There are many types of commercial and industrial mechanical pipe insulation types to choose from. Each type offers advantages and disadvantages depending on the application and when selecting pipe insulation for mechanical systems, one question we hear is: should you use foam rubber (elastomeric) or foam plastic (polyethylene) pipe insulation? Determining your project and performance requirements will simplify the product selection process while ensuring that the right pipe insulation is specified and installed to ensure long-term system performance.
This guide compares two types of closed-cell pipe insulation, elastomeric (foam rubber) and polyethylene (foam plastic) pipe insulation, across the key criteria that matter most to engineers, contractors, and facility owners, including thermal performance, condensation control, temperature limits, fire behavior, and cost.
Both materials can be used in HVAC, chilled water, refrigeration, and plumbing systems—and both feature a closed-cell structure designed to improve thermal efficiency and help control condensation for below-ambient (cold) piping systems. However, their performance can vary significantly depending on the application.
By understanding how these materials perform in real-world conditions, you can make a more informed decision about which insulation is best suited for your specific application or project requirements.
What is Rubber (AKA Elastomeric) Pipe Insulation?
Flexible elastomeric closed-cell foam pipe insulation, also known as rubber, is composed of synthetic rubber.
Common Foam Rubber (Elastomeric) Formulations
The two main foam rubber formulations that are commercially available are nitrile butadiene rubber with PVC (NBR/PVC) and EPDM (Ethylene Propylene Diene Monomer). A comparison between NBR/PVC and EPDM is available in a later section of this post.
Common Applications for Rubber (Elastomeric) Insulation
Rubber (elastomeric) insulation is most commonly used in commercial and industrial applications including HVAC, chilled water, refrigeration, and plumbing pipe systems.
Industry Reference Standard for Rubber (Elastomeric) Pipe Insulation
The industry reference standard is ASTM C534, Standard Specification for Preformed Flexible Elastomeric Cellular Thermal Insulation in Sheet and Tubular Form.
What is Foam Plastic (Polyethylene) Pipe Insulation?
In addition to foam rubber pipe insulation, another alternative is known as foam plastic (also known as polyethylene, polyolefin, poly, or PE).
Common Applications for Foam (Polyethylene) Pipe Insulation
Foam plastic pipe insulation is often installed on residential and light commercial piping systems.
Industry Reference Standard for Foam (Polyethylene) Pipe Insulation
The industry reference standard is ASTM C1427, Standard Specification for Extruded Preformed Flexible Cellular Polyolefin Thermal Insulation in Sheet and Tubular Form.
Rubber Versus Foam Pipe Insulation: Key Differences
Choosing between elastomeric (rubber) and polyethylene (foam) pipe insulation for your project depends on the application and comes down to how each material performs under real world conditions. Below is a comparison chart highlighting some of the key performance characteristics for each insulation material:
Performance characteristic | Rubber (elastomeric) | Foam (polyethylene) |
| Thermal conductivity (K-Value): Thermal Efficiency | Lower (better insulation) | Higher |
| Condensation Control | Excellent | Moderate |
| Continuous Service Temp (upper limit) | Higher (up to ~275°F depending on formulation) | Lower (typically up to ~200°F) |
| Fire Safety | ASTM E84 or UL 723 25/50 Rated | Less consistent, may melt or drip under test conditions |
| Material Cost | Higher upfront cost | Lower upfront cost |
Thermal Conductivity
The K-value, a common standard for thermal conductivity, measures how effectively a material resists heat flow—lower values indicate better insulation performance. Elastomeric (rubber) is typically offers a lower K-value than polyethylene (foam), making it more effective at maintaining system temperatures and improving the energy efficiency of a mechanical system. This performance advantage is especially important in refrigeration applications, where minimizing heat gain is a priority.
Condensation Control
Preventing condensation is one of the most critical functions of pipe insulation, especially for chilled water, refrigeration, and other below-ambient systems, and can lead to mold growth, corrosion under insulation (CUI), and system damage.
Both elastomeric (rubber) and polyethylene (foam) insulation use a closed-cell structure for moisture resistance. However, elastomeric insulation provides a more effective, continuous vapor barrier, helping prevent water vapor from reaching the pipe surface.
Polyethylene is known for low water absorption, but is generally less durable and suffers from a high increase in thermal conductivity (k-value) over time if moisture enters.
For applications where condensation control is critical, elastomeric insulation is typically the more reliable long-term solution.
