Does cellulose settle? · here’s what actually happens
Does cellulose insulation settle? A little, then it stops. About 90% on day one.
Any loose-fill can settle a little. But we pump ours dense and quote the settled R-value, so there’s little left to settle out of, and because we install R3.0 over the ~R2.5 code minimum, a minor settle over decades still leaves you above what the NCC asks. The real enemy of ceiling insulation isn’t settling. It’s gaps.
I’m Peter Johnson. After 40 years and 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 1986
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.
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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 $.”
- Phipages
P Peter
Alstonvale, 2024
“Connected with Comfort Zone Insulation and would recommend them”
- 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.”
- Nhipages
Nola M
Birtinya, 2024
“They were courteous and competent.”
- 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.”
- 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.”
- G
Gerry S
Fitzgibbon, 2023
“I used Comfort Zone and they have a done an excellent job.”
- Jhipages
Jennifer
Upper Caboolture, 2024
“Excellent customer service. Highly recommend. Has a profound knowledge of insulation products and has the customer best interest.”
- J
Jung K
Riverhills, 2023
“An experienced family operation. Highly recommend. Thank you for the great job!”
- Dhipages
Diane A
Ormeau, 2024
“Peter and crew did a great job I would definitely recommend them”
- D
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!”
- B
Benjamin H
Carseldine, 2019
“Very good explanation about their works. Advice of existing problems with the roof. Clean work. Very professional.”
- 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.”
- I
Ian G
Burnside, 2019
“Good information, communication and professionalism.”
- 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.”
- D
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.”
- G
Graham R
Riverhills, 2018
“Comfort Zone. Turned up ahead of time, completed in about 2 hours, cleaned up. All good. Very motivated installation team.”
- Thipages
Tony P
Redland Bay, 2023
“Very knowledgeable about insulation”
- A
Alex B
West Ipswich, 2018
“Fast, friendly, efficient.”
- Shipages
Steve
Redland Bay, 2017
“Excellent job and reasonable price.”
- L
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.”
- B
Brendon
Brays Creek, 2016
“Peter supplied and installed roof insulation for me. He was very informative and provided good advice.”
- Ghipages
Gerry S
Fitzgibbon, 2023
“I used Comfort Zone and they have a done an excellent job.”
- T
Trevor G
Brookside Centre, 2016
“Excellent tradesmen from Comfort Zone Insulation. They were punctual and cleaned up after. Highly recommended.”
- 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”
- J
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.”
- 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 specified settled density of around 35–50 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: there’s nothing left to settle out of. 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 blows it in light and airy so the bags go further, it slumps, and it opens up. Pack it to the right density and it stays put. 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 1986
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, ~35–50 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 |
Industry research finds settling is virtually nil once cellulose is packed to around 3.5 lb/ft³. That’s precisely why coverage charts are written at settled density. So 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, thirty years of making and pumping the stuff 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.
Thirty years of making it and pumping it
Settling timing is where I disagree with CSIRO — a day, not twenty years.
Clarke was right that it settles. I don't think he had the timing right. There's a bit of physics the settling argument usually leaves out.
The picture people have is a slow sag over twenty years, with your R-value quietly draining away. That’s not what I see in roofs. At the depth we install, cellulose does about 90 per cent of whatever settling it’s ever going to do within a day of going in. Come back in a decade and it’s sitting where it was sitting that first week.
What actually moves it is moisture, and I’ll be upfront about that. 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.
The bit that gets left out: settling makes it denser
Everyone treats a 10 per cent drop in depth as a 10 per cent drop in R-value. It isn’t, because the same amount of fibre is now packed into less space. Cellulose has a density where it performs at its best, and a pumped ceiling that settles a little moves towardsthat point rather than away from it. The fibre conducts heat a bit more slowly once it’s denser, and that offsets most of the thickness you lost.
That’s the practical difference between loose-fill settling and a batt going flat. A squashed batt is just a thinner batt, and it has lost exactly what it looks like it’s lost. Settled cellulose is a denser blanket, and the density is working in your favour.
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 small, gradual settle over many years 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 slow and minor in a dense install, measured over decades, not something that happens to your power bill next winter. By the time any of it could matter, you’re still 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 minor settle over decades 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 1986
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 1986
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 1986
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. The Australian Government's CSIRO says so plainly. And we won't pretend otherwise. But how much comes down to how densely it's installed. We pump our cellulose to a specified settled density (around 35–50 kg/m³), so it goes in already packed to the depth it will hold, not fluffed up to look thick on day one. At the dense end of that range settling is minimal. The R-value we quote is the settled R-value. There's nothing left to settle out of. The settling horror stories come from under-filled jobs blown 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 ~100 mm Australian ceiling install is a completely different animal, far less depth pressing down, far higher density. Industry research finds settling is virtually nil once cellulose is packed to around 3.5 lb/ft³, and the very reason coverage figures are quoted at settled density is 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. We're not going to tell you physics works differently for us. The point is the size and the timeframe. Pumped dense, any settling is small and happens slowly over years, not overnight. And we deliberately install around R3.0 when the NCC minimum for our climate zone is about R2.5 (roughly 20% over), so even a minor settle over decades still leaves you at or above what the building code actually asks for. You bought a buffer.
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 transferable Life-of-House Guarantee. 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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Send me your address and roof type and I’ll work out the settled R-value for your climate, then give you a fixed-price quote, pumped dense, gap-free, and backed by the Life-of-House Guarantee. No deposit, no upselling.