The Hidden Costs of ICF: The Value of Insulated Concrete Forms

As we continue the process of designing and building our home, we are at the stage where we are faced with making decisions. Our first big choice is critical to the rest of the design and has a big impact on the overall cost. The building envelope, otherwise referred to as the wall construction type, is a high cost item, and can affect aesthetics significantly. One of our goals is to create a design that is sustainable, and for an exterior wall, that usually equates to energy efficiency.

Insulated concrete forms (ICF) offer a high level of energy efficiency compared to traditional ‘stick built’ wood framed walls. ICF construction is essentially a concrete and foam sandwich which is put together like a set of Legos on site. Once the foam blocks are in place, concrete is poured in the center cavity and allowed to set. This forms a sound structure with excellent thermal properties. The disadvantage of this type of construction is the overall wall thickness; ICF walls tend to be very thick, and total wall assemblies (the structure plus interior finish and exterior cladding) can be upwards of 14 inches thick. It is easy to see that choosing ICF means giving up some interior space to the wall.

insulating concrete forms

insulating concrete forms (Photo credit: Frameform)

For our design, space is at a premium. We are on a relatively tight lot, and every square foot counts. During our late night study break, we took a walk and ended up discussing ICF as it relates to cost and square footage requirements. What we discovered was that at high level, ICF demands not only a cost premium, but a space premium. Here is what we worked through:

Using basic averages for our design, the house has about 620 linear feet of walls. If we multiply that out by 12 to convert feet to inches, we get 7,440 linear inches of wall. Next, we looked at the delta between an ICF wall thickness and a SIP (structural insulated panel) wall thickness. SIPs are similar to ICF walls in that they are a sandwich of foam and sheathing; typically a wood sheet is glued to the foam, or some types use steel studs (which is the kind we are considering). Basing our numbers on the products I’ve seen, there is a difference of about 5 inches between the two product types. That means for every linear inch of wall, we give up 5 inches of depth if we choose ICF construction. Length x width reveals that we lose 37,200 square inches to ICF; breaking that back into square feet for easy reference means we give up almost 260 square feet of space if we build with insulated concrete forms. That space is eaten up by the walls, and we’ll never get to enjoy it beyond the energy we save (i.e. dollars not spent on electricity).

The next big item we looked at was the cost of the lost square footage. If you build it, you pay for it, even if you never get to ‘use it’. For us, we multiplied out the cost for an ICF house by the lost 260 square feet and realized we would be spending a whopping $41,600 on lost space! Then we had to also account for the increased cost of ICF compared to our SIP alternative. The product I’m considering boasts that it comes in at half the price of ICF, so the delta between the two wall options means we’d spend an extra $20,000 to go with ICF over SIPs. Add the two numbers together, and we’d pay over $60,000 for lost space and the same R-value (which tells us how energy efficient the wall is). The increase in cost between the two walls types alone isn’t terrible, but once we account for the lost space due to increased wall thickness and look more closely at the two products side by side, we don’t add a lot of value for the increased cost.

Residential Application - Before

Residential Application – Before (Photo credit: PorterSIPs)

Granted, we may lose out on some sound transmission advantages and additional natural disaster resistance, but conceptually, a well made and properly installed SIP wall should perform on par with an ICF wall at a much lower cost – both financially and spatially. When it comes down to energy efficiency, we wouldn’t see any kind of significant savings going with ICF compared to SIP, as the cost broken down over time would take decades or even centuries to pay back.

Finally, as our builder pointed out, we would also need to accommodate the added weight of the ICF structure on the foundation. That means a costlier foundation design that requires more engineering and more material (concrete, re-bar, deeper form work, deeper excavation, etc.). One decision quickly affects a host of other components.

Now that we’ve taken a high level look at the hidden costs of ICF, we can start to see that paying a lot more for lost space doesn’t make much sense for us. The premium we pay for space in the city only compounds this figure. We’ll be taking a closer look at these wall type choices and doing more research on the pros and cons of each before settling on a final choice; maybe we’ll find something that surprises us. Do you have experience with an ICF or SIP home? Let us know in the comments!

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  • http://blog.SLS-Construction.com/ SLS Construction

    Pretty fair round up of pros & cons for your project – the only thing I didn’t see mentioned is issues caused when the webs don’t line up with interior walls, & trim outs – those can cause some interesting issues for someone not used to them.
    SIPS & ICF’s – expect increased estimates from sparky’s & plumbers – both add a time factor & a new way of doing things
    For my place, it will be ICF’s with a possibility of SIPS for the roof though I will definitely have an integrated slab between my first floor & basement for disaster reasons

    • http://www.architangent.com Brinn Miracle

      Another great point – for anyone who is unfamiliar with a product, it usually means an up-charge. Although the product we are considering has the option for pre-cut raceways and chases, it can still be an issue for those unfamiliar with it. Thanks for stopping by!

      • Les

        I’m a mechanical engineer, and also looking hard at building methods–energy, cost, and space consumption. Two things we keep running into–builders have made lots of stick homes, they are comfortable there–low risk for them–and they often have trouble selecting the ideal ICF block. In your case (like mine) the 4″ concrete with total of 9″ wall thickness might make a big difference in space loss. The second thing–and to me biggest thing is the blind (perhaps) following of R value. This isn’t the only variable, and maybe even a variable of low importance in a wall. Heat transfer thru a wall isn’t a big driver (like the roof,) rather it is thermal mass. In the days the heat goes way up in FL (and TX) but at night it cools off some bit. The mass of concrete is like momentum. It keeps the temperature stable resisting big swings in temperature. A smaller AC running longer easily keeps the slowly eroding cool from the previous night intact, then when the next night begins, again you get a “free” recharge of cool that carries you into the next day again. If it doesn’t make sense, consider air versus water–water has much more thermal mass. Big swings in temperature effect the water much less than air. Foam insulation is mostly air. It changes temperature easily, though doesnt transfer heat easily; concrete and foam both resists the transfer of heat AND resists change in temperature. This is the real engineering value in icf. Without that understanding, icf would make no sense.

