Core Foam Masonry Insulation: Our New Service Line

Bahl Fireproofing is adding masonry foam to its insulation work across Texas, Kansas, and Oklahoma. Core Foam Masonry Foam Insulation from cfiFOAM, Inc. is a two-part aminoplast foam injected into concrete block cores and double-wythe masonry cavities. This article covers what the product is, what the published whole-wall numbers actually are, where the foam does not belong, and how to specify it on a real project.

TLDR: Core Foam is masonry insulation, not a general-purpose foam, and the number that decides your wall is the whole-wall value, not the R per inch on the product sheet. The block density your architect specified moves the wall R-value more than the foam does. Same 8-inch unit, same foam, and cfiFOAM’s own series-parallel table swings by a factor of about 2 from lightweight block to normal-weight block. Read the block submittal before you read the R per inch.

The R-Value Mistake That Shows Up at Plan Review

An owner buys a 60,000 square foot CMU school addition on a design that shows foam-filled block cores carrying the wall’s thermal performance. The energy model closes. The block goes up. Then a plans examiner asks how the wall R-value was calculated, and the answer turns out to be the foam’s R per inch multiplied by the core depth. The wall gets recalculated by the code-recognized method, loses a large share of the number the model was built on, and somebody has to add continuous insulation to a wall that is already standing.

That is not a hypothetical failure mode. It is the predictable result of skipping the webs. Any number built from R per inch times core depth ignores thermal bridging through the block webs, and the webs are solid concrete running face to face, a straight thermal path around the foam.

The values that hold up are calculated by the series-parallel method, also called isothermal planes, which accounts for the heat that runs through the webs of a concrete masonry unit. CMHA TEK 06-02C lays out that method for single wythe concrete masonry walls, and cfiFOAM uses it for every whole-wall value in its Thermal Properties Data Handbook for Core Foam filled block walls. If a number in front of you was not produced that way, it is a marketing number, and it will not survive a plan review that asks the question.

What Core Foam Masonry Insulation Actually Is

Core Foam Masonry Foam Insulation is a two-part aminoplast foam made by cfiFOAM, Inc. of Knoxville, Tennessee. One part is a spray-dried resin, the other a foaming catalyst concentrate. The installer mixes the components before each job, the foam is combined with compressed air in specialized equipment, and it is injected into the hollow cores of a masonry wall. cfiFOAM describes it as a non-expanding foam that flows through the wall and fills irregular voids as it is placed.

The cured foam is light. The ICC-ES listing puts nominal density at 1.0 pound per cubic foot (about 16 kg/m3), and cfiFOAM’s product sheet gives a finished dry density of 1.0 plus or minus 0.5 pounds per cubic foot. The same sheet reports shrinkage under 0.5 percent, and a 72-hour cure is normally suggested before the wall is painted.

Thermal performance is measured under ASTM C518-21. ICC-ES listing ESL-1648 for Core Foam Masonry Foam Insulation reports R-4.6 per inch at a 75F mean temperature, and cfiFOAM’s test data adds R-5.0 per inch at a 25F mean. Use the 75F number. Federal insulation labeling under 16 CFR Part 460 is stated at a 75F mean, so 4.6 is the figure that belongs in a submittal. The 5.0 figure is the cold-side test point, and it should never appear without that qualifier.

Acoustically, cfiFOAM’s product sheet lists STC 54 to 60 in 8-inch block walls and STC 58 to 61 in 12-inch block walls, without naming the test standard or the block. Ask for the test report before either range goes into a submittal, because sound transmission class is a property of an assembly, not a material.

What Actually Goes Wrong on Masonry Insulation Jobs

I have been applying sprayed and injected insulation across Texas, Kansas, and Oklahoma for more than twenty years, and on masonry work the jobs that go wrong almost never go wrong because of the foam. They go wrong because the wall the foam went into is not the wall the energy model assumed.

