Insulated Concrete Forms

Insulated concrete forms (ICFs) are permanent forms for poured-concrete walls; the forms are typically stacked without mortar before concrete is poured, providing insulation and often reducing the amount of concrete needed for the resulting wall.

The insulation material varies from system to system, with the most common being high-density expanded polystyrene (EPS) foam, which, unlike extruded polystyrene (XPS), is produced with a non-ozone-depleting blowing agent. Some include recycled EPS foam, waste wood fibers, or a combination of EPS beads and portland cement.

Many manufacturers add borates, which are considered benign to humans and the environment, to the EPS foam to protect against wood-boring insects. However, most EPS foam also contains a brominated flame retardant, which has come under increased scrutiny because of environmental and health concerns (see EBN Vol. 13, No. 6). Some manufacturers recommend gluing seams between forms; the glues recommended may have high levels of volatile organic compounds.

The primary environmental benefit of ICF walls is their insulating performance; most have tested R-values around R-20, with some as high as R-25. The most reliable information for comparison is the “steady-state” R-value, which is calculated by keeping one side of a material at a constant temperature and measuring how much energy is required to keep the other side of the material at a different temperature.

When manufacturers refer to “effective” or “mass-enhanced” R-values, they are referring to the fact that high-mass materials that store heat can achieve better energy performance if outdoor temperatures fluctuate above and below the desired indoor temperature. Although Oak Ridge National Laboratory has developed a test to measure mass-enhanced R-value, testing procedures vary among ICF manufacturers and the ability to benefit from this higher R-value is highly dependent on climate, so listed effective R-values might be inaccurate or irrelevant.

For More Information

“Thermal Mass and R-value: Making Sense of a Confusing Issue,” EBN Vol. 7, No. 4

CSI Section 03 11 19 Introduction, BuildingGreen Suite
www.buildinggreen.com
(Click on “CSI divisions,” then on “Concrete,” then on “Insulating Concrete Forming.”)

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Thermal Mass and R-value: Making Sense of a Confusing Issue EBN: Feature - April 1998

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