EPS Outperforms XPS in R-Value Retention, Water Absorption

Studies show that as much as 25% of energy loss from a structure can be attributed to a lack of insulation.  Insulation R-value is directly correlated to maximum energy efficiency in a building envelope; higher R-values translate into increased savings.  It is important for designers to account for water absorption impacts of building materials when evaluating different insulation choices.

A test program conducted in August 2008 evaluated the field performance of expanded (EPS) and extruded (XPS) polystyrene foam insulation in a side-by-side, below grade application following a continuous 15-year installation period. 

When water and R-value retention were compared between EPS and XPS, the results demonstrated that EPS insulation outperformed XPS insulation with better R-value retention and a lower moisture absorption.

It is important to recognize the successful use of polystyrene foam insulation depends upon its correct installation using good building practice. The following design best practices should be considered for below grade applications:

• Direct water away from the foundation
• Ensure there is adequate subgrade drainage
• Use sealant, barrier, etc. to minimize leakage potential

Call or email the Palpac Team for more information on insulation applications.