PU/PIR, EPS, XPS and PE foam boards (illustration)

Building materials · Foam insulation

PU/PIR, EPS, XPS and PE foam – choosing the right foam insulation

Foam insulations reach low thermal conductivity at very low weight. They are the core of most sandwich panels and cold stores and the standard under floors and foundations – each with its own strengths and fire behaviour. This guide explains them and shows where mineral wool is the better choice.

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0.022 – 0.028
PU/PIR λ, W/m·K: 0.029 – 0.036
XPS λ, W/m·K: 0.031 – 0.038
EPS λ, W/m·K: Combustible
All foam plastics

Foam insulation types compared (illustration)

Foam insulation in steel buildings

Foam insulations are plastics expanded into millions of closed cells. Their gas-filled cells give very low thermal conductivity, so the same R-value needs less thickness than mineral wool. In steel buildings they appear mostly as the core of sandwich panels for walls, roofs and cold rooms, as boards under floors and foundations, and as thin PE foam underlays below roofs.

All foam plastics are combustible. Their fire performance depends on the type – PIR behaves better than PUR, fire-retardant grades exist for EPS – and on the protection around them. Where a building needs non-combustible insulation, choose stone wool.

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Ceramic and low-biopersistence fibre insulation and tested fire-resistant duct wraps for plant, ducts and services.

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Ceramic and high-temperature fibre insulation – illustration

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Fire-resistant insulation blankets and duct wraps – illustration

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Types

The four common foams

Typical properties and uses – compare actual product data sheets before you specify.

polyurethane · polyisocyanurate

PU / PIR

Lowest λ of the common foams. Core of insulated wall and roof panels and cold store panels; PIR has better fire behaviour than PUR.

expanded polystyrene

EPS

Light, economical and versatile – panels, floors, external insulation systems. Use fire-retardant (FR) grades in buildings.

extruded polystyrene

XPS

Closed-cell, strong and almost waterproof – floors, slabs on grade, cold store floors, inverted roofs and foundations.

polyethylene foam

PE foam

Thin, flexible, often foil-faced – under-roof insulation, pipe insulation and underlays.

Tiêu chuẩn & tuân thủ

Standards for foam insulation

Product standards commonly specified in our export markets.

Europe

EN 13163 · EN 13164Expanded polystyrene (EPS); extruded polystyrene (XPS) products
EN 13165 · EN 14509Rigid polyurethane (PU) products; self-supporting sandwich panels
EN 13501-1Reaction-to-fire classification

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United States

ASTM C578Rigid cellular polystyrene thermal insulation (EPS, XPS)
ASTM C1289Faced rigid cellular polyisocyanurate board
ASTM E84 · NFPA 285Surface burning; fire propagation of exterior walls with combustible components

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Australia & New Zealand

AS 1366Rigid cellular plastics sheets for thermal insulation
AS 5113 · NCCFire propagation of external walls; National Construction Code

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Nội dung chỉ mang tính tham khảo – chỉ dẫn kỹ thuật của dự án, phiên bản quy chuẩn được áp dụng và cơ quan có thẩm quyền là căn cứ quyết định.

Fire safety first

Match the insulation to the fire design

Building codes in many markets limit combustible insulation in external walls, high-rise buildings and escape routes, and insurers often require non-combustible or approved panels for warehouses and factories. World Steel checks the fire requirements of your market and building type and proposes foam, mineral wool or stone-wool-core panels accordingly.

Compare

Foam insulation vs mineral wool

Typical behaviour – a quick guide for early design.

Comparison
Property	PU / PIR	EPS	XPS	Stone wool
Thermal conductivity λ, W/m·K	0.022 – 0.028	0.031 – 0.038	0.029 – 0.036	0.033 – 0.042
Reaction to fire	Combustible (PIR better)	Combustible (FR grades)	Combustible	Non-combustible (A1)
Water absorption	Low	Moderate	Very low	Water-repellent grades
Compressive strength	Good	Moderate	High	Good in board grades
Max. service temperature	≈ 100 – 120 °C	≈ 75 – 80 °C	≈ 75 °C	Up to ≈ 750 °C
Acoustic absorption	Low	Low	Low	High
Typical use	Sandwich panels, cold stores	Panels, floors, ETICS	Floors, foundations, inverted roofs	Fire-safe panels, façades, roofs

FAQ

Câu hỏi thường gặp

What is the difference between PU and PIR?

Both are polyurethane-family foams. PIR (polyisocyanurate) has a different chemistry that gives better fire behaviour and temperature resistance than standard PUR.

EPS or XPS?

EPS is lighter and cheaper; XPS is stronger and absorbs almost no water, so it is preferred under floors, in foundations and in inverted roofs.

Can foam insulation be used in fire-rated walls?

Only in tested and approved systems. Where non-combustible insulation is required, use stone wool or stone-wool-core panels.

Which insulation is used for cold stores?

Usually PU/PIR sandwich panels for walls and ceilings and XPS under the floor slab – see our cold storage warehouse solution.

Choose the right insulation for your building

Tell us the building use, climate and fire requirements – we propose the insulation and quote it with the steel.

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