OK all you ICF guys out there, explain to me why an ICF makes sense (from an insulation standpoint), in a below-grade basement wall.  It seems to me that if you make the assumption that the ground stays at a constant temperature (probably pretty close to true), the ICF doesn't change how many BTU's of energy are used to heat the inside space.  All you are doing is heating and cooling the thermal mass of the concrete with the inside space air temperature (through the insulated wall).  I claim that a standard formed concrete wall with 5" of foam on the inside wall is exactly equivalent for energy use, but has the advantage that you can cool or heat the room more quickly.

Now, if you have an above grade wall with large outside ambient temperature swings, you have a different story.  The concrete thermal mass will tend to stay at the average ambient temperature, meaning it will require less energy to heat or cool the room.  However, if the ambient temperature swings are minimal, say in the tropics, again, I don't think it will make any difference.

Am I missing something?  I was going to use ICFs for my basement, but now I don't think I can justify the extra cost. 

[BTW, if your an electrical engineer, I think you can model the system fairly simply as a current source (the heater output) into a capacitor (the thermal mass of the room) to ground, tied to a resistor (the R value of the inside foam wall) into another capacitor to ground (the thermal mass of the concrete) tied to another resistor (the R value of the outside foam wall) which is tied to a voltage source which is nominally ground (the outside ambient temperature).  The voltage source can be changed to simulate the outside air temperature changing.  The voltage across each component is the temperature of that area.   If you think about how that circuit would work, you can see what I'm talking about.]

I would disagree, and here's why:

• Assume a ground temp of 50°, and a desired indoor temp of 70°...
• That gives a constant delta T of 20°...
• With no insulation(Call it R-1):
• For 1,000 sqft of wall you've got a heat loss of 20,000 BTU/hr...
• With an ICF inner wall of R-10:
• For that 1,000 sqft of wall the heat loss drops to 2,000 BTU/hr...
• With an ICF inner wall of R-20:
• For that 1,000 sqft of wall the heat loss drops to 1,000 BTU/hr...

Now, in all cases the heat that is 'lost' is passing thru the concrete. Now the question is: Is the heat warming the concrete(So, that you might get a return on it)? In the case of a standard poured concrete wall. Nope. It's passing through and trying to heat the ground. The thermal mass of the ground is huge. All heat is lost.

Now, for an ICF wall, less heat is lost. Is the heat lost being stored in the concrete? I doubt it. You see the concrete is thermally connected(at the footings) to that 50° ground. In the case of the R-10 interior insulation: Is the 2,000 Btu's that is escaping every hour, enough to overcome the the 50° ground temperature. Again, I doubt it. It's fighting too much 50° thermal mass.

So, the real solution in lowering your heating needs, is to lower the Heat Loss. So, no matter which system that you use, the key is increasing the R-Value between you and the concrete. And, don't forget that concrete floor!

Now, if you could get the concrete inside the wall at 100°, through that R-10 insulation you'd have a Heat Gain of 3,000 BTU/hr and it would be like trying to live in an oven.

Sorry JC, I probably didn't make myself clear in the initial statement. I believe a standard poured wall is equivalent (or better) than the ICF wall ONLY IF you insulate the inside of the poured wall with the equivalent 5 inches or so of foam that the ICF has, so that you get your R20. BTW, I hadn't thought about the heat loss through the footers. That makes the ICF wall even less efficient than the 5" insulated poured wall. And your right, you need to insulate under the floor as well to make any of this worthwhile.

Please remember, that while most ICF's have a total of R-20 worth of insulation, only 1/2(R-10) is on the inside.
I don't think that there is any heat loss through the footers(heat won't get there). My point is that the ground temperature is thermally conducted into the wall(from the footers), which is a good thing as it reduces the Delta T(especially in above grade applications).

The key is simply preventing the heat from escaping the 'Thermal Envelope'. Because once it does, I doubt that you'll see any benefit.

CB,

I am going to take a differenrt look at the concept of an ICF basement.  You guys seem to be arguing the thermal properties just fine.

I live in the Pacific Northwest where moisture is a huge concern.  If I am understanding my waterproofing contractors correctly, they are telling me that by having a thermal break on each side of the wall and isolating the footings from the ground with a product like fast foot, this prevents the "wicking" action you can get from a basement wall that doesn't have a thermal break on the outside.  I personally questioned that if you properly H2O proof a basement it should never be moist, but they assured me it was easier to H2O proof an ICF basement because of this feature.

I also look at it from a purely financial aspect.  Here contractors are charging $400 to $450 a cubic yard to install a conventional basement and if we assume a simple basement 20X40X8X8" I will give an example.

