- Is it possible my architect can't design an ICF home? He said that it was very uncommon in this area and could cost significantly more to build. He didn't entirely dismiss it but seemed to think it was a bad idea. - How big of a job would it be for another architect to change my guy's CAD from CBS to ICF prior to building? Are there floor plan design considerations I should be conscious of?

- Sounds like termites can nest in the foam and they should be pre-treated. Concrete obviously not. How long does that treatment last? Can it be treated a second-time years later? Termites are a big deal here.

- How much is the cost differential between CBS vs ICF vs wood-frame? First-floor will be CBS or ICF, regardless. Wood-frame only a possibility on second-story. I know it depends on a lot of specifics---but ballpark or a range?

- Does our selection of exterior wall have an effect on our floor system? In other words, should the ceiling of first story / floor of second story be concrete/wood/or what? I was told the way to go was a concrete plank for less sound transmission but could cause HVAC difficulties (no space for ducts so extra soffits needed). Would this screw up my R-value in the home?

One thing to remember is that you can build "faux" walls inside the ICF to house HVAC if you want. This also includes the equivalent of a framed out drop ceiling that can house the electrical and HVAC. YOu wonlt ahve to worry about cutting trusses as it won't be structural - just creating a space to stuff things. Something you may also want to look into at the design phase is if your insurance will give you discounts for building a certified IBHS FORTIFIED Home. Being in Florida, there are lots of specifications on how to build a hurricane-resistant home. The specs apply to any of the construction methods you are considering.

Posted By kfink85 on 09 Jun 2018 01:31 AM
Hello, my wife and I are building our first home. Our lot is on a salt-water canal (not sure if this matters for this discussion). We just started working with an architect and are still in the design phase. The home is going to be two-stories and between 3000-3500 living square feet with roughly 2000 of it on the first floor. 4000-4500 total square feet for the home when you count garage, lanai, etc.

The standard construction in our area is Concrete Block System (CBS) on first-floor and wood-frame on second-floor.

I have researched Concrete Block System (CBS) vs ICF vs wood-frame for hours and hours. I have gotten a lot of conflicting info from contractors and other forums/sites. Please help me put these questions to rest. Here goes:

(1)- Is it possible to have CBS on first-story and ICF on second-story? Would this even make sense to do? Or if you go ICF, go ICF all the way.

(2)- Is ICF more impact resistant to hurricanes than CBS? By how much? Max wind mph tested? I've heard 200 mph.

(3)- Is it possible my architect can't design an ICF home? He said that it was very uncommon in this area and could cost significantly more to build. He didn't entirely dismiss it but seemed to think it was a bad idea.

(4)- How big of a job would it be for another architect to change my guy's CAD from CBS to ICF prior to building? Are there floor plan design considerations I should be conscious of?

(5)- How much better of an R-value will ICF have vs CBS? I've seen the comparisons to wood-frame but not CBS. I was told the following: "The most energy loss is through glass surfaces, then the roof/ceiling, then the walls. Therefore, the most payback by far is to invest into energy efficient glazing (double or triple) and extra insulation in the ceiling." Is this true?

(6)- Sounds like termites can nest in the foam and they should be pre-treated. Concrete obviously not. How long does that treatment last? Can it be treated a second-time years later? Termites are a big deal here.

(7)- How much is the cost differential between CBS vs ICF vs wood-frame? First-floor will be CBS or ICF, regardless. Wood-frame only a possibility on second-story. I know it depends on a lot of specifics---but ballpark or a range?

(8)- Does our selection of exterior wall have an effect on our floor system? In other words, should the ceiling of first story / floor of second story be concrete/wood/or what? I was told the way to go was a concrete plank for less sound transmission but could cause HVAC difficulties (no space for ducts so extra soffits needed). Would this screw up my R-value in the home? ---------- Thank you so much for any advice that you all can provide.

