Choosing the right building materials for your construction project can make or break your finished masterpiece. If you don’t get things right during the construction phase, fixing them later becomes a costly undertaking. Because it’s often concealed in walls and other hard-to-reach spaces, one of the critical components you’ll want to get right from the start is your insulation selection.
Insulation directly impacts your building’s:
Energy bill
Comfort level
Material integrity
Without insulation to help regulate temperature, moisture and condensation can form, and will promote mold growth inside your building and wreak havoc. Maximize your insulation’s potential by using the right type for the job.
Types of Insulation Used in Construction
Insulation comes in many different sizes, shapes, and forms. Here are the common types of insulation used in construction today:
Fiberglass
Mineral wool
Polyisocyanurate
Polyurethane
Polystyrene
Concrete
These insulating materials can come in many forms, including loose fill, boards, batts, rolls, blocks, or spray foam. In this article, we’ll compare two of the common foam types that are installed in modular board form: XPS and polyiso insulation.
What is XPS?
Extruded polystyrene, or XPS, is a foam-based synthetic polymer material that has been melted and compressed into board form. Think of the packing materials for large, delicate items like a flat-screen TV or computer—this packaging is sometimes made of XPS.
The name you’ll hear on jobsites is “blue board.” That’s because the color is often baby blue, or sometimes pink. In construction, XPS is commonly used at the foundation or floor level and in other areas with high moisture.
What is Polyiso?
Polyisocyanurate, or polyiso, is another foam-based insulating material that is sandwiched and pressed between facers to create the board form. This process is called lamination. Consider an insulated garage door—the insulated panels are probably made from polyiso.
On job sites, polyiso is referred to as iso. You’ll find iso used over large portions of buildings, including wall assemblies, flat roof systems, and insulated panels.
Now, let’s take a look at a comparison of XPS to iso insulation.
Comparing XPS vs. Polyiso Insulation
Below, we’ll compare and contrast the different insulation properties of these two building materials.
Closed-Cell Foam Structure
While the chemical makeup of XPS and polyiso are very different, they do share some of the same material properties. For instance, both are a closed-cell foam composition.
Closed-cell means that the individual air bubbles that are inherent to the manufacturing process of these foam materials are closed and separate from each other. In other words, air cannot move from one bubble to the next inside the foam structure. This helps increase the thermal insulating value, improves moisture resistance, and enhances dimensional stability.
Thermal R-Value
Since the main purpose of insulation is thermal resistance, or keeping heat from escaping, let’s compare the thermal resistance capabilities of XPS to iso insulation. Typical extruded polystyrene rigid foam boards carry a minimum R-5 per inch, while polyiso boasts a better performance rating at R-6 per Inch. That means a 2” thick XPS board will have at least R-10 and a 2” thick polyiso board wins with R-12. A thinner profile with higher insulating value can lead to big savings on overall wall thicknesses and other building materials.
Versatility in Facers
One noticeable difference when comparing polyiso insulation to XPS is in the facers.
XPS is unfaced, meaning that the entire makeup of the board is made of a single material—extruded polystyrene. This can limit the applications, considering that XPS is often incompatible with adhesives.
Polyiso, on the other hand, is laminated to facer material on both sides of the foam. That means that the material you see on either side of iso differs from the foam core, and expands the physical properties available from the product.
Polyiso facers can be made of the following materials:
Coated Glass Fiber Mat Facers (Rmax Durasheath® for the building envelope)
Glass Fiber Reinforced Aluminum Facers (Rmax ECOMAXci® FR for exposed exteriors)
FR Treated Plywood (Rmax ECOMAXci® FR Ply for cladding attachment)
Reinforced Aluminum Foil Facers (Rmax Thermasheath® for the building envelope)
High-Temperature Applications
Building envelope surfaces, including walls and roofs, can reach extremely high temperatures well above the ambient air temperature. That means you’ll want to pick materials that can stand the heat inside your walls and roof.
When comparing xps to polyiso insulation in heat resistance, polyiso outperforms extruded polystyrene. Due to being a thermoplastic material, under extreme temperatures, XPS loses all dimensional stability and melts back into its molten components. In contrast, polyiso is a thermoset material that will not melt under the same high temperatures and remains stable.
Choosing the Right Insulation for the Job with Rmax
Picking materials for your construction project can be overwhelming. If you need help deciding which insulation to specify to meet your specific project needs, Rmax can help.
Reach out to your local Rmax representative today to narrow down your options.