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The Canadian ICF Thermal Study: What the CLEB Laboratories Test Measured, and What 58 Percent Better Really Means for Your House
Structure and ICF Evidence From a builder
The Canadian ICF Thermal Study: What the CLEB Laboratories Test Measured, and What 58 Percent Better Really Means for Your House
For twenty years people asked the ICF industry for proof instead of brochures. In 2017 it paid an accredited Canadian lab to put a real wood wall and a real ICF wall side by side in a hot box and measure them. Here is what came out, and the honest translation from a test wall to a whole house.
Short version: In March 2017 the Insulating Concrete Forms Manufacturers Association published a whole-wall thermal study by CLEB Laboratories (an SCC and ISO accredited facility near Montreal, formerly Air-Ins), comparing a standard 2×6 wood-frame wall with cavity insulation to a standard 6-inch-core ICF wall under the same conditions. The ICF wall showed a 58 percent higher effective R-value than the tested 2×6 wall and up to 60 percent lower energy transfer through the wall, with the thermal mass and the two continuous foam layers each measurably contributing. The test measured walls, not houses: a whole house also loses heat through the roof, the windows, the slab and air leakage, so the realistic whole-house heating saving for an ICF house over a code-minimum frame house in Ontario is in the 30 to 45 percent range, not 60.
What was tested
Two full-size wall assemblies, built as they would be on a site, were tested in a guarded hot-box apparatus that holds one side warm and one side cold and measures the heat flowing through. One was a 2×6 wood-frame wall with cavity insulation built to the code of the day; the other a standard ICF wall with a 6-inch (150 mm) concrete core and the usual EPS foam on both faces. Earlier comparisons by the Portland Cement Association, CMHC and HUD had relied on field studies or modelling; this was the first side-by-side test of the two walls in one accredited laboratory, which is why it mattered to the industry.
What it found
| Result | Measured |
|---|---|
| Effective R-value | The ICF wall tested 58 percent higher than the 2×6 wall |
| Energy transfer through the wall | Up to 60 percent lower for the ICF wall under the test conditions |
| Thermal mass | A measurable contribution from the concrete core, delaying and flattening heat flow |
| Continuous insulation | A measurable contribution from each foam layer, with no bridging through the assembly |
The association’s own illustration: two houses with 2,000 square feet of wall area each, one frame and one ICF, in extreme cold, with the ICF house saving on the order of $140 to $190 a month in equivalent electricity through the walls alone at North American average rates of the time. The full report was published by the ICFMA.
What it did not measure, and how to read it honestly
- It measured walls, not houses. A house also loses heat through the roof, the windows, the basement slab and air leakage at junctions. Build an ICF house with a leaky ceiling and double-pane windows and the walls will not save you 60 percent of anything.
- It compared against a 2×6 wall with cavity insulation only. The current Ontario code wall adds continuous exterior insulation, which narrows the gap; the ICF wall still has no bridges and the air barrier built in.
- The dollar figures were at average North American electricity rates; Ontario gas and heat pump costs are different, and gas vs heat pump operating cost is the arithmetic for a real house.
- The realistic whole-house number, from our own houses and the published comparisons, is 30 to 45 percent less heating energy for an ICF house against a code-minimum frame house of the same size, more against an older house. ICF R-value explains the three mechanisms the study confirmed.
Why the result is bigger than the R-value gap
On paper an R-22 ICF wall and an R-22 frame wall are the same. In the hot box they are not, for the three reasons the study separated: the frame wall’s batts are interrupted by studs at R-1.25 per inch (so its effective value is around R-17), the ICF wall’s foam is continuous, and the concrete core stores heat and slows the swing. Add that a frame wall in a real house also leaks air at every plate and the ICF wall does not, and the field gap is bigger than the lab gap. Air sealing an Ontario home covers the part no hot box can show.
What it means for your build
An ICF envelope with a properly insulated roof, triple-pane windows and an insulated slab is a house that heats for a fraction of what the frame house across the road costs; our showhome in Tiny Township has run about $100 a month at the coldest, with nobody living in it. The study is the lab evidence; the showhome is the one you can stand in. What ICF is is the hub, ICF vs stick-built the comparison, and building an energy-efficient home the order to do the rest in.
Related guides on this site
Sources and further reading
Questions people ask
What did the Canadian ICF thermal study find?
In an accredited hot-box test by CLEB Laboratories for the ICFMA in 2017, a standard 6-inch-core ICF wall showed a 58 percent higher effective R-value than a 2×6 insulated wood-frame wall and up to 60 percent lower energy transfer through the wall, with measurable contributions from thermal mass and the continuous foam.
Does an ICF house really save 60 percent on energy bills?
The 60 percent figure is heat through the wall in a lab test. A whole house also loses heat through the roof, windows, slab and air leakage, so a realistic whole-house heating saving for an ICF house over a code-minimum frame house in Ontario is about 30 to 45 percent, more against an older house, and more again with triple-pane windows and a tight roof.
Who ran the ICF wall study?
CLEB Laboratories, an SCC and ISO accredited testing facility in Quebec (formerly Air-Ins), commissioned by the Insulating Concrete Forms Manufacturers Association; the report was published in March 2017.
Building in Simcoe County or on Georgian Bay?
We are ICFhome.ca, a family builder in Tiny Township with 45 years of custom homes behind us. Pick the path that matches where you are.
Reviewed and updated October 2026. Costs are Ontario ranges, not quotes; code references are to the Ontario Building Code in force at that date.
good article and good explain about how to Saves 60% On Your Energy Bills.thanks for sharing this.
Could current construction be adapted to create the same benefits?
Not everybody is in a position to purchase a custom build.
Nice article. Some extra notes regarding some of the problems no one talks about in the construction industry. The ICF foundations are excellent if installed properly. We are in the foundation repair business and can tell you in advance the the people pouring these ICF basements should have experience pouring regular foundations first.Typically a carpenter or the builder gets someone to set ICF forms and pour it with out any knowledge of what happens when not done correctly.We have an article showing some of the problems in detail. https://nextstartech.com/shop/custom.aspx/icf-foundation-problems/36/ NextStar Technologies