (2 x 1/2" for plywood and 1" thick XPS foam). 

thanks!


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## Nelson (Oct 30, 2015)

Iron - I haven't noticed any potato chipping on the floor. I glued the foam to the conrete and then glued and tapcon'd the plywood to the foam. It's really sturdy. I made sure to put screws in around the corners to try and prevent and board from popping up. 

The issue I have is that I don't have a ton of ceiling height to play with so I didn't want to add an extra 1/2-5/8" of an inch. If you have the headroom, it wouldn't hurt to put the second layer of plywood down. It goes down pretty quickly.

What type of flooring are you putting over the plywood?

FYI -  I didn't put the carpet down on my floor for a few weeks and I didn't notice any edges moving at all during that time.

Good luck!


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## Nelson (Oct 30, 2015)

Are you planning to foam the entire cavity of your walls or are you just using foam for sealing the edges?


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## iron (Oct 30, 2015)

thanks nelson. i have also thought of using 1/2" plywood for the base, then a 1/8" underlayment to cover those seems. figured that would eliminate any potato chipping. we do have full height ceilings, so losing the extra is NBD. but, there would be less of a trip point coming from the garage into the basement, so it would be better to stay thin. 

planning to put down carpet as well.

for the foam, i was planning to do 2" thick for the entire cavity. it's been awhile since i looked at pricing, but i felt like that would come to $2k in insulation costs and would give me a nice enough R-value, compatible to the 2x4 walls in the upstairs. tempting to go thicker, but ultimately, i think there will be significant improvement simply by reducing the drafty air coming off the concrete. the previous owner that built the existing walls didn't insulate. when i replaced the outlets downstairs, it was a stream of cold air pouring in between the gaps. 

the real question for me is whether i demo the existing walls so that i can create a thermal break between concrete and studs or just leave it as is (which i don't know what it is yet since i haven't opened the walls)


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## Nelson (Oct 30, 2015)

The nice thing about spray foam is that you get the insulating factor and air sealing in one application. Air sealing is big so you want to get that right, obviously. I think 2" of foam would get you to about 13 r-value. I used Roxul batts (for 2x4 walls) and that is 15 r-value. I haven't done the cost comparison between foam and roxul but I seem to recall someone here posted it.

Are you doing the foam DIY or having someone do it for you?

I considered having someone spray foam for me since I was doing a relatively small section of wall but the timing of other projects pushed me to do the air seal and roxul route. We haven't had any really cold temps at this point, but I have been really happy with the performance. My walls are staying about 64F when the temps are in the 30s outside. At one point last year, when it was in the single digits, I measured the walls in that room and they were running in the 40s! Can't wait for some real cold temps to see how the walls are.


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## iron (Oct 30, 2015)

cool. sounds like a successful project you had.

yes, i'm planning on doing the install myself. it doesn't look too hard. only the wall temp requirement that's probably a PITA. our basement is relatively sizable. i haven't measured the actual wall length, but would guesstimate it around 120LF with 8ft ceilings

ETA: by the way, nelson, the drill you're using for installing the tapcons: is that just a regular drill? no hammer drill? do the tapcons come with a specific masonry bit?


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## semipro (Oct 31, 2015)

iron said:


> do the tapcons come with a specific masonry bit?


Yes, or you have to buy it separately.  
A hammer drill is faster.


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## Nelson (Oct 31, 2015)

Agreed - I would recommend a hammer drill - it will make life easier. When you buy the tapcons, read the back and it will tell you what size drill bit to use for the specific tapcon screw you are buying.


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