Hey all,

I have been a long-time reader and have learned a bunch from you guys [and gals] - thank you!

I'm going to be building a modern, ICF home but I am struggling with my wall options. Living in Zone 4, the recommended R-Value for walls is 31-51 (According to the Passive House Institute US - though I am not actively looking to be certified). My issue with ICF is it takes away my option to 'use' the exterior walls. What I mean, is, I cannot install in-wall speakers (Among other things). The home is also incredibly complex due to a whole-home Crestron system, Lutron Shades, Trufig flush-mount outlets, recessed security gates (Albeit, installed in the soffit on the exterior), etc., so I think it's important to 1) Make the install easy and 2) Make access easily available for WHEN things do go wrong in the future.

My architect recommended I do a concrete post and beam structure that is then tied into the ICF's, which would be used as a curtain wall. This way, I can have a 6" ICF whereas if I used the ICF for structural purposes, I would need a 10"+ ICF. The added cost will be minimal. The reason for 10" ICF is because the house is 3 stories, has lots of large overhangs, has a flat roof in the northeast and other heavy/demanding items.

I am estimating the wall to be 18.75" (Windows are by Zola):

• Exterior finishes: 1.5" (Conservative)
• Nudura 6" ICF: 11.25"
• 2"x6" Framing & Drywall: 6" (Again, I need space for speakers, outlets, etc.). Since the 6" ICF has an R-Value of 24, I can add more insulation.

That is wide. Very wide. I have searched high and low on Google, the forums and everywhere else to find examples. Unfortunately, I have only found a few and they were really hard to see. I have called a dozen or so local builders to see if they have done anything similar but they have not. Before I build examples, I was hoping you guys had any ideas that I may be missing or even any personal experiences. The windows will all be oversized (Including some floor-to-ceiling glass) and my ceiling heights are 12' on the main floor and 10' for the top two floors.

Any ideas or links to wide walls?

Thanks in advance!

How deep are these speakers that you need to install?

If you know exactly where you plan to install the speakers, you can install foam blockouts inside the ICF blocks to create a void in the concrete for the speakers. After the concrete is placed and sufficiently cured (a few days), you dig out the foam blockout to create the void for the speakers.

If you do go with the interior framed wall, do you really need a full 2x6 depth wall? If you went with a 2x4 wall, you have the depth of the 2x4 (3.5"), plus the depth of the interior side ICF foam (~2.5") to work with as the interior foam can be removed in locations were you need additional depth for the speakers.

I'd listen to your architect.

"Need space for speakers".
Normally with ICF, you'd simply cut the wire chases into the foam. But if you're going to build a interior service-chase wall, it's not so necessary.
Also, you can go to 24" OC walls, since

A: 2x6
B: Non-structural

Are your floors also going to be concrete? If so, make sure your top and bottom plates are pressure treated and rated for ground contact.

Also remember that the R-value of an ICF wall isn't determined by concrete thickness. But by the insulation used. And that you see best-use cases when the insulation is mounted to the exterior face.
Going with an interior fill wall will still net you a performance gain. But, in practice, you won't see optimal performance from the insulation.

With something like Rockwool, a 2x6 wall will net you R21. Plus the R24 of the ICF assembly. For a nominal R45.
Also, remember that your interior walls are non-structural. So you don't NEED 2x6. You could go with 2x4 or even 2x3 and simply space it back from the interior of the wall+framing assembly.

As for windows, you have to frame out the window to your finished wall specs.
Afterward, tape and flash out the window box.
Then your decision is simply "How do you want to mount said windows?"

If you mount them to the inside of the window box (either somewhere in the middle or all the way back), said window will enjoy additional shading.
If you mount them to the outside, simply make sure you have a proper mounting surface to screw it to.
In either case, make sure the window is properly taped and caulked in-place and that the window box has appropriately deep metal flashing on the sills.

If you're going to go with a uniform 10" wall, as Arkie suggested, simply box out cavities large enough for your purposes before pouring, so long as they don't compromise the wall structurally.
Make them slightly larger than you need and you can line them with foam panel and tape them out to avoid any condensation.
Keep in mind that a R31-R51 wall should have most of it's insulation on the exterior. So permanently cutting and removing squares of the interior insulation won't severely compromise the overall R-value.

