Setting the record straight

Is cellulose insulation dangerous? Short answer: no.

There are pages online, mostly from companies that make their money ripping insulation out, telling you cellulose is “toxic”, full of “lead and asbestos”, a fire hazard and a magnet for rats. I’m the bloke who manufactures it. Here’s the truth on each claim, with a source you can check.

I’m Peter Johnson. I’ve pumped cellulose into more than 6,000 roofs over 40 years, and I make it myself in Queensland. I also fit batts every week, so I’ve got no reason to tell you anything but what I actually see in the roof.

Get an honest quote Call Peter, 0414 586 315

A real call-out: an electrician was certain the rats in her roof were nesting in the cellulose and wanted it ripped out — she hadn’t realised she also had polyester batts. Watch where the rats actually were: all through the batts, not one in the cellulose.

Claim vs reality

The five things the removal pages get wrong.

Each claim, then what's actually true, with a real Australian source for every answer.

“Cellulose is toxic and contains lead, asbestos and formaldehyde.”

It doesn't. My cellulose is recycled paper treated with borate (borax and boric acid), and nothing else. There is no added lead, no asbestos and no added formaldehyde in it. Borax is a natural mineral salt that's been in laundry powders and home remedies for over a century, about as toxic to people as table salt. Lumping it in a list next to lead and asbestos is meant to scare you into a removal job. The Australian Government's CSIRO actually notes it's glass-fibre and rockwool that may cause temporary skin, nose and eye irritation, and that cellulose is easy to handle.

“Cellulose is a fire hazard.”

It's treated with a borax / boracic-acid fire retardant during manufacture, and Sustainability Victoria's Energy Smart Housing Manual states plainly that this treatment ensures that, if the material does ignite, the flame will not spread. Borax melts around 734°C, roughly 200° above house-fire temperature. Hold a blowtorch to a handful and it chars and glows but won't carry a flame. Watch the test below and judge for yourself.

“Cellulose is a magnet for mice and rats.”

This is the one that gets me, because it's backwards. In 6,000 roofs I've pulled rat nests out of batt-insulated ceilings nearly every week, and I have NEVER pulled one out of a roof we pumped with cellulose. Have a look at the pest-control and removal pages making this claim: they don't show you a single photo of a rodent in cellulose, because rodents nest in the soft, loose voids that cut-to-fit batts leave. Dense-packed cellulose has no soft voids to burrow into, and the borate means there are no insects living in it for rats to feed on. I'm so sure of it I back it with a $1,000 Rodent Reward.

“Cellulose has been banned / has disappeared / doesn't meet current standards.”

Cellulose is made and sold in Australia right now, including by us, here in Queensland. It's manufactured to the current Australian materials standard AS/NZS 4859.1 and fire-tested to AS/NZS 1530.3, and it has had its own Australian Standard since 1981 (AS 2462). The Australian Government's yourhome guide says every insulation material sold in Australia must meet AS/NZS 4859. A product that's manufactured to the current standard and sold nationwide hasn't been banned and hasn't disappeared.

“Cellulose settles and causes ceiling sag or roof collapse.”

Cellulose R-value is rated at its settled density, and a correct install is pumped over-thick to that spec, so the rated R is what you keep. The settling stories come from under-filled cowboy jobs, not from correctly dense-packed cellulose. We install to a specified density and back it with a written Life-of-House Guarantee. “Roof collapse” from a properly pumped ceiling is just not a thing.

Sources: yourhome.gov.au (Insulation) for the standards and reflective-foil notes; Sustainability Victoria, Energy Smart Housing Manual for the fire-retardant statement; and CSIRO, Thermal Insulation for the handling note.

Show me, don't tell me

Rats nest in batts. Look at any roof.

The pest-control pages say cellulose is a “magnet for mice”, then illustrate it with photos of rodents in batts. Here's what I actually pull out of roofs.

Pale fibreglass batts torn open and burrowed into by rodents living in the insulation under a metal roof — Fibreglass batts torn open and burrowed into, rodents living in the insulation.

Rat nest matted into chewed white polyester batt insulation under a roof eave — A rat nest matted into chewed batt insulation under an eave.

Rodent urine staining and droppings soaked into a ceiling sheet, revealed when old batts were lifted — Rodent staining soaked into a ceiling, revealed when old batts were lifted.

