Pipe insulation · Elastomeric foam
AEROFLEX Tube Insulation
- Tube bore
- 6–165 mm
- Wall thickness
- 6–50 mm
- Service temp.
- -57 – 125 °C
Elastomeric foam vs glass wool for air-conditioning: what is the difference?
In short
Elastomeric foam is a closed-cell synthetic-rubber foam whose body itself resists water-vapour flow, so it is widely used on chilled-water and refrigerant pipes. Glass wool is a fibrous insulation that air can move through, so on cold work it depends on a foil facing or vapour retarder with every joint sealed; it is widely used on ductwork and hot pipes. Neither suits every job: choose by location, operating temperature and the values in each product's datasheet.
Why the difference matters
Air-conditioning has surfaces colder than the surrounding air (chilled-water pipes, refrigerant lines, supply ducts carrying cool air) as well as hot ones. If moist air reaches a surface below its dew point, the vapour condenses: the insulation gets wet, pipes corrode and water drips onto ceilings (why AC pipes drip). Each material keeps vapour out in a different way, which directly affects where it is used and how it is installed.
Cell structure and moisture
- Elastomeric (closed cell) — small, separate gas cells. The manufacturer describes the vapour resistance as spread through the full insulation thickness rather than concentrated in one surface layer. Slits, seams and ends still have to be glued closed.
- Glass wool (fibrous) — the spaces between fibres are connected, so vapour can pass through the body. Cold work needs a vapour retarder such as reinforced foil, with joints, tears and punctures sealed using tape that matches that facing. If the facing is damaged, moisture can collect inside the insulation.
Read more: what is a vapour barrier and closed-cell vs fibrous insulation
Where each is typically used
| Elastomeric foam | Glass wool | |
|---|---|---|
| --- | --- | --- |
| Structure | Closed cell | Fibrous (needs a vapour retarder on cold work) |
| Common forms | Pre-formed tubes, sheets, rolls | Duct-wrap rolls, boards, pipe sections, flexible duct |
| Typical jobs | Chilled-water pipes, refrigerant lines, fittings and valves | Duct exteriors, duct liners, high-temperature pipes |
| Facing | Mostly unfaced; some grades foil-faced | Usually factory foil or other facing |
| Installation | Slide on, or slit and glue with the maker's adhesive | Wrap or line, fix with adhesive/pins, seal joints with foil tape |
This table shows general tendencies, not fixed rules: elastomeric sheet can also insulate ducts and glass-wool pipe sections are used on pipes, depending on the product and job conditions.
Operating temperature: check each datasheet
Service temperature ranges differ by formulation and product, so avoid assuming "elastomeric handles X" or "glass wool handles Y". Examples from the datasheets of products we sell:
- AEROFLEX tube (EPDM): -57 to 125 °C per the manufacturer
- ArmaFlex Class 1: -50 to +105 °C per the manufacturer (with an extra condition when fully bonded to the surface)
- SCG PCI (glass-wool pipe section): 10 to 540 °C per the manufacturer
These values apply only to those products. Check the current datasheet of the exact product before ordering.
There is no single thickness for every job
The thickness needed to prevent condensation depends on the pipe temperature, the surrounding air temperature and humidity, and the pipe size. Calculate from actual conditions: see how to choose pipe insulation and dew point and condensation.
How installation differs
- Elastomeric — on new pipes slide it on before connecting; on existing pipes slit it lengthwise and glue with the adhesive the maker specifies. Install without stretching, close ends and fittings, and protect it from sunlight (UV) outdoors as the manufacturer advises.
- Glass-wool duct wrap — wrap with the foil facing outward, avoid compressing it thin at duct corners, fix with adhesive or pins as the maker recommends, and seal every joint with foil tape that matches the facing.
With both, most problems come from unsealed joints and insulation crushed at hangers. Read why insulation joints and sealing matter.
Common mistakes
- Choosing by price or habit without checking whether the surface is cold or hot, indoors or outdoors.
- Using glass wool without a vapour retarder, or with a torn facing, on cold work.
- Using elastomeric foam beyond the temperature range in that product's datasheet.
Sources
- ASTM C534/C534M — Standard Specification for Preformed Flexible Elastomeric Cellular Thermal Insulation in Sheet and Tubular Form
- ASTM E96/E96M — Standard Test Methods for Water Vapor Transmission of Materials
- Armacell — ArmaFlex Application Manual and information on moisture in closed-cell insulation
- NAIMA / Insulation Institute — installation guidance for fibrous-glass duct wrap
- Manufacturer documents: AEROFLEX Tube, ArmaFlex Class 1, SCG PCI, Micro Duct Wrap FRK
Related products
Categories and example products for this topic
- AEROFLEX Tube Insulation — Closed-cell elastomeric tube for chilled and refrigerant lines, -57 to 125 °C
- ArmaFlex Class 1 Tube — Elastomeric tube for AC and refrigeration pipes; vapour diffusion resistance μ ≥ 10,000
- Micro Duct Wrap FRK — Glass wool for wrapping ducts, with a reinforced foil facing (0.02 perm max)
- SCG PCI / PCIF — Glass wool section for steel pipes, hot or cold, service range 10–540 °C
Pipe insulation · Elastomeric foam
Armacell ArmaFlex Class 1 Tube
- Tube bore
- 6–168 mm
- Wall thickness
- 6–50 mm
- Service temp.
- -50 – 105 °C
Duct and HVAC insulation · Glass wool
Microfiber Micro Duct Wrap FRK
- Thickness
- 25–50 mm
- Density
- 16–32 kg/m³
- Thermal conductivity (λ)
- 0.033–0.038 W/m·K
Pipe insulation · Glass wool
SCG PCI / PCIF
- Pipe size
- ½–18 in
- Thickness
- 25–50 mm
- Service temp.
- 10 – 540 °C