        I hope your home is wonderful and exceeds your hopes in all ways. Sorry for my soap box, but too many builders don’t understand the physics here, and their fear of different can cost us big if we don’t understand. Thermal mass, not R value is the point of ICF over stick for an energy/value discussion. Peace–LV

        • http://www.architangent.com Brinn Miracle

          Hi Les, Thanks for your insightful comment. I agree that we have to fight against ‘the way it has always been’. In regards to thermal mass, it is definitely a consideration that all of us should make. You’re right – a big thick concrete wall will retain heat and slowly release it over time, helping to maintain temperature. For our project (in the sweltering heat of Texas, where ‘winter’ is about 40 degrees on a bad day), I was inclined to think that a large mass of concrete would prove detrimental to indoor comfort, since the retained heat would be slowly dissipating inside over time. If a south facing concrete wall is heated all day, I’m not sure that our night time temperatures would be low enough to help ‘even out’ the heat gain on the wall. What are your thoughts on a large thermal mass in hot-humid areas like Florida and Texas? We are pursuing a rainscreen system that will create natural convection and lessen the heat’s effect on the building. The roof choice is next on my list – likely a paver/deck system on top of the structure. Thanks for stopping by!

          • Refer-Engineer

            Hello
            Im getting to pull the trigger on how I build my house in Central Wa. Looking at ICF real close ,But SIP may be the way?
            Im in a fire prone area,I have ton of rock (Big Ones) a few hundreds on a cliff behind me.
            It gets very hot and cold ,so heating and cooling is a issue,
            But electricity is cheap,2.7 cents a k,w, yes 2.7.
            I have not seen much information on SIP. Are they Energy star rated ?
            Will ASHRAE have anything on SIP?

          • http://www.architangent.com Brinn Miracle

            Hi there, you may want to start by visiting http://www.sips.org/ for more information on SIPs and finding providers in your area. Also, you could consider metal insulated panels, which are similar to SIPs but constructed with metal instead of wood. Here are two manufacturers of metal insulated panels. http://texas.transconsteel.com/products/ultraframe/ and http://www.thermasteelcorp.com/ – In reality, SIP and ICF are both good choices, it will likely come down to cost, availability and familiarity of construction technique from your builder. There are advantages and disadvantages to both sides.

          • ANSLQ32

            ICF with ICF roof, best fire protection.

          • Savine

            Hi Brinn! Sounds like you’ve done alot of homework! Great discussion and I also appreciate all the comments from those with experience with ICFs. I am in the process of designing my own house and stumbled across this site in my own research into ICFs. I live in a similar climate (Norman, OK) so I totally understand your concern for thermal mass retaining heat that would be released into the interior when our nights can be 90 – 100 degrees in the summer with high humidity. I have been studying passive solar design for many years and have wrestled with this dilemma in designing my own house. Adequate roof overhangs will help shade a structure, but quite a challenge with a three-story house. The west side may be especially prone to overheating with the afternoon sun. Maybe you might be able to install some light-weight awnings. I was surprised that ICF walls would be placed on a slab foundation. I thought they would be placed on a stem wall. I’ve also wondered how windows are placed in an ICF wall since there would be considerable weight on top of them – I suppose a hefty header over the window? My only objection to ICFs is that cement, used in concrete, is such a high-embodied energy product to produce. I suppose long-life and durability might justify it. I have also considered a hybrid mix of strawbale walls for the north and west walls since they are so insulative as well as breathable (they can help regulate humidity levels) and much more fire-proof than wood frame. Talk about wall thickness, though! Strawbale walls can be 18+ inches thick! I also was thinking about incorporating interior rammed earth walls for thermal mass to reduce temperature swings and for heat storage during winter months – working with winter sun angles.
            Well, good luck with the build! I am excited for you!!!

          • http://www.architangent.com Brinn Miracle

            Hi Savine, thanks for joining in the conversation! Hot/humid climates can definitely be a challenge for selecting the right systems. It sounds like you’ve done a lot of research already and are thinking about all the right things. I would imagine you get more tornadoes in your area than we do, so ICF would be a great choice for your location. If you have the room, you could do an ICF wall with additional external cladding that would help mitigate any heat gain & keep it dry. For windows, you are correct – a pre-engineered ICF design would incorporate headers to bear the weight above the windows. Sounds like you have lots of choices ahead of you – best of luck!

  • architectrunnerguy

    Is your anaylsis just done with the exterior wall costs or mixed in with everything else? Your $160/sf ($41,600/260SF), while very low for a whole house, would suggest the latter.

    • http://www.architangent.com Brinn Miracle

      Yes, you’re exactly right. We took the lost square footage and multiplied by the price per SF that we are using for the house to get the $41k.

  • architectrunnerguy

    Ok. Won’t let me reply to your reply so I’ll just tack my thoughts on here.

    Let me start off by saying I’m not a big fan of the thick ICF walls but your $/SF anaylsis relative to wall thickness (260 sf=$41, 600) may be slightly skewed.

    Sure, it’s convienantly easy to take the total cost of a house and divide it by the SF but in your sf/ linear wall thickness you’re still going to have expensive and fixed costs no matter how thick the walls are.

    First off…..Kitchens…expensive, bathrooms….expensive, nice interior finishes….expensive and you still have those costs irregardless if the walls are 1″ thick or 1 yard thick. Many others here too like window costs and door costs will be the same. Or roof costs or that really neat glass tile you like for the master bath. None of which are related to wall thicknessess but can add significantly to the cost of a house.

    And second, you have fixed costs that are entirely independant of the wall thickness. Grading and site work, permits, insurance, sewer and water connections, and yes, your builders fee.

