Dow High Performance Underlayment
Existing Wall (Residing) - Installing High Performance and High Performance Underlayment LF
Dow High Performance Underlayments Product Brochure (289KB PDF)
DOW High Performance Underlayment is an extruded polystyrene foam insulation that is fanfolded into 50-foot lengths. Recommended as underlayment over old siding to provide a solid, level surface for new siding materials. It is heat-bonded between various facers and then pin-perforated for vapor permeance.
Facers Available:
Plastic/Plastic (P/P). Bonds the insulation between strong plastic film facers.
Available in 0.25" and 0.375" thickness.
Plastic/Reflective Plastic (P/R). Bonds the insulation between a strong plastic film facer and a metallicized, reflective plastic film facer.
Available in 0.25" and 0.375" thickness.
Kraft/Foil (K/F). Bonds the insulation between a kraft paper facer and a foil facer.
Available in 0.25" thickness.
Kraft/Kraft (K/K). Bonds the insulation between kraft paper facers.
Available in 0.25" thickness.
| Nominal Board Thickness** |
Product R-Value† |
Board Size |
Edge Treatment |
Min Compressive Strength†† |
| 0.25" |
1.0 |
4' x 50' |
Square Edge |
15 psi |
| 0.375" |
1.5 |
4' x 50' |
Square Edge |
15 psi |
Building Code Compliance
Meets IBC/IRC requirements for foam plastic insulation. See ICBO-ES ER 2257, BOCA-ES RR 21-02, NES NER 699, Und. Lab. Inc.® Classified, see Classification Certificate U589.
**Not all product sizes are available in all regions.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.
††Vertical compressive strength is measured at 10% deformation or at yield, whichever occurs first.
