DuPont™ Styrofoam™ Brand Ultra SL Extruded Polystyrene Foam Insulation

Commercial | Residential | Multifamily | Wall

Thermal performance for lasting efficiency

Durable and moisture resistant, Styrofoam™ Brand Ultra SL Extruded Polystyrene Foam Insulation provides continuous insulation as part of a complete 4-in-1 wall system.


DuPont™ Styrofoam™ Brand Ultra SL Extruded Polystyrene Foam Insulation

Styrofoam™ Brand Ultra SL Extruded Polystyrene 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
Lockable edges speed installation
  • Easy to use
  • Moisture Resistant
  • Resistant to moisture infiltration, condensation, and freeze-thaw cycles

    Physical properties

    Method Unit Value
    Thermal Resistance per inch @ 75°F mean temp. 1.75” 2.125” 2.5” 3.0”1 ASTM C518 ft2 •h•°F/Btu, R-value, min. 10.0
    - - 12.0
    - - 14.0
    - - 16.8
    Compressive Strength2 ASTM D1621 psi, min. 25
    Water Absorption ASTM C272 % by volume, max. 0.3
    Water Vapor Permeance 1.75” 2.125” 2.5” 3.0”3 ASTM E96 perm, max 1.1
    - - 0.8
    - - 0.65
    - - 0.50
    Maximum Use Temperature - °F 165
    Coefficient of Linear Thermal Expansion ASTM D696 in/in•°F 3.5 x 10-5
    Flexural Strength ASTM C203 psi, min. 50
    Flame Spread ASTM E84 - 50
    Smoke Developed ASTM E843 - 155

    1 Values are consistent with the criteria of ASTM C578 and the FTC R-value rule (16 CFR Part 460).

    2 Vertical compressive strength is measured at 10 percent deformation or yield, whichever occurs first. Since Styrofoam™ Brand Extruded Polystyrene Foam Insulations are visco-elastic materials, adequate design safety factors should be used to prevent long-term creep and fatigue deformation. For static loads, 3:1 is suggested. For dynamic loads, 5:1 is suggested. Contact DuPont for design recommendations.

    3 These numerical flame-spread and smoke-developed ratings are not intended to reflect hazards presented by this or any other material under actual fire conditions.


    Available sizes


    Thickness1 (in) R-Value2 Board Size3 (ft) Edge Treatment
    Styrofoam™ Brand Ultra SL 1.75 10.0 4 x 8 8’ Shiplap
    2.125 12.0 4 x 8 8’ Shiplap
    2.5 14.0 4 x 8 8’ Shiplap
    3.0 16.8 4 x 8 8’ Shiplap

    1Not all product sizes are available in all regions. Additional product sizes are available by custom order. Consult your DuPont sales representative about other sizes and lead-time requirements.

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

    34’ x 10’, 4’ x 12’ lengths available through special order.