1. Yes.  It's possible to have CBS on the first story and ICF on the second.  There's almost always a way to mate two different construction techniques.  The thing is, SHOULD YOU.  With concrete block (the standard two-void type), if you experience cracking in the block at all, you get water infiltration into the wall structure itself.  While ICF is generally more expensive, it has the bonus of being a monolithic, solid wall construction.  I'd be in favor of ICF or concrete sandwich (with the insulation inside and a ply of concrete on both ends).
2. Depends on the concrete block system used.  If they're filling the concrete blocks with concrete on every course, maybe?  Generally, a solid concrete wall will fare better than a concrete wall with voids inside.
3. It's possible that your architect simply has no experience with ICF, and thus, distrusts it.
4. You'd be better off asking an architect what would be involved in converting such plans.  From what I understand, though, conversion should be relatively straightforward.
5. CBS, by itself, has the minimal R-Value (not NONE, but not something you want to just rely on).  You need to insulated it to have an appreciable R-Value.  By the nature of the product, basic ICF products generally deliver about an R20 or so by default.  You can get fancy with thicker blocks and foam inserts and all that.  But the baseline is generally around 20. 
   
   And yes, the windows are the lowest R-value in generally ANY wall construction.  So they tend to bleed the most heat on a per-surface-area.  However, you generally have more wall surface area to worry about.  So if the wall is bleeding heat as well, that's not a Good Thing.  So investing in ultra-high-end windows nets you NOTHING if you're radiating heat out of every wall assembly or through air infiltration.
6. Yes, while termites won't EAT foam, they use it to burrow towards potential food.  So you get termites AND your wall assembly is compromised.  You can use borate-impregnated ICFs if you want.  But you'll always want to have an "inspection strip" cut from the foam to deliver a 6" clearance from ground clutter/landscaping.  It won't STOP termites, but it'll allow you to inspect for dirt tunnels along the wall and (hopefully) catch migration attempts early.
   
   You can't really re-treat ICF foam.  And it'll be a more traditional call to the exterminator.
7. Costs depend on a lot of factors, including proximity.  If you get ICFs shipped from a local supplier, it's considerably cheaper than getting them shipped from some manufacturer in Bumsville, Idaho.  You'll want to source ICF suppliers/vendors/contractors in your area, talk about what you're looking for and get some general quotes.  You'll also want to talk to local concrete suppliers to see if they will deliver what you want.
   
   Generally, after all the shouting, construction, etc.  ICFs generally add about 10% to the cost of the project (at least that's what just about every project I've seen has quoted).
   
   YES, it's possible to do ICF on the first level and stick on the second.
8. No.  With ICF, you can have multiple choices of floor system.  You can go concrete floors with ICF.  You can go standard stick frame flooring, or wood/metal truss flooring or combination flooring.  Basically with concrete flooring, you want to PLAN your layouts before the pour.  And yes, there are generally no "rafters" to string HVAC through.  So  something like a dropped ceiling can be put in to simply mimic the space normally left by rafter bays or through trusswork.
   
   If you're worried about concrete and thermal bleed, look at the flooring offerings from various ICF vendors.  Essentially pre-insulated forms that you put in place and then pour concrete over/into.
   
   Also, you may or may not want to consider alternatives to forced air heating/cooling.  It may be that something like a Ductless system (where all you're running are the refrigerant lines) might be a more sensible and economical option.  It all really depends...
   

Posted By newbostonconst on 19 Jun 2018 01:05 PM
Sailawayrb. How much does the effective R-value increase in as concrete thickness increases?

So most ICF is R-22.
thus, ICF with no concrete has an effective R-value of R22,
ICF with 4 inches of concrete has an effective R-value of R40?
ICF with 6 inches of concrete has an effective R-value of R?
ICF with 8 inches of concrete has an effective R-value of R?
So does 10 inches of concrete have an effective R of a really high number?

Wondering if it is linear and the values. I know it is diminishing returns on pay back as you add more concrete.
Thanks in advanced.