Coarse or fine · the grades of Cellulose Fibre Insulation
Coarse or fine, the grade of Cellulose Fibre Insulation is a looks thing.
Some Queensland manufacturers mill their cellulose fibre coarse, with big paper flakes you can still read. We mill ours fine. Neither grade insulates better. The R-value comes from density and thickness while the fire behaviour comes from the fire-retardant loading, so both grades pass the same Australian standards. We mill finer for one reason: it looks better going in.
I’m Peter Johnson. The photo on this page is coarse-grade cellulose fibre we pulled out of a roof after roughly 30 years. It was still dry, still loose, still doing its job. Here’s what the grades actually are, what the standards actually test and what that old fibre proves.
Coarse grade, ~30 years in a roof
still dry, still loose, print still readable
Here’s the deal
A “grade” is just how finely the paper is milled.
Cellulose Fibre Insulation starts as recycled paper. Every manufacturer shreds that paper, treats it with fire retardant, then mills it into fibre. How far you take the milling is the grade. Mill it lightly and you get a coarse grade: bigger flakes, some with the newsprint still readable. Mill it further and you get a fine grade: a uniform grey fibre with no recognisable pieces of paper left in it.
Different Queensland manufacturers have settled on different grinds over the years. That’s not a quality ladder. It’s a factory choice, the same way two bakeries slice the same loaf at different thicknesses. Coarse or fine, it’s the same recycled paper carrying the same class of fire-retardant treatment, pumped into a ceiling at a specified density to reach a specified R-value.
What decides how the product performs isn’t the flake size. It’s the density it’s installed at for R-value and how much fire-retardant chemical is in the fibre for fire behaviour and vermin resistance. Those are the numbers the standards actually check, so that’s what the rest of this page walks through.
A coarse grade up close, after roughly 30 years in a roof. You can still read the print on the flakes. Our own product is milled much finer than this, yet in a ceiling both do the identical job.
AS/NZS 4859.1:2018, Section 4
The Australian standard has a whole section for cellulose fibre. Flake size isn’t in it.
AS/NZS 4859.1:2018 is the Australian standard for thermal insulation materials. Cellulose Fibre Insulation gets its own dedicated Section 4. Here is every technical requirement in that section, next to the question that matters: does the grind come into it?
| What Section 4 checks | The requirement | Does the grind matter? |
|---|---|---|
| Physical (Clause 4.2.1) | Stabilised density must sit between 20 and 70 kg/m³ | No. Coarse and fine grades both settle into that band. |
| Corrosion (Clause 4.2.2) | The fibre must not corrode metal, tested against the percentage of treatment chemical in the product | No. It’s a chemistry test. The chemical loading is what’s on trial, not the flake size. |
| Moisture (Clause 4.2.3) | Moisture absorptance under 20%, tested to ASTM C739 | No. Recycled paper fibre behaves the same either way. |
| R-value (ASTM C687 pathway) | Thermal resistance measured on the material at its installed density and thickness | No. The test measures the blanket you end up with, not the size of the flakes in it. |
So when two Queensland factories mill at different grades, both products front up to the identical checklist. Density band, corrosion, moisture, R-value at installed density: pass those and you’re a compliant product, whatever the grind. That’s why I’ll never tell you a competitor’s coarser product is inferior. It isn’t. AS/NZS 4859.1:2018, Standards Australia (Section 4, Cellulose Fibre Insulation) ↗
Fire
The fire test doesn’t care about the grind either. It cares about the chemical.
Fire isn’t tested inside AS/NZS 4859.1 at all; that standard’s own scope leaves fire performance out. Fire runs through the National Construction Code instead. NCC 2022 requires the Spread-of-Flame Index and the Smoke-Developed Index of a material to be determined under AS/NZS 1530.3, with insulation materials needing a Spread-of-Flame Index of 9 or less (and a Smoke-Developed Index of 8 or less where the Spread-of-Flame Index is over 5).
What gets a recycled-paper product through that test is the fire-retardant loading. Ours is boric acid, milled through every kilogram of fibre. Hold a flame to treated cellulose fibre and it chars where the flame touches, then it stops. It will not carry the flame across the blanket. Coarse grade or fine, the chemistry does that work, which is why compliant products of any grind behave the same way. Ask us for the current test certificate on our product any time; we’d rather show you the paperwork than quote numbers from memory.