The pattern repeats. A design team runs the wall on a lightweight unit. At bid time the block package gets value-engineered to a heavier, cheaper unit from a different plant. Nobody re-runs the wall, because the substitution reads like a masonry decision rather than a thermal one. The foam performs as specified, and the assembly still lands short, because the concrete around the foam changed.

The second thing we see is a core that was never fillable. Bond beams, grouted cells carrying reinforcement, and mortar droppings on a web all block the path the foam has to travel, and injected foam takes the route of least resistance. If an obstruction splits a cell, the foam stops, and you have a void you cannot see from either face.

Both failures are preventable on paper, before anybody drills a hole. Get the block density off the approved submittal rather than off the specification’s generic call for concrete masonry units, then read the reinforcing and grouting drawings and decide, cell by cell, what is actually open.

Why Block Density Moves the Wall R-Value More Than the Foam Does

Here is the whole argument in two numbers. Take one 8-inch concrete masonry unit with three 1-inch webs and its cores filled with Core Foam. In 85 pound per cubic foot lightweight block, cfiFOAM’s series-parallel wall value is R-8.21. In 135 pound per cubic foot normal-weight block, the same unit with the same foam is R-4.02. Nothing about the insulation changed, and the wall lost more than half its resistance to the concrete alone.

That is a swing of about 2 times, driven by a material decision most people treat as structural. Below are cfiFOAM’s published whole-wall values for Core Foam in ungrouted units with three 1-inch webs, air films included. cfiFOAM publishes these values for 8-inch and 12-inch units only.

Two qualifiers belong with that table. First, it assumes no grouted cells. Reinforcement pulls the number down fast: the same 8-inch, 85 pcf unit drops to R-6.62 with grouted rebar cells every 96 inches and to R-5.54 at 48 inches. cfiFOAM’s handbook tabulates those reductions for vertical rebar and bond beams, so read the grouting drawings before you read the table.

Second, web geometry matters as much as density. The table above assumes three 1-inch webs. The same 8-inch, 85 pcf unit calculates at R-9.67 with three 3/4-inch webs and R-11.95 with two 3/4-inch webs, because less web means less concrete carrying heat around the foam. So ask a block supplier not only what the unit weighs, but how many webs it has and how thick they are.

For compliance, cfiFOAM’s handbook gives a U-factor and heat capacity for every cell in its tables, which is what COMcheck asks for. Confirm the path against the energy code your jurisdiction adopted, or the Standard 90.1 tables where that path is open to you.

Core Foam and Fire: Reading the ASTM E84 Result Correctly

Tested to ASTM E84, the standard test method for surface burning characteristics of building materials, and UL 723, Core Foam at a nominal 1.0 pound per cubic foot and up to 3.5 inches thick has a flame spread index of 25 or less and a smoke developed index of 450 or less, per ICC-ES listing ESL-1648. That is the result as the listing reports it: a ceiling, not an exact score.

Class A is a threshold, not a test result. Under Section 803.1.2 of the 2021 and 2024 IBC, a Class A interior finish means a flame spread index of 0 to 25 and a smoke developed index of 0 to 450. The listed result sits inside that band, which is why cfiFOAM calls the product Class A. Keep the two ideas separate, because a threshold and a score are different things.

A second code provision quotes ASTM E84 numbers, and it is the one people conflate with Class A. Section 2603.3 of the 2021 IBC limits foam plastic insulation to a flame spread index of not more than 75 and a smoke developed index of not more than 450, tested in the maximum thickness intended for use. ESL-1648 cites Section 2603.3 for Core Foam across the 2015 through 2024 IBC. That is a foam plastic rule in Chapter 26, not an interior finish classification in Chapter 8. Section 2603.4 separately requires a thermal barrier over foam plastic, with exceptions at 2603.4.1. Whether an exception reaches foam concealed inside masonry cores is a call for the licensed architect or engineer and the authority having jurisdiction, and the adopted edition varies across the three states we work in.

