Crosslinked polyethylene, commonly known as PEX, is a flexible polymer-based tubing material developed in Europe during the 1960s. Since the 1980s, PEX has become an increasingly common alternative to traditional copper tubing in the North American market, especially for residential, high-rise residential, commercial plumbing, and HVAC applications.
While copper tube remains a proven and widely used material for many plumbing and mechanical systems, PEX offers several practical advantages that make it attractive for contractors, installers, and building owners.
Why PEX Tubing Is Commonly Used
- PEX tubing is valued for its flexibility, durability, and ease of installation. Compared to copper, PEX offers several benefits, including:
- Flexible tubing that can simplify routing and reduce the number of fittings
- Resistance to corrosion, chlorine, and hard water
- Reduced risk of pitting and pinhole leaks
- Greater resistance to freeze-related damage compared to rigid piping materials
- Reduced transmission of unwanted noise and water hammer
- Lightweight handling and transport
- No flame required for joining
- Less risk of jobsite theft due to no scrap value
- Faster installation with quick joining options
- Proven durability throughout the product life cycle
For many projects, these advantages can help simplify installation, reduce labor challenges, and support system performance.
PEX-A, PEX-B, and PEX-C Tubing
PEX tubing is commonly categorized as PEX-A, PEX-B, or PEX-C. These designations refer to the manufacturing method used to crosslink the polyethylene material. PEX-A is generally produced using the peroxide method, PEX-B is commonly produced using the silane method, and PEX-C is produced via an electron beam method.
For insulation purposes, the specific type of PEX—whether PEX-A, PEX-B, or PEX-C—typically does not affect insulation selection. Insulation requirements instead depend entirely on tubing size, operating temperature, system application, and project needs to help reduce heat loss, control condensation, and optimize system performance.
Common PEX Sizes and Applications
PEX tubing for the North American market is most often produced in nominal tube sizes (NTS) that match the outside diameter of copper tube sizes (CTS). Typical nominal diameter ranges include ¼ inch to 3 inches and are available in both coils and straight lengths.
Depending on the application, PEX tubing is commonly used within a continuous service temperature range of 32°F [0°C] to 180°F [82°C].
Common applications include:
- Hot and cold water plumbing for residential and commercial buildings
- Hydronic piping
- Chilled water
- Radiant heating and cooling
- Residential fire protection systems
- Reclaimed water (purple pipe)
PEX is also code-compliant for plumbing applications and is recognized by major codes and standards, including the International Plumbing Code (IPC), Uniform Plumbing Code (UPC), International Residential Code (IRC), and NSF requirements for safe drinking water.
Why Insulate PEX Tubing?
Like other plumbing and mechanical piping materials, PEX tubing may require insulation depending on the system application, operating temperature, building environment, and project specifications.
Insulating PEX tubing can help:
- Reduce heat loss in hot water and hydronic systems
- Improve energy efficiency
- Freeze protection
- Support condensation control on chilled water lines
- Help protect surrounding materials from moisture-related issues
- Support long-term system performance
National model energy standards and codes, including ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, and the International Energy Conservation Code® (IECC®), establish minimum insulation thickness requirements for heating and hot-water piping operating at temperatures of 105°F [40°C] and above. The required insulation thickness is generally determined by the piping system’s service or operating temperature and the nominal pipe or tube size.
Pipe insulation can also help maintain more consistent hot-water temperatures by reducing heat loss as water travels through the piping system. According to the U.S. Department of Energy (DOE), insulating hot-water pipes can deliver water that is approximately 2°F to 4°F warmer than comparable uninsulated piping. For residential applications, the DOE estimates that insulating hot-water pipes can provide annual water-heating energy savings of approximately 3% to 4%.
Proper insulation thickness is especially important for preventing surface condensation, commonly called “sweating,” on below-ambient (cold) systems. Insulation should be selected based on its thermal conductivity ( K-value), along with the tubing size, operating temperature, ambient temperature, and relative humidity. These conditions can fluctuate throughout the day and across seasons, making properly calculated insulation thickness an important part of consistent condensation control.