    So, do your math without a kitchen cost, bathroom cost or the stuff and more that I referenced above.
    Your way of crunching the numbers is a little bit like comparing two refrigerators, one for $1000 and the other for $1200, on a 2000SF house but instead of comparing direct cost to each other you’re multiplying the costs difference by 2000SF (it would a be $400,000 “difference”). Silly I know and there’s area involved here but hopefully you get my drift.
    And as an aside, while I don’t know the building costs in Houston, $160/SF sounds very low. Far better to budget high and be pleasantly surprised than budget low and loose sleep. And that’s coming form an architect who, together with his wife, have built three houses for ourselves over 35 years. And we’re STILL MARRIED!
    Doug

    • http://www.architangent.com Brinn Miracle

      Doug, you are right – this was a very preliminary ‘high level’ comparison we did during a walk one night. We came home after discussing it, threw some numbers down and took a look at the big picture (which still remains true regardless of whether you incorporate cost per SF to build the whole house or just the isolated wall system) – ICF wall thickness takes up space that you pay for but don’t get to use. That was our main conclusion, and the delta between just the two wall types was $20k alone (not accounting for the lost space due to thickness). It started to lose appeal at that realization. It’s something that not everyone thinks of from the beginning when considering ICF.

      As for the costs per SF, we’re actually already working with a builder and we’ve gotten our preliminary estimates in at $150/SF including fees (that was also confirmed by another builder we considered). We’ve had a few meetings to date and will get into the details this summer. Most houses here that are better quality spec types can be constructed at $80-100 SF. Above average quality semi-custom comes in around $150 and high end custom usually starts around $200+ for Houston.

      We’ll have to chat more about your experiences sometime – I’m sure you have a lot to share!

      • architectrunnerguy

        BTW, I like your house but I think I’d work to get more identity for the front door. If you have Christopher Alexanders “Pattern Language” he talks about the importance of that in pattern 110: “Place the main entrance of the building at a point where it can be seen from the main avenues of approach……..” (pages 540-544 is the full description)

        • http://www.architangent.com Brinn Miracle

          You’ve pin pointed the element that has bothered us since the beginning. :) We really wanted to have the front door be on the tall stair volume facing the street, but the stairs will not work any other way and must be placed where the door would go. I’ve looked at it over and over, and my only last scheme to try is to make discontinuous stairs between the first level and second to try to squeeze in a straight run portion on the first floor and have it still end in the same place with enough headroom. It was the one program element we couldn’t accommodate without sacrificing other more important pieces. If you have any ideas, I’m all ears.

  • CW

    Wouldn’t merely extending the design of the house out 5 inches solve all the handwringing over “lost space”? Also, I’m told that there are other benefits with regards to hanging drywall etc that should be factored in and why would you not subtract energy savings from your projected costs? I hear the concrete helps keep houses significantly cooler in climates like your… I am getting ready to build and am leaning towards ICF !

    • http://www.architangent.com Brinn Miracle

      Hi CW,

      Great questions. For our situation, we are in a small city lot, and that means we are literally building to the limits of the property. We do not have any ‘extra room’ to extend the house into, so the only direction our walls will go is inward. Space is at a premium in our case, and so eating away ‘just 5 inches’ adds up to losing almost an entire room of our house in square feet. If you are planning to build on a large lot, then it would not be as much of an issue for space, but you still pay for ‘space you don’t use’. There is a value attached to that lost space that we have to consider, and for our situation the value is very high. We asked ourselves, “Would I rather have an extra room in the house or thick walls that perform the same as thinner walls?” When you ask it like that, it makes sense to try something other than ICF. As for energy savings, ICF and SIPs construction are very comparable. I have found that SIPs may even give us a greater energy efficiency than ICF (Remember: Each product is different, and installation is a big part too!). The marginal difference in utility savings between ICF and SIP construction would take decades or even centuries to pay back the added cost of ICF. Both are very efficient, so really either one would be a good choice.

      • ANSLQ32

        Use ICF roof as well. The payback is not why you are building your home. A comfortable, safe place designed the way you want, in the location you want is. I don’t know your costs, but I do know that the monthly difference in mortgage payments between a $500,000 stick home, and a $550,000 ICF home is very, very little. Don’t know your energy costs in Houston, but I bet the savings with ICF will be greater than the monthly difference in those two mortgages. Throw in insurance savings with the ICF roof, walls, foundation, you will surely have lower total monthly costs of ownership from day one.

        • http://www.architangent.com Brinn Miracle

          Payback is another way of evaluating opportunity cost. I could pay an extra $50k and continue to make interest payments on it (if it is wrapped into a mortgage), or I could take that same money and invest it into something that would generate income that I could use for other wants/needs. The concept of ROI is something that helps us make those judgments on opportunity cost, and evaluate what really happens with ‘just a little more money’. It often turns out that the end results are not ‘worth it’ from a value standpoint.

          As an example, if we said that solar panels would take 50 years to break even before I would start receiving free energy, then that option would be of very little use to me, as I would not be living in the house 50 years from now, and that same $50k could ‘work for me’ in better ways over that length of time. I could earn more money investing it than what I would gain from energy savings. However, if those same solar panels would break even in 10 years, it becomes a more realistic option, as I would receive a direct benefit from spending my money on them and would start to actually see money back in my pocket over a shorter time horizon. Likewise, the interest I would pay over the course of 30 years on $50k more construction costs, in addition to the lost cash flows (due to higher mortgage payments) may not be in my best interest if I could make more money doing something else with the same amount of capital.

          While the purpose of building a home is not to get a return on investment, decisions made on the margin are influenced by ROI. The opportunity cost of one decision compared to another certainly brings up the idea of the value, cost, time line, and ultimately, happiness. I would be happier saving $50k, knowing I still had a home that was comfortable, safe and designed the way I wanted. Ultimately, it is an individual decision, and this is where we landed.

