In the world of insulation, foam board insulation is a popular choice due to its high R-value and excellent thermal resistance. With several types of foam board insulation available, it’s important to understand the differences between them to make an informed decision for your insulation needs. In this comprehensive guide, we will explore the various types of foam board insulation, including expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (Polyiso). Let’s dive in and explore the characteristics, benefits, and applications of each type.
1. Expanded Polystyrene Foam (EPS)
Expanded polystyrene foam, commonly known as EPS, is a versatile and cost-effective option for insulation. EPS is often used in a wide range of applications, including roofs, walls, floors, below-grade installations, and even in structural GeoFoam applications. This type of foam board insulation offers the highest average R-value per dollar, typically ranging from 4.6 R per inch. Its affordability makes it an attractive option for both residential and commercial projects.
EPS insulation is approved for ground contact and below-grade applications, and it can be treated to resist insects. One of the key advantages of EPS is its ability to resist water absorption over the long term. This makes it an ideal choice for areas prone to moisture exposure. It is recommended to use EPS over house wrap or in conjunction with a factory-laminated option to enhance its performance. EPS is available in both faced and unfaced varieties, with faced products acting as vapor retardants and specialty products serving as vapor barriers. Additionally, EPS retains its R-value over time, providing long-term insulation benefits.
2. Extruded Polystyrene Foam (XPS)
Extruded polystyrene foam, also known as XPS, is another popular type of foam board insulation. Recognizable by its distinctive blue, green, or pink color, XPS offers a balance between cost and R-value. It is commonly used in wall and below-grade applications. XPS insulation is recyclable and provides an R-value of approximately 5 per inch, making it a cost-effective option for achieving energy efficiency.
XPS insulation comes in both faced and unfaced variations, with different plastic facings available. Unfaced XPS has a perm rating around 1, making it semi-permeable. Thicker and faced XPS is stronger and can have a lower perm rating. While XPS is considered a vapor retarder, it is not a vapor barrier. It is worth noting that XPS has the tendency to absorb more moisture over the long term compared to other insulation types. Therefore, its warranty may not honor R-value retention over extended periods in high-moisture environments.
3. Polyisocyanurate Foam (Polyiso)
Polyisocyanurate foam, commonly referred to as polyiso or ISO, is primarily used in roofing applications. Although it is not as widely used in other areas, it offers excellent insulation properties for specific needs. Polyiso insulation has an average cost of around 70 cents per square foot for a 1-inch-thick panel, though prices may vary by region. It provides a standard R-value of 5.8 per inch, making it a favorable choice for achieving energy efficiency in roofing systems.
The manufacturing process of polyiso involves liquid foam, which is then sprayed against a substrate to form a rigid panel. Due to this process, all polyiso panels come with facings, which significantly impact the panel’s durability and perm rating. Foil-faced panels are considered impermeable and should not be used with an interior vapor barrier. On the other hand, more permeable panels are faced with fiberglass and can be used without creating a vapor barrier.
It is important to note that polyiso foam is not recyclable, which should be considered when evaluating its environmental impact. However, its high R-value and suitability for roofing applications make it a valuable option for achieving energy efficiency.
Comparison Table: Foam Board Insulation Types
To further understand the differences between EPS, XPS, and polyiso foam board insulation, let’s compare their key characteristics side by side in the table below:
| Characteristic | EPS | XPS | Polyiso |
| Typical R-Value | 4.6 R per inch | 5 per inch | 5.8 per inch |
| Cost | Affordable | Mid-range | Varies by region |
| Applications | Versatile | Walls, below-grade | Roofing |
| Moisture Resistance | Excellent | Moderate | Dependent on facing |
| Environmental Impact | Recyclable | Recyclable | Not recyclable |
Choosing the Right Foam Board Insulation
When choosing the right foam board insulation for your project, several factors should be considered. The location of the house, insulation goals, and budget will play significant roles in the decision-making process. Let’s summarize the benefits of each type to help you make an informed choice:
Benefits of EPS Foam Board Insulation
- Versatile and suitable for various applications, including roofs, walls, floors, and below-grade installations.
- Highest average R-value per dollar, making it an affordable option.
- Approved for ground contact and below-grade applications; can be treated to resist insects.
- Excellent long-term resistance to water absorption.
- Available in faced and unfaced varieties, with faced products acting as vapor retardants.
- Retains 100% of its R-value over time.
Benefits of XPS Foam Board Insulation
- Balance between cost and R-value, making it suitable for wall and below-grade applications.
- Recognizable by its distinctive color, allowing for easy identification.
- Recyclable and a cost-effective choice for achieving energy efficiency.
- Comes in faced and unfaced variations, with different plastic facings available.
- Provides a semi-permeable barrier.
- Absorbs more moisture over the long term, warranty may not honor R-value retention in high-moisture environments.
Benefits of Polyiso Foam Board Insulation
- Ideal for roofing applications, providing excellent insulation properties.
- Offers a high R-value per inch, contributing to energy-efficient roofing systems.
- Comes with facings that impact durability and perm rating.
- Foil-faced panels are impermeable and should not be used with an interior vapor barrier.
- Not recyclable, but offers valuable insulation benefits for specific needs.
Conclusion
Foam board insulation is a reliable choice for enhancing energy efficiency and thermal resistance in various building applications. Understanding the characteristics and benefits of different types of foam board insulation is crucial for making an informed decision. Whether you opt for expanded polystyrene (EPS), extruded polystyrene (XPS), or polyisocyanurate (polyiso) foam board insulation, each type offers unique advantages and applications.
Consider the location, insulation goals, and budget of your project when choosing the right foam board insulation. EPS provides versatility, affordability, and excellent moisture resistance. XPS offers a balance between cost and R-value, with easy identification and moderate moisture resistance. Polyiso excels in roofing applications, providing high R-value and durability.
By evaluating these factors and comparing the characteristics of each foam board insulation type, you can select the most suitable option to meet your insulation needs and achieve optimal energy efficiency in your building project.