Continuous Service Temperature
The upper continuous temperature threshold of rubber (elastomeric) is higher than that of foam plastic. Depending on the type of rubber, this can range from 220℉ [104℃] (NBR/PVC foam rubber) to 257℉ [125℃] (EPDM foam rubber) while foam plastic’s upper continuous temperature threshold is 200°F [93℃].
Fire Safety
This criteria is important to pay attention to. Foam rubber usually passes ASTM E 84 or UL 723 25/50 flame spread/smoke-developed index up to 2” [50 mm] thick. However, foam plastic has been known to melt, drip, or delaminate during the same test procedure. In other words, foam plastic’s fire performance is less predictable and in some cases does not pass at greater thicknesses such as 1-½” [38 mm] and 2” [50 mm].
Cost
Foam plastic typically costs less than rubber.However, the project application, performance characteristics, and owner project requirements may be more important than up-front cost of materials.
Which is Better: Rubber or Foam Pipe Insulation?
A safe conclusion when comparing rubber versus foam plastic pipe insulation is that While both materials offer closed-cell construction, elastomeric (rubber) insulation is generally preferred in commercial and industrial applications (includingHVAC, chilled water, and refrigeration) due to its lower thermal conductivity, higher continuous operating temperature, more reliable condensation control, and more predictable fire behavior.
Polyethylene foam insulation, on the other hand, is more commonly used in residential and light commercial applications where performance demands are lower and upfront cost is a primary consideration.
Comparing NBR/PVC and EPDM Foam Rubber Insulation
To drill this comparison down another level, what should you look for when comparing NBR/PVC and EPDM foam rubber insulation? Both NBR/PVC and EPDM meet ASTM C534, are made from synthetic rubber compounds and utilize a closed-cell structure and smooth outer skin that serves as a vapor barrier. However, differences in material composition can influence performance characteristics across various operating conditions.
What Are The Performance Advantages of AEROFLEX EPDM™ Versus NBR/PVC?
There are a number of performance advantages of AEROFLEX EPDM when compared to NBR/PVC elastomeric insulation, including:
Chemical Polarity of Material Composition
AEROFLEX EPDM is nonpolar (hydrophobic), which means that it does not induce or react to moisture. This characteristic can support more stable performance in high-humidity or condensation-prone environments.
NBR/PVC is hygroscopic or attracted to moisture and may exhibit greater sensitivity to moisture depending on the application and exposure conditions.
Thermal Conductivity
Both EPDM and NBR/PVC insulation are designed to provide low thermal conductivity. AEROFLEX EPDM material formulations are engineered to maintain consistent k-values across core product lines.
Water Vapor Permeability
Water vapor permeability (WVP) is a key factor in condensation control. AEROFLEX EPDM maintains low WVP across core product lines, which can help limit moisture absorption over time when properly installed.
Corrosion Considerations
Material composition can influence interaction with metallic piping. AEROFLEX EPDM is noncorrosive on metallic piping, including stainless steel, when used in accordance with industry standards.
Continuous Operating Temperature (Upper Limit)
AEROFLEX EPDM insulation is typically rated for higher continuous service temperatures of up to 257℉ [125℃], while NBR/PVC formulations generally have lower upper temperature limits depending on the specific product.
UV Resistance and Environmental Durability
AEROFLEX EPDM is more UV-resistant than NBR/PVC; although not UV-proof, EPDM will degrade at a slower rate than NBR/PVC, which may make it more suitable for applications with incidental or prolonged exposure to sunlight.Additional protective measures (such as jacketing) may still be required depending on installation conditions.
Mold Resistance
AEROFLEX EPDM does not contain organic food sources such as binder and oils which can sustain microbesmaking it a good choice for mold resistance; the addition of EPA-registered antimicrobials are necessary.
PVC Content
Material composition may be a consideration for projects with specific environmental or material transparency requirements. for building owners seeking PVC-free building materials, AEROFLEX EPDM contains ultra-low PVC content (< 1% by weight), while NBR/PVC insulation incorporates PVC as part of its base composition. This distinction may be relevant for projects with sustainability goals, material disclosure requirements, or restrictions on PVC-containing materials.
Flexibility and Installation Conditions
EPDM is known to stay more flexible than NBR/PVC during cold-weather installations, which can be beneficial during installation in colder environments or when insulating irregular surfaces.
Summary
While both AEROFLEX EPDM and NBR/PVC elastomeric insulation are widely used and meet established industry standards, differences in moisture interaction, temperature limits, and environmental durability may influence material selection based on your specific application requirements.
To learn more about AEROFLEX EPDM, click here.
