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Dow Thermax

Please call 1-877-944-7697 for price and availability

Product Description

THERMAX™ Sheathing is a non-structural, rigid board insulation consisting of a glass-fiber-reinforced polyisocyanurate foam core laminated between 1.0 mil smooth, reflective aluminum foil facers on both sides. The reinforcement, along with chemical modifications, contributes to fire resistance and dimensional stability. THERMAX™ Sheathing can be installed exposed to the interior without a thermal barrier and is especially appropriate for hourly rated assemblies.

Building Code Compliance

Complies with ASTM C1289 Type I, Class 2. Meets IBC/IRC requirements for foam plastic insulation. See ICC-ES ESR-1659. FM 4880 – see Factory Mutual Approval Guide. UL Classified. Calif. Std. Reg. # CA T383. Miami-Dade NOA 08.0320.01 DOT Docket 90 Mass Transit Vehicle Insulation.

THERMAX™ Sheathing consists of a high-performance foam core laminated between 1.0 mil smooth, reflective aluminum foil facers on both sides that contribute to fire resistance and dimensional stability.

Related Information


THERMAX Sheathing Product Information Sheet

THERMAX™ Advantages Exposed – Sell Sheet

THERMAX™ Sheathing Product Information (Residential)

Sleep Knowing Your Homes Are Up To Fire Code ... THERMAX™ Sheathing add peace of mind.

Start off on the right Foot With THERMAX™ Sheathing and THERMAX™ White Finish Insulation

THERMAX™ White Finish Insulation Product Information

Dow Polyisocyanurate Insulation 15-Year Limited Thermal Warranty

THERMAX(TM) 0.50 Inch Insulation Sheathing MSDS

THERMAX(TM) 0.75 Inch Insulation Sheathing MSDS


THERMAX™ Sheathing Product Information Sheet

Joint Closure Systems for Enhanced Protection Against Air and Moisture Product/Installation Information

THERMAX™ Advantages Exposed – Sell Sheet

THERMAX™ Insulation Exposed Interior Wall Applications in Metal Buildings with Low Humidity

THERMAX™ Metal Building Guide Specification


Nominal Board Thickness(1), in R-Value(2)(3) Board Size, ft Edge Treatment Min Compressive Strength(4), psi
                .50     3.3  4' x 8' / 4' x 9' / 4' x 10'  Square Edge                    25
                .75     5.0  4' x 8' / 4' x 9' / 4' x 10'  Square Edge                    25
                1.0     6.5  4' x 8' / 4' x 9' / 4' x 10'  Square Edge                     25
               1.50     9.8  4' x 8' / 4' x 9' / 4' x 10'  Square Edge, Shiplap                    25
                2.0   13.0  4' x 8' / 4' x 9' / 4' x 10'  Square Edge, Shiplap                    25


(1) Not all product sizes are available in all regions.

(2) R means resistance to heat flow. The higher the R-value, the greater the insulating power. R-values are expressed in ft2• h•°F/Btu. R-value determined by ASTM C518.

(3) Consult your Dow Seller or Technical Service Group for information on different R-values.

(4)  Vertical compressive strength is measured at 10% deformation or at yield, whichever occurs first.

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