LINE: ask a price

Pipe insulation

How to choose pipe insulation

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

Four pipes of increasing diameter in a row, each fitted with a matching insulation tube in dark grey foam or beige fibre.
In short

First ask whether the pipe is cold or hot. Cold lines mainly need to stop condensation, so they need a material or facing that resists water vapour continuously; hot lines focus on reducing heat loss and keeping touchable surfaces safe. Then check that the insulation's service temperature range covers the pipe temperature, choose a bore size that matches the pipe's outside diameter, and take the thickness from a design for the real conditions — not one number for every job.

Cut-away of an insulated pipe showing the pipe, insulation with a bore that fits the pipe, sealed lengthwise seam and butt joint, a support that does not crush the insulation, and UV protection outdoors 123456
  1. 1The pipe — for example a refrigerant or chilled-water line
  2. 2Pipe insulation: choose a bore that fits the pipe, and a thickness for the temperature and site conditions (no single thickness suits every job)
  3. 3Lengthwise seam: bonded or sealed the way the manufacturer specifies
  4. 4Butt joint between lengths: tight and sealed
  5. 5Hanger or support: the insulation should not be crushed thin — support it as the manufacturer recommends
  6. 6Outdoors: protect from sunlight and weather as the manufacturer specifies

1. Cold line or hot line?

Cold lines (refrigerant, chilled water)Hot lines (hot water, steam, process)
---------
Main problemCondensation drips, lost coolingHeat loss, hot surfaces dangerous to touch
What is neededOuter surface warmer than the dew point + continuous vapour resistanceInsulation that withstands the pipe temperature, thickness enough to meet the designed heat loss
Read moreDew point and condensation, Vapour barrierService temperature

2. Service temperature range

Every insulation has a temperature range the maker states for use. It must cover the lowest and highest temperatures the pipe will see, including start-up and shutdown. Examples from the makers' documents for products we sell:

ProductTypeService temperature per maker's document
---------
AEROFLEX TubeClosed-cell EPDM elastomeric-57 to 125 °C
MAXFLEX FR TubeClosed-cell EPDM elastomeric-57 to 125 °C
Armaflex Class 1Closed-cell elastomeric-50 to +105 °C
SCG PCIPre-formed glass-wool pipe section10 to 540 °C

These are material ranges; they do not mean any job within the range works without design. Check the latest document before ordering.

3. The bore must match the pipe

Pre-formed tube insulation is sized by the inside diameter of the insulation, which must match the outside diameter of the pipe.

  • Copper, steel and plastic pipes with the "same size" name may have different outside diameters. Measure, or read the actual pipe specification, and compare with the insulation maker's size table.
  • Too loose a bore leaves an air gap between pipe and insulation; on a cold pipe, condensation can form in that gap.
  • Too tight a bore stretches the insulation, thinning the wall and putting the joints under tension so they may open later.

4. Wall thickness comes from design

The thickness needed depends on pipe temperature, the temperature and humidity of the surrounding air, pipe size, the insulation's thermal conductivity and the goal (prevent condensation, limit energy loss or limit surface temperature). Many insulation makers provide calculation software or tables. Let the system designer set it, or send us your site details to check.

There is no "standard thickness" for every pipe

A thickness that is enough for a pipe in a conditioned room may not be enough for the same pipe in a hot, humid ceiling void under the roof. Do not reuse a number from another job without checking the real conditions.

5. Closed-cell elastomeric or glass/stone-wool sections?

Closed-cell elastomericPre-formed glass/stone-wool pipe sections
---------
Vapour resistanceIn the material itself; glue the joints as the maker instructsRelies on a vapour-retarding facing/jacket when used on cold pipes
Common usesRefrigerant, chilled-water and hot-water pipes within the material's rangeHot and process pipes above the elastomeric range
FlexibilityBends with the pipe, easy around fittingsRigid sections, cut and fitted at fittings

Neither is better for every job. Details in Elastomeric vs glass wool in HVAC.

6. Outdoor installation

Many elastomeric insulations need UV protection outdoors, such as a coating or jacket as the maker specifies. Glass/stone-wool needs a jacket against rain and mechanical damage. Follow each maker's instructions, as methods and time limits differ.

7. Do not forget joints and accessories

The right insulation only works when every joint is sealed. Use the adhesive, tape and method the maker recommends. See Sealing insulation joints and Accessories.

Sources

  • ASHRAE Handbook — Fundamentals, chapter Insulation for Mechanical Systems
  • Armacell — ArmaFlex Application Manual and insulation thickness calculator information
  • National Insulation Association — Condensation Control Calculator and Insulation Outlook articles
  • Manufacturer documents: AEROFLEX (AF/OCT 2024), ArmaFlex Class 1 TDS (APAC), MAXFLEX FR Standard (FLEX 08/24), SCG Insulation for Industrial: Pipe

Related products

Categories and example products for this topic

Pipe insulationInstallation accessories
  • AEROFLEX Tube Insulation — Cold lines to hot water: service range -57 to 125 °C, bore 6–165 mm
  • ArmaFlex Class 1 Tube — AC and refrigeration pipes: service range -50 to +105 °C, wall thickness 6–50 mm
  • SCG PCI / PCIF — Hot and cold steel pipes: pre-formed glass wool section, service range 10–540 °C
  • ROCKWOOL ProRox PS — Hot industrial pipes: split stone wool section up to 650 °C, finished with metal cladding
See related products Help me choose

Related knowledge