          • ANSLQ32

            …For example, if you really want to maximize your savings, buy the cheapest shack and car, live on beans and rice…..just joking. BBA Finance with real estate, risk, insurance minor here. If you are building for investment only, make two floors rentals, live in one. But you don’t want that, you want something special on that exact lot. SO,,,it is not for investment purposes, it is for your personal use, pleasure and comfort. It is for you and your family. $50k over 30 years for a home your great grand children and beyond will use is rather an AWESOME ROI and Fantastic Value..! In effect you will be giving your children a mortgage free home to move into or rent our for decades after you pass. Opportunity cost for ICF blows away all other materials, long term.
            A better example of home ideas that don’t pay off is spending $12,000 on new triple paned windows for a fifty year old house with overall r-value of 12 or even 28, there will never be a payback in energy cost, so that purchase is done on ‘looks’ only. Best to replace with single pane glass. (or build a new ICF home…lol).
            Insurance costs will be lower with ICF, as in your house won’t burn down. Shingles won’t fly away….termites won’t eat the SIP…etc.
            I have yet to find a study on SIP construction that matches ICF in any of these areas that insurance companies cover..this alone will reduce if not match the cost from an additional $50,000 ($253 @ 4.5% over 30) borrowed, even if given SIP/EPS (that will leak air) matches ICF in energy cost. Make up the difference in car payments by holding onto the depreciating asset longer.

            anyway, how about some pictures of the project? In downtown OKC, nice townhomes (non-icf) go for $300,000 up to $950,000 for a three story with elevator. Where in Houston is the home?

          • http://www.architangent.com Brinn Miracle

            We did consider just pitching a tent on the lot, but decided it might disappear when we went to work. :) (the property is about 3 miles west of Downtown)

            I’m not going to assume my kids or grandkids would live here, as I don’t want to assume they want the same life as me. They may have aspirations of living elsewhere or just different tastes (also, I want them to work for a living, and understand the value of things by buying their own stuff!). So we’ve only planned to live in it for our lifetime, then sell it or donate it to charity. We do have the capability of renting out the first floor, as well. We designed it to be an efficiency unit with separate entrance to act as a Mother-in-law suite or potentially house other guests (paying or otherwise). You might enjoy an article I wrote on ROI in relation to remodeling for another blog: http://blog.archability.com/?p=225 – my husband is a fellow finance grad (MS Finance, CFA level 3 this year), so we often talk about the real estate market, investment properties and the like. If we had more money, we would probably do more real estate investments, actually.

            You can find pictures of the house in a variety of blog posts (try the ‘projects’ blog category, then anything to do with ‘dream home’). The latest post is this one with progress renderings: http://architangent.com/2014/05/just-another-brick-in-the-wall/

            more on the metal insulated panels:
            http://architangent.com/2014/02/metal-insulated-panels/

            You might enjoy this one, when we did a quick financial analysis on combining our property with adjacent ones:
            http://architangent.com/2013/04/dream-home-diving-into-details/

            Thanks for reading and all the comments!

          • ANSLQ32

            The tent is funny..!! Park an RV on it. lol. I am thinking of getting a small RV as a mobile office.

            A neat trick I learned from my real estate mentor, will the property to skip a generation, meaning your kids, and maybe grandkids will not be able to sell it. Put conditions on the deed when it is conveyed upon your passing. The example I was given was that the girls were given the mineral rights, (easy money if oil or gas found), the boys were given surface rights, to WORK the farm.

            For an interesting house, (links that I post don’t stay on, so ‘dot’ is used)

            http:// money dot cnn dot com/video/pf/2012/09/27/pf-pensmore-home.cnnmoney

          • Teresa

            Wow, what planet are you from, our kids should work so we can donate the house to charity..so people9 who were too lazy to work can have it…

          • http://www.architangent.com Brinn Miracle

            Not all charity cases start with laziness, nor is it wrong to offer assistance to those who cannot help themselves while requiring those who are able to support themselves to do so. When I said ‘donate to charity’, I meant donate to a non-profit organization such as a shelter, church or other entity that would benefit from a centrally located house that could effectively be used for all sorts of things. Obviously, donating a house to a poor individual doesn’t make sense, as they cannot afford the taxes.

          • ultravomit

            Solar panels only take 7 years to pay back these days. FYI

      • Teresa

        72there are no thin walls that perform as well as ICF, for the 1522 sq ft basement the ICF cost me 18,000.00 more. but I saved 10,000 on interior finishing ( 2 x 4’s , insulation, vapour barrier, plug covers that stop air transfer, etc. this is our 4th house and I would never have anything else again!

    • ANSLQ32

      You should do it. Find a plan and builder that will do the ICF foundation and roof.
      All combined gives the greatest energy and insurance savings for life.

    • Teresa

      Ours is a walkout and the wall is never even cool to the touch in winter with only flexcoat on that wall!

  • lynda

    I suggest reading the Building Science (Joseph Lstiburek) opinions on Thermal Mass. A lot of folklore has been passed around by the Concrete Industry. Don’t get me wrong, the building system is still good, but there are multiple layers of costs. All “thick wall” building costs extra in property tax, too.

    (Be careful with a 4″ core of concrete, Les, it is extremely hard to consolidate the concrete, and it’s easy to end up with voids. A lot of ICF contractors use substandard techniques to overcome the problem)

    • http://www.architangent.com Brinn Miracle

      Our builder mentioned the same issue with the 4″ cores. He typically recommends 6″ or larger for that reason. I’ll look into the reading you suggested. Thanks!