One thing this foam does not do is make a block wall more fire resistant. cfiFOAM states that its masonry foam neither adds to nor detracts from the fire-resistance rating of a CMU wall. A wall’s rating comes from the tested or calculated assembly and has to be confirmed against the applicable listing. The third-party evaluation that does exist, ICC-ES ESL-1648, covers R-value, surface burning, and federal labeling, not fire resistance.

Core Foam Compared With the Other Masonry Cavity Options

Four materials compete for the same job and do not occupy the same place in the wall. Loose-fill mineral and injected foam go inside the block cores. Rigid board and mineral wool batts go in the drainage cavity of a multi-wythe wall or behind furring. That distinction decides half the comparison before performance enters it.

The Core Foam row comes from cfiFOAM’s handbook and the perlite row from CMHA TEK 06-02C. Both use the series-parallel method, but the two sources assume different web geometry, so read the comparison as a direction, not a decimal. Use current manufacturer data sheets for board and batt values, since those change by product line.

Where Core Foam Does Not Belong

The limitations are the most useful part of any product conversation, and cfiFOAM publishes them plainly. We repeat them on every masonry job we quote.

It is not for flotation, horizontal applications, or waterproofing. It is never injected into a wet wall: the cores have to be free of standing water and the exterior face free of visible wetness. It should not see extended contact with surfaces above 190 degrees Fahrenheit, which is 88 degrees Celsius, where it shrinks, chars, and stops working as insulation. And as covered above, it is not a way to buy fire-resistance rating.

cfiFOAM positions Core Foam for the cores of concrete block walls, typically in commercial and institutional new construction, and publishes separate guidance for filling the cavity of double-wythe masonry walls. We also install it in standing block walls through drilled holes. If somebody proposes an application outside those, the burden is on them to produce the manufacturer’s written support, and we ask for it.

The product is also not a replacement for anything we already do. Steel-frame buildings, metal building envelopes, and exposed deck work are spray foam and sprayed fiber jobs. Masonry cavity assemblies are where this foam earns its place, and the choice starts with the wall type, not the R-value chart.

What the Energy Code Does With a Foam-Filled Block Wall in Texas, Kansas, and Oklahoma

Here is the compliance trap, and it is specific to Core Foam. The prescriptive mass wall rows in the energy code are written in continuous insulation, abbreviated ci, and continuous means uninterrupted by framing or webs. Foam inside block cores is interrupted by every web, so it is cavity insulation and generally does not satisfy a prescriptive ci row on its own. That does not mean the wall fails. It means you comply through the U-factor path, an added continuous layer, or the Standard 90.1 tables where the adopted code opens that door.

Which number you owe depends on the edition your jurisdiction enforces. In the 2021 IECC, Table C402.1.3 is the insulation component R-value method and Table C402.1.4 is the assembly U-factor method, and that edition puts above-grade mass walls at R-5.7ci in Climate Zone 2, R-7.6ci in Zone 3, and R-9.5ci in Zone 4 for most occupancies, higher for Group R. Those figures govern only where a jurisdiction amended up to the 2021 edition, as Dallas has. Everywhere else the value comes off the opaque envelope table in the adopted edition, for the project’s climate zone and assembly.

Then the three states diverge, and this is where a national article stops being useful. Texas is on the 2015 IECC, effective November 1, 2016 under 34 Texas Administrative Code 19.53(a). Oklahoma is on the 2006 IECC with ASHRAE 90.1-2003 and state amendments, effective September 14, 2022, which is a 2022 effective date on a 2006 edition. Kansas names the 2006 IECC as the state standard for new commercial and industrial structures under K.S.A. 66-1227, but Kansas is a home-rule state, so adoption and enforcement belong to the local jurisdiction. Wichita, for example, is on the 2024 IBC, and that tells you nothing about which energy code the same department enforces.

The sharpest version of this sits inside one Texas metro. Dallas enforces the 2021 IECC. Fort Worth is still on the 2015. The same foam-filled block wall gets reviewed against two different editions twenty miles apart, and no state-level answer warns you which one you are in.

