Real World ICF Thermal Performance

The REAL WORLD ICF INSULATION PERFORMANCE and significant energy savings experienced each month have been demonstrated by satisfied home and building owners for decades.

We decided to take an objective scientific look at the real difference between ICF walls and the traditional wood framed cavity walls used in the majority of the US. This first test looked at walls that are code compliant for Climate Zones 1-5. Future studies will compare other types of walls systems and insulation.

In 2016 the ICF Manufacturers Association commissioned an independent scientific study comparing a wood framed cavity wall to a standard 6-inch core ICF wall.

Why do ICFs work so well?

Insulating Concrete Forms sandwich a solid reinforced concrete core between two 2.5″ thick panels of dense EPS foam. This foam is extremely good insulation and delivers unparalleled energy efficiency. Why?

The heating or cooling experienced during the day or night is stopped from influencing the inside temperature through both the EPS foam insulation and the concrete core. While the EPS foam works as an effective insulation it’s the thermal inertia of the concrete core that adds the greatest advantage. The concrete is heavy and dense and resists changing temperature. Think about the evening after a hot summer day when the sidewalks and streets are still warm late into the night. The concrete, once heated, stays warm for a long time. The opposite (cold concrete) is true as well. 

This thermal inertia of concrete helps stabilize the wall temperature. Combined with the insulation on both sides of the wall, preventing either exterior temperature changes or interior heating and cooling from affecting the wall temperature on the other side. By staying so stable, the inside temperature must only be conditioned to change a few degrees either direction, requiring very little energy.

Real World Thermal Performance Independently Proven

icf thermal performance

The study was surprisingly revealing; confirming dramatically superior energy-efficiency performance and an overall better R/RSI-value being achieved by the ICF Wall assembly.

For decades, the ICF Industry has been asked to provide definitive proof that thermal mass, the airtightness and continuous insulation features of ICF walls deliver real, quantifiable benefits in terms of overall energy-savings and achieved R/RSI-values. Many studies have been conducted in the past by the Portland Cement Association (PCA), the Canada Mortgage and Housing Corporation (CMHC) and the Department of Housing and Urban Development (HUD) all of which were either based on limited field comparisons or thermographic computer modeling. This is the first time an SCC and ISO accredited and an internationally recognized testing facility has been commissioned to evaluate a realistic side-by-side comparison of these two types of wall assemblies within a single study.

The reported results confirm the following when building with ICFs:

  • 58% better overall R/RSI-value than the insulated wood frame cavity wall
  • 60% better energy savings than the insulated wood frame cavity wall
  • Measurable effect directly attributable to thermal mass & continuous insulation on both sides of the wall assembly
  • The 2″x6″ wood framed cavity wall required 38.9 kWh to maintain steady state and the ICF wall only required 15.6 kWh of energy to do the same work.
  • This is a consumption of 132,828 BTU for the wood-framed cavity wall versus only 53,209 BTU for the ICF wall.


The CLEB Study test the walls conditions under “steady state.” What does that mean?

steady state

  1. Physics – A stable condition that does not change over time or in which change in one direction is continually balanced by change in another.


When we say that each wall is tested at “Steady  State” it literally means that the amount of heat required to be delivered to the interior side of the test wall to maintain the interior space at a constant temperature of 70°F (22°C) is exactly consistent with the rate of heat flow that is transmitting through the wall (due to ITS exterior condition being maintained at -31°F (-35°C).

ICFs By the Numbers

What does this mean for consumers?


Seeing is Believing


For more questions about this study or actual BuildBlock ICF performance, connect with us in person at +1-866-222-2575 or


Real World ICF Thermal Performance March 23, 2017

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