Gonna illustrate with images from QuadLock.
This isn't an endorsement of QuadLock, these images simply make it easier to make my point.
Note: You should be able to click on all the images to go to the full-size versions if necessary.

Note: Please forgive me. I'd hotlink the images at appropriate size and link back to the main images so you could "upsize" for a closer look. Unfortunately, the forum doesn't allow this. As such I've provided the links to the images in question.

Basic Panel-to-R-Value: http://www.quadlock.com/images/icf_components/R-Values/ICF_Walls_R-Values_ab.png

More elaborate Panel-to-R-Value: http://www.quadlock.com/images/icf_components/R-Values/ICF_Walls_R-Values.png

You could then keep your 10" concrete pour wall. Go with Plus Panel forms with an extra panel.
This would give you a nominal R53.
You'd also have 4" of foam to the interior you could remove (and don't forget the half inch for the surface drywall), meaning you'd only have to box out 2-3 inches into the concrete wall, and you'd still retain structural integrity with a 6-7" wall in that location.
It would still leave you with a nominal R34 of foam on the exterior of the wall.

Another option would be to stick with the basic R22 panel. Then place an extra panel both inside and out. This would also get your a nominal R52 (it just wouldn't perform as well as the previous example. And it'd allow you to box out your speakers entirely within 6" of foam without compromising the concrete at all. Granted, those spots would only have a nominal R26 (as half the foam is gone), but it's still entirely on the exterior of the wall, giving you your thermal break.

Then you simply pick your tie width to match your desired wall cavity depth.

Wall Tie Dimensions: http://www.quadlock.com/images/engineering/QL_Ties_Dimensions.jpg

Note: There are also 12" orange "extender" ties. So you can fine-tune things.

Extender Tie Examples: http://quadlock.com/images/engineering/ICF_extender_tie_widths_single3D.png

Posted By Arkie6
How deep are these speakers that you need to install? If you know exactly where you plan to install the speakers, you can install foam blockouts inside the ICF blocks to create a void in the concrete for the speakers. After the concrete is placed and sufficiently cured (a few days), you dig out the foam blockout to create the void for the speakers. If you do go with the interior framed wall, do you really need a full 2x6 depth wall? If you went with a 2x4 wall, you have the depth of the 2x4 (3.5"), plus the depth of the interior side ICF foam (~2.5") to work with as the interior foam can be removed in locations were you need additional depth for the speakers.

The speakers are up to 6" deep. Therefore, a 2x4 would not work unless I cut into the concrete but that's not something I want to do because as I stated in my original post, I want flexibility (Ex. if I decide to move the speakers to another exterior wall in a corner room.).

Posted By Dilettante on 16 Sep 2018 12:13 AM
I'd listen to your architect.

"Need space for speakers".
Normally with ICF, you'd simply cut the wire chases into the foam. But if you're going to build a interior service-chase wall, it's not so necessary.
Also, you can go to 24" OC walls, since

A: 2x6
B: Non-structural

Are your floors also going to be concrete? If so, make sure your top and bottom plates are pressure treated and rated for ground contact.

Also remember that the R-value of an ICF wall isn't determined by concrete thickness. But by the insulation used. And that you see best-use cases when the insulation is mounted to the exterior face.
Going with an interior fill wall will still net you a performance gain. But, in practice, you won't see optimal performance from the insulation.

With something like Rockwool, a 2x6 wall will net you R21. Plus the R24 of the ICF assembly. For a nominal R45.
Also, remember that your interior walls are non-structural. So you don't NEED 2x6. You could go with 2x4 or even 2x3 and simply space it back from the interior of the wall+framing assembly.

As for windows, you have to frame out the window to your finished wall specs.
Afterward, tape and flash out the window box.
Then your decision is simply "How do you want to mount said windows?"

If you mount them to the inside of the window box (either somewhere in the middle or all the way back), said window will enjoy additional shading.
If you mount them to the outside, simply make sure you have a proper mounting surface to screw it to.
In either case, make sure the window is properly taped and caulked in-place and that the window box has appropriately deep metal flashing on the sills.

