Blog Post

Considerations of Insulating Concrete Forms (ICFs)

A look at what distinguishes the different types of ICFs.

ICFs (Insulating Concrete Forms) are permanent, stay-in-place forms for making insulated poured-concrete walls, floors, and roof decks. Most of them are made with expanded polystyrene (EPS) foam produced with a non-ozone-depleting blowing agent (unlike XPS, an option to avoid from some manufacturers), while others are made with EPS beads (typically from recycled sources) or mineralized recycled wood chips glued together with portland cement.

Generally, the pure-foam sort are direct replacements for standard removable forms and are used to make regular, flat poured-concrete walls with an equal amount of insulation on both sides; while the cement-bonded foam-bead or wood-chip type usually have voids that get filled with concrete to make structural grids, columns, or "waffles" encased in insulation. This is usually the way it is; there's some overlap and variation.

From here on, it gets tricky and sticky. Pretty much all EPS (and ICFs are no exception) contain brominated flame retardants (BFRs), usually Hexabromocyclododecane (HBCD) — which is persistent and bioaccumulative with health consequences not fully known but suspect enough that engaging The Precautionary Principle seems well advised... at the least. Cement-bonded mineralized wood products don't contain BFRs.

To protect against potential damage from insects, some EPS foam used in ICFs contains borates, which are benign to humans and the environment. Even though the cement-bonded variety are most often void-type forms (rather than simple flat wall forms) that usually result in less concrete use, the forms themselves are about 15% cement — enough so that the overall cement content of the finished wall is about the same as, and potentially more than, a solid concrete wall. This matters because the production of a ton of cement generally releases a ton or more of greenhouse gas emissions.

However, while cement-bonded forms don't reduce environmental impacts up front, the insulation does reduce emissions from space conditioning over the lifespan of the building compared to uninsulated walls, and in most climates that's a far weightier consideration. The cement-bonded forms are also less insulative per inch than pure foam — but the void-type ICFs (which are usually cement-bonded, compared to the flat-wall type that are usually pure foam) typically provide more, though less effective, insulation material.

Comparing thermal performance between the two types requires careful research and thought... which is easier said than done. An embarrassing number of ICF manufacturers prominently and breathlessly promote amazing "mass-enhanced" or "effective" R-values. These numbers are an attempt to capitalize on a real phenomenon, but are generally presented in an entirely misleading way. "Effective R values" aren't consistently derived from one manufacturer to the next, and are climate-, site-, and project-specific.


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For comparison purposes between not only ICFs but all wall systems, steady-state R-values should be the prize number, and mass effect considered as a subsequent part of the equation. If the sales literature doesn't provide a steady-state R-value right up front, engage your BS detector. Most ICFs have a steady-state R in the lower 20s.

In almost all situations, mass should ideally be insulated on the outside, and not on the conditioned interior. A few ICF products are configured to provide more insulation on the outside of the wall and less on the inside; in climates where the average diurnal temperature is outside of the comfort zone — particularly in places with long, cold winters — this configuration is highly preferable. Almost as an aside in the midst of these bigger issues, it should be noted that some manufacturers recommend gluing the forms together in the field; their recommended adhesives may be high VOC.

Published July 3, 2009

(2009, July 3). Considerations of Insulating Concrete Forms (ICFs). Retrieved from

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August 5, 2009 - 8:21 am

There seems to be a lot of talk lately about the use of foam insulation and as in the past it is all just a matter of opinion without any credible test data to back it up. The ICF Industry seems to be dodging more and more bullet’s, every time it proves to be substantially better than the larger more well know conventional types of construction. The truth of the matter is that ICF construction has been proven to be one of the most energy efficient methods of construction to date and it is gaining market share so fast that it is making some of the conventional methods very nervous.

Construction time can be cut in half if done with professionals, the structure has proven it can survive category #5 Hurricanes sustaining 250 mph. winds.

The energy bills on ICF construction have shown up to 75% savings and have made it feasible to introduce Solar and other alternative forms of energy because the BTU requirements are reduced such that we have been able to reduce HVAC by up to 75% as well.
One of the things that our opponents seem to like to mislead the public on is R Value. It is true that most R Values of ICF products are in the low 20’s, but whether by design or just pure ignorance, they omit the fact that the overall wall performance in an ICF can reduce the BTU heat loss (this is the formula that is used to calculate the size of heating and cooling equipment) by almost three times.

HBCD is a standard fire retardant used in many consumer flammable materials, such as clothing, carpet, furniture fabric ect…. What is different about these products is that they are in constant contact with us and we generally wash and clean them regularly. The problem with this is that in these case’s, traces of HBCD makes its way into the ground water and although I have seen no hard data to measure the impact it has on our environment, it is cause for concern. When HBCD is used in the production of construction materials such as EPS made ICF, it is exposed only during the construction phase and is covered both inside and out. When in contact with the ground it is covered with a water proof membrane that does not contain HBCD.

When we combine ICF and alternative energy together, we not only create a concrete structure’s that has been proven to with stand the elements for century’s, but we create a structure that can eliminate our need for fossil fuel when use for new construction. (ouch)!!

Each time I see these articles it makes me wonder who is behind it, who is writing the script? Before we throw the “baby out with the bath water” we should indeed see hard data to prove the case either way.

Murray Snider

July 6, 2009 - 3:44 am

Insulating Concrete forms are good but they are a little bit expensive. Foam insulation is one cheap way to achieve the same results.

July 7, 2009 - 11:34 am

And now that you've examined the latest 'constructs' perhaps a word or two about autocalved aerated concrete (AAC), or, as we perfer, aerated autoclaved concrete--as it is made--are in order.

You might want to tab into Michael McDonough's data base...