NCC 2022 Vol. One, Specification 3, Clause S3C3 (form of test: AS/NZS 1530.3) ↗NCC 2022 Vol. One, Specification 7 (indices for insulation materials) ↗
Batch flame-testing our fine-milled fibre at the factory. Each clump has had a flame held to it: the fibre chars in a small crater where the flame touched, then self-extinguishes. The charring stops because of the boric acid loading, not the grind.
Vermin
There is no Australian vermin rating. For any grade, from anyone.
Here’s something most insulation websites won’t spell out: no numbered Australian vermin or fungal-resistance standard exists for loose-fill Cellulose Fibre Insulation. AS/NZS 4859.1 does carry an insect-resistance clause, but it applies to wool insulation (Clause 5.2.3). There is no equivalent clause for cellulose fibre. So if anyone quotes you a numbered “vermin rating” for a loose-fill product, ask which standard the number comes from. AS/NZS 4859.1:2018, Standards Australia ↗
What the industry actually relies on is the borate treatment. Rats, mice, cockroaches and silverfish avoid borate-treated fibre; it’s the same class of chemistry that does the fire work. That loading is measured by weight in the product, so once again the coarse grades from other Queensland manufacturers carry it the same way our fine grade does. The flake size has nothing to do with it. We’ve documented what rodents do to the alternatives in our guide to rodent damage in roof insulation.
“Won’t it settle or rot?”
That photo up top is the answer: roughly 30 years in a roof, still working.
People ask whether recycled paper can really last in a Queensland roof. We don't have to argue the point. We can show you fibre that already did it.
The coarse-grade fibre in the hero photo came out of a roof that had carried it for somewhere between 20 and 30 years. Look at what decades in a hot Queensland roof cavity did to it: nothing much. The flakes are intact. The print is still readable. It’s dry, it’s loose, it hadn’t rotted, matted or turned to dust. It was still sitting at depth doing its job; the only reason it came out was that the owner was renovating.
That’s the strongest answer I can give to the settling and rotting worries. A product that was milled coarse decades ago, installed with the equipment of the day, was still performing when we vacuumed it out. Today’s product, pumped dense to a settled density with modern gear, starts from a better position than that fibre ever had. The full story on settling is in our guide: does Cellulose Fibre Insulation settle?
What decades in a roof proved
- Still dry after decades under a Queensland roof, with no rot or mould in the fibre.
- Still loose and still at depth. It hadn’t collapsed into a mat or blown into corners.
- The borate treatment was still in the fibre, which is why vermin had left it alone.
- A coarse grade did all that. The grind never was the thing keeping it working; the density and the chemistry were.
So why do we mill finer?
Because a fine grade looks better in your roof. That’s it.
After everything above, you might wonder why we bother milling our fibre finer than some other factories do. The answer is simple: appearance. A fine grade pumps into a ceiling as an even, uniform grey blanket. There are no recognisable bits of newspaper looking back at you when you put your head through the manhole. When a customer or a building inspector looks at one of our jobs, it looks like a manufactured insulation product, so that’s the finish we choose to put our name on.
It costs us more milling time per bag to get there. We think the finish is worth it. But we won’t dress that up as a performance advantage, since the standards make clear it isn’t one. If you’re comparing quotes between Queensland manufacturers, compare the installed R-value, the installed density, the service and the guarantee. Don’t let anyone sell you a grind, in either direction. See how the product itself stacks up against the alternatives in cellulose fibre vs polyester and the full case in why cellulose fibre.
Straight answers
Grade questions people ask.
Is fine-milled Cellulose Fibre Insulation better than coarse-milled?+
No. The grade is a looks thing. The R-value of a pumped ceiling comes from the density and thickness of the blanket, which is exactly what the Australian standard measures. The fire behaviour comes from the fire-retardant loading. The vermin resistance comes from the borate treatment. None of those change with how finely the recycled paper is milled. We mill ours fine because it goes into a roof looking neater. That is the whole reason.