If you're going to go with a uniform 10" wall, as Arkie suggested, simply box out cavities large enough for your purposes before pouring, so long as they don't compromise the wall structurally.
Make them slightly larger than you need and you can line them with foam panel and tape them out to avoid any condensation.
Keep in mind that a R31-R51 wall should have most of it's insulation on the exterior. So permanently cutting and removing squares of the interior insulation won't severely compromise the overall R-value.

Gonna illustrate with images from QuadLock.
This isn't an endorsement of QuadLock, these images simply make it easier to make my point.
Note: You should be able to click on all the images to go to the full-size versions if necessary.

Note: Please forgive me. I'd hotlink the images at appropriate size and link back to the main images so you could "upsize" for a closer look. Unfortunately, the forum doesn't allow this. As such I've provided the links to the images in question.

Basic Panel-to-R-Value: http://www.quadlock.com/images/icf_components/R-Values/ICF_Walls_R-Values_ab.png

More elaborate Panel-to-R-Value: http://www.quadlock.com/images/icf_components/R-Values/ICF_Walls_R-Values.png

You could then keep your 10" concrete pour wall. Go with Plus Panel forms with an extra panel.
This would give you a nominal R53.
You'd also have 4" of foam to the interior you could remove (and don't forget the half inch for the surface drywall), meaning you'd only have to box out 2-3 inches into the concrete wall, and you'd still retain structural integrity with a 6-7" wall in that location.
It would still leave you with a nominal R34 of foam on the exterior of the wall.

Another option would be to stick with the basic R22 panel. Then place an extra panel both inside and out. This would also get your a nominal R52 (it just wouldn't perform as well as the previous example. And it'd allow you to box out your speakers entirely within 6" of foam without compromising the concrete at all. Granted, those spots would only have a nominal R26 (as half the foam is gone), but it's still entirely on the exterior of the wall, giving you your thermal break.

Then you simply pick your tie width to match your desired wall cavity depth.

Wall Tie Dimensions: http://www.quadlock.com/images/engineering/QL_Ties_Dimensions.jpg

Note: There are also 12" orange "extender" ties. So you can fine-tune things.

Extender Tie Examples: http://quadlock.com/images/engineering/ICF_extender_tie_widths_single3D.png

Yes, my architect is more than capable and I trust his judgement. I'm just not so sure about the thick walls. I was hoping some members here had experience with them or had any online resources to share.
Sure, I can cut runs for wire in the foam but I cannot install a 6" deep speaker, etc. As you stated, the R-value of concrete is minimal; it comes mostly from the foam, which is why I'd like to limit cutting into it. Hence the desire for traditional forming inside of an ICF structure. As I pointed out above, a 2x6 would be 'needed' since the 3.5" depth of a 2x4 would not be sufficient and I would prefer to keep the foam in tact.
Has anyone been inside a home with thick walls? What are your thoughts?

Again, no, 2x6 isn't required for non-structural walls. You simply space the 2x4 wall out from the ICF wall 2-3 inches. As long as it's affixed to the floor and ceiling (or all 4 walls are joined by a common top-plate in a dropped ceiling situaiton), you're golden.
Keep the insulation, as much as possible, on the exterior of the ICF wall. Any insulation you install on these partition walls should be more about acoustic deadening than chasing R-value. Unless you're going for some ridiculous level of R-value.

Posted By Dilettante on 17 Sep 2018 04:52 AM
Again, no, 2x6 isn't required for non-structural walls. You simply space the 2x4 wall out from the ICF wall 2-3 inches. As long as it's affixed to the floor and ceiling (or all 4 walls are joined by a common top-plate in a dropped ceiling situaiton), you're golden.
Keep the insulation, as much as possible, on the exterior of the ICF wall. Any insulation you install on these partition walls should be more about acoustic deadening than chasing R-value. Unless you're going for some ridiculous level of R-value.

Sorry, but the 2x6 would be needed to get the depth of 6" for in-wall speakers; it has nothing to do with structural. A 2x4 would only give e 3.5" (Plus 2.x" of foam), which won't work.

You're missing the point.
If you need a 6" space, you can get them with a 2x6, sure.
You can also get it with a 2x4 by simply moving the 2x4 structure away from the wall a couple inches.

