Does cellulose settle? · here’s what actually happens
Does cellulose insulation settle? A little, and we pump it deep enough to allow for it.
Any loose-fill can settle a little. But we pump our premium cellulose insulation dense and quote the settled R-value, so settling is minimal, and because we install R3.0 over the ~R2.5 code minimum, a little settling over the life of the product still leaves you above what the NCC asks. The real enemy of ceiling insulation isn’t settling. It’s gaps.
I’m Peter Johnson, insulating homes since 1988, 6,000-plus roofs. Here’s the straight story on settling: the bit that’s true, the scary numbers that don’t apply to a proper job, and the thing that actually wrecks ceiling insulation that nobody talks about.
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1988
Pumped to settled density
the R-value you’re quoted is the one you keep
Real reviews, real jobs
What our customers say
Genuine Google & hipages reviews from Comfort Zone customers across SE Queensland.
- J
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.”
- Ahipages
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 $.”
- I
Iain V-B.
Brisbane
“Quick and polite service. Great follow-up advice and photos sent for our records. Above and beyond what we expected. Would highly recommend.”
- Ghipages
Gerry S
Fitzgibbon, 2023
“I used Comfort Zone and they have a done an excellent job.”
- Jhipages
Jung K
Riverhills, 2023
“An experienced family operation. Highly recommend. Thank you for the great job!”
- 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 installation work.”
- Bhipages
Benjamin H
Carseldine, 2019
“Very good explanation about their works. Advice of existing problems with the roof. Clean work. Very professional.”
- Ihipages
Ian G
Burnside, 2019
“Good information, communication and professionalism.”
- Dhipages
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.”
- Ghipages
Graham R
Riverhills, 2018
“Comfort Zone. Turned up ahead of time, completed in about 2 hours, cleaned up. All good. Very motivated installation team.”
- Ahipages
Alex B
West Ipswich, 2018
“Fast, friendly, efficient.”
- Lhipages
Luke D
Mcdowall, 2017
“Peter did a good job. It was a quick and clean service. I'm happy to recommend!”
- Bhipages
Brendon
Brays Creek, 2016
“Peter supplied and installed roof insulation for me. He was very informative and provided good advice.”
- Thipages
Trevor G
Brookside Centre, 2016
“Excellent tradesmen from Comfort Zone Insulation. They were punctual and cleaned up after. Highly recommended.”
- Jhipages
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.”
- Phipages
P Peter
Alstonvale, 2024
“Connected with Comfort Zone Insulation and would recommend them”
- Nhipages
Nola M
Birtinya, 2024
“They were courteous and competent.”
- Jhipages
Jennifer's E
Upper Caboolture, 2024
“Excellent customer service. Highly recommended. Has a profound knowledge of insulation products and has the best interest of his customer.”
- Jhipages
Jennifer
Upper Caboolture, 2024
“Excellent customer service. Highly recommend. Has a profound knowledge of insulation products and has the customer best interest.”
- Dhipages
Diane A
Ormeau, 2024
“Peter and crew did a great job I would definitely recommend them”
- 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!”
- Mhipages
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.”
- Jhipages
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.”
- Jhipages
Jack
Pottsville, 2023
“Excellent communication and informative. Professional.”
- Thipages
Tony P
Redland Bay, 2023
“Very knowledgeable about insulation”
- Shipages
Steve
Redland Bay, 2017
“Excellent job and reasonable price.”
- Bhipages
Bruce H
Kuluin, 2023
“Prompt and efficient quoting.”
- Ghipages
Gerry S
Fitzgibbon, 2023
“I used Comfort Zone and they have a done an excellent job.”
- Thipages
Tamara
Underwood, 2023
“Peter is honest, hard-working and came on time. Knew excally what he was talking about and answered my questions. Would 100% recommend”
- Shipages
Sterling G
Ashgrove, 2023
“Comfort Zone were very knowledge with great communication and follow up”
- Ghipages
Graham R
Riverhills, 2018
“Comfort Zone. Turned up ahead of time completed in +- 2 hours cleaned. All good. Very motivated installation team”
- Jhipages
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”
- Ehipages
Eileen C
Cedar Vale, 2021
“Quality work, good customer service, prompt”
- Chipages
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.”
- Jhipages
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.”
- Qhipages
Quinton
Coomera, 2020
“Professional installation without any short cuts. True to their word with high integrity. Response from Comfort Zone Insulation”
- Ghipages
Gary P
West Kempsey, 2020
“Came & Gave a free quote”
Here’s the deal
Yes, loose-fill can settle, so the trick is how it’s installed.