The 2021 IECC also carried the first climate zone map update since 2003, and roughly ten percent of US counties changed, nearly all to warmer zones, but a jurisdiction still on the 2015 IECC is judged against the 2015 map. So do not read a county’s climate zone off a map graphic. The governing list is Table C301.1 in the adopted edition.

How to Specify Core Foam and How to Get a Bid

Masonry insulation is a paper problem before it is a field problem. This is the order we work in and recommend to design teams.

1. Pull the block density off the approved submittal, not off the specification’s generic call for concrete masonry units. The density decides the wall, and it is the most likely thing to change between design and bid.
2. Ask the supplier about web configuration. cfiFOAM tabulates 3-web and 2-web units with 1-inch and 3/4-inch webs, and the same block density can land more than 40 percent apart depending on which one you get.
3. Look up the wall value in cfiFOAM’s handbook for that unit size, web configuration, density, and grouting, and write the source and the density into the energy model notes so the next person can audit it.
4. Pick the compliance path before the block ships. Prescriptive ci row, U-factor path, or the 90.1 path where the adopted code allows it. Core Foam usually points you away from the prescriptive row.
5. Map the cells that are actually open. Bond beams, grouted reinforced cells, and control joints change what can be filled and what counts as unfilled.
6. Check the exposure against the limitations. No extended contact with surfaces above 190 degrees Fahrenheit, nothing horizontal, no wet walls, and nothing that relies on the foam as waterproofing.
7. Get a project bid. There is no citable published installed price for masonry cavity fill in this market, and any per-square-foot figure circulating as an industry number came from a lead-generation site.

On the wall itself, cfiFOAM’s guide specification calls for 5/8-inch to 7/8-inch holes drilled to reach each column of cells, roughly 8 inches on center, starting about 4 feet above the finished floor and repeated every 10 to 14 feet up the wall. The same specification calls for an installer trained and authorized by the manufacturer, and infrared scans of the filled wall at the architect’s request. Verify the hole geometry against the project specification before it goes into a submittal, since layout depends on unit size, bond pattern, and grouting.

We are rolling this service out across the territory we already cover, on commercial, institutional, educational, and industrial masonry projects, and existing clients can add a masonry scope to an active job by calling or emailing us. Three follow-up guides are in production and will publish here over the next several weeks: our upcoming guide to Core Foam installation, our full R-value and fire safety breakdown, and our Core Foam versus K-13 comparison. Until those are live, this article is the hub.

Related Reading

• K-13: The Complete Contractor Guide is the hub for our sprayed fiber work, where steel-frame and exposed deck buildings usually land instead of masonry Core Foam.
• K-13 versus fiberglass batt insulation for commercial buildings runs the same selection logic as the table above on a different pair of materials.
• Commercial spray foam insulation guide covers the envelope side of our work, including the code obligations that follow any foam plastic.

Frequently Asked Questions

What is Core Foam made of? It is a two-part aminoplast foam: a spray-dried resin and a foaming catalyst concentrate. The installer mixes the components before the job, and the foam is combined with compressed air and injected into the cores. cfiFOAM, Inc. of Knoxville, Tennessee makes it.

What R-value does the foam provide? The material figure is R-4.6 per inch at 75F mean temperature under ASTM C518-21. The wall figure is different, because the block webs bridge heat around the foam. For an 8-inch unit with three 1-inch webs and filled cores, cfiFOAM’s series-parallel values run from R-8.21 in 85 pcf block down to R-4.02 in 135 pcf block.

Is Core Foam fireproof? No, and cfiFOAM does not claim it is. Its ASTM E84 result is a flame spread index of 25 or less and a smoke developed index of 450 or less, which meets the Class A threshold for interior finish. The foam neither adds to nor detracts from a wall’s fire-resistance rating, so a rated wall still has to be confirmed as a listed or calculated assembly.