Does the grade change the R-value?+
No. Under AS/NZS 4859.1:2018 the thermal resistance of loose-fill insulation is measured with the material installed at its working density and thickness, using the ASTM C687 test method. The test measures the finished blanket, not the flake size. A coarse grade installed at its chart density delivers the R-value on its chart the same way a fine grade does.
Do the coarser grades from other Queensland manufacturers meet the same standards?+
Yes. Every Queensland manufacturer of Cellulose Fibre Insulation works to the same Section 4 of AS/NZS 4859.1:2018 for density, corrosion and moisture, the same ASTM C687 pathway for R-value and the same NCC fire-hazard test in AS/NZS 1530.3. A coarser mill from another factory is not a lesser product. We compete on service, on price and on how the job looks, not by rubbishing another manufacturer's grind.
Is there an official Australian vermin rating for Cellulose Fibre Insulation?+
No. There is no numbered Australian vermin or fungal-resistance standard for loose-fill Cellulose Fibre Insulation. AS/NZS 4859.1 has an insect-resistance clause for wool insulation (Clause 5.2.3) but no equivalent clause for cellulose fibre. The vermin resistance the industry talks about comes from the borate treatment in the product, which vermin avoid. If a salesman quotes you a numbered vermin rating for any loose-fill product, ask him which Australian standard the number comes from.
Will Cellulose Fibre Insulation still be working after 20 or 30 years?+
Yes, when it went in at the right density. The photo at the top of this page is coarse-grade cellulose fibre we took out of a roof after roughly 30 years of service. It was dry, it was loose, the newsprint on the flakes was still readable and it was still holding its depth. That is what a properly installed job looks like decades later, coarse grade or fine.
The documents
Every claim on this page, linked to where it came from.
- AS/NZS 4859.1:2018, Thermal insulation materials for buildings, Part 1 — Standards Australia ↗ — Section 4 (Cellulose Fibre Insulation): stabilised density 20–70 kg/m³, corrosion tested against the chemical percentage, moisture absorptance under 20% to ASTM C739; R-value for loose-fill via the ASTM C687 pathway; fire performance excluded from the standard’s own scope; insect-resistance clause applies to wool only (Clause 5.2.3).
- NCC 2022 Volume One, Specification 3 'Fire hazard properties', Clause S3C3 — ABCB ↗ — the Spread-of-Flame Index and the Smoke-Developed Index must be determined in accordance with AS/NZS 1530.3.
- NCC 2022 Volume One, Specification 7 'Fire hazard properties' — ABCB ↗ — for insulation materials other than sarking-type materials: Spread-of-Flame Index no more than 9, Smoke-Developed Index no more than 8 where the Spread-of-Flame Index is more than 5.
The 20-to-30-year figure for the coarse-grade fibre in the photos is our own job record from the removal, not a laboratory claim. Where this page states our own product’s test results, ask us for the current manufacturer’s test certificate; we show the paperwork rather than quote numbers from memory.
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What our customers say
Genuine Google & hipages reviews from Comfort Zone customers across SE Queensland.
- A
Angela M.
SE Queensland
“The fact that I can't even tell it's 6 degrees outside when I wake up in the morning speaks for itself. Have wasted so much money attempting to heat and cool an uninsulated home. Worth every $.”
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P Peter
Alstonvale, 2024
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Jessa B.
Brisbane
“It dropped about 4 degrees straight away, and we added another 3 with the second job. I appreciate Peter's honesty, and the team showed pictures before and after.”
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Birtinya, 2024
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Brisbane
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Upper Caboolture, 2024
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Gerry S
Fitzgibbon, 2023
“I used Comfort Zone and they have a done an excellent job.”
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Jennifer
Upper Caboolture, 2024
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Jung K
Riverhills, 2023
“An experienced family operation. Highly recommend. Thank you for the great job!”
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Diane A
Ormeau, 2024
“Peter and crew did a great job I would definitely recommend them”
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David H
Sunshine Coast, 2021
“Completed the job as quoted and to a high standard. Great personal service. Would highly recommend Comfort Zone for ceiling installation work.”
