Celotex polyisocyanurate insulation board (C) Daniel FriedmanCelotex® & Dow® Polyisocyanurate Insulating Foam Board
Foam board properties, history, asbestos, facings

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Celotex & Dow polyisocyanurate foam board insulation:

This article gives the history and properties of Celotex® Thermax and other foam board insulating products. Celotex® foam board insulation was later purchased by Dow Chemical who continues to market polyisocyanurate foam insulating board. Page top photo: Celotex® Tuff-R polyisocyanurate foam board insulation.

This article series assists building buyers, owners or inspectors who need to identify foam board insulation and to address possible presence of asbestos in buildings.

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Celotex™ Foam Board Insulation: History, Properties, Asbestos Content

Celotex Thermax TM Insulating board  (C) JW

Typical Polyisocyanurate insulation R-Values

Polyisocyanurate insulation products have an R-value of about R 7.04 to R 7.20 per inch. Shown in the photo, Celotex Thermax solid foam insulating board with aluminum foil facing. With a stabilized 3/4" air space on one side of this insulating board its R-value at 1" increases to R10.

1/2" Celotex Thermax was rated at R 3.8, increasing to R 6.4 with the air space we specified above.

4" Celotex Thermax was rated at R 28.8, increasing to R 31.6 with the air space we specified above.

Celotex Thermax Polyisocyanurate Foam Certifications

According to product markings we show below, modern Celotex or more recently Dow polyisocyanurate insulation complies with requirements of ICBO, BOCA, SBCCI, CABO, ICC, HUD/FHA, Federal Specification HH-I-1972/1, Class 2, ASTM C 1289, Type 1, Class 2. The product is described in ICBO Report #3223, SBCCI #9574A, and BOCA #89-45.

In Canada see CCMC Evaluation Report #08433-L. The product shown below also is stamped with logos of NAHB, ETL, Good Housekeeping, and Energy Star.

Readers may also want to review IAQ and health questions discussed at POLYISOCYANURATE FOAM and IAQ.


Question: was asbestos used in Celotex Thermax foam core insulating board sheathing?

Jason Wojnowiak said:

I have a picture of some Celotex. [Shown above - Ed. ] [Click to enlarge any image]

Would you know if this has asbestos?

This question was posted originally at CELOTEX ASBESTOS PRODUCTS

Reply: some Celotex Thermax™ laminate insulating board products contained asbestos at least in patent disclosures


Celotex Thermax™ as illustrated by your first photo above was (and is currently as a Dow Thermax™ product) a foil-faced insulating board comprised chiefly of foam insulation, laminated with aluminum foil or possibly kraft paper.

Asbestos appeared in some, probably not all, foam insulating boards made up to the early to mid 1980's, particularly or more likely in fire-resistant products that incorporated a layer of asbestos paper.

Celotex foam board insulation interior view (C) InspecApedia JW Closeup of cross-section of Celotex Thermax foam insulating board (C) InspectApedia

The second photo you provided later [above] has been cut-open.

Enlarging the photo (enlarged view above) I don't see any sign of an asbestos paper, though of course a closer look in the field would be in order.

Celotex Thermax labeling information & specifications (C) JW

[Click to enlarge any image]

Above and then below we show your images of the labeling and text on this Celotex Thermax insulating board. Readers will want to click to enlarge each image to read the details of the Celotex insulation specifications.

This insulation meets several standards and specifications including Energy Star ratings - a rating that well post-dates asbestos-based insulation for in-home use. The company's stamping describes this product as a "Glass fiber reinforced polyisocyanurate foam board with reflective aluminum foil facers."

Celotex Thermax labeling information & specifications (C) JW

Patents Establishing Use of Asbestos in Some isocyanurate foam products

Foil faced and structural laminate type insulating boards using foam and aluminum or other facings have patents that help identify the product contents.

Watch out: you are absolutely right to ask if asbestos ever was used in insulating foam boards. Indeed the patent I cite above as well as at least one other patent describe possible use of asbestos in these insulating board products.

