Performance with Perks
Expanded Polystyrene (EPS) Advantage
Economical
Expanded Polystyrene (EPS) is more economical than extruded polystyrene (XPS) and polyisocyanurate (PolyIso) products. EPS products cost less when comparing relative R value. Typically, an EPS alternate solution with the same R rating will be 10-30% lower cost.
Local Manufacturing
Expanded Polystyrene (EPS) is manufactured locally by Canadian owned companies. This means by specifying EPS products you are supporting your local community. It also means you have a better LEED® rating since your product has lower emissions from transportation.
Environmental & Health
There are many environmental benefits to Expanded Polystyrene (EPS) over alternate technologies such as extruded polystyrene (XPS) and Polyisocyanurate (ISO) insulations.
Our standard Expanded Polystyrene (EPS) products have between 15-25% recycled bead. Virgin and ECO-R (up-to 35% regrind) are available upon request.
98% natural air by volume
CFC-, and HCFC-free
No blowing agents, no off-gassing
Local manufacturing, less freight
LEED® points may apply
R-Value Stability and Reporting
During the manufacturing of Polyisocyanurate (Polyiso) and extruded polystyrene (XPS) blowing agents become trapped within the closed cells. These products are often attributed with having an R-Value of 5-6 per inch. Much of their increased thermal resistance is attributed to these gasses. Over time these Polyiso and XPS will lose a portion of these gases as the material as they experience natural wear from the environment. As a result it has been found that Polyiso and XPS have decreasing R-values during their 50 year life span.
One example of this being brought to light is within the CAN ULC S701.1:2017 report. In the interim report CAN ULC S701.1:2017 it is expressed that Expanded Polystyrene (XPS) is not intended to off-gas, however, they acknowledged that it in fact does off-gas. XPS manufacturers advertise an R-value of 5.0 per inch. However, new standards requires XPS to be measured based on LTTR (long-term thermal resistance) based on 180 d to estimate the 5 year value. XPS R-Values according to CAN ULC S701.1:2017 are:
XPS Type 2 & Type 3 – R-value of 4.6 / inch (RSI 0.81 / 25 mm)
XPS Type 4 – R-value of 4.71 / inch (RSI 0.83 / 25 mm)
Independent research studies have suggested that XPS R-values will continue to fall as the XPS off-gases the blowing agent. 50 year design life of XPS has not be reliable established. Where as, EPS products are confirmed to have stable R-values across the EPS 50 year design life span. Having stable and reliable R-values are important when designing a structure.
Theoretical Long-Term R-Value
Third Party Resources:
CAN ULC S701.1:2017 - Rigid Insulation - canada.ul.com
EPS Industry Alliance - Effective R-values - Full Report - epsindustry.org
Technical Bulletin - XPS & Polyiso - Long-Term Thermal Resistance & R-Value Performance - Download
Technical Bulletin - Below Grade Testing Confirms R-Value Retention - Download
Referenced Studies:
Zhu, Z. P. (May 2009). Effect of Loss of Blowing Agents on Thermal Insulation Properties of Polystyrene Foams. Journal of Heat Transfer. ASME.
Kang, C. J. (n.d.). Aging of Thermal Insulation Materials by Accelerated Laboratory Test Methods. Korea Institute of Construction Technology
VO, & Paquet. (May 2004). An Evaluation of the Thermal Conductivity of Extruded Polystyrene Foam Blown with HFC-134a or HCFC-142b. Journal of Cellular Plastics. Sage Publications.
AFM Corporation. (December 2017). Long-Term Thermal Resistance Data. AFM Corporation.
R & D Services, Inc. (March 1, 2019). Long-Term Thermal Resistance Measurements According to ASTM C1303 on “Extruded Polystyrene (XPS) Rigid Foam Board”. Interim Report: RD19119. Cookeville, TN: R & D Services, Inc.
Dimensional Stability
EPS billets are aged prior to cutting to ensure any excess moisture is removed after the compression process. Our cutting tolerances are 1/16” on critical dimensions or typical sheet thickness, 24” (+/- 1/8”), and over 48” (+/- 3/16”).
Dimensional stability are determined according to the requirements of ASTM D2126. According to CAN ULC S701.1:2017 the dimension stability, maximum percentage of linear change for both EPS and XPS is 1.5%.
Third Party Resources:
CAN ULC S701.1:2017 - Rigid Insulation - canada.ul.com
Water Retention & Dry Potential
During in-situ studies evaluated by third party laboratories it has been found that extruded polystyrene (XPS) has higher water retention and greater loss of R-value than reported using standard laboratory experiments tested to ASTM C272. In 2012 the Oak Ridge National Laboratory published finding that indicate XPS below grade systems can experience 10-44% loss of performance in energy savings when subject to moisture accumulation ranging from 8-16%.
When tested side-by-side in field experiments expanded polystyrene (EPS) outperformed the extruded polystyrene (XPS) product. Although both products are impacted by the water the EPS product demonstrated a dry potential. These findings have been reviewed by laboratory studies such as those performed by Intertek Testing Services NA Ltd, who conducted tests on various polystyrene foam products. The laboratory tests were performed to ASTM C1512, Standard Test Method for Characterizing the Effect of Exposure to Environmental Cycling on Thermal Performance of Insulation Products. Although XPS demonstrated a lower initial accumulation of moisture it also showed that it retained 100% of the moisture during environmental cycling, indicating no dry potential. Over the seasons EPS products will release moisture while the XPS products will continue to see moisture further build up within the material.
Durability
Great White Foam offers a large range of EPS grades that allow varying durability to fit the requirements and function of the job. Many people associate expanded polystyrene (EPS) with a brittle product found in traditional packaging. The brittle expanded polystyrene is most often a lower density product. EPS Molders does offers low density GWF5 (5 psi), but EPS Molders also manufactures higher density materials up-to and including GWF60 (60 psi). Less durable expanded polystyrene products such as GWF5 utilized for underground applications requiring product to compress or in some situations collapse to create voids. For a durable material that can be walked on without breaking we recommend EPS type 2 (GWF15) which has 15 psi compression resistance minimum at 10% deformation.