- Thipages
Timea
Highland Park, 2023
“I was extremely satisfied with the service they provided. They gave a very thourough explanation of the materials used, the way the work will be carried out and the price I had to pay was the exact amount quoted, no hidden costs included. They arrived on time, well prepared and workwas carried out exactly how they said it would be, they were super efficient, well prepared and were kind enough to even clean up after themselves. The services they provided was second to none! I don't hesitate to recommend them for any insulation job!”
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Benjamin H
Carseldine, 2019
“Very good explanation about their works. Advice of existing problems with the roof. Clean work. Very professional.”
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Mark
Pottsville, 2017
“Michelle, we are done - Peter from comfort zone insulation was very helpful. very honest with his recommendations - in fact he told me that the product my daughter had if installed correctly was superb. Thanks Peter you are a champion and i would recommend you to any person that was wanting professional advice and old school service.”
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Ian G
Burnside, 2019
“Good information, communication and professionalism.”
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Jessica
Pottsville, 2016
“This business offers a fantastic product that other businesses did not. Pump in ceiling insulation. Knowledge of the industry second to none.”
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Danny D
Boondall, 2018
“He explained everything he was going to do and the different types of insulation they used. He talked through the different options but made a recommendation for the one most people use, which is the one I chose. He was very understanding towards what I needed and not about himself.”
- Jhipages
Jack
Pottsville, 2023
“Excellent communication and informative. Professional.”
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Graham R
Riverhills, 2018
“Comfort Zone. Turned up ahead of time, completed in about 2 hours, cleaned up. All good. Very motivated installation team.”
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Tony P
Redland Bay, 2023
“Very knowledgeable about insulation”
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Alex B
West Ipswich, 2018
“Fast, friendly, efficient.”
- Shipages
Steve
Redland Bay, 2017
“Excellent job and reasonable price.”
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Luke D
Mcdowall, 2017
“Peter did a good job. It was a quick and clean service. I'm happy to recommend!”
- Bhipages
Bruce H
Kuluin, 2023
“Prompt and efficient quoting.”
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Brendon
Brays Creek, 2016
“Peter supplied and installed roof insulation for me. He was very informative and provided good advice.”
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Gerry S
Fitzgibbon, 2023
“I used Comfort Zone and they have a done an excellent job.”
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Trevor G
Brookside Centre, 2016
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Tamara
Underwood, 2023
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John G
Beaudesert, 2019
“Peter is an honest person who provided me with the information I wanted then performed a good job with great results for the benefit of myself and my family.”
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Sterling G
Ashgrove, 2023
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Graham R
Riverhills, 2018
“Comfort Zone. Turned up ahead of time completed in +- 2 hours cleaned. All good. Very motivated installation team”
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Jung K
Riverhills, 2023
“An experienced family operation. Highly recommend. Thank you for the great job!”
- Khipages
Kathy A
North Lakes, 2023
“We connected with Peter through HiPages and he was prompt, professional and even came back after the job was complete to assist with a question we had. We would highly recommend Peter for further insulation works.”
- Dhipages
David H
Sunshine Coast, 2021
“Completed the job as quoted and to a high standard. Great personal service. Would highly recommend Comfort Zone for ceiling installationn work.”
- Shipages
Sue H
Sunshine Coast, 2021
“Incredible customer service”
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Eileen C
Cedar Vale, 2021
“Quality work, good customer service, prompt”
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Craig M
Woody Point, 2021
“Called within 5 minutes of request. Very knowledgeable and explained job in great detail, provide great advice in prior preparation for works required. Very friendly and helpful.”
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Jenny C
Plainland, 2021
“Although I did not hire Peter I was impressed with the initial contact and the knowledge he was willing to impart. I was treated with respect which I appreciated. I would have hired but I received a lower quote.”
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Quinton
Coomera, 2020
“Professional installation without any short cuts. True to their word with high integrity. Response from Comfort Zone Insulation”
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Gary P
West Kempsey, 2020
“Came & Gave a free quote”
Whatever the grade, the job is only as good as the density it’s pumped at.
Send us your address and roof type. We’ll give you a fixed price for Australian-made Cellulose Fibre Insulation pumped to its settled density, backed by the Life-of-House Guarantee, with no inspection needed first.