Remember, a 2x6 isn't 6". It's 5.5". So if you need EXACTLY 6" from the exterior wall and don't want to cut foam, you space the 2x6 half an inch from the wall to give yourself the necessary clearance.

A 2x4 wall isn't 4". It's 3.5". So if you need EXACTLY 6" from the exterior wall and don't want to cut foam, you space the 2x4 2.5" from the wall to give yourself the necessary clearance.

Visual: http://evilnet.net/WallSpacing.png

The only reason you're putting in the walls to begin with is to have something to affix these devices to and still provide a flat surface once the sheetrock goes on.
You COULD achieve the same thing with bulkheads, it just doesn't look as clean.

Before I built additional wall depth just for speakers, I would first research if using shallow mount speakers would satisfy audiophile aspects. They make a lot of high fidelity shallow mount speakers these days that don’t need more than 2” of depth.

For thick ICF walls we like to install the door and windows flush to the exterior side as is done for conventional 2x stick construction. For the doors, we wrap the interior exposed opening sides and top with drywall, use round corner molding and then texture/paint this to match room. For the windows, we wrap the interior exposed opening sides and top with wood stained to match the windows and trim these edges with wood stained/painted to match the house trim. We like to use marble to cover the interior window sills as we feel the contrast looks beautiful and that marble is more durable than wood for a window sill application. Please see photo:

The added bonus in using 2x4 spaced off the ICF is you have that space for easy fishing of wires for future mods.

Yep.

Thank you again, everyone. I have been doing a TON of reading / speaking with professionals relating to the construction of ICF (Which is why I'm late responding).

Dilettante - the reason I said 2x6's is because the ceiling heights will be 10' - 12' tall; 2x4 studs at that height is a no-go. I'm not sure about LSL's in 2x4 such as Timberstrand (I'm sure they're straight being that they're engineered) but I would have to check loads/deflection and such for this length. Being that it's a modern home, straight, sharp walls are a must. My initial 6" width included the drywall, even though I plan on using 5/8

sailawayrb - unfortunately, I definitely need 5"+ for speakers, wiring/smurf tubes, outlets, ets. Thank you for the window detail!

Since I'll be framing out the inside of the ICF, it makes sense to add insulation. However, that brings me to thermal mass. Typically you want to insulate the exterior, but that would add to the wall depth. Would thermal mass even come into play since it'll be behind 5/8" drywall, 6"-7" of stud/air and then 2 5/8" EPS? In zone 4, my temperature swing is on average, 20 degrees between high and low. Options:

1) Keep the R-24 that's standard with the ICF
2) Increase wall thickness 2" to add EPS, bringing me to R-33
3) Insulate the studs with R-15 Rockwool, bringing me to R-39

Okay, I can understand eschewing stock lumber because of worries about wall straightness.

I'd honestly be SHOCKED though, if an LSL in 2x4 wasn't sufficient. This isn't an actual load-bearing wall. You're going to have fiittings on the back for electrical and your sound system and that's about it.

Also, honestly, it doesn't make a hell of a lot of sense to insulate the interior walls much more than minimum. You're not really getting full value out of the insulation. You're also mucking around with where the dewpoint in your wall ends up.

IF you're still gonna go rockwool in the framed walls anyhow, I'll look at going with the Safe N' Sound product (for additional noise deadening). Rather than pure insulation value.

According to the spec sheet (https://www.weyerhaeuser.com/application/files/4215/0169/3500/TJ-9003.pdf):

Size: 2x4
Lateral Load (PLF): 15
Wall Height: 12'
Vertical LBS: 1,100
Deflection Ratio: L/203 (144/203=.71 inch)

I know nothing about studs/loads/etc., but it looks to be higher than code. However, I do want to limit cracking. I'll be applying a level 5 drywall finish. On walls with heavier finishes, I would assume a 2x6 would be best. Any thoughts on whether or not the 2x4 would be sufficient? It's $10 less expensive per stud than a 2x6!! Also, is the lateral load high for an interior, non load bearing wall? EDIT: USG recommends a minimum deflection of L/240. (https://www.usg.com/content/dam/USG_Marketing_Communications/canada/product_promotional_materials/finished_assets/cgc-construction-handbook-ch02-framing-can-en.pdf)