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.

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:

Thermal Loss Thwarted

Originally printed in Architectural Products Magazine, Features Special Report, Insulation, Nov 2013

By:  Alan Weis, Contributing Writer


FULL article (pdf)

Architectural Products, Nov 2013

Architectural Products, Nov 2013

When it comes to insulation, R-value- the measure of thermal resistance – seemingly rules.  In other words, the higher the R-value the better the thermal resistance.  But there’s more to the story than that according to industry experts.  “An insulation product’s R-value is only a starting point for understanding how well it works, says James Hodgson, general manager for Premier SIPS.

In fact, Hodgson says it’s crucial to evaluate the whole-wall R-value of the assembly, since the insulation is only one part of creating a tight, well-insulated envelope.  For example, he claims DOE research shows that a 4.5-in. structural insulation panel (SIP) wall rated at R-14, out-performs a 2×6 stud wall with R-19 fiberglass insulation.  “It comes down to significantly less air leakage, thermal bridging and convective looping for a better performing assembly,” says Hodgson.

Insulation, unfortunately, is too often treated as an afterthought, as Hodgson says it ends up getting fit around the structural systems instead of being an integral part of them, making it difficult to seal leaks.  SIPs, he notes, address this by incorporating both in one assembly.


Longevity is another consideration when it comes to R-values.  “It’s common for building professionals to look at R-value per inch at the time of installation, “says Ram Mayilvahanan, product marketing manager with Insulfoam.  “Yet, it makes more sense to evaluate insulation’s long-term thermal performance and the return on investment.”


Insulfoam EPS insulation not only offers a high initial R-value, it also doesn’t lose R-value with time.

His company manufactures HD composite roof insulation, which bonds expanded polystyrene (EPS) foam to a high-density polyiso cover board, a combination that has high thermal efficiency and provides significant field labor savings.  Plus, Mayilvahanan says it can be used to achieve UL Class A fire ratings on combustible roof decks without the use of gypsum or other cover boards.

“Many rigid foam insulations experience thermal drift, which is a loss of R-value over time as insulating gases within them dissipate and are replaced by air,” Mayilvahanan continues.  “Some materials lose up to 20% of their insulating capacity during their time in service.”  One the other hand, EPS insulation, he explains, not only offers a high initial R-value, it also doesn’t lose R-value with time.  And, it can be used in wall, roof, below-grade and under-slab applications.

Continue to read FULL article (pdf) where further insulation consideration and types are described by industry experts.

“The push toward comprehensive green design has raised awareness that many building systems must work together for optimum performance,” says Mayilvahanan.  “It’s not just insulating the structure appropriately, but also right-sizing the HVAC systems and educating owners and occupants on how to operate the building for high energy efficiency.”


More info on Insulfoam:  Website  |  Read blog articles  |  Follow on LinkedIn

More info on Premier SIPs by Insulfoam:   Website  |  Read blog articles  |  Follow on LinkedIn


Insulation Choices: EPS or XPS?

Originally posted in Concrete Construction

As a specifier, architect and contractor….you must make well-informed decisions when it comes to below-grade, under slab, and cavity wall insulations in your projects.  Below are two informative articles listing the similarities and differences between both EPS (expanded polystyrene) and XPS (extruded polystyrene) insulations.

Insulation Choices:  Whether to use EPS or XPS can be a matter of cost.

Originally posted in Concrete Construction, November 2013, written by Mayilvahanan, Insulfoam’s Product-Marketing Manager

EPS insulation helps reduce heat loss through concrete foundations and floor slabs.

EPS insulation helps reduce heat loss through concrete foundations and floor slabs.

What’s the difference between XPS insulation and EPS insulation, other than a single letter? For installation on concrete foundations and under floor slabs, the rigid foam insulation you choose can make a difference of tens of thousands of dollars on a project. A careful evaluation of these materials’ performance attributes against the project’s needs can dramatically shrink labor and material costs. The savings could mean the difference between a profitable job and one you just have to chalk up to experience.

When it comes to concrete and insulation, contractors tend to be most familiar with extruded polystyrene (XPS). Yet, expanded polystyrene (EPS) performs as well or better than XPS, and at a substantially lower cost. Below are three important factors to consider when comparing these two insulations for any belowgrade or under-slab applications, read FULL article to see more side by side comparisons of EPS and EXP for these insulation factors:  1.) Compressive strength  2.) Moisture retention  3.) Insulating capability.

Full Article:  Insulation Choices

EPS vs XPS:  Insulation industry advances with EPS developments

Originally posted on Concrete Construction, February 2014, written by Frank Keisecker, ACH Foam’s VP of Sales and Marketing

There is much competition among polystyrene insulation manufacturers for the below-grade, under slab, and cavity wall insulation market. Claims made by the XPS (extruded polystyrene) industry are conflicting with that of EPS (expanded polystyrene) manufacturers. The validity of some claims is debatable. Specifiers, architects, and contractors must make well-informed decisions.

Read FULL article to thoroughly understand the similarities and differences between EPS and XPS insulations.  Key differences include: 1.) Moisture resistance 2.) Environmental impact  3.) Long-term R-value  4.) Compressive strength   5.) Panel sizes  6.) Cost per R-value.

Full Article:  EPS vs XPS


Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

2012 IECC Code Changes: Insulation of Radiant Heating Systems

2012 IECC Code Changes

2012 IECC Code Changes


Don’t get caught out in the cold as the new 2012 IECC takes effect.  Make sure you plan for cost effective solutions to your insulation concerns.

Read more in significant code changes to the 2012 International Energy Conservation Code, Insulation of Radiant Heating Systems (pdf)

Insulation Levels in Reroofing Projects to Comply with New Construction Requirements

Originally posted on Construction Magazine Network, written by Sharon Glorioso

When existing roofs (that are part of the building’s thermal envelope) are removed and replaced, and when the roof assembly includes above-deck insulation, the energy code now requires that the insulation levels comply with the requirements for new construction, according to a proposal approved by International Code Council at public comment hearings held in October 2013.

As a result of this proposal approval, the 2015 International Energy Conservation Code (IECC) includes new language that provides unambiguous direction on how the energy code provisions apply to roof repair, roof recover and roof replacement.

Each year about 2.5 billion square feet of roof coverings are installed on existing buildings.  The opportunity to upgrade the insulation levels on these roof systems occurs once every several decades when the roof is replaced or even longer when existing roofs are “recovered.”  Until recently this requirement was prescribed using vague and confusing language.

Read full article on the clarification to the 2015 IECC definitions

Long-term is the Right term – LTTR and Insulfoam Insulations

Insulfoam SP Roof Insulation

Insulfoam SP Roof Insulation

Long-Term Thermal Resistance (LTTR) rocked the building world in early 2014 with the announcement of lowering R-values for a number of insulation products – products that lose stability over the longer term.  But NOT Insulfoam insulations.

  • During manufacturing, Insulfoam does not use any ingredients that degrade or destabilize over time
  • Insulfoam insulations DO NOT lose R-value even over the long-term, a characteristic that has been verified by independent long-term testing

With Insulfoam, you get what you pay for: an insulation product that retains the same R-value when first purchased.  Which is why Insulfoam insulation is backed by a LONG-TERM thermal warranty.  For more information, contact your local Insulfoam rep.


Insulfoam Geofoam

Insulfoam Geofoam

Industry Articles on EPS Insulations:

Premier SIPS by Insulfoam

Premier SIPS by Insulfoam

Visit Insulfoam.com

Contact your local Insulfoam rep