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.
For best results, seal joints with tapes or joint closures from Dow.
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.
U.S. Residential
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 (496KB PDF)
Installation Procedures for THERMAX™ Sheathing: Closed Crawl Space (124KB PDF)
Installation Procedures for THERMAX™ Insulations: Exposed Basement Applications (215KB PDF)
Installation Procedures for THERMAX™ or STYROFOAM™ Brand Rigid Insulation – Closed Crawl Space (414KB PDF)
THERMAX™ Advantages Exposed – Sell Sheet (253KB PDF)
THERMAX™ Sheathing Product Information (Residential) (56KB PDF)
Sleep Knowing Your Homes Are Up To Fire Code ... THERMAX™ Sheathing add peace of mind. (140KB PDF)
Start off on the right Foot With THERMAX™ Sheathing and THERMAX™ White Finish Insulation (274KB PDF)
Dow Polyisocyanurate Insulation 15-Year Limited Thermal Warranty (95KB PDF)
| 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 |
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(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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06 16 13 – Insulating Sheathing
07 20 00 – Board Insulation
07 21 13 – Board Insulation
07 22 19 – Sloped Roof Deck Insulation
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U.S. Commercial
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 (496KB PDF)
Installation Procedures for THERMAX™ Insulation in High-Humidity Metal Buildings (156KB PDF)
Joint Closure Systems for Enhanced Protection Against Air and Moisture Product/Installation Information (146KB PDF)
THERMAX™ Advantages Exposed – Sell Sheet (253KB PDF)
THERMAX™ Insulation Exposed Interior Wall Applications in Metal Buildings with Low Humidity (366KB PDF)
THERMAX™ Metal Building Guide Specification (460KB PDF)
CAD Details for THERMAX™ Sheathing
| 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. Since STYROFOAM™ Brand Extruded Polystyrene and Dow polyisocyanurate insulation products are visco-elastic materials, adequate design safety factors should be used to prevent long-term creep. For static loads, 3:1 is suggested. For dynamic loads, 5:1 is suggested. |
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06 16 13 – Insulating Sheathing
07 20 00 – Board Insulation
07 21 13 – Board Insulation
07 22 19 – Sloped Roof Deck Insulation
We're here to help. If you're not finding the information you need, please let us know.