Cellulose settles. Any loose-fill insulation can settle a little over time. The Australian Government’s CSIRO says so plainly. What decides how much is the install density. We pump our cellulose to a density of 35 kg/m³, so it goes in already packed to the depth it’ll hold, not fluffed up to look thick on day one.
That matters because the R-value we quote you is the settled R-value. It’s the figure the coverage charts are built around. It’s what our transferable Life-of-House Guarantee is written against. In plain terms: we allow for a little settling when we pump it in. We didn’t sell you day-one fluff in the first place.
The settling horror stories people hear about loose-fill all trace back to the same thing, an under-filled job. A cowboy pumps it in light and airy so the bags go further, it slumps, and it opens up. Pack it to the right density and settling is minor. The Australian Government’s yourhome guide tells you how to protect yourself in one line: ask your contractor for a guaranteed settled R-value, not a day-one number. That’s exactly what we install to.
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1988
Cellulose pumped to a settled density, full-depth and even. Packed right, it holds its depth. This is what “rated at settled density” looks like in a real roof.
Where the “20% settling” line comes from
The 20% settling figure comes from a different job entirely.
If you've read that cellulose settles 20%, or loses 6–10% of its R-value, that's real research. But read the fine print. It describes a deep, low-density North-American attic blow, not a dense Australian ceiling pump.
| The “cellulose settles a lot” studies | How we pump a ceiling | |
|---|---|---|
| Depth | Deep attic blow, ~250–300 mm | Shallow ceiling, ~120 mm, far less weight pressing down |
| Density | Low, ~24–34 kg/m³ (light open blow) | Dense, 35 kg/m³, packed to hold |
| How “settling” was measured | Forced in a lab by striking the ceiling. The Oak Ridge researchers said it “may or may not” represent real in-service settling | Real roofs, packed once to settled density and left alone |
| R-value quoted as | Day-one thickness (so settling eats into it) | Settled density, the number you keep |
Coverage charts for cellulose are written at settled density, so the number you’re sold is the number you keep. The takeaway isn’t “ours never moves”. It’s “we install it dense and quote you the settled figure, so you’re not paying for fluff that disappears.”
“It’ll blow around and there’ll be nothing left”
CSIRO's project leader called the blow-around claim erroneous in 1996.
Someone was told their cellulose needed a sprayed-on coating or the wind would shift it all to one end of the roof. They asked CSIRO. We hold a copy of the reply.
Both pages of the letter, 25 July 1996. We’ve blacked out the name and address of the person who wrote in, and taken CSIRO’s logo off the letterhead. They don’t allow their logo on a commercial site without permission and an agreement, so it comes off rather than us paying for it. The letter itself is untouched, and the highlighting was already on our copy when we got it.
It was written by Robin Clarke, then Project Leader of CSIRO’s Building Insulation Project, and he signed it himself. Worth knowing who he was writing to: someone in a dispute with a cellulose installer. He wasn’t doing our industry a favour.
On his own credentials he wrote that almost all thermal testing of insulation in Australia was done at his division under his supervision, and that over ten years that came to about 60 formal test measurements on cellulose fibre alone. Then he dealt with the spray-coat claim, which he’d been told meant that without it there would be “nothing left in 2 years”:
“I am able to confirm that this is an erroneous statement.”
In ten years he’d had exactly one verbal report of insulation stacking up in a roofspace, from a builder in Gippsland, and even that one he couldn’t rule out as someone or something having been up there. Against it he set “literally hundreds of conversations” with builders, installers and homeowners where nobody reported it. And in a formal settlement study his division ran for an industry client, measuring movement in a number of roofspaces, he recorded “no bulk movement of material”.
He also checked how common the spray coating actually was. The industry association told him it was used on under 10% of houses nationally, and virtually never in Victoria or South Australia. His comment on that: the fact usage is so low “does nothing to support the proposition that it is essential”.
Now the three bits that don’t suit me
The whole letter is up there for you to read, page two and all. Check what I’ve quoted against it.
- He says all loose fill settles a bit. His answer is that installers should put in about 10% more thickness up front to allow for it. He was blunt about the trade too: installers of cellulose had “a very poor understanding of this issue” because they took no measurements and rarely went back. On the trade, he had a point. It’s exactly why we install to a settled density and photograph the finished depth rather than eyeballing it. On the settling itself, making and pumping the stuff since 1988 has me disagreeing with him, and I set out why in the section below.
- Open eaves are a real exception. He allowed that some movement at the edge of a ceiling is “plausible” on windy days in a house with very open eaves. If your eaves are sealed the normal way, he said it doesn’t arise.