The electrician who said “no way” to pump-in cellulose — and what changed his mind in the roof.

I’m so confident rats won’t nest in our cellulose that I back it with a $1,000 Rodent Reward. You can also read the honest version of the rodent question in rats in insulation.

“A fire hazard”? Watch the test

A blowtorch on bare cellulose.

Cellulose is treated with a borax / boracic-acid mix. Sustainability Victoria puts it plainly: that treatment “ensures that, if the material does ignite, the flame will not spread.” In this test I flame-tested 20-year-old cellulose against brand-new batts. Have a look at what happened.

I won’t print a specific fire rating unless I can show you our own AS 1530 certificate, but the government’s own wording and the test back what you see.

Source: Sustainability Victoria, Energy Smart Housing Manual (Fire safety) →

Follow the money

What do they want to pump in instead?

Usually foil (anticon) and blown fibreglass. I install batts too, and the polyester ones are genuinely good, so I’m not knocking glasswool’s fire behaviour. My point is narrower and it’s about what holds up in a real roof.

Reflective foil only works clean and with an air gap. The Australian Government’s yourhome guide notes that once foil is dusty or in contact with another surface its performance “diminishes towards zero”, and that condensation can form on the underside. In a 20-year-old roof that foil is usually torn, dusty and degraded, like the photos here, so it’s doing very little.

Blown and cut-to-fit products still leave the gaps. Loose batts are cut to bays and leave the soft voids rodents nest in, and gaps wreck the effective R-value. Dense-packed cellulose is one seamless, full-contact blanket with none of that.

See cellulose vs fibreglass batts, side by side →

Torn, degraded foil-backed glasswool anticon blanket exposed under a lifted sheet on an old red corrugated metal roof, too damaged to reseal — Degraded foil-backed anticon, torn and too far gone to reseal, a 20-year-old roof.

From the tools, on YouTube

Don't take my word for it, watch the roof.

A tradesman's review: why pump-in cellulose beats batts.

The roof in the video at the top of this page belongs to a customer who left us her own review — watch the homeowner’s video review.

More real-roof videos on our YouTube channel →

Straight answers

Cellulose myth questions, answered.

Does cellulose insulation contain lead or asbestos?+

No. Australian cellulose insulation is recycled paper treated with borate (borax and boric acid). It contains no added lead, no asbestos and no added formaldehyde. Any page that lists cellulose alongside lead and asbestos is describing what's in the bag incorrectly, usually to sell you a removal job.

Is cellulose insulation toxic or bad for your health?+

No. Borate is a low-toxicity mineral salt used because it's safer than many alternatives. The Australian Government's CSIRO notes it's glass-fibre and rockwool that may cause temporary skin, nose and eye irritation, and that cellulose is easy to handle (we still wear dust masks while pumping, as you would with any loose-fill).

Do rats and mice nest in cellulose insulation?+

In my experience, no. After 6,000 roofs I pull rat nests out of batt-insulated ceilings most weeks and have never pulled one out of a cellulose-pumped roof. Rodents nest in the loose voids that cut-to-fit batts leave; dense-packed cellulose has none, and the borate means no insects live in it for rats to feed on. We back it with a $1,000 Rodent Reward.

Is cellulose insulation banned in Australia?+

No. Cellulose is manufactured and sold in Australia today, including by us in Queensland, to the current standard AS/NZS 4859.1 and fire-tested to AS/NZS 1530.3. It has had a dedicated Australian Standard since 1981. It is neither banned nor obsolete.

Removal companies told me to rip out my cellulose and pump in fibreglass or foil. Should I?+

Get a second opinion from an installer, not a sales rep, before you remove anything. Correctly installed cellulose lasts the life of the house. Reflective foil only works with a clean surface and a maintained air gap (the Australian Government's guide notes its performance 'diminishes towards zero' once it's dusty or touching another surface), and in an old roof that foil is usually torn and degraded. If your existing cellulose is sound, topping over is usually the better job.

Read the full case for cellulose fibre →

Been told to rip your cellulose out? Get a second opinion first.

I’ll tell you honestly whether your existing insulation is sound or not, and I’ve got no reason to sell you a removal job you don’t need. Fill in the simple online form and you’ll have a detailed quote within 48 hours for most houses.

Get ya Quote started Now!Call Peter, 0414 586 315