THERMAX™ Sheathing

A rigid foam insulation that effectively reduces condensation for exceptional moisture protection.

THERMAX™ Sheathing is specially designed to have a Class A fire rating and can be used in a range of concealed and exposed applications, above and below grade. Because of the improved fire performance it is best suited for hourly rated assemblies. It has nominal 1.0 mil, smooth aluminum foil facers on both sides.

Used In

  • Insulate residential and commercial walls
  • Residential closed (non-vented) crawl spaces
  • Interior basement walls
  • Interior walls of metal buildings

Product Advantages

  • Can be installed exposed to the interior without a thermal barrier
  • Reinforcing facers, along with chemical modifications, contribute to fire resistance and dimensional stability
  • Suited for hourly rated assemblies

Typical Physical Properties

These properties are typical but do not constitute specifications.

THERMAX™ Sheathing - U.S. Residential

Nominal Board Thickness(1), in R-Value(2)(3) Board Size, ft Edge Treatment
.50 3.3 4 x 8, 4 x 9, 4 x 10 Square Edge
.75 5.0 4 x 8, 4 x 9, 4 x 10 Square Edge
1.0 6.5 4 x 8, 4 x 9, 4 x 10 Square Edge
1.5 9.8 4 x 8, 4 x 9, 4 x 10 Square Edge, Shiplap
2.0 13.0 4 x 8, 4 x 9, 4 x 10 Square Edge, Shiplap

(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.

THERMAX™ Sheathing - U.S. Commercial

Nominal Board Thickness(1), in R-Value(2) Board Size, ft Edge Treatment Min Compressive Strength(3), psi
0.5 3.3 4' x 8' / 4' x 10' Square Edge 25
.75 4.9 4' x 8' / 4' x 10' Square Edge 25
1.0 6.5 4' x 8' / 4' x 10' Square Edge 25
1.25 8.1 4' x 8' / 4' x 10' Square Edge 25
1.50 9.8 4' x 8' / 4' x 10' Square Edge, Shiplap 25
1.55 10.1 4' x 8' / 4' x 10' Square Edge, Shiplap 25
2.0 13.0 4' x 8' / 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) Vertical compressive strength is measured at 10% deformation or yield, whichever occurs first. Since Dow polyisocyanurate insulation is a visco-elastic material, 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.

Downloads

MSDS

Warranty

Have a question?