DuPont™ Thermax™ (ci) Exterior Foam Insulation

Commercial | Residential | Multifamily | Wall

Designed for easy installation and continuous insulation

With its unique fiberglass reinforced foam core, Thermax™ (ci) Exterior Insulation delivers one of the highest R-values available for immediate insulation and weather protection on the job site. 


Featured resources
Thermax™ (ci) Exterior Foam Insulation Product Information Sheet
Thermax™ Wall System Installation Guide

DuPont™ Thermax™ (ci) Exterior Foam Insulation

DuPont™ Thermax™ (ci) Exterior Foam Insulation* is a moisture-resistant, durable and lightweight extruded polystyrene foam board with shiplap edges designed specifically to be used as a continuous insulation (ci) and installed over block, concrete or metal stud backup behind masonry or stone veneers. Manufactured with a patented carbon-black technology, Styrofoam™ Brand Ultra SL Insulation features an R-value of 5.6 per inch (RSI of 0.97 per 25 mm)**, the highest of all extruded polystyrene foam insulation products. With its closed-cell structure offering advanced long-term thermal performance and moisture control, Styrofoam™ Brand Ultra SL Insulation with shiplap edges maximizes the performance of the entire wall assembly.


Features & benefits

Feature Benefit
Easy to cut, handle, and install
  • Easy to use
  • Moisture Resistant
  • Reduces the potential for condensation within the wall assembly

    Physical properties

    Method Unit Value
    Thermal Resistance1 ASTM C518 R-value, min 6.5
    Compressive Strength2 ASTM D1621 psi, min. 25
    Water Absorption ASTM C209 % by volume, max. 0.1
    Water Vapor Permeance3 ASTM E96 perm, max <0.04
    Maximum Use Temperature - °F 250
    Flexural Strength ASTM C203 psi, min. 55
    Flame Spread ASTM E84 - 25
    Smoke Developed ASTM E84 - <450

    1 Aged R-value at 1” of cured foam @ 75°F mean temperature. R-value expressed in ft2 •h•°F/Btu. R-value determined by ASTM C518 using the aging process in ASTM C1289 (90 days @ 140°F).

    2 Vertical compressive strength is measured at 10 percent deformation or at yield, whichever occurs first.

    3 Calculated flammability values for this or any other material are not intended to represent hazards that may be present under actual fire conditions.


    Available sizes


    Thickness (in.) R-Value Board Size (ft.) Edge Treatment
    Thermax™ (ci) Exterior Foam Insulation 0.625 4.1 4 x 8, 4 x 12 Square Edge
    1.0 6.5 4 x 8, 4 x 12 Square Edge
    1.55 10.1 4 x 8, 4 x 12 Shiplap
    2.0 13.0 4 x 8, 4 x 12 Shiplap