Excerpt from Hipchen: The structural laminate of the present invention has at least one but preferably has two facing sheets, one on either side of the foam core. These facing sheets can be constructed of a wide variety of non-flammable materials such as asbestos, glass fibers, or metals.

In the broadest aspects of the invention, any metal can be employed such as copper, brass, iron, steel, or aluminum. Aluminum is the preferred metal because of its ductility and ease with which it can be manufactured into a material of suitable thickness.

Celotex is the original assignee of this patent. That does NOT tell us what Celotex products actually contain when marketed.

Here is a later patent citing asbestos in foam insulating boards:

Notice that where fireproof or fire resistant products were being marketed asbestos was more likely to appear.
Excerpt from Ohashi:

This invention relates to novel fireproof laminates using a urethane modified polyisocyanurate foam as a core material.

More particularly, it relates to fireproof laminates having excellent fireproof property and low-smoke development, which are obtained by using the above core material having a defined density and an asbestos paper lined with a metal foil as a surface material for at least one side of the core material and piling them one upon another at a total thickness of a defined range through self-adhesion of the urethane modified polyisocyanurate foam.

In the U.S. in the 1980's Celotex Thermax insulating board was described by the Celotex Company (Jim Walters corporation, Tampa) as an insulating sheathing board with an R-value of 5.4 for a 3/4" thick board: higher R than its competitors at the time as it was compared with foam insulating board sold by Dow, WR Grade and Simplex. (Popular Mechanics, October 1984, advertisement p. 139)

In July 2001 Celotex's rigid foam insulation business was purchased by Dow Chemical which explains why most web searches for Celotex Thermax insulating board will turn up Dow Chemical company listings for Thermax products.

I have not found reports of use of asbestos in foam currently-marketed (2016) insulating foam board products. But laminated foam insulating board products sold in North America up to about the mid 1980's might indeed contain asbestos, particularly in special fire-resistant applications.

At FOAM BOARD INSULATION TYPES you can see more photos of Celotex-branded foam insulating board, principally a polyisocyanurate foam product.

Constituents & Properties of Modern Insulating Foam Board from Dow Chemical

Dow Chemical Super Tuf R foil faced foam insulating board (C) Daniel Friedman Dow Super Tuff R foam insulating board R values (C) Daniel Friedman

Modern foam insulating board products may use fiberglass or other reinforcing fibers however. Shown above: Dow Super Tuff R foil faced insulating foam board at a Home Depot store in Poughkeepsie, NY. This product is rated by the Dow Chemical company as R 3.3 in 1/2" board and R 6.5 in 1" thickness board.

Shown in our second photo above in which some shopper (not me) peeled back part of the foam board facing, you may see that some insulating board products use aluminum foil only on one side, facing the other side with paper or plastic.

The Dow Chemical company notes that the installer can obtain an additional R 2.8 if the insulation is installed with an air space on the reflective side - the side without printing.

Contemporary Thermax branded insulating board or sheathing board, a Dow Chemicals product, is described by DOW as follows:

THERMAX™ Heavy Duty Insulation consists of a glass-fiber-reinforced polyisocyanurate foam core faced with nominal 4 mil embossed white thermoset-coated aluminum on one side and 1.25 mil embossed aluminum on the other. It can be installed exposed to the interior without a thermal barrier.

Dow Chemical currently markets several versions of Thermax™ to meet different needs such as building insulating sheathing, heavier duty insulating sheathing or insulating board for metal buildings, etc. Here is a copy of one of the current Thermax™ Sheathing products now produced and sold by the Dow Chemical Company and an example Dow Chemical MSDS for a typical Thermax insulating sheathing product.


Continue reading at POLYISOCYANURATE FOAM and IAQ possible health hazards?, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CELOTEX ASBESTOS PRODUCTS includes a history of key dates for the Celotex corporation.






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POLYISOCYANURATE FOAM BOARD at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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