  • Laura

    Thanks for your article! I have a question… I read in the second paragraph “Once the foam blocks are in place, concrete is poured in the center cavity and allowed to set.” Then later in the article you wrote “Finally, as our builder pointed out, we would also need to accommodate the added weight of the ICF structure on the foundation. ” So I am wondering if the concrete is poured in the cavity, why would the ICF weigh on the foundation? I must be missing something here. Thanks!

    • http://www.architangent.com Brinn Miracle

      Hi Laura, in ICF construction, much like other wall types, the foundation will fully support the footprint of the wall. That means the entire wall width will rest on the foundation, and the foundation will need to support the weight of the wall. In this case, concrete is poured in between two vertical panels of foam, and that entire ‘sandwich’ is sitting on top of the foundation. As a comparison, we could do the same wall out of wood framing, but since wood is so much lighter than concrete, the foundation would support much less weight. ICF walls will naturally be heavier than other types of construction, and the foundation design must accommodate that extra weight – typically through implementing a deeper foundation with more reinforcing steel (which add cost). Hope that answers your question!

  • Albert

    Has anyone considered the cost impact of using ICF regarding
    property tax assessment?

    Because an ICF wall is thicker and square footage for
    property assessment is calculated using exterior dimensions. If we look at the ICF
    home vs 2×4 walled home and both have exactly the same interior square footage
    (all the rooms are the same size), the ICF home will have a larger total square
    footage when it comes to tax assessment calculations.

    I am having a very tuff time understanding why I would want
    to use ICF now. I understand all the claims
    made regarding the cost savings over time using ICF. Regardless of all those claimed cost savings,
    the bottom line the increased square footage also means increased property
    taxes. With one home using ICF and
    another using 2×4 walls, and both with identical interior square footages. In this scenario, I have not read much
    regarding the cost penalty due to increase property taxes as a result of the
    increased square footage when it comes to property tax assessments Does anyone have thoughts around this topic?

    • http://www.architangent.com Brinn Miracle

      Albert, the increase in square footage from an ICF wall in terms of taxation would be minimal. Imagine a 40×60 house with traditional studs – 2400 SF house total. Let’s say we increase the thickness of the wall by a foot. That means you would be in a 2500 SF house with the added thickness. Not a lot, especially when you consider the tax rate is likely around 3%. 3% on an additional 100 SF is rather inconsequential. However, the benefits of ICF are often comparable to those of a SIP or MIP (structural insulated panels with OSB or metal studs).

  • Cameron Ware

    Interesting article and well written. Since I have completed over one million square feet of ICF in Texas I would like to add some thoughts:
    600 plus linear feet of walls is a large house probably with many rooms and furnishings – basically a non-trivial investment. Thus the disaster advantages of the ICF would be significant since it is several times stronger than your typical SIP and up to 9 times stronger than stick construction. If you are in a hurricane area this fact would matter to most folks.
    The 4 hour UL fire rating of ICF vs. 1-2 hour rating for typical SIPs was not mentioned.
    Superior STC characteristics of ICF 50-60 out of the box were not mentioned. Most SIP STC ratings are similar to stick with foam construction. Higher end SIPs are available that have similar STC characteristics.
    SIPs have done a good job in the market claiming they are half the price of ICF. This have not been my experience. The truth is that your better SIPs cost more than ICF and your typical SIP costs only slightly less than ICF. I know this because I bid against them occasionally. Most of our homes increase the overall cost of the house by a few percentage points when compared to stick construction.
    Rarely do the SIPs have equivalent or equal R-value to ICFs. This is because (particularly for the thinner SIP varieties that your considering) they typically take the cavity R-value and use that for the wall assembly R-value. Actually, most SIPs (except the high end) are short circuited by wood just like an open or closed cell foamed stick-house. Stick builders make the same claim — advertising they have an R-value of 20 when they actually have a R-value of 13 due to the wood. Wood typically has an R-value of 1 per inch of thickness.
    The first net-zero school in the United States is in Kentucky is built out of ICF.
    You might consider talking to a builder who has done both. Regards.

    • http://www.architangent.com Brinn Miracle

      Hi Cameron, thanks for the comment. You have many great points, and I think ICF is still a great product for the right projects. In our case, we simply cannot give up the additional inches of wall thickness and still have a comfortable interior proportion. We’re building to the limits of our tiny infill lot, so we need to make our walls as thin as possible. If we had more room, I would definitely consider ICF in another light for the hurricane resistance and STC values that you mention. In our case, we’re pursing a steel and Expanded polystyrene structural panel that is produced by a steel fabrication company. The quote we got on the wall system, all the interior partitions and all of the joists was quite good and keeps us on track for our budget. I haven’t bid our project to ICF to see the actual difference since we know we can’t use it (space concerns), but I’d be curious to see an actual quote come in for a true comparison. I’ll be learning more about the metal SIP product next week when we meet the manufacturer, and I’m hoping to see more information to validate the claims on STC, R-values and the like. Thanks for weighing in!

      • ANSLQ32

        I suggest you look at pictures of steel frames demolished by high winds, both from tornadoes and hurricanes.

        I don’t mean to be rude, but money must not be an issue with you. A few square feet is more important to you than a lifetime of energy savings. And protection from perils.

        Attached is photo of ICF house after Hurricane Katrina storm surge.

        • http://www.architangent.com Brinn Miracle

          In our area, hurricane damage is typically from projectile objects/flying debris or falling trees, not storm surge or wind alone. We are over 50 miles from the coast. No doubt ICF withstands wind forces better than steel, but I think you don’t understand the project constraints fully.

