One of the distinguishing characteristics of my project is my choice to use insulating concrete forms. There are a few reasons behind it, and I think it would be appropriate to discuss some of my thinking that went into this decision.

When I describe ICFs to people I meet, I usually say

picture a four-foot long styrofoam Lego. The builder stacks these large Legos, interlocking them to form the exterior walls. The interior is hollow, and once enough wall height is reached, rebar is added to the inside of the blocks, and a truck comes and pours concrete into the interior of the Legos. It takes several pours, but what you wind up with is a one-piece concrete house, with two inches of styrofoam insulation on the inside and outside walls.

That's my layman's explanation of the technology, and it really captures most of the essential points of the technology. But really there's quite a bit more to ICF technology, and I think the benefits are compelling. (Note: I am not a builder, and I don't work for an ICF manufacturer or dealer. I'm just a homeowner interested in building technology, and discovered ICF doing research into energy efficiency and superinsulation.)

For me the biggest win is the energy efficiency. The insulation of the forms themselves yields R-22, and the effect of the thermal mass of the concrete inside can give an effective insulation value of R-50, depending on various conditions. Since the wall is monolithic, the potential for air leaks is removed, and this is factored into the effective R-value as well.

Another plus is the quiet. ICF homes are very well-insulated from exterior noise as well. In my situation, this isn't a huge bonus, since I'm not going to be close to the road or a neighbor's house. But there is a fairly constant 10-15 mph wind blowing in my location (I'm building at the top of a rise, with no tree cover nearby), and the noise from that should be kept outside effectively.

My contractor has a good deal of experience in commercial construction using ICF, and tends to apply commercial techniques and standards to residential projects as well, "overbuilding" the footings by residential code requirements, but making them confirm to commercial requirements. I like a certain degree of overengineering, too many homes today are built to the minimum standard. Since this is a custom home project, I expect to overengineer several aspects of it.

ICFs are easy to cut on the job site and can be used to make complex wall shapes. I don't have a need for any rounded or angled walls, my project will be quite simple in terms of exterior lines. But ICFs can be cut with a hand saw. The bracing of the forms is critical, but not a lot of specialized equipment is required to work with them.

Different sources have quoted me different figures for the incremental cost of building with ICFs. They all fell in the range of 3%-10% above the cost of 2x4 stick framing. I felt that made the benefits outweigh the costs. Part of the reason for the range (as I am coming to understand) is that an experienced contractor can realize some efficiencies in material and labor costs, and an experienced architect can design some efficiencies in material and labor costs (minimizing the number of required cuts by making wall dimensions multiples of a whole block length for example). I'm planning on using some of the most experienced people in my area for my project, and I am expecting to get definite cost management results from them. Plus I'm starting with a design that has some inherent efficiencies (a single rectangular footprint).

From the outside, an ICF home looks identical to a conventional stick framed home. The forms have firring strips on eight inch centers, so all exterior finishes work just fine. From the inside, the same applies--all interior finish options are available. The only visual indication that you're in an ICF home is the deeper window returns that are necessary because of the twelve inch wall thickness. On the other hand, ICF homes give a very "stable" or "solid" feel in a sort of intangible way. The walls do not yield to pressure, the quieter interior, and the complete lack of drafts combine into a sensation that you sort of perceive as solidity. Of course the floors contribute to that as well, so I am making sure that the floor system is in keeping with the overall impression of the house (which is to say I want it to be quiet and unmoving).

Farther down the list of benefits is the resistance to pests. There really is nothing for a colony of termites to feed on, so termite control becomes a non-issue. The insulative properties of the polystyrene make it less likely for moisture to condense, which should contribute to mold resistance. Of course, the management of air circulation is important as well for mold control. But since ICF construction is effectively leak-proof, ventilation needs to be designed into the home.

And resistance to tornados is another benefit, possibly an important one in my part of the country. Some people are building "safe rooms" using ICFs, and using normal methods for the rest of their construction. Of course, in rural Kansas, a "safe room" has more to do with tornadoes than intruders.

ICFs are considered environmentally friendly, since trees are not used to manufacture them, as well as the energy savings they provide. Since trees are a renewable resource, this didn't make it high on my list of benefits, but I suppose it counts for something.

I chose to use Eco-Block brand ICFs for my project. This was driven in part by the availability of trained contractors in my area. The Eco-Block reps were instrumental in connecting me with builders and architects, as well as referring me to some homeowners who had used this system. A much less detailed site than mine, but a nice collection of photos of an ICF house project, can be found here. I've also visited a few job sites locally to see projects in various stages of completion. I'm completely satisfied that ICF is the right alternative for my project.

As I explain it to people, I'm placing a bet that energy costs in the future will tend to go up. The more they do, the more attractive my ICF home will become from a savings perspective, and from a resale value perspective.

6 comments

I would consider looking into some of the newer forms of solar energy. You can now get Structural Standing Beam roofing panels with built in amorphous silicon solar cells. Unlike older crystalline solar cells, the am-sil cells produce power even when overcast and will even produce power when part of the panel is in shade. The cost is fairly cheap, even when compared to traditional roofing methods and it is very easy to install. Doing it right would make you completely independent from the grid. I plan on doing something along those lines when I build my own house. Email me if you wanna talk more about it.

posted by Ian Wendt @ 12/17/2002 1:52 PM CST

If you keep any equipment on a small turbine could power it for free, but there would rarely be a surplus unless the equipment was off (Mp3 server, etc.) The cost of the smaller units is relatively cheap. You probably pay alot less than I do for electricity, so it probably would take alot longer to pay for itself. I live in california and once I go over the baseline it $.24/kwh !!! I think the baseline is 300 kwh per month..

posted by Eric Claussen @ 8/8/2002 5:02 PM CST

Eric,

I did look into wind power. My site is perfect for it in every way (on a rise, no trees, ten acres, steady wind). But my state doesn't have legislation in effect to make the utility company buy back power at retail (spin the meter backwards), so there is not even a prayer of recouping my capital costs for the turbine and mast. I was seriously disappointed.

posted by linear @ 8/7/2002 11:47 PM CST

With a constant 10-15 mph wind you should look into a wind powered generator. Could offset the electric bill a little. www.homepower.com has alot of great info on energy efficiency and renewable energy resources.

posted by Eric Claussen @ 8/7/2002 5:55 PM CST

I am also planning an ICF home. I will be following this page closely.

Good Luck

posted by Eric Claussen @ 8/7/2002 5:26 PM CST

I saw a great hometime season where they where building a "house with character" and they used ICF's very impressive... took a while to setup the blocks but after they were in place, they poured the walls in one day!... concrete roxor!

posted by eddie_dane @ 8/2/2002 9:58 AM CST