Conventional 23.75 yard is $9500 to $10687.50 this is just the concrete walls, not the footings nor the furring of the walls for insuation.

ICF Basement @ $10 to $11 a square foot installed 960 sqft of wall space is $9600 to $10560.00 not including the footings.

If I wanted 5 inches of insulation on the interior now I could buy 2 to 2 1/2 of foam and apply it and achieve the 5 inches cheaper and in less time, plus not put pressure treated lumber in my basement.

Just a few thoughts

ICF Contractor

cabinboy your right icfs are better above grade no matter what climate your in, and maybe you should consider doing your whole house. Your looking for proof in numbers why not talk to people that have icf basements and see how they feel, I have several customers that love their basements and wouldn't do a standard poured wall again. I'm not quite sure they have a standard formula for comfort.

You guys win. I'll probably do an ICF basement, with SIPs on the walkout wall.

I still do not understand the comparison on cost from poured to ICF. It seems some of the ICF contractors are gouging when then do ICF.

Here is the point if you are a contractor doing Poured walls you have a huge investment in equipment, you have to store the equipment you have to clean the equipment and you have to remove it after every job.

Then you have to insulate the foundation and stud the interior for finishing. With ICF you have a much smaller investment in equipment, (bracing) the wall is already insulated, and has studs in it ready for interior finishing.

With poured wall you may be able to install a little faster than ICF but you still have to tear down and cleanup after it is done again the tear down of the bracing is much faster. So if we compare apples to apples then I would say that the ICF contractor has to start looking at his real project cost and stop gouging the customer because he is using ICF.

When we look at all of the other things like waterproofing , backfill, attaching floor systems,ect: they are the same regardless of which type of wall is being poured.

We have gone head to head with well trained and well organized crews on this subject, and in most cases can beat there time start to finish with the ICF some times it is a draw but not very often, Our Icf is done before the poured wall guys are and the poured wall still has to be insulated and studded.

If as an ICF contractor you think it takes more time to do ICF then get some traning on the ICF construction, and also get some training on job site organization both of these will show you how much faster you can do ICF so that you do not have to gouge the customer for your own inabilities.

If you are new to ICF the above should help, so you do not have to charge your customer for your learning curve.

In this industry the employee turn over seems fairly high so the other thing to consider is that training new people all the time is very costly, so if you have good employees doing a good job pay them accordingly and keep them it is money well spent and will cost you less than training new ones on a regular basis.

In this case why SIP for the walkout? Assuming you will already have to do an ICF corner or return, providing extra wall stability, is there another reason not to complete the basement portion with ICFs?

Are you planning on using SIPs for above grade? Not really clear in your posts, however, I imagine a very short load of SIPs, if not using also above grade, would be cost prohibitive. That, and the issue about backfilling AFTER the deck is on, what happens if the SIP portion of the walkout is the supporting wall for the floor??? Job sits until the SIP order arrives....sounds like 2 crane visits to me?

Ok I am using TF System in a basement wall application. 9' with at least 2' above grade. Judging from what I have read here I was using a 4" outside layer and 2 1/2" inside layer. Should I invert the two and make the inside 4"? I would have thought the idea was to insulate more where the biggest differential in what temps you are separating. Inside the I dea would be to maintain an average temp. In NY State I am sure the below grade is less than the 50 degrees mentioned here especially in the winter. So witch is correct?
Thanks
Vinnie

Actually, winter or summer the relative temps are 50-52*, and I don't believe paying for 4" on either side is worth the cost in a basement application. 2.5" inches on each side should be sufficient and I don't think you'll find any statistics saying other wise. Most people that build basements only with ICF's love there basement's in all climates, but generally all say the same thing after one year " boy I wish I would have built my whole home out of ICF's"

Dave

The object of any type of insulation is to prevent the flow of heat(in or out). So, if you increase the foam only on side of an ICF, think about where the heat is. If it's on the inside(cold temperature area), add any additional foam there. If it's on the outside(Florida for instance), add the additional foam there.

I'm sure that other opinions may exist, so let's hear them.

Ok, I've designed my families house and cleared the land...I've decided to go with NUDURA based on the lack of follow thru from other ICF providers. I have an architect looking at my computer drawings and adding some fine tuning. I've located a NUDURA distributor in my area and an engineer but what I keep hearing is "DON'T USE ICF BELOW GRADE...IT NEVER WORKS AND YOU'LL BE SORRY IF YOU DO".

No BS...all I need to know is does ICF really work BELOW GRADE? I live and am building in NC TX (between Abilene and Weatherford).