          Money is absolutely a factor for us. We’ve saved over many years, sacrificed a lot to get here, and have hung our future earning potential on this project. We’ve been very careful in how we approach the project, even splitting up large costs into separate debts in order to make it affordable for us. It is the reason why we are looking at every component closely, making value judgments and making compromises. I would ideally prefer ICF construction, but not only is it more expensive, it would cause some interior spaces to become cramped. Our property is very small, and we can’t afford more land, so we have to start at the maximum footprint and work inwards. When the walls get too thick, the interior spaces feel much too small, and even pose some code minimum problems – we’re literally at the limits. It was a compromise for us to give up on the ICF and go with a different wall system. The alternate wall system we selected is actually very affordable, and since it is 6 inches of solid EPS foam, the lifetime energy savings are actually comparable to what we could get with ICF. So for less upfront cost, comparable lifetime energy savings and moderate disaster protection (brick exterior), we also get comfortable interiors that we can afford. It comes down to risk tolerance and minimization of risk. No decision can be made in a vacuum.

          • ANSLQ32

            Thanks for the reply. Building a home is exciting and I hope you are happy with your decision.

            ICF is best in minimizing risk. All of it. Find on youtube Texas Tech Study ICF for video of 2×4 flying through everything but ICF. I posted it here, but video must not be allowed. I am in OKC, yes, a home and person has more risk with flying debris than actually having the tornado go right over you. Last year’s F5 in Moore, OK took the wood (SIP I think) roof and siding right off a home with ICF walls. A pickup was tossed into the wall, not through it. The ICF walls were still standing, all of them. The steel beamed bowling alley was totally demolished and twisted. The steel frame railroad bridge was twisted and pushed over 60 feet. The new concrete hospital had the windows blown out and cars landed on its roof, but it was still standing. The bowling alley was right next door. A new 7-11 was just east of the hospital, not ICF, there was no sign it ever existed except for the steel lines coming up from fuel tanks.

            Over time, your walls and roof will leak. Air and water. Not so with ICF roof and walls. If you used anything other than arcrylic or cement tiles on roof, you will have to replace them in less than 30 years; $15-30,000. Not so with ICF roof.

            If 260 square feet that important in a three story home, make it four story. Or get a different lot. Change the floor plan to more open.

            On affordability, I posted earlier your monthly cash flow could be better with ICF in not only energy, but insurance savings. Lifetime ownership costs are lower with less repairs, no termite treatments, water leaks rotting wood…and the ICF home (with ICF roof) will last your children’s lifetime as well… think of the savings they will have with no mortgage, and when energy costs take up even larger portions of the average income.

        • kongfuzi

          WOW! Was the building still structurally sound so that it could be remolded for a substantially lesser cost than rebuilding from scratch? Otherwise, the cost of demo would actually increase the cost of starting over. No question it would have protected the people on the second or third floors (I presume the surge wasn’t that high. Pretty impressive.

        • captgears@gmail

          Captgears@gmail

  • John Mcguire

    Just a couple of notes from someone who had an ICF home built and from someone who has lived in one for the past 5 years

    THICKNESS – Yes your right the windows are thicker….. but you get a free window seat with every window :)

    FOUNDATION – Arent you doing an ICF foundation ? Most ICF homes are the same wall from the foundation up to the roof

    ENERGY EFFICIENCY – I would in general “ignore” ratings …. they don’t seem to always measure reality very well…and as professional sales and ad man I usually ignore most “HYPE” around efficiency claims.. I have an ICF home , 2800 sq feet…. sits on 20 acres of OPEN farm ground south of Chicago………. I spend about the same to heat and cool this home as I did for an 1100 sq foot home built just 10 years earlier….. and this is even more impressive considering that the ICF home is heated via Propane, vs the nat gas on my previous home…. propane costs 2 to 3 times more than nat gas

    A few things i found out being in an ICF house

    1 – Put in a service panel for small utilities….. a lot of utility companies cant drill thru the walls… for me I had them basically build in a tiny window open near some of the other utilities…..and just finished it over with brick and drywall and foam…… Most phone companies and such can drill thru ICF walls…. unless they hit the rebar then good luck :)

    2- Expect to hear some big POPs in the house……. I’m use to a house settling….. but what i have found with this home is that the outer walls and inner walls seem to settle at different rates….. not so bad that I’m getting cracking in the walls…. but this house will pop really loud sometimes :)

    3 : Local code – My home has some of the foundation exposed above grade…. and in Illinois we had to get a special permit for a poured wall over a certain height…. and since my ICF goes all the way up to the roof I’m almost 2 and a half stories above grade… wasnt hard to get… but the arhitect had to have an engineer sign off and modify the plan slightly

    4 : INSURANCE SAVINGS – In Illinois you get ZERO insurance discount for an ICF home….. I have 8” concrete walls with full brick on the outside…… my walls are almost 12 inches of solid concrete, rebar and brick…. but the insurance companies don’t care…. the only ICF discount you can get is if you are in a hurricane zone… if your lucky they will treat it like brick construction

    5 : QUIET – This house is QUIET – Again I’m on 20 acres of open farm ground….. when its windy as heck out or a big storm is going on I can hardly tell…….. also you cant hear cars pull up to your house…. so get a good doorbell cuz you wont hear them driving up unless your windows are open

    All in all I’m happy with ICF…. it cost me a little more, but not a crazy amount more… and the house is efficient, quiet and well it feels like a real building… and during the big storms we’ve had recently I feel very secure

    • http://www.architangent.com Brinn Miracle

      Hi John, thanks for the great tips/pointers. The foundations in Texas are typically some variation of a slab on grade since we have clay soils and a high water table. No basements or crawlspaces, typically.

      • ANSLQ32

        Beam on pier. Cost more, but from day one you have a very solid and level foundation. Not sure about Houston, but a builder in Dallas uses this method.

        • http://www.architangent.com Brinn Miracle

          You’re absolutely right – pier and beam foundations are the way to go around here for our soils type, though they are more expensive than slab on grade. Smaller, older homes are slab on grade, and cheaper spec homes sometimes still implement them as well. Taller structures and higher end builders opt for the better system.

