How to Choose the Right Insulation Material: A Five-Step Selection Framework

Direct answer: insulation material selection is a five-variable problem — service temperature, fire performance required by the governing code, moisture exposure, mechanical duty, and installed cost over the asset life. Evaluating these five factors in that order can help project teams narrow down suitable insulation options and avoid unnecessary specification changes.

Most enquiries start with a material name. The useful ones start with a temperature, a location and a performance target.

Base the selection on the maximum design temperature, including any specified operating variations and project safety requirements — not the normal operating temperature alone. Where the specification defines a margin or an excursion condition, apply that; no single percentage fits every line.

Continuous versus excursion: a product rated for continuous service may allow short excursions above it; the reverse is never true. The rating belongs to the system: binder, facing and jacketing all affect a mineral wool product's maximum service temperature, so the figure must come from that product's datasheet.

As a rough map: organic foams sit in the low band; mineral wool covers the mid band and beyond; calcium silicate and ceramic fibre take the highest temperatures.

Under EN 13501-1, construction products are classified A1 to F: A1 is non-combustible, A2 is limited combustibility, and B to F are combustible, with additional classes for smoke (s1–s3) and flaming droplets (d0–d2).

Three qualifications matter in practice:

1. A1 does not make a building system fire-rated. Reaction-to-fire classification describes how a material contributes to fire growth; resistance ratings for a wall, roof or floor come from testing the complete assembly.
2. A single-material test result is not the assembly result. Cladding, fixings, membranes, joints and substrate all change the outcome. Where a rated assembly is required, ask for the assembly test report.
3. National and local codes differ. The same product may be accepted on a high-rise facade in one jurisdiction and rejected in the next.

A datasheet line saying "Class A" without a standard reference and a classification report is not evidence.

Thermal conductivity is measured dry. Buildings and plants are not.

Closed-cell insulation materials generally offer better resistance to water penetration than open-fibre insulation. Their actual moisture performance depends on the product structure, joints, facings and installation quality. A closed-cell section with open joints is, in practice, an open-cell system: water enters at hangers, flanges and terminations.

For below-ambient service, the vapour barrier goes on the warm side and must be continuous through joints, hangers and penetrations. For hot service, the risk inverts into corrosion under insulation (CUI). Industry guidance summarised from API RP 583 places the carbon steel CUI window broadly between about −4 °C and +175 °C, with the highest risk around 60–120 °C, and notes chloride stress corrosion cracking risk in austenitic stainless steel at roughly 50–175 °C.

This is where foam glass (cellular glass) earns its place. It is closed-cell and inorganic: water absorption is typically ≤0.5% and water vapour permeance ≤0.007 ng/(Pa·m·s) across our MY-FG range, and performance does not depend on a separate vapour barrier staying intact. For CUI-prone lines, cold service and buried piping it is often the most defensible choice — at higher material cost, and with the trade-off that it is brittle and needs skilled installation.

Pipe sections and shaped parts for these applications: foam glass pipe insulation and foam glass boards.

A material that crushes loses its thickness, and thickness is the insulation.

• Compressive strength is graded, not guessed. EN 13164 expresses it as a class — CS(10/Y)300 means at least 300 kPa at 10% deformation. That defines the class; each product carries its own declared value.
• Do not infer compressive capacity from density. Two boards of similar density can differ in compressive behaviour and creep. Specify the declared class and, for sustained loads, the creep data.
• Foam glass comes in load-bearing grades. Our MY-FG series spans roughly 0.50 to 2.40 MPa depending on grade — used under tanks, cold-store floors and pipe supports, selected against the actual load case.
• On pipework, allow for movement. A hot carbon steel line expands measurably; rigid sections need expansion joints or the seams will open.

For below-slab and floor applications, see XPS insulation.

The board is usually the smaller part of the number. The system adds jacketing, vapour barriers, adhesives, fasteners, vapour stops, labour and waste. A material 15% cheaper per cubic metre and 30% slower to install is the more expensive choice.

Compare lifecycle cost, not unit price: material, auxiliary materials, installation labour, maintenance access, and replacement or rework over the service life.

Then size the thickness by calculation, not habit. ISO 12241 gives the rules for heat-transfer properties of building equipment and industrial installations — heat loss, surface temperature and the condensation check come from the same model, using the declared λ at the design mean temperature.

Declared λ values are comparable only at the same mean temperature and test standard. "Refer to TDS" cells are product-specific: a specification written against a family average will not survive a submittal review. Foam glass values are from our MY-FG data, tested to GB/T 10294 and ASTM C177.

1. A thickness with no target. "50 mm" is not a specification; a target surface temperature is.
2. Treating A2 as A1, or comparing λ measured at different mean temperatures.
3. Buying on board price while ignoring the 60–120 °C CUI band. Jacketing, labour and rework are where budgets actually go.

• Chilled Water and Refrigeration Systems: Closed-cell elastomeric insulation is commonly considered for condensation control, subject to proper joint sealing and vapour barrier design.
• High-Temperature Industrial Piping: Rock wool and calcium silicate insulation can be considered according to operating temperature, fire requirements and product specifications.
• Moisture-Sensitive Industrial Applications: Cellular glass insulation is worth evaluating where low water absorption and vapour resistance are important.
• Building Floors and Roofs: XPS insulation can be considered where compressive strength and dimensional stability are important.
• Building Facades and Interior Applications: Glass wool and rock wool can be evaluated according to thermal, acoustic and fire performance requirements.

The final selection should always consider operating conditions, applicable standards, installation methods and verified product data.

Related ranges: rock wool pipe sections · glass wool · calcium silicate pipe · closed-cell rubber foam

What is the single most important factor in insulation material selection? The maximum design temperature. It eliminates more candidates than any other variable, and a material used above its rated temperature fails regardless of its thermal conductivity.

Is mineral wool better than foam glass? Neither is universally better. Mineral wool wins on cost, temperature range and fire performance; foam glass wins where moisture and CUI dominate. The application decides.

Can I use PIR for chilled water pipes? It is done, but closed-cell elastomeric or cellular glass are usually considered first below ambient, where a continuous vapour seal matters more than a low λ.

Why does A2 fire class sometimes get rejected on facades? Because A2 is limited combustibility, not non-combustibility. Many high-rise facade rules require A1, and local interpretations vary.

How is insulation thickness actually determined? By calculation. ISO 12241 covers heat loss, surface temperature and condensation checks; inputs are design temperature, ambient conditions, declared λ at mean temperature, and the acceptable surface condition.

Send the line list or drawing schedule — design temperature, pipe or duct size, indoor/outdoor or buried, fire requirement and any CUI concern — and we will return a shortlist with the relevant product data sheets.

Request a material shortlist and quotation →

Prepared by Myreal Energy Saving (Shanghai) Co., Ltd. Technical content for specification support, not a product offer. Confirm values against the current data sheet for the selected grade.