- He wouldn’t promise R2.5 in a 90 mm space. He called that unachievable with cellulose and put it at R2.2 to R2.4 instead, adding that packing it denser doesn’t fix it because the fibre performs best at about 40 kg per cubic metre and gets slightly worse either side of that. He called the shortfall “fairly minimal”, but it’s a shortfall. If you need a certain R-value in a shallow space, that’s a depth conversation before you buy, not an argument afterwards.
Twenty years in a roof
A twenty-year-old cellulose job — no rat nests, no smell, same depth.
We vacuumed this one out because the owner was replacing ceilings, not because anything was wrong with it. Twenty years in a Queensland roof: no rat nests, no droppings, no smell, and it came out at the depth it went in.
Vacuuming out a 20-year-old cellulose job
A 20-year-old cellulose job vacuums out clean — no rats, no rodents, no piss or shit, and no fibres in the air.
Read the transcript
So we're just vacuuming the cellulose out of the ceiling and you can see here we've already done a lot of the rest of the roof and we're just up to here and so this is how the job's done. Good as gold. And we've got another guy down on the truck who's filling the bags up and clipping them up as we go and you can see how easy it is to vacuum it up with the machines that we use. This would be a big pile to do if we're trying to do it with a normal vacuum cleaner. So if you want a quote for vacuuming your ceiling out we're happy to do that and as you can see it's not an issue if you ever needed to do any work with the roof or ever had any damage or that, we can just pull the stuff out again and obviously the insurance company normally pays for us to come and vacuum it up if you've had a roof leak or something. So it's just as easy to pull this out as it is to pull batts out.
Making it and pumping it since 1988
Where I disagree with CSIRO on settling.
Clarke was right that it settles. I don't think it keeps going the way people picture it. There's a bit of physics the settling argument usually leaves out.
The picture people have is a slow sag, with your R-value quietly draining away. That’s not what I see in roofs. Our premium cellulose insulation settles a little at first, then the fibres knit together and hold their own weight, so the insulation keeps the depth that keeps your home comfortable. We allow for that little bit of settling when we pump it in, and in all my jobs I’ve never had to come back for settling.
What actually moves it is moisture. Cellulose takes up atmospheric moisture, and under a tile roof a decent rain event pushes damp air right through the cavity. That added weight presses the blanket down a little. The same thing flattens fibreglass batts in those roofs, which is why you so often find old batts in a tile roof lying thinner than the day they went in.
Our premium cellulose insulation depth chart
We pump our premium cellulose insulation to the depth in the second column and measure it from the ceiling before we leave. It can settle to the depth in the third column and still give the R-value on your certificate, so the figure you paid for is the figure you keep for the life of the product.
| R-value | We pump it to | Still that R-value down to | Bags per 100 m² |
|---|---|---|---|
| R2.0 | 80 mm | 70 mm | 18 |
| R2.5 | 100 mm | 88 mm | 22 |
| R3.0 | 120 mm | 105 mm | 26 |
| R3.5 | 140 mm | 123 mm | 31 |
| R4.0 | 160 mm | 140 mm | 35 |
| R4.5 | 180 mm | 158 mm | 39 |
| R5.0 | 200 mm | 175 mm | 44 |
| R5.5 | 220 mm | 193 mm | 48 |
| R6.0 | 240 mm | 210 mm | 53 |
- We allow for about 10% settling over the life of the product, so the depth we pump to already has that built in and the R-value on your certificate stays the same while the depth is at or above the minimum.
- Laboratory testing of cellulose made to our formula measured R3.0 at about 105 mm. That test is where the minimum column comes from, so every depth in the chart is one you can check with a ruler.
- Measure the depth from the ceiling, not from the top of the joists. The ceiling is where the insulation starts working, and joist heights vary from house to house.
- Bags per 100 m² is our planning figure. Our quote is a fixed price, so how many bags the job takes is our cost, not yours.
Which is also why we pump to a settled figure rather than a fluffed-up day-one number. The R-value on your quote is the one that’s still there after it’s done its settling. Measure what’s in your roof and read the R-value off.
You bought a buffer
Even if it settles a little, you’re still over what the code asks.
Here in South East Queensland (NCC climate zone 2) the minimum added ceiling insulation the building code asks for is about R2.5. We install around R3.0 as standard, roughly 20% over. So a little settling over the life of the product still leaves you at or above the figure the code actually requires. You paid for a margin, and the margin does its job.
Settling isn’t a cliff. It’s minor in a dense install and allowed for over the life of the product. If any of it could ever matter, you’d still be sitting on more insulation than Brisbane’s climate calls for.