          • ANSLQ32

            With three story, you should consider it. Cost?, vs lifetime of stability? You decide. It is going to cost me $8-10,000 to have jack screws to level my house built on OK clay in 1991, slab on grade. If building new, and I will soon, I might as well put that cost up front and stretch it out over the loan. Even if it means I must settle on a smaller house. As an added bonus, the foundation will easily support ICF walls and roof.

    • ANSLQ32

      ICF roof, that is where insurance savings comes in. No asphalt shingles for hail, wind damage, and of course water damage.

      Your example of energy savings is impressive.

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  • Matthew

    Sorry if this seems rude, but your linear feet analysis strikes me as very large. Forgive me if these seem like condescending questions but I just can’t seem to wrap my head around the numbers. I’m assuming that you’re only using icf on the exterior walls yes? And that you didn’t count the basement because that would require poured concrete and insulation anyway? I can see you arriving at your numbers if you counted all the interior walls of your house (i.e the perimeter of each room) but not if you just counted the outside wall.
    600 linear feet of outside wall would be 2 floors of a 50′ x 100′ house, or if you counted the basement 3 floors of a 50′ x 50′ house. Again, I’m not trying to pick apart your very real point about the lost space, but… 260 sq/ft and $41,000 seems bonkers.

    • matthew

      Oh wow (I’m a dummy), I just realized that this is BLOG and visited the previous post that included the schematics of your house and answered all my questions on my own. Disregard the above post. Beautiful house by the way.

    • http://www.architangent.com Brinn Miracle

      Hi Matthew, our house footprint is approximately 32′ x 58′ and it is 3 stories tall, even 4 stories at the staircase up to the roof decks. We have several places where walls jog in and out to break up the massing, adding up the linear footage quickly. We live in Houston, so we don’t have basements typically. You can see the floor plans on previous posts to get a feel for where the walls are.

      • ANSLQ32

        that jogging is expensive. if cost is a concern, don’t do it. ICF including roof, is a lifetime of energy savings, even with an air handler/hehumidifier system that Houston homes might need.

        • http://www.architangent.com Brinn Miracle

          The jogs in the plan would certainly add some cost in form work for pouring concrete, but not substantially (according to our builder). The material increase for the metal SIP construction we selected is negligible. Cost will always be a concern, but it is about balancing design with costs. In our case, we need the jogs to provide light (without giving neighbors a view directly into our house) and to reinforce the design concept of intersecting masses. If you flattened it out, the design would suffer.

          • ANSLQ32

            Take out the jogs, get square feet back. Use Solar screens for daytime blocking of view, (and solar heat gain on windows) and celled shades for night time blocking of view and for added insulation over windows. These shades can be rated at r-4.

  • Larry

    Briefly I will answer some of the questions raised in the comments. My experience with ICFs for the last 13 years does not represent many of the assumptions and comments contained in this article. First, building above grade 4″ inch core ICF walls is not a problem for a professional installer creating a 9″ wall above grade. Secondly, if one had a 6″ Sip wall you would loose approximately 162 sq. ft. of floor space in contrast to ICF. We do 6″ core below grade 11″ out to out that is less than an 8″ poured form wall with 2″ exterior foam with a 31/2″ studded out basement wall.
    The main point is that if one has space on the lot to build the cost for the wall being wider is very small. The ICF blocks labor and cost per block size is virtually the same except concrete used. At best you have 3-6″ more of roof to add to your cost. You are trading safety from fire and storm, quietness, less energy consumption and comfort for pennies. Simple points like considering stucco where you would have to add 4″ to SIPs are not even considered in this example.
    The trades if not familiar with the system always complain like most of us when something is different. We have found many willing to learn the few differences actually saving money after getting aquainted with ICFs. HVAC can be sized much smaller in all cases especially if combined with other energy saving measures.
    Finally, ICF structures lends itself to more flexibility in design.

  • windgineer

    I have been thinking about this for a while. My company, Strong Fort Construction (www.strongfort.com), is installing our first ICF house right now: http://facebook.com/strongfort. You can see pictures there. I am beginning to wonder if the cost/benefit of some form of foam coated with strengthened composite materials would offer a better fit for most home owners. Concrete is so strong that I am not convinced you would want to do away with it altogether, but it would definitely lower the cost if we could get rid of most of it.

    • ANSLQ32

      Short term thinking. Use at least 4 inches concrete with foam in place. Reduced energy bill for a LIFETIME…! Use ICF roof.

  • John Santana

    I think that space is a little, very little one, problem, comparing with the posibility of fire that consume all your house because of wood not giving you any time to go out to safe your life and your family too. Beside, look at this way. If you build your house with ICF, you´ll save all money you cannot imagine in the future, just because your house is stronger than the others. Why american can´t see the advantage of invest having in mind the future in a long term? And 5 inches won´t be a solution for a comfortable room. I think that your problem is that you couldn´t buy a bigger lote, not the method of construction…

  • ANSLQ32

    ….’energy prices must rise…’ Pres Obama. This will become a huge factor in home building materials.

  • ANSLQ32

    If the project started, some photos would be great!

  • Thomas Michael

    I would like to correct some misnomers about both sipp and ICF. As a builder who started building ICF and SIP structures in the Late 80’s I would like to clear the air. Most builders will not entertain alternative building methods and will also put a negative spin on building methods they are not familiar with.

    You cannot compare ICF and SIP construction. I have build ICF structures that have survived multiple hurricanes including Katrina and Sandy and other ICF structures that withstood tornados. SIP structures in general will not.

    As for cost SIP in general are more expensive. Recently I did a cost comparision of ICF to 2×4 wood framed wall structure. My cost basis was based on finished wall cost in a high wind zone to moderate wind zone. ICF was on par with standard 2×4 wall in cost. The added cost of steel in use of the wood framed wall leveled the cost. SIP was considerably more expensive.

