Posted By ICFHybrid on 19 Mar 2013 03:04 PM

Is that with standard 1/2" sheetrock?

The 55 STC is specifically with 5/8" on the source side, but only 1/2" on the receiver side.
Getting up to 71 STC required the addition of a " 2-1/2" non load bearing steel stud cavity".

…which interestingly enough is TF System’s new TransForm vertical ICF product that is being used for the 72,000 SF Pensmore build.  Unfortunately, this new TransForm product is currently about twice the cost of their original ThermoForm vertical ICF product.

Well, I joined this forum today in hopes of narrowing down my decision on ICF or poured concrete walls (and if ICF, who recommends I/C/I vs C/I/C) for a basement. I didn't realize I would have to read through 3,394 posts that amount to a Richard measuring contest, but I can appreciate each person's passion on the topic.

Here is my situation: I live along the I-64 corridor between Richmond and Williamsburg. I have been inside homes with block basements as well as homes with poured concrete basements, both finished and unfinished. I was totally impressed with the poured concrete basements over blocked basements and always said if I built a new home, I would have a poured basement. That was before I stumbled on ICF during my research. Now, I am torn and undecided.

I wish to build a log home over a full 9'tall walk out basement. Initially, this will be unfinished to save cost (more later on that issue). My rationale is this: My wife and I want a smaller square foot home we can easily keep up as we get older, but we need extra space when our five kids (and future grand kids) visit. So the idea is to build a 2000-2500 sq ft log home over a full basement and the full basement would be the overflow area for sleeping rooms and large parties/dinners.

I understand the long range cost savings of the ICFs, however, the reality is that the basement will only be used periodically for entertaining and sleepovers, so if you ask me if I would rather put my construction cost towards more sq ft upstairs or better insulation in the basement, I'm going to say I want more sq ft in the log home. My understanding is that I have to fireproof (drywall) ICF for fire codes. What I don't know if drywall alone in a basement equates to taxed sq ft (I will find that out this week). I know there are a lot of factors to consider in order to give me a reasonable answer, so I will add that I plan to install a radiant floor heating in the basement slab and I will also have a fireplace/wood stove in the basement to heat the basement when we are using it for visits/events.

So my question is this: Throw out the future cost savings argument for now: For materials and labor in my area, how much more (%) will ICF plus drywall for 200 linear feet of basement cost me versus just going with a poured basement (that I really do not care if it is insulated and walled at this point). If the price difference is small, then yes, obviously I will pay a little more for ICF so long as it does not qualify my basement for taxed square footage and it doesn't decrease my sq ft I can build topside.

Also, is there a simple answer to this question (without going into logarithms, NASA statics calculations and 9 pages of Richard measuring): How thick of a poured concrete basement wall would I need to pour to get the equivalent energy savings (thermal mass) of ICF (thickness recommended in my area). In other words, would it be less expensive to simply pour a thicker poured wall than going ICF?

Lastly, what are the pros/cons of I/C/I vs C/I/C ICFs and are pests/rodents eating away the insulation really a problem?

Thanks for everyone's time.

In other words, would it be less expensive to simply pour a thicker poured wall than going ICF?

Not if you mean thicker concrete. But a poured wall with EPS foam either in the forms or attached to the outside of the wall may be.

Is there any truth to posts on the Internet that rodents eat the insulation (wherever the insulation is placed) and would that cause structural weakness at all if for instance the insulation between inner/outer concrete is gone and now has a void? It's on the Internet, so it must be true, :-)

We build ICF houses in Virginia and you are under the 2009 IECC so you have to have a certain amount of interior insulation on your basement wall to begin with, it would usually be R11 if you are building to "just" meet code compliance, so the point here is you will need some kind of insulation on your interior wall regardless of the composition of the basement wall. Another criteria is whether you will be "finishing" the basement area, if so then the ICF has an added benefit of being ready to receive drywall, along with complying with the code requirements.There are numerous other reasons to use ICF, none that i am going to go into, i assume you have already googled most of them. the point i would make is this, if you are trying to compare a strip form concrete basement wall or cmu wall to an ICF wall, then you have missed the whole point of using ICF and i would suggest you need more research on ICF, if however you are completely money driven then ICF is obviously not an option at all, it is without a doubt 2x the cost of a strip form wall and 1.5 cost of a CMU wall. I see this problem alot with clients in that they are trying to compare costs of ICF straight up with the cost of strip form walls in just the basement! it is analogous to comparing a formica countertop to a granite countertop and then standing back looking at the whole kitchen and trying to figure out whats wrong with this picture, in other words you can't do the comparison that way and if you do then you better be finishing the basement! otherwise it makes no sense and you should just build your wood house to "meet code". ICF construction by its nature is "Code+" construction and in my opinion the only way to capture the true benefits of ICF construction is to take it to the roof plates and spray foam the attic, its all about air-tight envelope, that makes the numbers work much better and usually we can get the pay back in 5 years or less, it is after all an investment decision as well.if you have plans we can do the cost analysis so you can see the comparisons between a traditional house and an ICF house.
Virginia also offers a property tax credit if the house exceeds 30% increase in energy performance from their baseline house, every ICF house we have built so far as exceeded that requirement, there are other incentives to build energy efficient as well, if youi go to the dsire website it explains those as well.
finally i have lived in 2 different ICf houses, i would never go back to a stripform or cmu foundation again, i am actually between ICF houses, sold my last one a bit sooner than i anticipate and i am living in a "traditional" stickframe concrete basement(albeit finished basement), the temperature difference is outrageous between the upstairs and downstairs, just incredible, i had forgotten the intangibles!

the bug thing not an issue if you cover the icf, the only time i have seen animals in the ICF is where it has been laying around(usually waiting to start a project), and yes rodents do understand the value of insulation! but in a finished house there is no weather exposed components or there isn't suppose to be, the rest is just normal termite and insect remediation you would normally do on any house.
hope that helps, let me know if you want the wood vs icf comparison done.
good luck and Happy New Year.

