XPS vs EPS

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

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)

• 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

• 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
  • 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
  • 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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