• Is Polystyrene A Good Insulator?

    | by Holly Wood

    Is polystyrene a good insulator? With values ranging from 0.034 to 0.038 W/mK, it may not hold the title of best thermal insulator, but its unique properties make it a compelling choice for insulation in various applications.

    It’s important to note that many seek polystyrene for its non-thermal properties, including its impressive compressive strength and moisture-resistant attributes, which are notably prominent in XPS insulation.

    In this discussion, we will explore the reasons behind polystyrene’s recognition as an effective insulator, examining its unique properties and identifying the specific situations where it excels, even if it doesn’t secure the top position for thermal efficiency.

    We’ll explore both expanded polystyrene insulation (EPS) and extruded polystyrene insulation (XPS) to give you a well-rounded view of this versatile material.

    Understanding Polystyrene Insulation

    Polystyrene insulation, commonly referred to as polystyrene foam or simply polystyrene, is a type of thermal insulation material known for its excellent insulating properties.

    It is available in various forms, including expanded polystyrene (EPS) and extruded polystyrene (XPS) boards, foam boards, and beads.

    The key to its insulating capabilities lies in its unique cellular structure, which traps air or tiny air bubbles within the material.

    Thermal Properties

    Polystyrene boards exhibit a thermal conductivity ranging from 0.034 to 0.038 W/mK – not necessarily a low thermal conductivity range in the grand scheme of insulation materials. When it comes to thermal insulation efficiency, XPS foam boards far outperform EPS insulation boards.

    However, it’s worth noting that neither offers the highest thermal conductivity values in the insulation market.

    For instance, phenolic insulation boasts an impressive thermal value of 0.018 W/mK, making it the top choice for exceptional thermal protection.

    Types of Polystyrene Insulation – EPS & XPS Insulation

    Both EPS and XPS insulation materials offer excellent thermal performance. EPS insulation boards earn recognition for their lightweight insulation properties and cost-effectiveness, rendering them a popular choice for residential projects. Most commonly, people recognise EPS in the form of Styrofoam and packing peanuts.

    On the other hand, XPS insulation, often used in inverted roofs and exterior walls, is a great thermal insulator that offers excellent moisture resistance. It is especially suitable for applications that require water-resistant properties.

    To greater understand the difference between both of these materials, take a look at our comprehensive blog on the Differences Between XPS and EPS.

    Applications in the Construction Industry

    The construction industry widely employs polystyrene insulation boards to maintain the warmth and energy efficiency of buildings.

    You can apply them to walls, roofs, and floors to insulate against heat transfer. The closed-cell structure of polystyrene helps to reduce heat loss and maintain a comfortable indoor environment.

    Safety Considerations

    When working with polystyrene insulation, it’s important to take safety precautions.

    Wearing safety glasses is crucial, especially when using hot wire machines or cutters to shape the material. These tools enable precise cutting of polystyrene boards, ensuring a snug fit in construction applications.

    Environmental Impact

    As is the case with all materials, it’s important to consider their environmental impact.

    Polystyrene is a plastic resin, and its manufacturing process can involve the use of a blowing agent. However, some polystyrene insulation products are designed to be eco-friendly and have a reduced environmental footprint.

    It’s always important to check the manufacturer’s manual if environmental impact is a concern for you.


    So is polystyrene a good insulator? Polystyrene insulation, whether in the form of expanded polystyrene (EPS) or extruded polystyrene (XPS), is indeed a good insulation material, owing to its closed-cell structure, compressive strength and occasional moisture resistance (XPS).

    That being said, while it is good, it is simply only good enough. Polystyrene finds its niche in applications where thermal values are less critical, prioritising factors like compressive strength.

    What it lacks in performance it certainly makes up for in cost-effectiveness. Also, when used correctly, it can help reduce heat transfer, lower energy bills, and improve the overall energy efficiency of buildings.

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