Posted By rainman on 17 Apr 2013 06:31 PM
Ok, I've designed my families house and cleared the land...I've decided to go with NUDURA based on the lack of follow thru from other ICF providers. I have an architect looking at my computer drawings and adding some fine tuning. I've located a NUDURA distributor in my area and an engineer but what I keep hearing is "DON'T USE ICF BELOW GRADE...IT NEVER WORKS AND YOU'LL BE SORRY IF YOU DO".

No BS...all I need to know is does ICF really work BELOW GRADE? I live and am building in NC TX (between Abilene and Weatherford).

Of course ICF works below grade, it is recognized by code and has been done thousands of times. The important fact is that the ICF must be waterproofed with a peel & stick EPS approved membrane. Like any below grade wall, proper drainage is important.

Who is telling you to not use ICF below grade? Your engineer and/or architect?

Maybe that's their roundabout way of saying "don't build below grade". With frost protected shallow foundations on flat lots, I tend to agree.

In the part of TX that I'm located in the real issues we face are expansive clay and limestone the size of large trucks.  I think the engineer is possibly unfamiliar with the product and/or had 1 or 2 bad experiences with it and therefore just prefers not to deal with it.  I think my best bet is locate another engineer although this one comes highly recommended.

My engineer is telling me not to use ICF below grade and that he will engineer my walls to be 12"...it's making me nervous to be honest.  I think he's over engineering the basement.  He says that "ICF basements never work, they will always leak and most of the time bulge; if you build ICF below grade, you'll be sorry".  After hearing that I was kind of like..."WTH!!!  I can't build a house to turn around and demolish it and rebuild it".

This engineer comes very highly recommended but I really think I need to find another one that has extensive knowledge in ICF engineering.  My architect on the other hand is really cool old dude that is retired and now just keeping busy by working with ICF designs.  I think I've decided on a product to use and just need to find a way to really get comfortable with it, touch it and just play with the blocks but I don't think distributors allow that.  Any suggestions on how to get over this kind of "FEAR"?

Hi Rainman, I'm the original poster, way back in 2007. So, in the summer of 2007 we used ICF's for our basement walls, one of which is 8 feet below grade. On that side, when we excavated for the footers, there was water collecting, probably from an underground seep. We did all the perimeter drain stuff (perf pipe), which I have always been skeptical about, and used ICF's (we did it ourselves, but had a professional do the pour to minimize the chance of blowouts). Everything went very smoothly (advice: brace, brace, brace). The ICF outside walls were covered with a waterproof membrane (liquid when applied, I think they sprayed it on, but can't remember for sure). Then we backfilled, as carefully as possible so as not to disrupt the membrane or foam. Bottom line: never any hint of wetness in the basement, even in the corners where water was present before the footers went in. As advertised, basement doesn't feel like a basement -- no excess humidity, nice and warm when heated up (we're at 10000 feet in Colorado). People have slept down there with no complaints. My two cents.

Posted By rainman on 17 Apr 2013 11:39 PM
My engineer is telling me not to use ICF below grade and that he will engineer my walls to be 12"...it's making me nervous to be honest.  I think he's over engineering the basement.  He says that "ICF basements never work, they will always leak and most of the time bulge; if you build ICF below grade, you'll be sorry".  After hearing that I was kind of like..."WTH!!!  I can't build a house to turn around and demolish it and rebuild it".

This engineer comes very highly recommended but I really think I need to find another one that has extensive knowledge in ICF engineering.  My architect on the other hand is really cool old dude that is retired and now just keeping busy by working with ICF designs.  I think I've decided on a product to use and just need to find a way to really get comfortable with it, touch it and just play with the blocks but I don't think distributors allow that.  Any suggestions on how to get over this kind of "FEAR"?

Find yourself another engineer. It's laughable & scary that he is making such comments. Maybe his only experience with ICF is a waffle wall, yes those are problematic because of the voids and it lacked the solid monolithic design of modern ICF's. A 6" or 8" core with a solid concrete & rebar reinforced ICF wall will not leak and will not bulge when properly done.

Posted By Lbear on 18 Apr 2013 12:37 AM
Find yourself another engineer. It's laughable & scary that he is making such comments. Maybe his only experience with ICF is a waffle wall, yes those are problematic because of the voids and it lacked the solid monolithic design of modern ICF's. A 6" or 8" core with a solid concrete & rebar reinforced ICF wall will not leak and will not bulge when properly done.

I would agree with this advice...find someone competent...ICF is often used successfully below ground.

Relative to "ICF fear", get trained or hire someome competent. You might want to consider TF Systems vertical ICF so as to NOT have to touch/mess with blocks...

Relative to protecting/waterproofing below ground ICF, does anyone have experience using Platon?

Platon