Can You Use EPS as an Alternative to Rigid Insulation?

White, tapered EPS rigid insulation boards laid out on roof.

Rigid foam is a commonly used insulation product for commercial wall and roofing applications. It is a favorite among contractors for its reliability and long-lasting performance.

However, with shortages of raw materials currently happening nationwide, availability has been significantly impacted. Roofers now need to find alternative insulation products that are equally effective and versatile as rigid insulation.

Previously, rigid insulation was such a desired and preferred insulation product that many turned a blind eye to EPS products. But the shortages have provided the perfect opportunity for educating on the merits of EPS. It is factory-mutual approved, has UL classifications and is a widely accepted code-approved product that delivers consistently for decades.

Let’s take a closer look into some reasons why rigid insulation is a favorite among commercial contractors and see how EPS insulation products perform in comparison.

Why Is Rigid Insulation Popular?

White EPS rigid insulation boards installed on the roof underneath gray cover boards.

Why is rigid insulation so popular and highly demanded? The simple explanation is that it works. It is one of the most effective insulation materials available, suitable for moisture control and fire safety while the included facers make installation simple and cost-effective. It operates as a complete insulation system that greatly appeals to builders and contractors and keeps them coming back to the product time and time again.

As manufacturers are striving to be more environmentally conscious, rigid insulation has become the primary product to support sustainability efforts. Since no ozone-depleting blowing agents are used, it has zero global warming potential (GWP), and the product is largely manufactured with recycled materials.

But just because it is the more popular option on the market does not mean there aren’t alternatives that deliver the same performance and environmentally-friendly attributes, such as EPS.

Comparing EPS and Rigid Insulation

UL Rating

While EPS and rigid insulation share similar UL ratings, these ratings largely depend on the roof membrane and cover boards used. When using EPS insulation, using a direct metal deck will still achieve a UL Class A, B or C UL-rated roof assembly.

The closed-cell nature of EPS is a shared quality with rigid insulation — therefore, it is an excellent moisture and weather barrier with the rating to prove it.


Rigid insulation is known to have the highest R-value per inch. But EPS has the highest R-value per dollar, making it the more cost-effective option. The R-value of EPS also does not diminish over time and provides a more stable and longer-lasting R-value than other insulation products.

The R-value of EPS typically outlasts the lifetime of the structure it is installed in and rarely needs replacing, even after decades of use.

EPS also comes in a wide range of thicknesses to achieve the same level of insulation as the available rigid insulation products.

Can They Both Be Used With the Same Roofing Type?

Yes, they can!

Like rigid insulation, EPS can work with almost any roof system and almost all of the major roof manufacturers. EPS is actually known for its versatility and flexibility.

EPS insulation comes in a variety of sizes and thicknesses, and it can even come tapered or be wire cut on-site to adapt to specific design needs. EPS is commonly and successfully used in tapered roofing, built-up roofing and direct-to-deck roofing systems.


A stack of four EPS rigid insulation boards. They are all shaped in wedges of varying thickness. The thickest board is on the bottom and the thinnest board is on the top.

Rigid insulation is available in a range of thicknesses up to four inches. With EPS insulation, which is also available in a wide range of thicknesses, it can exceed four inches as a single unit. So, if the insulation needs to be thicker, EPS products can deliver without the need for layering, making installation easy and time-effective.


Rigid insulation is very easy to install, adding to the reasons why it’s the leading product in commercial insulation. Fortunately, EPS installation is very similar and just as simple. The basic process attachment methods are the same, but there is one key difference in installation.

Since EPS comes in thicker options, it does not need to be layered. Since rigid insulation has a higher R-value, it often is manufactured in thinner sheets than EPS. But when a thicker layer is necessary to achieve the appropriate R-value, it is easy to use a single sheet of EPS to meet the zone requirements.

Roofing Leaks

Water is seen as an enemy to insulation, and often the biggest fear is that moisture will leak through the insulation and cause mold or structural damage.

Rigid insulation’s closed-cell nature and facers limit water permeability significantly more than extruded polystyrene alternatives (XPS), making it the superior choice between the two in high dew point zones.

EPS is also closed-cell in nature and does not readily absorb moisture from the atmosphere. Plus, it releases water faster than alternative products, so EPS insulation will dry quickly and thoroughly if it does get wet.

Choose Atlas for Your EPS Insulation Needs

Stack of four white EPS rigid insulation boards. The top two are tapered. The bottom two are not.

While rigid insulation is a trusted favorite among commercial contractors, EPS insulation products can offer the same beloved qualities and is a great alternative, especially with the production of rigid insulation products being slowed due to raw material shortages. Atlas EPS products come with a limited lifetime warranty for the R-value, so users can be assured that the R-value will remain stable and reliable for the entire life of the structure.

To learn more about how EPS compares to other insulation alternatives, contact one of our Atlas representatives today. We are happy to help you with all of your roofing needs and discuss how EPS can serve as an effective alternative to rigid insulation during shortages.