Is Insulation Flammable? Fire Safety and Insulation Materials Explained

18 August 2026

Most insulation sold in Australia is either non-combustible or treated to be fire-retardant, but it depends on the material and its facing. Bulk mineral fibres like glasswool and rockwool don’t burn, while spray foam, EPS and some foil or paper facings can. Because Australian building rules set strict fire requirements, highly flammable insulation can’t legally be sold for standard building use. Here’s the full material-by-material breakdown.

If you’re about to insulate or you’ve just noticed the material already sitting in your roof worrying about fire risk is completely reasonable. The good news is that the insulation industry in Australia is heavily regulated for exactly this reason. This guide explains, which materials burn and which don’t, how our fire standards actually work, what to use in bushfire zones, and how to keep your insulation safe once it’s installed.

Is insulation flammable? The short answer

It comes down to what the insulation is made from:

Bulk mineral fibre - glasswool and rockwool is non-combustible.

These are made from spun glass or stone and simply do not burn. Glasswool (like Knauf Earthwool and Fletcher Pink Batts) is classed as non-combustible when unfaced; rockwool (mineral wool) is one of the most fire-resistant materials available.

Some materials are combustible. Spray foam (polyurethane/PIR), EPS/polystyrene board, and certain foil or paper facings can ignite and must be used with the right protection.

Cellulose is fire-retardant, not fireproof.

It’s an organic (paper-based) material treated with fire-retardant chemicals so it chars and resists flame spread rather than burning freely.
Crucially, in Australia insulation must meet the fire requirements of the National Construction Code (NCC). That means genuinely high-risk, highly flammable insulation isn’t sold for typical residential building work in the first place so the question is less “will it burst into flames?” and more “which fire-safe material is right for my home and location?”

How insulation fire performance is measured in Australia

Australia doesn’t rely on marketing words like “fireproof.” Fire performance is measured against defined standards, and the NCC (Building Code of Australia, BCA) sets out where and how those requirements apply. Three plain-English terms are worth knowing:

Non-combustible – the material effectively does not burn or contribute to a fire. This is the highest bar.
Fire-retardant – the material is treated or designed to resist ignition and slow flame spread, but it is not non-combustible.
Flammable / combustible – the material can ignite and burn, so it needs protection (like a thermal barrier) or shouldn’t be used where fire performance matters.
Behind those labels sit the AS 1530 series of tests:
AS 1530.1 – Combustibility. A sample is heated in a furnace at around 750°C to determine whether it can be deemed non-combustible. It’s the most stringent test, passing it is what lets glasswool and rockwool be called non-combustible.
AS 1530.2 – Flammability of materials (including facings and foils). This matters because a non-combustible batt can still carry a combustible foil or paper facing. The facing is tested and given a flammability index.
AS 1530.3 – Fire-hazard indices for materials such as batts and loose fill, rating four things on 0-10 scales (lower = safer): Ignitability, Spread of Flame, Heat Evolved, and Smoke Developed.

When you compare products, this is why the data sheet matters more than the sales pitch, the numbers under AS 1530 tell you how the material and its facing genuinely behave.

Which insulation materials are flammable (and which aren't)?

Here’s how the common insulation materials compare. Confirm exact classifications against the current product data sheet before relying on them, they change with facing and test method.

Material	Fire behaviour	AU classification*	Best use
Glasswool / fibreglass	Does not burn; unfaced batts non-combustible	Non-combustible (AS 1530.1) if unfaced	Ceilings, walls, general
Rockwool / mineral wool	Withstands ~1,000°C+; does not ignite	Non-combustible (AS 1530.1)	Fire-rated walls, acoustic, high-risk
Polyester	Melts/burns under sustained flame	Combustible; check indices	Acoustic, low fire-risk areas
Cellulose	Treated with fire retardant; chars	Fire-retardant (not non-combustible)	Loose-fill ceilings
Spray foam (PU/PIR)	Combustible; ignites, emits smoke	Combustible; needs thermal barrier	Sealed cavities w/ barrier
Reflective foil / sarking	Foil non-combustible; backing may burn	Check flammability index (AS 1530.2)	Roof/wall radiant barrier
EPS / polystyrene	Combustible; melts and ignites	Combustible	Only in fire-rated systems

Glasswool / fibreglass batts

Spun from glass, glasswool is non-combustible when unfaced and one of the most widely used insulation types in Australian homes. Brands like Knauf Earthwool non-combustible glasswool and Fletcher Pink Batts insulation fall into this group. Watch the facing, though a foil or paper facing can be combustible even when the batt itself isn’t.

Rockwool / mineral wool

Made from spun stone, rockwool withstands very high temperatures, commonly cited as around 1,000°C or more without igniting. It’s the go-to choice where fire performance is the priority, such as fire-rated and party walls, and it doubles as an excellent acoustic insulator.

Polyester insulation

Polyester is soft, non-irritant and popular for acoustic use, but it will melt and burn under a sustained flame. It’s often treated to improve fire behaviour, so always check the indices before using it where fire matters.

Cellulose

A recycled paper-based loose-fill product treated with fire-retardant (typically borate) chemicals. It’s flame-retardant and chars rather than burning freely, but it is not non-combustible, so don’t describe it as fireproof.

Spray foam (PU / PIR)

Polyurethane and PIR spray foams are combustible, can emit significant smoke, and must be protected behind a thermal barrier. They’re generally not suitable for bushfire-prone areas or anywhere a non-combustible material is required.

