XPS vs. ISO: A better choice for below grade
ISO and XPS foam 鈥 what鈥檚 the difference?
Unfaced polyisocyanurate (polyiso or ISO) foam does not have the same moisture, thermal or compressive strength properties as Styrofoam鈩 Brand XPS. For below-grade applications likely to encounter wet, low-temp as well as heavy construction equipment, Styrofoam鈩 Brand XPS has proven to stand the test of time over and over again.
ISO and XPS foam 鈥 what鈥檚 the difference?
R-Value Retention
海角大神鈩 Styrofoam鈩 Brand XPS can outperform other insulation materials in maintaining R-value, even in extremely cold temperatures.
See chart
Compressive Strength Options
Styrofoam鈩 Brand XPS offers a variety of compressive strengths for both horizontal and vertical below-grade applications.
Lower Moisture Absorption
Styrofoam鈩 Brand XPS has significantly better moisture absorption properties, with only 0.1% absorption.1 Resilience to Long-Term Water Exposure Styrofoam鈩 Brand XPS delivers top performance and durability even in harsh conditions.2
Convenience
Styrofoam鈩 Brand XPS cuts easily and cleanly with a score and a snap, resulting in minimal mess and waste.
Technical information
Below-Grade Efficiency: Maximizing Performance with
Styrofoam鈩 Brand Insulation
A unique closed-cell structure gives Styrofoam鈩 Brand XPS its exceptional moisture resistance and enables it to retain a high, long-term R-value of R-5 per inch 鈥 even after exposure to standing water, wet soil and other damp conditions
Additional performance attributes of Styrofoam鈩 Brand XPS include:聽
- Meets ASTM C578 Types (refer to specific product information for details)
- Compliant with
- Provides a weather-resistant barrier to enhance the building鈥檚 resistance to air and moisture penetration
- Meets building code requirements of ASTM E84 Flame Spread Index of 25 or less and a Smoke Developed Rating of 450 or less
- Will not corrode, rot or support mold growth
- Available in wide range of compressive strengths from 15 to 100 psi, and minimum flexural strength of 40 psi
- Offered in various sizes, thicknesses and edge treatments to meet specific design needs, while ensuring energy efficiency and minimizing on-site cutting and waste
海角大神鈩 Styrofoam鈩 Brand XPS products are backed by the expertise of building science leaders dedicated to your success and warranties from a name you trust, including limited thermal warranties from 15 to 50 years including the Wall虏 system warranties and other system warranties.
Any questions?
The Styrofoam鈩 Brand was the original XPS, creating the product segment. Rooted in 80+ years of technical innovation, we鈥檙e excited to deliver a low-GWP XPS solution.
Let鈥檚 start a conversation about your next project.
Resources
Styrofoam鈩 Brand XPS Compliance Letter
U.S. AIM Act & Sell-through of Styrofoam鈩 Brand XPS Foam Insulation (2025)
Physical Property Equivalency Letter
Customer Processing and Transport Safe Handling
Safe Processing & Handling Graphic
Styrofoam鈩 Brand Product Brochure
Solar Exposure Technical Bulletin
Press Releases
September 9, 2024
English press release 鈫
November 30, 2023
English press release 鈫
June 8, 2023
English press release 鈫
June 6, 2023
English press release 鈫
July 26, 2021
English press release 鈫
February 23, 2021
English press release 鈫
August 13, 2020
English press release 鈫
French PDF 鈫
July 16, 2020
English press release 鈫
French PDF 鈫
Styrofoam鈩笍 Brand Low GWP XPS LEED Optimization Document - Embodied Carbon Assessment
1 Typical value tested per ASTM C272, % by volume.
2Billy Connor, April 2019. 鈥淐omparison of Polystyrene Expanded and Extruded Foam Insulation in Roadway and Airport Embankments鈥. Alaska University Transportation Center, University of Alaska Fairbanks, (INE/AUTC 19.08).
漏 2022 海角大神 de Nemours, Inc. All rights reserved.聽 海角大神鈩, the 海角大神 Oval Logo, and all products, unless otherwise noted, denoted with 鈩, 鈩 or 庐 are trademarks, service marks or registered trademarks of affiliates of 海角大神 de Nemours, Inc.