EPS vs XPS vs Polyiso insulation | Everything you need to know

August 14, 2020

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EPS, XPS, and Polyiso. Three types of board insulation used in home construction that look very similar. In this article, we’re going to look into how they are made and compare their physical and chemical properties.

Expanded Polystyrene (EPS)

EPS is derived from the monomer styrene, a compound composed of a benzene ring (C6H6) and ethylene. The polymer chain called polystyrene is formed through a heating process using an initiator like benzoyl peroxide. The polystyrene is then dropped into water to create beads, which are expanded using blowing agents such as propane, pentane, and methylene chloride. These expanded beads are molded together, creating a structure with significant open spaces between them. EPS is known for being 98% air and only 2% plastic, making it an excellent insulator. Its versatility makes it widely used in various applications, including building construction, packaging, cushioning, and disposable food containers.

Advantages of EPS

EPS offers several advantages, such as the highest average R-value per dollar, excellent insulation capabilities, no thermal drift or loss of R-value over time, and being environmentally friendly without using chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs). Additionally, EPS is resistant to mold and mildew and is 100% recyclable.

Disadvantages of EPS

On the downside, EPS insulation panels are coated with a bromine fire retardant (HBCD), which can be harmful to health. They can also attract ants and termites, and their flammability and lack of biodegradability contribute to trash pollution.

Extruded Polystyrene (XPS)

XPS, often referred to as Styrofoam, is chemically similar to EPS, but instead of being formed into beads and expanded, it is foamed up with additives and blowing agents during the extrusion process. This results in a tightly packed closed-cell insulation structure. Just like EPS, XPS is 98% air and 2% plastic, providing excellent insulation properties. It is used in various applications, especially in wetter environments due to its moisture and mildew resistance.

Advantages of XPS

XPS insulation is relatively inexpensive, offers excellent insulation capabilities, has no thermal drift, and is also 100% recyclable. Its compressive strength is superior to that of EPS, making it suitable for applications below grade, below slab, and on basement walls.

Disadvantages of XPS

The use of hydrofluorocarbons (HFCs) as a blowing agent for XPS has a high global warming potential, although certain HFC compounds have been banned. Like EPS, XPS panels are coated with a bromine fire retardant (HBCD) and can attract ants and termites. Their flammability and non-biodegradability are also concerns.

Polyisocyanurate (Polyiso)

Polyiso is manufactured by combining three main components: MDI (methylene diphenyl diisocyanate), polyol, and a blowing agent. The exothermic chemical reaction during mixing causes the liquid blowing agent to expand, creating tightly packed gas-filled cells. Polyiso panels are faced with foil or paper, and the foil-faced panels act as an exterior vapor barrier.

Advantages of Polyiso

Polyiso boasts the highest R-value per inch, is stable over a wide temperature range, and is commonly used in commercial roof construction. Its low water absorption and vapor transmission, along with the use of a hydrocarbon blowing agent, contribute to its eco-friendly properties.

Disadvantages of Polyiso

The main drawbacks of polyiso insulation are its higher cost compared to EPS and XPS, use of halogen fire retardant (TCPP) which can be harmful to health, and limitations in very low temperatures due to the condensation of trapped gases.

Conclusion

In conclusion, each type of insulation has its own set of advantages and disadvantages. Consider your specific needs and environmental concerns when choosing the right insulation for your home construction project. Whether it’s EPS, XPS, or Polyiso, understanding their properties will help you make an informed decision for a comfortable and energy-efficient living space. If you need further assistance or have any questions, feel free to reach out, and don’t forget to prioritize the eco-friendly options for a sustainable future.