Reflective foil / sarking

The foil itself is non-combustible, but the backing and adhesive can burn, so foil products are rated for flammability under AS 1530.2. Check the flammability index before use as a radiant barrier.

EPS / polystyrene board

Expanded polystyrene is combustible, it melts and ignites and should only ever be used within a properly designed fire-rated cladding system, never exposed.

Fire-rated insulation options for Australian homes

If fire performance is a priority, these are the materials to look at:

Non-combustible glasswool – a practical, cost-effective choice for most ceilings and walls. See the Bradford insulation range and Knauf Earthwool options.
Rockwool / mineral wool – the top performer for fire-rated walls, party walls (shared walls between dwellings) and service penetrations, plus excellent acoustic control.
James HardieFire fire-rated insulation – a purpose-built fire-rated solution for applications where a certified fire system is required.
Where each is typically used:
Ceilings – non-combustible glasswool or rockwool. Browse ceiling insulation.
Walls (including fire-rated & party walls) – rockwool or fire-rated systems. Browse wall insulation.
Roof – non-combustible batts and correctly rated sarking. Browse roof insulation.
Service penetrations / acoustic + fire – rockwool. Browse acoustic insulation.

Not sure what suits your build? Our guide to insulation types and their applications breaks it down further.

Insulation for bushfire-prone areas (BAL ratings)

If your home is in a designated bushfire-prone area, insulation choice becomes a compliance issue, not just a preference. Construction in these zones is governed by AS 3959 – Construction of buildings in bushfire-prone areas, which assigns a BAL (Bushfire Attack Level) – from BAL-LOW through BAL-12.5, 19, 29, 40 and BAL-FZ (Flame Zone) based on your exposure to radiant heat, embers and flame.

For higher-BAL zones, the rule of thumb is:

Use unfaced non-combustible batts – glasswool or mineral wool.
Avoid foil and paper-faced batts and many spray foams, which introduce combustible elements.

This is especially relevant across regional and peri-urban Victoria, where large areas are bushfire-prone. Because getting this wrong has life-safety and compliance consequences, always confirm the required specification with your building surveyor and match it to the correct BAL. Our team can help you select compliant, non-combustible products for your rating.

Fire risks and safe installation

Here’s the part that surprises people: most insulation-related fires don’t start with the insulation itself. They start with an external heat source, and combustible material nearby is drawn in. The usual culprits:

Recessed downlights that get hot and sit too close to (or buried under) insulation.
Flues and chimneys where insulation is packed against a hot surface.
Old or faulty wiring in contact with insulation.

To keep things safe:

Maintain manufacturer clearances around downlights and heat sources, or use IC-rated (insulation contact) fittings and approved downlight covers.
Keep insulation clear of exhaust flues and chimneys.
Have old or damaged wiring checked by a licensed electrician before topping up or replacing insulation.

Professional installation is the simplest way to get clearances, facings and product selection right the first time. See our professional insulation installation service.

How to choose fire-safe insulation for your home

A quick checklist before you buy or install:

Match the material to the location and BAL. Ceiling, wall, party wall and bushfire zones all have different needs.
Favour non-combustible materials (glasswool, rockwool) wherever fire performance matters.
Check the fire rating on the data sheet – look at the AS 1530 indices, not the marketing.
Use the correct facing. A non-combustible batt with a combustible facing may not meet your requirement.
Install to clearances around downlights, flues and wiring or have it installed professionally.
Follow the NCC and confirm compliance with a professional or building surveyor for any fire-rated application.

Not sure where to start? OZ Homes can recommend, supply and install the right fire-rated insulation for your home. Request a free quote and talk to our team.

Frequently Asked Questions

Is insulation flammable?

It depends on the material. Bulk mineral-fibre insulation such as glasswool and rockwool is non-combustible, while spray foam, EPS and some facings are combustible. Cellulose is treated to be fire-retardant. In Australia, insulation must meet NCC fire requirements, so highly flammable products are not sold for standard building use.

Can insulation catch fire?

Most insulation does not ignite on its own. Fires usually start from an external heat source – recessed downlights, flues or faulty wiring and can then involve combustible insulation or facings. Correct clearances and professional installation greatly reduce the risk.

Which insulation is the most fire resistant?

Rockwool (mineral wool) is generally the most fire resistant, withstanding temperatures above 1,000°C without igniting. Non-combustible glasswool and products like James HardieFire are also excellent fire-rated choices.

Is glasswool / fibreglass insulation fireproof?

Unfaced glasswool is classed as non-combustible under AS 1530.1, so it will not burn. However, foil or paper facings can be combustible, so the facing matters when fire performance is critical.

Is spray foam insulation a fire hazard?

Polyurethane spray foam is combustible and must be protected by a thermal barrier. It is generally not recommended for bushfire-prone areas or where a non-combustible material is required.

What insulation is suitable for bushfire-prone (BAL) areas?

For higher BAL ratings under AS 3959, use unfaced non-combustible batts (glasswool or mineral wool) and avoid foil/paper-faced batts and many spray foams.

Is roof or ceiling insulation flammable?

Roof and ceiling insulation is commonly non-combustible glasswool or rockwool. The main fire risk is heat from recessed downlights or flues, so keep insulation clear of these or use IC-rated fittings.