The cost of uncontrolled condensation can be high. Moisture can reduce insulation system performance, damage ceilings and other building materials, and affect equipment located below the tubing. Although PEX itself does not corrode, condensation may contribute to corrosion on metallic fittings, valves, supports, and connected equipment. Selecting the appropriate insulation material and thickness can help prevent costly repairs and the premature replacement of insulation, equipment, and surrounding building systems.
In HVAC, chilled-water, radiant-heating, and plumbing systems, insulation plays an important role in helping the system operate as intended. The right insulation should be compatible with the tubing size and suitable for the energy-efficiency, thermal-performance, and condensation-control requirements of the application.
Simplifying Field Installation and Repairs
For contractors and installers, PEX tubing simplifies routing through tight spaces, reduces the total number of fittings, and speeds installation times compared to rigid piping materials. Because PEX utilizes simple mechanical connections, it eliminates the safety hazards and dry-piping requirements of copper soldering, as well as the messy chemical primers, harsh fumes, and extended cure times associated with gluing CPVC. These benefits are especially valuable when addressing unexpected field repairs or tight-deadline modifications that require water lines to be restored immediately.
Closed-Cell Elastomeric Insulation for PEX Tubing
Flexible, closed-cell elastomeric tube insulation is a proven choice for PEX tubing because of its closed-cell structure, flexibility, and ease of installation.
Closed-cell elastomeric insulation helps provide thermal performance while supporting condensation control in below-ambient applications. Its flexible design allows it to fit around tubing, while properly matched tube sizes help simplify installation in the field.
For contractors and installers, this combination can be especially useful on projects where speed, flexibility, and clean installation are important. Pairing PEX with flexible, closed-cell elastomeric insulation can further improve jobsite efficiency. The insulation’s flexible, slip-on design accommodates standard tube sizes, helping provide a secure fit in the field. Tube insulation is also available with a factory-applied closure that can help reduce installation time while providing a secure, consistent longitudinal seam.
Tested Performance with AEROFLEX EPDM™ Insulation
AEROFLEX EPDM closed-cell elastomeric insulation has been tested as a composite assembly with PEX tubing and meets ASTM E84 25/50 requirements, with a flame spread index of less than 25 and a smoke-developed index of less than 50.
Available in preformed unslit and pre-slit self-seal tubes for a wide range of PEX sizes, AEROFLEX insulation supports plumbing and HVAC applications with continuous service temperatures from -297°F to 257°F (-182°C to 125°C). It is available in ASTM E84 25/50-rated thicknesses up to 2 inches (50 mm) and provides inherent resistance to microbial growth.
This tested assembly performance gives engineers, specifiers, contractors, and project teams added confidence when selecting insulation for PEX tubing in applicable plumbing and HVAC systems.
A Practical Solution for Modern Piping Systems
As PEX continues to be used across residential, commercial, and mechanical applications, insulation remains an important part of system design. Whether the system uses PEX-A, PEX-B, or PEX-C, closed-cell elastomeric insulation can help support thermal performance, condensation control, and installation efficiency.
AEROFLEX EPDM™ closed-cell elastomeric insulation offers the flexibility, closed-cell performance, and tested compatibility needed to support today’s PEX tubing applications.
Learn more about AEROFLEX EPDM Elastomeric Pipe Insulation.
Sources:
Plastics Pipe Institute – https://plasticpipe.org/BuildingConstruction/BuildingConstruction/PEX.aspx
IAPMO – https://iapmo.org/codes-standards-development/code-development/uniform-plumbing-code
International Code Council (ICC) – https://codes.iccsafe.org/content/IRC2024V2.0
NSF – https://www.nsf.org/knowledge-library/water-plumbing-systems-study-results
ANSI/ASHRAE/IES Standard 90.1 — Piping Insulation Requirements –ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/90_1_2019_aq_20220729.pdf
U.S. Department of Energy — Insulate Hot Water Pipes https://www.energy.gov/energysaver/do-it-yourself-savings-project-insulate-hot-water-pipes
