If you are thinking about building a concrete structure, you may be wondering what level of insulation you can expect from your ICF blocks.
You can find out about concrete insulation by looking up its R-value. You also can look up your geographic region to find out what kind of R-value you will need to keep the interior of your home comfortable.
What is R-Value?
Don’t know a lot about insulation? You might not be sure what R-value is.
R-value is a number that tells you how well a material is able to resist the flow of heat.
Materials with high R-values are strong insulators. Those with low R-values are weaker insulators.
That means that a high R-value material can help you save money on heating and cooling a structure.
With a lower R-value material, you will either need to add more in the way of insulation, or you will need to pay more to keep the interior of your building comfortable.
US Insulation R-Value Chart
Before we talk about the R-value of concrete, it helps to have some context for your own project.
First, you will need to identify the R-value zone you are in:
For example, if you live in Florida, you are in zone 1 or 2. But if you live in Maine, you are in zone 6 or 7.
You can then check out this R-value insulation chart:
The chart lets you know what ICF-values you need for your walls, attics, floors and crawlspaces based on your geographical zone.
You will notice that across the board, the R-value requirements for walls are similar. Variations for attics, crawlspaces, and floors are greater.
Now that you know how to find out what R-value you need for your region, we can move onto the next section in our concrete R-value guide.
Let’s talk about how well concrete insulates a structure.
Specifically, let’s find out what the R-value is for ICF blocks. Not familiar with ICF blocks? ICF stands for “Insulated Concrete Forms.”
Picture a structure in the shape of an “H.” It joins together a pair of concrete walls. Between the concrete walls is open air. Each of the concrete walls has a layer of insulation material on either side of it. These “H” components are Insulated Concrete Forms blocks.
ICF blocks have a lot of benefits. They are sturdy, easy and quick to install, do a great job blocking noise, are lightweight and cost-effective to transport, and resist fire, weather, mold, and pests. They also are energy-efficient.
That brings us back to talking about R-value. Now that you know what an ICF block is, you can see how the structure of each block is designed specifically to provide an insulating effect.
So, what is the R-value of ICF blocks?
Let’s see what a few different sources have to say.
Consulting firm Building Science Corporation says, “Using two-dimensional heat flow analysis shows that there are few thermal bridges from the interior to the exterior on an ICF wall. A 9” foam ICF form with 5” of EPS has a whole-wall R-value of approximately R-20.”
Manufacturer Fox Blocks writes, “The clear R-Value of an Fox Blocks is R22, however current Energy codes recognize the lack of thermal bridging in an ICF and the contribution of the mass concrete on the influence of the thermal performance. Whole wall calculations indicate a Fox blocks wall assembly provides an R24 rating.”
Manufacturer Quad-Lock says, “ICF walls consist of a center cavity to contain concrete between two layers of EPS which provide two largely continuous layers of insulation rated at R-22 and higher. From a whole-wall perspective, an ICF wall actually lives up to the advertised R-values because thermal bridging is absent.”
So, most of the products you find will offer R-values ranging anywhere from R-20 to R-24.
As impressive as those values are, ICF block technology is still evolving toward higher R-values.
ICF Builder: The Insulating Concrete Forms Magazine, writes, “An increasing number of homeowners and designers are going ‘beyond green’ and calling for insulation beyond the R-23 or R-25 ICFs typically provide. They’re asking for R-Values in the 30s, and in some cases even more. Coupled with that, Canadian and U.S. Energy Codes are calling for higher insulation values as well.”
The article describes products that are able to deliver R-values ranging up to R-30 for factory-assembled ICF blocks.
Such high R-value blocks may be ideal for passive houses (and there is demand out there for higher R-values yet). But consumers should keep in mind that they are not as cost-effective as regular ICF blocks at this point in time.
As the article points out, “Regular ICFs are far above current code requirements, and most energy loss is through the roof and windows anyway.”
The article quotes Hank Pfeiffer, COO of Reward Wall Systems as explaining, “I think they’re finding that money may be better spent on focusing on roof insulation, windows, connections, and penetrations. Air infiltration is a big deal, and eliminating that may be a better first step than adding foam.”
Conclusion: Concrete ICF Block R-Values Should Be Sufficient for Most Purposes
It is pretty amazing that there are ICF block products out there that are rated as high as R-30. But if you check the chart that we shared with you earlier, you will discover that you probably do not need such a high R-value for your own walls.
Regardless of the zone you are in, the R-values listed for 2×4 walls range from R13-R15, and those listed for 2×6 walls range from R19-R21.
As it is common to see R-values of R-20 or R-22 for concrete ICF blocks, you should be covered in that department.
What about your attics, floors, or crawlspaces, where you might need higher R-values? For those, you can consider adding more insulation to augment the R-value of the ICF blocks.
The great thing about ICF buildings is that even if they list R-values that are comparable to those listed for framed buildings, they often require less power to heat and cool.
Why? As Quad-Lock explains, “The secret lies in the combination of reduced conduction & convection, and high thermal mass. The result is a building with a lower appetite for energy and vastly improved comfort inside the building due to more consistent temperatures, lack of drafts, and superior sound absorption.”
Quad-Lock follows up with a reminder that windows play a critical role in energy performance.
So, the bottom line is this: A concrete ICF building that is well-designed and which features energy-efficient roofing, doors and windows can help you cut costs for heating and cooling significantly. And that is the case even if you go with regular ICF blocks. You do not need to spend an arm and a leg on advanced R-30 blocks to experience the insulating advantages of ICF construction.