Can Core Foam be used in existing buildings? Yes. We inject it into standing block walls through small drilled holes rather than by opening the wall. The limits match new work: the cores have to be open and dry, and grouted or obstructed cells cannot be filled.

How is this different from spray foam insulation? Spray foam is applied to a surface, adheres to it, and forms a continuous plane across a roof deck or a wall. Masonry Core Foam is injected into a closed cavity and is interrupted by the webs of every block. They serve different assemblies, and Core Foam does not replace spray foam on steel-frame or metal buildings.

Does Core Foam settle over time like loose-fill insulation? cfiFOAM’s product sheet reports shrinkage under 0.5 percent, unlike gravity-dependent loose fill that can settle and bridge. What does create voids is an obstructed cell that stopped the foam during injection, which is an installation issue rather than a material one.

What does masonry cavity fill cost per square foot? There is no credible published installed price for this work in Texas, Kansas, or Oklahoma, and we will not invent one. Cost turns on unit size, how many cells are fillable, access, and whether the wall is new or a retrofit. Get a project-specific bid.

Key Takeaways

The block decides the wall, not the foam.

• Same 8-inch unit and same fill, cfiFOAM’s values run R-8.21 in 85 pcf block and R-4.02 in 135 pcf block.
• That is about a 2 times swing from a decision most teams treat as structural.
• Re-run the wall any time the block package changes.

Use the series-parallel table, not R per inch times core depth.

• Series-parallel, also called isothermal planes, accounts for thermal bridging through the webs.
• Web count and thickness move the number too: two 3/4-inch webs calculate well above three 1-inch webs.

Quote the 75F R-value.

• R-4.6 per inch at 75F mean temperature is the design figure under ASTM C518-21.
• The 5.0 figure is the 25F mean test point and should never appear without that qualifier.

Keep the fire numbers straight.

• Listed result: flame spread 25 or less, smoke developed 450 or less on ASTM E84.
• Class A is a threshold of 0 to 25 flame spread and 0 to 450 smoke developed, and the listed result sits inside it.
• The foam neither adds to nor detracts from a masonry wall’s fire-resistance rating.

The limitations are the specification.

• Not for horizontal applications, flotation, or waterproofing.
• Never injected into a wet wall: no standing water in the cores and no visible wetness on the face.
• No extended contact with surfaces above 190 degrees Fahrenheit.

Three states, three different code answers.

• Texas is on the 2015 IECC, Oklahoma on the 2006 IECC with ASHRAE 90.1-2003, Kansas on the 2006 IECC under home rule.
• Dallas enforces the 2021 IECC while Fort Worth holds the 2015, twenty miles apart.
• Read the edition and the climate zone off the jurisdiction, never off the state.

If you are specifying or building a masonry wall and you want a crew that reads the block density off the submittal, calculates the wall by the series-parallel method instead of a construction table, confirms which energy code edition your building department enforces, and tells you up front where this foam does not belong, that is the work we do throughout Texas, Kansas, and Oklahoma. Call me at 512-387-2111 or email ross@bahlfireproofing.com to walk a wall section, or Contact Bahl Fireproofing to get a masonry scope priced. Our Core Foam masonry insulation page covers the service itself, and our service areas across Texas, Kansas, and Oklahoma page shows where we work.

This article provides general educational information about masonry insulation, thermal performance, and passive fire protection, and it is not engineering, legal, or code-compliance advice. It does not replace project-specific direction from a licensed architect or engineer. Product specifications including R-value, density, shrinkage, and acoustic ratings are revised by manufacturers, so confirm current values against the manufacturer’s latest published data sheet, and note that product suitability depends on project-specific conditions. Fire-resistance ratings depend on the tested or calculated assembly and correct installation and must be confirmed against the applicable listing. Code citations reference a specific edition and the adopted edition varies by the authority having jurisdiction, and installation must follow the manufacturer’s written instructions and be performed by a qualified applicator, so confirm current requirements with your local building department before specifying or installing.