XPS Insulation Tests Confirm Diminished R-Value When Exposed

Originally posted on ConstructionRepair.net

EPS Industry Alliance release new comparative test results

The EPS Industry Alliance (EPS-IA) recently completed a series of tests on extruded polystyrene (XPS) to examine the effects of moisture absorption and R-value in different field applications. Two new technical resources look at the behavior of rigid foam insulation exposed to water, specifically related to the materials drying potential and R-value retention.

When evaluating XPS material samples extracted from roofing and below grade applications, in these long-term installations, XPS did not maintain its initial R-value.

Buildings have been and always will be exposed to moisture. It is not a good thing or a bad thing; it is merely another component of the building design process. When materials are exposed to moisture, the ability to dry is key to maintaining thermal resistance.

This issue is addressed in Drying Potential of Polystyrene Insulations Under Extreme Environmental Cycling Conditions , which evaluates the free-thaw cycling effects on rigid foam plastics as prescribed by ASTM C1512. The test results indicate XPS exceeds the recommended water absorption threshold dictated by ASTM C578 by a factor of 2.4, and, test data rendered by Intertek Testing Services show that in-situ water absorption from XPS samples taken from four different locations is widely variable from 5 – 60% by volume.

Standardized laboratory testing, while not intended to replicate in-situ, real-world conditions, substantiate expanded polystyrene (EPS) performance claims to deliver consistent R-value in building environments that may be exposed to moisture. XPS producers claim its lower moisture absorption rate is a benefit; however, this is based on flawed logic. XPS R-values begin to deteriorate at only 0.03 percent, meaning its tolerance for water absorption is extremely low.

This phenomenon is demonstrated in the test results published in XPS Insulation Extracted After Field Exposure Confirms High Water Absorption Diminished R-value . On the other hand, EPS demonstrates excellent drying abilities and has a much higher tolerance for moisture exposure while still delivering the same R-value throughout the life of the building.

Expanded polystyrene exhibits superior moisture-related performance properties over XPS. It has higher vapor permeability, meaning it helps promote drying in a wall system. As shown in the EPS-IA technical bulletins, EPS is inherently more capable of tolerating moisture absorption than XPS.

Even at 3.0 – 4.0% moisture absorption, expanded polystyrene insulation delivers consistent R-value of 3.1 – 4.3 per inch.

When evaluating rigid foam insulation performance properties, non-standardized testing, modified test methods or testing not intended for the materials being evaluated should be viewed with skepticism. EPS-IAs new information comparing EPS and XPS moisture absorption and R-value retention is based on testing conducted by a third-party, certified testing laboratory and relies on industry recognized standards ASTM C1512. ASTM C518 and others.

EPS-IA is confident these new documents will be a valuable resource for architects, contractors and consumers that are seeking the best possible insulation for their construction projects. For more information on expanded polystyrene and the results of EPS-IAs new test results please contact Betsy Steiner, EPS-IA Executive Director, at emsteiner@epsindustry.org or 800-607-3772.

Question & Response: XPS, EPS, and Dock Flotation

Useful references to support this article:  NEW moisture absorption data regarding XPS, moisture absorption and the effects on R-Value was released in March 2014.  Read more in the updated summary and in subsequent 2008 test program documents:

Originally posted on Construction Specifier online, Author Response to Reader Question, February 18, 2014

After the feature, “Out of Sight, Not Out of Mind: Specifying Thermal Insulation Below-grade and Under-slab” ran in our December 2013 issue, we received a letter from retired architect, Joseph S. Bond. Mr. Bond wrote that the article in question “seems to reverse the findings” from both his personal and professional experience with expanded and extruded polystyrene (EPS and XPS):

I am a retired architect, and may not have the best current information on EPS and XPS, but when these two products were mistakenly used as ‘flotation’ for lake docks and later removed, the XPS bales were like new and had no water soakage beyond the first (1/8 in.). However, I remember the EPS bales were waterlogged to the extent it took two people to even carry the bales. On top of this, the EPS bales showed a lot of disintegration due to freeze-thaw.

My observations may have been on EPS that had much less density (1-1/2 -2 #) than implied by The Construction Specifier article, but many reading will probably have the same concerns and begin to question the piece’s validity.

We asked the article’s author, Ram Mayilvahanan, to respond.

Mr. Bond raises a frequently discussed point about the long-term problems that arise when using rigid foam insulations that do not conform to ASTM standards.

Since insulation, especially below-grade, is out of sight, it can also be out of mind when it comes to ensuring the product being used at the job site matches the product that was specified.  As with other building products, there are numerous companies making rigid foam insulations, often with varying degrees of quality.  We building professionals share the responsibility in making sure the selected right-foam manufacturer can consistently deliver product that meets the specified performance.

To ensure performance on key factors, including moisture resistance, it is crucial to not only specify foam insulation that has been manufactured and tested to meet ASTM C578, Standard Specification fro Rigid, Cellular Polystyrene Thermal Insulation, but also to ensure the manufacturer supplying the foam insulation can consistently deliver quality product.  A manufacturer’s longevity and track record with past projects should help in assessing this.

As an example, the floating green on the 14th hole in the world-famous Coeur d’Alene Golf resort in Idaho – considered on the of the coolest shots in golf- was built with EPS.  It continues to be a testimony to well-engineered flotation insulation.  Projects like this help establish the ability of manufacturers to deliver quality product.

Mr. Bond’s observation is a timely reminder for us building professionals that it pays to make sure the right product gets to the job site.

EPS QUESTIONS?

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

Ram.Mayilvahanan@insulfoam.com

Connect with Ram on LinkedIn  |  Follow Insulfoam on LinkedIn

Read more on Insulfoam.com

New Below Grade Data Released: EPS vs. XPS Insulation

The EPS Industry Alliance (EPS IA) has released NEW moisture absorption data regarding XPS, moisture absorption and the effects on R-Value through the latest Technical Bulletin, EPS Below Grade Series 105:   XPS Insulation Extracted After Field Exposure Confirms High Water Absorption & Diminished R-Value, March 2014 (pdf)

EPS IA March 2014

EPS Below Grade Series 105, March 2014

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.

In 2013, an independent testing laboratory was again commissioned to evaluate the R-value and water absorption from XPS insulation samples extracted from several field locations and applications. A summary of the 2013 test results reconfirm there is no correlation between the results from standardized laboratory test methods and actual field exposure for XPS water absorption.  Further, the significant loss of R-value associated with XPS water absorption is shown in the summary.  

Read Full Technical Bulletin Summary (pdf)

“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 to understand that in-situ water absorption can diminish the thermal performance of building materials and designers must account for this when evaluating different insulation choices.”

 

Read more on the technical background expanding on the moisture resistance comparison between EPS and XPS conducted in the 2008 test program: