Hi, I'm not sure what to do so I hope someone can offer some advice. I know everybody loves ICF but... My builder is keen to use it for our basement foundation. It will be a full unfinished basement about 1400 sq ft. I don't plan on finishing it. Who knows maybe in 10 years but not in the foreseeable future. We won't be using ICF for the house. Can you tell me how much more it might cost compared to just a regular poured foundation? Can we just leave it as is or will we have to finish it? Thanks for any information.

If you use ICF, what you'll be buying upfront will be an insulated foundation. In the future, when you go to finish it, that will be exactly what you need down there.

In the meantime, you will reap the benefits of the insulation in terms of some energy savings, but without knowing all the particulars of your location and build it is hard to say what the cost-efficiency of that will or won't be.

ICF needs sheetrock for fire code, but you should check locally to see if that will be required for your use of the basement as "unfinished" space.

Just curious, why a full unfinished basement vs a shallow frost protected monolithic slab on grade?

my guess would be storage, future use, possible storm protection, etc. I would never consider building a home without a basement, at least in my area.

How about a fully exposed "basement" or full-floor garage at less cost than a buried one? The storm issue (and a safe room) could be addressed with above ground concrete. I have yet to see any compelling arguments for building underground since they started doing FPSF. Water leaks, humidity/condensation, radon, cost, lack of windows, egress, etc.

Cost of an ICF basement will depend on your location, but will generally be $11 to $14 per sqft of wall.If building code requires you to add sheetrock, figure another buck. Insulation will result in energy savings on HVAC.

Thanks everybody for the responses.
ICF - i found out we do have to drywall and one coat of mud for code. My builder says if we do poured concrete then that will have to be framed and insulated as well.
Jonr - I've lived with and without a basement and I prefer having a basement. I have a large family and as Izerarc says it's very handy for storage. Plus, maybe this is silly but I really, really wanted part of it as a root cellar. Building on slab does have it's drawbacks as well. A "fully exposed basement"? Wouldn't that be a first floor? Then that would count as liveable space which would mean I would have to have a killer septic system. Apparently any space above grade counts around here, still waiting for my septic quote and I'm scared.
Brucepolycrete - I have a quote for ICF walls, $25/sq ft, I believe that's based on floor space. I just wasn't sure about the poured concrete..
Thanks again everybody for your input.

I really, really wanted part of it as a root cellar.

Sherri,

I am just completing a root cellar in my ICF basement. If you do use ICF, I have a couple considerations for you;

1. Make sure you do full ICF walls on the portion that you want to be the root cellar. In other words, don't rely on interior framing to wall off the root cellar once the basement is up.
2. Make sure the slab is UNinsulated in the root cellar portion. OF course, I'm also going to remind you that the other (heated) portions need to have a couple inches of foam insulation under the slab. I just paid $0.82/sf for 2" of DOW FOAMULAR 150 underslab.

I think your quote of $25/sf for floor space is high. If that is just for the ICF portion, you really should be coming in under $20/sf. If you still want to do ICF, you should investigate other contractors as well.

Again, this is dependant on your area/climate, but a recent report in Canada, showed a typical ROI when using ICF is between 3-5 years. That was true across the country. Even if you're not finishing for 10 years, the incremental costs of upgrading to ICF should be paid off with your energy savings well before this point.

Again, this is dependant on your area/climate, but a recent report in Canada, showed a typical ROI when using ICF is between 3-5 years. That was true across the country. Even if you're not finishing for 10 years, the incremental costs of upgrading to ICF should be paid off with your energy savings well before this point.

Posted By ICFBdr on 10 Aug 2011 02:48 PM
Again, this is dependant on your area/climate, but a recent report in Canada, showed a typical ROI when using ICF is between 3-5 years. That was true across the country. Even if you're not finishing for 10 years, the incremental costs of upgrading to ICF should be paid off with your energy savings well before this point.

Really? 

I'm not sure what that even means- let's see the report.

In a mad rush to track down the original report I was unsuccessful (I will look a little deeper when I have more time). I did find one very brief article, which is far from a scientific study that lists these findings. A quick search on google will return many websites returning this same stat (I sincerely hope this is not a misquoted statistic that has simply been regurgitated countless times for a sales pitch).

http://insulated-concrete.com/blog/?p=26

To be honest, I may be confusing details on 2 seperate tests - as I read through another article in my frantic search and came across this one, which I remember reading a while back and cites model testing done in 5 different areas of Canada:

http://www.nbec.net/documents/COSTEFFECTIVELEVELSOFTHERMALINSULATIONFORBASEMENTSINCANADIANHOUSING-TEDKESIK.pdf

This article simply states that the lowest Lifecyle Energy Cost for any foundation type is ICF, but does not detail any ROI.

Foam in any inhabitable space must be covered (drywall) per IBC, IRC, and IFC. Not a good idea to keep it exposed.

Posted By ICFBdr on 10 Aug 2011 05:53 PM
In a mad rush to track down the original report I was unsuccessful (I will look a little deeper when I have more time). I did find one very brief article, which is far from a scientific study that lists these findings. A quick search on google will return many websites returning this same stat (I sincerely hope this is not a misquoted statistic that has simply been regurgitated countless times for a sales pitch).

http://insulated-concrete.com/blog/?p=26

To be honest, I may be confusing details on 2 seperate tests - as I read through another article in my frantic search and came across this one, which I remember reading a while back and cites model testing done in 5 different areas of Canada:

http://www.nbec.net/documents/COSTEFFECTIVELEVELSOFTHERMALINSULATIONFORBASEMENTSINCANADIANHOUSING-TEDKESIK.pdf

This article simply states that the lowest Lifecyle Energy Cost for any foundation type is ICF, but does not detail any ROI.

