I am planning to build a house and I am roughly costing different techniques to see which ones cost more. Based on some rough costing data, it looks like ICF is 3x expensive than SIP panels and it is far less energy efficient. Here is some cost breakdown:

Using Nudura, one of the cheaper solutions available with an 8" thick concrete wall of 160 linear feet 10 feet high. The cost is about $4.8-$5.2 for the Nudura blocks per sqf of wall. Concrete pour would be about $3500-$4000. Rebar about $1200. Then add some misc expenses for some basic labor and shipping, etc. Assuming most stacking is done by me. The cost is $12,500 and it would take quite a bit of my own labor (opportunity cost).

Now, for the Acme SIP panels, The same same exterior wall with laid up panels which me and a couple of buddies can carry and lay up very quickly would cost $4,300.

So, ICF construction is about 300% more expensive than SIP panels by this calculation. Not only that, but SIP panels are R-48  insulation value. The ICF has an R-value of 24. So, with ICF, I just lost half the thermal value. And, it appears, ICF eliminates any thermal mass potential benefit by placing the insulation on both sides of the concrete, so its thermal mass is not even a benefit. Both are very air tight.


There are certainly advantages to ICF I can see. It is a bit more termite resistant (though the SIP panels are mostly insulation which termites don't like either). It is structurally stronger and can stand up to higher wind speeds (good for tornoado alley or hurricane prone places).

But, for a normal house that plans to only last the life span of the builder (40-50 years) in a place that is not a hurricane target, what exactly is the advantage of ICF considering it costs 300% more money for less insulation value?

I am trying to figure out if ICF actually provides any value or if it is just a way to spend more money and receive less.

I considered steel SIP's for my house before going ICF. They weren't that much cheaper- maybe no cheaper, but I don't recall. Either makes a good house. I went ICF because it was easier for one old man, working alone. I also had an ICF contractor nearby that coached me, rented me forms, and did the filling. The advantages of ICF are of course the strength, and they are also very quiet. SIP's can transmit sound in some situations. In our mild SC climate, the thermal mass effect is amazing, we go for months at a time without using the HVAC. Despite being insulated, there are 100 tons of concrete in the walls, and thus very slow to change, especially in the sharp ups and downs we get in the mountains. I think in a climate that stayed very hot or very cold for long periods, ICF wouldn't perform as well. I've always thought that the best of both worlds would be an ICF basement with SIP walls and roof.

Acme Sips are $6.87 per sq ft according to their web site for a total of$10992. Is this below grade or above. Either way why the 8" block?

You are right. I misplaced a decimal. I was wondering how in the world it could be so cheap. With that resolved, my very rough estimates make ICF / Acme SIP panels are much closer So, in that case, I think ICF is definitely the winner.

Just for sanity sake, do you think my estimate of $13k or so for a 160 linear foot 10 foot tall exterior walls is about right (basically a 40' x 40' square)? I would be laying the block though I would hire an ICF guy to inspect it. Of course I would not be doing any of the concrete pour or anything else. I want to make sure I am not making any other stupid mistakes.


Basically, the calculation is for 160 linear feet 10' high and 8 inch walls:

160*10*4 = $6400 for the blocks

((160*10)*(8/12))/27 = 40 cubic yards of cement @ $90 a yard = $3600

Rebar = $1200

Labor = $1000 for ICF inspection

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Total = $12200

Do you see any big errors or things I am missing that would materially drive the price up? (More than 15%) Does $13k sound reasonable in this scenerio?

Missing cost for concrete pump, footing, etc. $1000 for labor? Usually labor + parts adds up to 60% of a project cost plus another 40% for profit. I give you $13K if you build me one…

You'll need to make or rent bracing. As I learned building my own house, there are hundreds of 'small' costs that really add up. You need a foam gun and a lot of cans of foam. Material for door and window bucks, whether PT lumber or purpose-made materials. I used Fox, and they make special clips to hold the blocks together so they don't float up with the concrete. I also used giant wire ties in the corners. You'll need some kind of sill material at the top of the wall, and fasteners such as J-bolts to secure it. You'll need some kind of ledger system for the floor(s) and the related hardware. The list goes on and on. Every construction method has it's own set of costs and skills. Despite my house being ICF, with steel internal studs and a metal roof, my first nail order was some 18,000 nails, and I had to order more! Where do all of those nails go?

