What is an Insulating Concrete Form?

by Erik North on December 19, 2011

What is an Insulating Concrete Form?

 

ICFs (insulating concrete forms) have gained popularity but still live in that middle ground with SIPs and geothermal heating: move further than 10 feet outside the energy industry and homeowners may give you an odd look when discussing them. Everyone is familiar with poured concrete foundations but what are insulated concrete forms and how can they help you build a more efficient home?

What is an Insulating Concrete Form – A Boring Wiki-style Definition

A standard poured concrete wall uses forms so the wall stays in place as it cures. Insulated concrete forms are interlocked foam insulation that acts as the forms and becomes a permanent part of the wall. The forms come in either panels or stacked Lego-like blocks.

The ICFs are most commonly constructed from XPS or EPS foam, reinforced with steel rebar increasing the assembly’s tensile strength.


 
Once the concrete has set, the interior wall can be finished with drywall and the exterior with stucco or brick facing.

What is an Insulating Concrete Form – Advantages

With no offense to any foundation contractors out there, ICFs have a whole boat load of advantages over standard concrete foundations. ICFs have a much higher R-value than standard concrete walls. Once set, the final R-value may approach R-20 compared to R-2 or 3.

The much quieter foam board insulation acts as an excellent sound dampener. Concrete is not. Because there aren’t any seams or joints in the standard building sense, there’s a reduced level of air leakage.
When used for constructing wall assemblies, ICFs make a very strong frame.

What is an Insulating Concrete Form – Disadvantages

Of course, there are some otherwise everything would be build from insulating concrete forms.

Yes, very generally speaking, ICFs cost more than standard foundations or stick construction. If you’ve built walls out of insulation and concrete, adding a window or an addition is not easy (think cutting through concrete).


 
I’ve talking about foundation insulation and pest problems before. An ICF wall will be more pest resistant than a stick built one, that’s not the case with foundations. Expanded and Extruded polystyrene particularly have issues with bugs burrowing into the foam. This may require adding protective facing to limit pest access.

Insulating concrete form buildings can be built very strong, tight and well insulated; what’s not to like? Well, compared to standard construction, they can be more expensive and pest infiltration necessitates taking structural precautions. If you’re serious about building an efficient home, an ICF foundation is an excellent choice.

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