    Foundation cost is relative to your soil condition. A CMU wall costs 30% more then an ICF wall. The extra footing size to carry additional weight of an ICF wall is nominal. It is obvious the builder giving his opinion has no masonary experience nor does he understand that an ICF foundation is no different that a standard poured foundation less the insulation.

    Most standard pour foundation contractors add little rebar in their installation contrary to code requirements.

    I built a test structure on Long Iand NY in the town of Cutchogue. The structure is a French Country house with a wrap arround porch and attached two car garage. It has a full basement with 10″ ceiling and all the framing is steel from Excalibur Steel Structures. The roof is foamed in with seven inches of closed cell spray foam. Comparing my costs today on that structure to wood structures built in a high wind zone it is 5% less expensive to build an ICF building. It uses on average 65% less energy then a newly constructed home of equal size and 85% less energy then older homes in the same neighborhood. It is designed to withstand 200+ mph winds and inpacts in excess of 120 mph. During hurricane Sandy you could not hear the wind outside unless you opened a door or window.

    The example above an asumption was made that ICF walls are 14 inches thick. The assumption was wrong. An 8″ concrete cored ICF wall when finished is but your single structure could have been done with a 6″ or 4″ wall design.

    If you’re building a 40×30 home with a full basement the cost of the wall system is approximately $17,000 installed, that would include all materials, and labor. That could be done on a 4″ wall system with no loss of space. A rebar design would be required but that would only add approximately $1500.

    To Sum all of this up If you know your product and how it can be constructured one would find that ICF can and is the most viable construction method and is cost effective. Utilizing Steel Framing and floor joists would lower costs also and would decrease construction time adding to the savings. A steel stud today cost the same as a wood stud but steel is over 200 times stronger when in a wall assembly. Steel floor joists are less expensive the a TJI joist and when using the ICF system they are preintegrated into the wall system decreasing installion labor and time.

    It all comes down to cost, time and energy savings. ICF and Steel give you both an I have yet to find SIP or wood framed wall sytems to Beat ICF and Steel.

    • Violet56

      Hi Thomas, I realize that this blog is somewhat dated, but I noticed not only your excellent information and understanding of the ICF building issues, but also the recent date on your post and hope my post will result in a response. I do not live on the east coast, I live in central oregon in the high desert foothills of the Cascade Mountain Range (Bend, OR) and our main disaster risk here is forest fire. This past June, although I live right in town for a third time in my 30 years here a major fire came within 1.5 miles (and yep we got evacuated). So I would be building in an semi-arid hot short summer-long cold winter climate (4K feet elevation) that is subject to wide daily temp swings (50 degrees easy) and am surrounded by many, many, square miles of pines, juniper trees, ect. SO that said I am very interested in your comments about fire resistance. Could you expand upon this?? I am looking to build a very modest home (single level/no basement, 1200 sq foot maximum cottage) and am just about sold on ICF construction..
      Any further info would be greatly appreciated…

  • BuildBlock ICF.

    Check out http://www.buildblock.com Ton of information to help you make the right choice.Plus we can find you a great installer and help you to cut cost by experienced personal.

  • Dan

    Your financial analysis is fundamentally flawed. You refer to the “lost” value of the square footage you won’t have with ICF. While you do lose that “value” you also save the construction costs associate with that extra area. You also will have tax savings as almost all Texas county valuations are done on a square footage basis and Texas real estate taxes can be very high. Finally your utility costs will be lower, marginally, because you won’t be heating and cooling that space. But otherwise it’s a good way of looking at this issue in confined spaces.

    • http://www.architangent.com Brinn Miracle

      Hi Dan, you have to keep in mind that the lost space to the wall thickness still costs money, since it is a material we pay for (whether it is concrete and re-bar, or whether it is insulation and drywall). Square footage is typically measured from the outside of the wall inward, so the thickness of the wall would actually be taxed as ‘interior space’ that we don’t get to use. While the utilities would definitely be lower, the alternate wall system we are proposing to use is almost as good as ICF in terms of energy savings, so this point is moot when comparing the two. We’ll end up saving considerable energy costs over time with either system.

  • B.d. Bmw

    I’m building an ICF house because I want a strong structure. I live in the hurricane zone so it isn’t if it is when one visits again. Currently own a Hebel built home and have lived the advantages of a strong exterior, low noise levels and insulation efficiency. I have looked into SIP and would consider it if I was not in ground zero Florida for hurricanes. I don’t mind the loss of sq ft or increased cost for the peace of mind knowing the structure will most likely be there once a hurricane blows through.
    Love to see the finished product of your home…

  • Teresa

    I love my ICF basement, loved the fact that I id not have to 2×4 frame it and drywall can go right on it, as can things like flex-rock or texture or stucco..with no problem In Northern my Canada, my ICF basement ( 1522 sq feet) compared to my last house with concrete (920 square feet) has save us money – our hearing costs are almost 50% less for 50% more space! Also I now have wonderful large window ledges that my plants love..never do anything else. GO ICF!!

  • B.d. Bmw

    The advantage of ICF is more important if you live in a hurricane high velocity zone like I do. SIP would not withstand the hurricanes. Loss of space is a concern and is just the cost of having a home that can survive the conditions you live in. If you don’t need a strong structure like this SIP is an excellent choice.
    SCIP is also a good choice but not many companies across the company know how to build on sight which is a drawback.
    SIP is still a good deal better than stick frame construction as it yields a tighter building envelope…

  • Al

    My family bought a 2002 constructed ICF ranch-style home in WI last fall, it having about 4200 finished square feet. We are very, very pleased with the low costs to heat and air-condition this home. We notice no draftiness and are pleased that we do not even have to supplement the AC with a basement dehumidifier. Another thing we enjoy is how very little outside noise gets into the living area and how few insects get into the home during the summer compared to our stick-built previous homes.. If I were to build new, I would pay the extra for ICF construction.