Smart shopping makes a huge difference. To anchor my window and door bucks, I used 4" galvanized lag screws on the concrete side of the lumber. I used about 500 in all. At the big box store, they were $1.47 each. From an industrial supplier, they were $.27 each, for a savings of $600 on one minor line item. The ONLY things I found cheaper at big box stores were Simpson brackets and NM (Romex) cable. I shopped online, ebay, and craigslist. A local lumber yard was 'dumping' fiber cement siding products during the FL real estate bust, and I got all of my siding and trim materials for 25 cents on the dollar.

Posted By BuildNewb on 04 Nov 2017 07:25 PM
...And, it appears, ICF eliminates any thermal mass potential benefit by placing the insulation on both sides of the concrete, so its thermal mass is not even a benefit...

I'm not sure where you got that information, but that is not correct.  Several studies online show slightly better building performance if all of the wall mass is on the interior, but that is not the same as saying that there is no benefit to having the concrete mass in the middle of the wall. For any change in temperature outside the wall, the mass of concrete inside the forms must change accordingly before that temperature change is felt at the inside of the wall.  That change in temperature of the concrete is the mass effect and it often delays the outside temperature effects at the inside of the wall by several hours, and often by that time the temperature outside the wall may have reversed its direction.  The mass of the concrete inside the forms tends to dampen out and delay the peak outside temperature effects.

You get the most benefit from the thermal mass in warmer climates and especially in desert climates where the day/night temperature swings above and below the desired temperature inside the home.

Also, if you are building above ground single story ICF walls, there is little if any reason to go with 8" thick concrete.  6" thick concrete is more than sufficient and will save you ~25% on your concrete cost.  From a strength perspective you could go with 4" concrete, but 4" walls are really congested with rebar and ties making it hard to pour and consolidate the concrete.  For this reason, 6" ICF is probably the most commonly used forms for above ground single story walls.

Posted By BuildNewb on 04 Nov 2017 10:58 PM


Labor = $1000 for ICF inspection

That $1000 seems awful high just for an inspection of the forms.  The local ICF distributor that I bought my forms from came out and inspected my stacked ICF walls at no cost, but I did end up paying him and his crew on the day of the pour to do the concrete placement and consolidation.  It cost me around $750 for the labor to pour the walls ($125/hr for 3 people for 6 hours) and around $600 for the concrete pump truck cost (4 hour minimum at $125/hr).

Another adjustment is the fact that your not going to need 1600sq ft of forms unless you have no windows or doors in the walls. You will have some waist but that can be lessened by the type of form that you use. I just sold a R 42 5.5" core wall system for $3.25 per sq ft plus shipping as a illustration of what's possible if you do your homework.

Are you taking into account the $1000's you will 'not' spend on wood for all of the outside walls, lower 'framing' costs since all they have to build are inside walls and roof(should' be around half), the lower cost of HVAC with ICF.....possible lower home owners insurance..... etc.....?

ICF hands down. No wood to rot, endless amounts stronger. No crane to rent or scaffolding depending on panel sizes. SIP has its place but

Figure 12-14 sqft normally. $4.00 is avg labor costs plus materials operating expenses and profit. Smaller jobs go up as the big expenses like the pump is harder to spread out. You can use a line pump to save $ but you will need additional help to hold the hose, vibrate and adjust walls. Have to love weekend warriors that don’t value their time and equipment.

Need bracing and Lts of misc tools to make the job go easier and faster, although I’ve seen guys show up with all tools in a 5gal bucket lol.

Openings, corners and heights are where the $ goes.

Pay for pre pour-inspection and pouring. You only get one shot.

ditto......

If you want to sort out exactly how ICF (or any other wall construct) will perform in your actual seasonal climates, we developed this software several years ago:

Borst ICF Performance Calculator

The actual season climate and location of the thermal mass determines how much of a benefit the thermal mass will provide in terms of effective R-value. For standard ICF construction using our Rogue River, Oregon outdoor temperature profiles, this is R21.38 in Spring, R66.15 in Summer, R63.42 in Fall, and R21.07 in Winter. So this is an average annual ICF performance of R43.07 or 1.86 higher performance than the conventional R23.10 R-value. This does NOT include the reduced air infiltration benefit that ICF (or any other wall construct) can also provide. As a result, we don’t require or use any AC to address our 90F+ average highs including the several 115F days that we get each year. The interior thermal mass and high effective R-valve of the ICF walls keeps the interior of house from never exceeding 70F.

Arkie's description of how and why ICF can have a significant thermal mass effect is correct.