Based on the principles of science and engineering, Dow Styrofoam XPS outperforms EPS, and delivers maximum energy savings.

XPS vs EPS 1

XPS Performance Data Summary

XPS Performance Data Summary

  • 77% more density. The higher the density:
    • The greater the moisture resistance
    • The higher the R-value
    • The greater strength
    • The tighter the structure (closed cell)

Higher R-Value

  • 28% higher R-value
    • The higher the R-value, the greater the resistance to heat flow
    • One cubic inch of Styrofoam XPS contains millions of tiny cells
    • Unique closed-cell structure helps block transfer of heat and cold
    • Provides maximum energy savings

Higher Compressive Resistance

  • 250% higher compressive resistance
    • Compressive Resistance—the amount of force needed to deform the XPS insulation
    • The higher the compressive strength, the harder it is to damage the insulation
    • A higher compressive strength helps keep walls more uniform and straight when placed over existing siding

Effectively Handles Water Vapor Permeance

  • Effectively handles water vapor permeance
    • Water Vapor Permeance—the amount of water in the vapor state that passes through a product or system
    • EPS insulation has a 5.0 perm rating
    • Vinyl siding has a .05 perm rating
    • When a substrate is laminated (such as EPS and vinyl siding), it takes on the properties of the lower of the two—which would be the .05 perm of vinyl siding
    • Dow 3/4″ T&G XPS insulation has a   perm of 1.1—it will not trap vapor moisture
    • Dow XPS is not attached to the siding so  it does not take on the .05 perm
    • By maintaining its consistent perm rating,   Dow XPS allows harmful moisture to escape the home
    • Dow XPS also creates an effective drainage plane, allowing rain and  wind-driven water to escape quickly through siding weep holes

Provides Superior Moisture Resistance

  • Provides superior moisture resistance
    • Water Absorption—the volume of a liquid that becomes trapped in a product
    • 3/4″ XPS takes on .1% water vs. EPS at 4.0%
    • For every 1% moisture absorption, you lose 5% of   the R-value
    • If the R-value of 3/4″ of Type I EPS = 2.7 per inch, it will reduce to 2.16 after taking on 4.0% moisture
    • Wet insulation loses thermal integrity and facilitates energy loss
    • XPS’ high density and closed-cell structure block moisture penetration
    • In a water vapor freeze/thaw test, XPS retained 98% R-value!

Test Data Proves—XPS Insulation Delivers on Every Key Factor

  • Higher density
  • Higher R-value
  • Higher compressive strength
  • Effectively handles water vapor permeance
  • Superior moisture resistance





















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