What is elastomeric foam insulation and what is it used for?

5 min read · Written by our team · Updated 26 Sept 2026

Black flexible foam insulation tubes of several sizes and a rolled sheet, with one tube fitted over a copper pipe.

In short

Elastomeric foam (elastomeric insulation) is a flexible synthetic-rubber foam with a closed-cell structure, made as pre-formed tubes, sheets and rolls. Its main job is insulating chilled-water and refrigerant pipes to reduce cooling loss and prevent condensation. Some products also suit hot-water pipes within the temperature range in their datasheet. When installed outdoors it should be protected from sunlight as the manufacturer advises.

What it is made of

Elastomeric insulation is made from natural or synthetic rubber mixed with various additives and expanded into a foam. ASTM C534 is the specification for this insulation in sheet and tubular form and divides it into grades by operating temperature range.

Two main formulation families are common on the market:

NBR-based (often blended with PVC) — a widely used formulation, for example in air-conditioning and refrigeration.
EPDM-based — for example AEROFLEX tube and MAXFLEX FR. Manufacturer information states that EPDM degrades under UV more slowly than NBR/PVC.

Each brand and product has its own formulation, service temperature, fire test results and thermal conductivity. Read them from that product's datasheet rather than judging from the rubber family alone.

Why air-conditioning uses it

Closed cell — manufacturers state that the vapour resistance is in the insulation body; for example, ArmaFlex Class 1 states that no extra vapour barrier is needed (what is a vapour barrier).
Flexible — follows pipes, bends and fittings; slides onto new pipes, or is slit and glued onto existing ones.
Many sizes — a range of bore sizes and wall thicknesses to match pipe sizes.

It only prevents condensation when the thickness is sufficient for the conditions and the joints are fully glued (why AC pipes drip, sealing insulation joints).

What it is used for

Chilled-water pipes in central air-conditioning and refrigerant lines in split systems
Refrigeration pipework, fittings, valves and vessels that must not condense
Hot-water pipes, for products and temperature ranges stated in the datasheet
Foil-faced sheets for under roofs and on ceilings, such as AERO-ROOF

Temperature range: check the product's datasheet

Examples from the manufacturers' datasheets of products we sell: AEROFLEX tube -57 to 125 °C and ArmaFlex Class 1 -50 to +105 °C, while for MAXFLEX FR STANDARD the manufacturer recommends operating temperatures up to 100 °C. These figures apply to those products only.

Outdoors: protect from sunlight

UV light and weather can degrade the rubber surface. Many manufacturers require an outdoor installation to be covered with their UV-protective paint or coating, or clad with metal or PVC jacketing. Even though EPDM degrades more slowly, manufacturers still recommend protection. Follow the instructions of the brand you use.

Things not to generalise

No single thickness suits every pipe; it depends on pipe temperature, air humidity and pipe size (how to choose pipe insulation).
Fire test results differ between products; check the standard and result in the datasheet.

Sources

ASTM C534/C534M — Standard Specification for Preformed Flexible Elastomeric Cellular Thermal Insulation in Sheet and Tubular Form
Armacell — ArmaFlex Application Manual (outdoor UV protection, gluing) and ArmaFlex Class 1 datasheet (APAC)
Aeroflex — AEROFLEX brochure (Thailand) and EPDM vs NBR/PVC information (Aeroflex USA)
MAXFLEX — FR STANDARD catalogue
AERO-ROOF brochure