Well said, Bill. MGFarmVA, I sent you a private message with more info.

Bill - which ICF product do you use and what is the price of your ICF concrete mix, if I may ask?

MG -
When doing the comparison add the cost of the stud wall and insulation to the cost of the cast in place basement if you need it to meet code.

Find a few ICF installers in your neighbourhood and let them price the plans. ICF pricing can vary greatly from area to area.

No additional thickness of concrete will make up for insulated mass. If the mass is not within the insulated building envelope, it will be an energy loss. So if you want to go for mass and c.i.p. concrete, at the least you would have to put a number of inches of foam on the outside of the wall.

You will find lots of ici product to choose from but very few cic products. They are normally limited to precast panels or shotcrete. Both have a lot of thermal bypass due to the reinforcing.

While it is true that under some circumstances, rodents will tunnel through the foam. They do not "eat" it as it has no food value to them. The foam in an ICF has no structural value so the rodents cannot hurt the structure of the building.

Thoughts everyone - building central florida home, on a central florida sandy-soil hill. We are looking to do a steel bar reinforced basement under the home. We are interested in hurricane and tornado protection (did anyone see what the F3 did to Lady Lake and the Villages a few years back?....)

ICF or Poured Concrete???

Thanks in advance to anyone who has some thoughts they are willing to share on this topic!!

In terms of strength, ICF is poured concrete, it's just a matter of how you form it and insulate it. With non-ICF, you can attach rigid foam afterwards or you can drop rigid foam into the forms. Cost will be highly dependent on local quotes.

Engineers view ICF as a "poured in place" concrete wall. It's basically a solid poured concrete wall where the "forms" (EPS foam) stay in place and are not removed.

The R-value of concrete is about 0.1 per inch. The R-value of EPS is about 5 per inch. A typical ICF has about a total EPS thickness of about 5 inches or a total R-value of about 25. 25 divided by 0.1 is 250 inches (or about 21 feet) and is about the concrete thickness that you would need in order to have a similarly insulated wall. Somehow I think that thick a wall will cost more than the ICF wall…

So if the end goal is an insulated concrete wall, ICF makes good sense. If you just want an uninsulated concrete wall, a standard poured wall makes good sense. Either wall can be made as strong as you need. Like Lbear indicated, the only difference is that the forms remain in place (i.e., don't need to be subsequently removed) with the ICF wall and become the insulation, and the forms typically must be subsequently removed for the standard concrete wall (i.e., with perhaps some associated increased labor cost).

Posted By blacksunshine6973 on 31 Oct 2014 09:43 AM
Thoughts everyone - building central florida home, on a central florida sandy-soil hill. We are looking to do a steel bar reinforced basement under the home. We are interested in hurricane and tornado protection (did anyone see what the F3 did to Lady Lake and the Villages a few years back?....)

ICF or Poured Concrete???

Thanks in advance to anyone who has some thoughts they are willing to share on this topic!!

Given the deep soil temperature in central Florida is approximately 72F to 75F, you don't really need any insulation on your basement walls if the top of the walls are at or below grade level.  If you have a portion of your basement walls exposed above grade level, you could insulate just that portion with a couple inches thickness of borate treated EPS foam.  A poured concrete wall would likely save you some money since with the ICF wall you would be paying for a lot of insulation that you don't really need.

Thanks for all the replies on the insulation values. Any thoughts on settling with icf vs poured concrete? From what I understand, because the ground is heavy sandy clay soil and not rocky soil, homes tend to undergo a lot of settling, and you do see many homes up there with cracks, etc. I am wondering if one or the other is stronger against settling.

Blacksunshine, ICF is poured concrete. The only difference is that with ICFs, you don't remove the forms. Your concern should be with the footing design and reinforcement regardless of whether you use traditional removable forming system or a stay in place system like ICF.

Brucepolycrete, are there any seams in the concrete with icf or is it poured as one structure within the forms? Any thoughts on footing/foundation design and reinforcement?

Cracks occur because of differential settling (and other things), not settling. So besides making it stronger (rebar, thicker concrete, wider footings), you should also look at water management such that the footings stay evenly dry. For example, a sheet of sloped plastic just below the perimeter surface can divert water away from the foundation. Avoid irrigation and plants near the foundation. Think about water coming off the roof or running down the walls (wind driven rain)

If you are really concerned about it, you can use a frost protected shallow ribbed mat/raft slab that is post tensioned (no basement).

Posted By arkie6 on 31 Oct 2014 11:50 PM

Posted By blacksunshine6973 on 31 Oct 2014 09:43 AM

Given the deep soil temperature in central Florida is approximately 72F to 75F, you don't really need any insulation on your basement walls if the top of the walls are at or below grade level.  If you have a portion of your basement walls exposed above grade level, you could insulate just that portion with a couple inches thickness of borate treated EPS foam.  A poured concrete wall would likely save you some money since with the ICF wall you would be paying for a lot of insulation that you don't really need.

Arkie - I wonder if there would be some significant advantage in using ICF as it might prevent condensation during times when the basement walls would be the coolest surface in the house?

Having the minimum footing width given the soil properties and the type of building (i.e., the effective building weight/loading) is what mitigates settling. Your local building regulator will likely tell you what this minimum footing width and other associated design parameters must be. I would certainly expect that condensation would be an issue to consider and address in Florida.

The PM gives you the required footing size based on soil and what's being placed on top of it. Pour the footing and walls in one step and your saving time and money.