Clearly there's a lifecycle cost benefit to insulated vs. uninsulated, and ICF can be a cost-effective way to hit R16-20.  But even assuming  uninsulated vs. 1400' of floor area and the mid-range $2.50/foot estimate in the blog article,  it's unlikely that it'll be at a break-even point on cash in 3-5 years heating with natural gas in an 80% burner.  1400' x $2.50= $3500, which means it would need to save $700 in fuel every year to break even on a simple-payback basis, which would be literally half the heating costs of many code-min 1400' houses in US climate zone 5. 

It might be that short if heating with an 85% oil burner at current pricing though.

But the thought of building ANY new construction without at least some foundation insulation seems like a bad idea, even in areas where it's not required by code.  But whether R16+ makes economic sense depends on climate, and in much of the warmer US zones R8-10 is more appropriate (and cheaper than ICF.)

I am from an area that can range in temperature from -40 to +40 Celsius, so energy savings can be significant (local code does not require any basement insulation).

Our concrete costs can reach $270 per meter. Simply being able to pour a 6" ICF foundation, rather than an 8" standard concrete foundation will save a few dollars in concrete, given the high prices. There are contractors that actually underbid standard foundations and use ICF (this does not include cost of adding gypsum board). At these rates a 3-5 year return is entirely possible, since your marginal cost of construction to go ICF can be very minimal.

Just to use some rough numbers (although pretty accurate for my area):

Monthly Cost of ICF Home



Estimated House Cost
Standard Home Increase ICF Home
Size (Sq Ft) 1000 (same) 1000
Cost/ sq ft $200 (plus 5%) $210
Total Cost $200,000 $210,000

Monthly Mortgage
Interest = 5%
Amortization = 25 yrs
Monthly Payment $1,163.00 $1,221.00

Estimated Monthly Heating/Cooling Costs $150 (less 40%) $90

TOTAL MONTHLY COSTS $1,313.00 $1,311.00

This assumes a cost increase of 5% to construct with ICF (US study found average increase between 0.5% and 4%), interest rates of 5% (higher than expected), and energy savings of 40% on heating (typically less for cooling loads, but in my situation, we deal with more days requiring heat than A/C).

My point - be sure to price out both options and look at energy savings. Different areas can vary greatly given differences in labour, material, and energy costs. At the end of the day - I would never trade my ICF foundation for anything else, even if costs were equal or slightly higher, since I do not have a damp cold basement to hide in when the wife has a to-do list ready. In other words, my dog house is very comfortable.

40% compared to something that nobody should do? Sounds biased to me. Why is 6" ICF OK but 6" poured isn't?

In upstate NY that icf foundation would cost about $15000 with floor, waterproofing,parging using an 8" form

Here is an article from ICF Builder Mag citing this data (look about half way down the page to the article titled "Energy Efficient ICFs"):

http://www.icfmag.com/back_issues/oct-nov_06.html

Remember - this is talking about FULL HOME construction with ICF. It compares it to 2x4 construction, which is minimum code, but I will admit that I can't remember the last time I saw a home framed that wasn't at least 2x6 construction (or stagger-stud).

As far as I know, our local code officials require an 8" poured concrete foundation (NBC 2010 does lists requirements for 6" concrete foundations, but I have never seen this done and as far as I know, it is not allowed), but do allow 6" ICF, since it is an engineered system with greater rebar schedules. Some cities in my area do require 8" ICF for all foundations.

Comparing ICF to a piece of crap 2x4 construction (that doesn't actually meet current code in many US locations) isn't a valid argument- it's an irrelevant & unconvincing straw-man type argument. The article doesn't provide a citation or footnote for the "...recent study by the Portland Cement Association..." to be able to look at the actual data or methodology used.

The notion stated in the article that a stick built assembly needs to be a foot thick to achieve R22-R26 whole-wall R performance is also complete BS. A 2x4" wall with cellulose cavity fill + 3" of exterior iso sheathing (a fairly standard retrofit option) beats R26 pretty comfortably.

They quote in the article:

“All the test data currently available shows that ICF construction has the best combination of energy efficiency and strength for building external walls,” confirms Ann Crocker, co-owner of Energy Smart Solutions, a Dallas-based residential contractor. “What we have found is that the homeowner will save at least two-thirds on their energy costs compared to wood frame 2x4 construction with fiberglass batt,”

Well, duh. A 2x4 wall with fg batts has a whole-wall R value of only ~R10, and then only if installed perfectly. This isn't rocket science. Building 2x4 w/batts in new construction without exterior foam or other enhancements wouldn't meet code in MA (but it probably does in TX.) The most typical new construction I see near me is 2x6 + 1-1.5" of XPS or iso, which has thermal performance quite comparable to R22-R26 ICF (and actually meets code. :-) )

The real comparison would be between ICF vs. insulating the foundation (or whole building) to similar whole-wall U-values &/or structural capacities & similar tightness using methods other than ICF. On raw thermal performance ICF doesn't have any edge over comparable U-value construction by other methods, but it's usually structurally superior.

"The most typical new construction I see near me is 2x6 + 1-1.5" of XPS or iso, which has thermal performance quite comparable to R22-R26 ICF"

I think you might be makin' that up.