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About Polyiso

Polyiso Insulation

Polyiso is a closed-cell, rigid foam board insulation used primarily on the roofs and walls of offices, health facilities, warehouses, retail and industrial manufacturing facilities and educational institutions. Because of its high thermal performance, it is the product of choice for energy-aware homebuilders and consumers.

Polyiso is one of North America’s most widely-used and cost-effective insulation products and has been cited by the U.S. Environmental Protection Agency for its responsible impact on the environment. Polyiso roof insulation offers:

  • The highest R-value per inch

  • Outstanding installed cost advantages

  • Exclusive third-party, thermal performance certification

  • Only high-thermal foam to meet both FM 4450 and UL 1256 fire tests

  • Nationwide availability

Highest R-value

Inch for inch, Polyiso has the greatest energy efficiency performance or R-value of any building insulation product on the market. Higher R-value per inch means less Polyiso material is required. The result: greater energy efficiency, reduced energy waste, and lowered costs for both materials and labor.


Polyiso’s cost effectiveness has been confirmed repeatedly through multiple studies. One payback study released by PIMA, (the trade association of the Polyiso industry) showed increasing the thickness of Polyiso on a roof deck significantly reduces energy costs and provides positive returns on the cost of installation



Based on consensus standards in both the United States and Canada, Long Term Thermal Resistance (LTTR) is a scientifically supported way to calculate the 15-year, time-weighted average R-value of roof insulation. Most Polyiso manufacturers have adopted the LTTR method as the exclusive means to measure thermal performance of permeable-faced Polyiso roof insulation.

The ASTM C1289 standard is used to predict a foam’s R-value equivalent to the average performance of a permeably faced foam insulation product over 15 years. The LTTR method provides users, specifiers and designers several advantages including:
  • A technically supported, more descriptive measure of the long-term thermal resistance of polyiso insulation - a 15-year time - weighted average;

  • An advanced test method, based on consensus standards in the United States and Canada;

  • A method that applies to all foam insulation with blowing agents other than air, such as Polyiso, extruded polystyrene and polyurethane; and

  • A better understanding of thermal performance of foam.

Superior Performance in Fire Tests

Polyiso passes both the ANSI UL 1256 and FM 4450 fire tests without a thermal barrier. Polyiso, a thermoset material, stays intact during fire exposure in the ASTM E84 or "Tunnel Test.” It forms a protective char layer and remains in place during the test, thereby meeting all building code requirements and contributing to a fire-safe building. For more information on Polyiso’s performance in fire tests, consult the Technical Bulletins section. (Fire Performance in Roof Systems) (Fire Test Definitions) (Class A and Class 1 Roof Assemblies Are Not the Same)

Compressive Strength

Compressive strength refers to the ability of a rigid foam board to resist deformation and maintain its shape when subjected to a force or load. Common construction compressive strength applications require polyiso to maintain its shape during installation as well as during use. Polyiso insulation boards are available in a range of compressive strengths. The ASTM Specification of Polyiso Insulations, C 1289, states that all Polyiso products should have a minimum stated compressive strength of 16 psi. For more information on Polyiso’s compressive strength, please consult Compressive Strength.

Environmentally Responsible

All Polyiso insulation manufactured by PIMA members utilizes an EPA compliant hydrocarbon-based blowing agent which has zero Ozone Depletion Potential (ODP) and virtually no Global Warming Potential (GWP); it also meets both CFC- and HCFC-free specification requirements.

Other Unique Properties

  • Polyiso is stable over a large temperature range (-100°F to +250°F) and can be used as a component in roof systems utilizing hot asphalt.

  • Polyiso has low density, good adhesion to facers, low water absorption and low vapor transmission.

  • Polyiso is not affected by oil-based waterproofing compounds, insecticides or fertilizers when properly protected.

QualityMarkcm  Certification Program

The PIMA QualityMarkcm certification program allows participating Polyiso manufacturers to certify the Long Term Thermal Resistance (LTTR) values of their Polyiso insulation products through an independent, third-party. This program was designed to be a benchmark for all roof insulations. The certification gives consumers an easy way to identify quality products that meet or exceed listed LTTR values. 

For over ten years, LTTR values for roof insulation under the

QualityMarkcm certification program have been reported and certified in accordance with the testing requirements of ASTM C1289 "Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board.” This latest update of ASTM C1289-11 features important improvements regarding the prediction of long-term thermal resistance ("R”) value for a variety of polyiso insulation boards primarily used in roofing applications.

The PIMA QualityMarkcm certification program will begin reporting LTTR values in accordance with ASTM C1289-11 on January 1, 2014.  To participate in the Certification program, a Class 1 roof is suggested to have a design R-value of 5.7 per inch. Polyiso is unique in that the R-value increases with the thickness of the foam, so three inches of polyiso has a higher R-value per inch than two inches.


The following is a list of polyiso manufacturers participating in the PIMA QualityMarkcm certification program: Atlas Roofing Corporation

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