Ceiling R-value, zone 2
That ~20% gap between what we install and what the code asks is the buffer. A little settling over the life of the product eats into the top of it, not into your compliance, and not into your comfort.
The thing nobody warns you about
The real enemy of ceiling insulation isn’t settling. It’s gaps.
Worry less about a few millimetres of settle and more about this: a rating only counts if the insulation actually covers the whole ceiling. That's where batts quietly fail, and where pumped cellulose wins.
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1988
Batts: cut to fit, shoved around, gappy
Batts are cut to fit and nearly always leave gaps over wires, battens and around fittings. Worse, over the years the sparky, the plumber and the air-con installer climb up there, shove them aside and leave them open. Even a small uninsulated percentage of a ceiling drags the effective R-value down sharply, per Sustainability Victoria’s government nomogram. That’s why an R5 batt often isn’t an R5 once it’s lived in your roof a few years.
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1988
Cellulose: no cut lines, dense, stays put
Pumped cellulose fills right into every corner as one seamless blanket, no cut lines, no gaps over the wiring. And because it’s dense, it’s hard for other trades to push out of the way, so the job you paid for stays in good condition for decades. A gap-free R3.0 beats a gappy R5 every single time. The rating you bought is the rating you actually get.
So when someone tries to scare you about cellulose settling a few millimetres, ask them what their batts look like after ten years of tradesmen walking through them. Mine still look like the day we pumped them. See cellulose vs fibreglass batts →
One exception
Water, not gravity, is what compacts a packed ceiling.
There’s one situation where a properly-packed cellulose ceiling can compact a little, and it’s not the product’s fault. On an older tile roof that lets a fine mist of water in during heavy rain (through gaps between tiles, a tired whirlybird or a small leak), that incidental moisture adds a bit of weight on top of the cellulose. Over many seasons of wetting and drying, that can press it down slightly.
That’s a roof problem, not an insulation problem. Cellulose is hygroscopic: it handles incidental moisture and dries back out, regaining its dry performance once the water source is fixed. The fix is the roof, not ripping out good insulation. If we ever see it on a job, we’ll tell you straight where the water’s really coming from.
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1988
Where a roof leaks, cellulose tends to hold the damage to one spot and dry back out, which actually helps us find the leak. The insulation isn’t the problem; the roof is.
Straight answers
Settling questions I get asked most.
Does cellulose insulation settle?+
Any loose-fill insulation can settle a little over time, and the Australian Government's CSIRO says so plainly. We pump our premium cellulose insulation to 35 kg/m³ and to the depth in our depth chart, which already allows for about 10% settling over the life of the product, so the R-value on your certificate stays the same. The settling horror stories come from under-filled jobs pumped in light and airy, not from a roof packed to the right density.
Doesn't cellulose settle by 20%? I read that somewhere.+
That figure, and the lab number of a 6–10% R-value drop from a 9% settle, comes from deep North-American attic blows: loose-fill piled 250–300 mm thick at a low density of about 24–34 kg/m³, and in the lab study the settling was forced by hitting the ceiling, which the US Government's Oak Ridge researchers themselves said 'may or may not' represent real in-service settling. A dense, shallow 120 mm Australian ceiling install is a completely different animal, far less depth pressing down, far higher density. Coverage figures for cellulose are quoted at settled density, so the number you're sold is the number you keep.
If it settles a bit, do I lose R-value?+
If a layer loses thickness, it loses some R-value with it, so we pump our premium cellulose insulation deep enough to cover it. R3.0 goes in at 120 mm from the ceiling and laboratory testing of cellulose made to our formula measured R3.0 at about 105 mm, so it can settle about 10% and your certificate still says R3.0. On top of that we install R3.0 where the NCC minimum for our climate zone is about R2.5, so you bought a buffer twice over.
Will cellulose leave gaps the way batts do?+
No, and this is the part that actually matters for your power bill. Batts are cut to fit and nearly always leave gaps over wires, battens and around fittings, and over the years electricians, plumbers and air-con installers shove them out of place and leave them open. Even a small uninsulated percentage of a ceiling drags the effective R-value down sharply (per Sustainability Victoria's government nomogram). Pumped cellulose fills in as one seamless blanket with no gaps, and because it's dense it's hard for other trades to move, so your ceiling stays in good condition far longer. A gap-free R3.0 beats a gappy R5 every time.
Does your guarantee cover settling?+
Yes. We install to a specified settled R-value and back it with our Life-of-House Guarantee on cellulose, transferable for $150. We allow for a little settling when we pump it in. The Australian Government's yourhome guide tells you to ask your contractor for a guaranteed settled R-value rather than a fluffy day-one number. That's exactly what we install to, and what we stand behind.
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