Guide · Dust in the house · Cellulose Fibre Insulation
Is my cellulose coming through my ceiling? Here is what a customer found when he checked.
Almost never. A plaster ceiling is sealed, and settled Cellulose Fibre Insulation does not blow around. The grey fluff in your vacuum is house dust. The only way through is a gap around an old downlight.
A customer in Brisbane’s southside got in touch in September. Dust kept turning up around the house and the vacuum was full of it, so he figured the cellulose in his roof had to be coming through the ceiling. Fair enough, that is what it looks like when you don’t know what you are looking at. He did the right thing. He went up, took photos of what was in the roof, then pulled a real pinch of it out and put it next to what was in his vacuum. The photo is below. They are two different things, and that one picture answers the question better than I can.
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1986
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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.”
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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”
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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.”
- 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.”
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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.”
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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.”
- 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”
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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.”
- 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”
A plaster ceiling is sealed. Loose-fill does not fall through plasterboard.
Your ceiling is sheets of plasterboard screwed to the joists, with the joints set and painted. Nothing granular comes through that. In forty years of putting Cellulose Fibre Insulation into Queensland roofs I have never seen it come through a ceiling after the job. While we are pumping, a few crumbs can drop through a gap around a light fitting, and the crew vacuums those up before they leave. After that it does not move, because once it is down it does not blow around.
The one exception is an old-style downlight with an open gap around the can. If fluff is reaching the room, that is the only door it has, and the fix is the fitting, not the insulation. The US cellulose industry’s own installation standard says it plainly: “Holes in ceilings or sidewalls that would allow the insulation to escape should be sealed” CIMA Technical Bulletin, Feb 2023, p.5 ↗. Your Home says older halogen and incandescent downlights “cannot be covered with insulation as it is a fire risk” and “should be removed and replaced with IC-4 rated LEDs” Your Home, Insulation ↗. We recommend replacing halogen and 240-volt fittings with sealed IC-4 rated LEDs, which is a job for your electrician. That closes the door and takes a fire risk out of the roof at the same time. Our guide to downlights and insulation covers the ratings and clearances.
It looks light. It is heavier than batts.
People assume Cellulose Fibre Insulation blows around because it goes in through a hose and looks fluffy on the way in. It is denser than the batts it replaces. CSIRO’s own table puts loose-fill cellulose fibre at about 35 kilograms per cubic metre, against 8 for a low-density glass fibre batt and 16 for a medium-density one CSIRO, Thermal Insulation, 2021, Table 1 ↗. That is two to four times the weight for the same thickness. It knits into itself and lies flat on the plasterboard. Look at Andrew’s roof: it is level, it has a crust, and nothing is drifting.
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1986
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1986
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1986
Comfort Zone insulation.team
Family-owned insulation manufacturer, making comfy homes since 1986
His roof had two real problems, and neither was dust.
First, it was not deep enough. Whoever put it in years ago did not put enough in, so the R-value is down. That is an easy fix: we top it up to the depth the code wants and leave a depth marker so you can see it. The second problem was nothing at all, and that is the point. It had been in that roof for a long time and his photos show no rat nests, no droppings and no tunnels through it, which is not what I find when I pull old batts out.
If you’re worried about cellulose coming in through your downlights, you should be a lot more worried about fibreglass particles because they’re far smaller. Peter Johnson
That is my opinion from forty years of pulling both products out of roofs, and it rests on two measured sizes. Glass wool only gets into the air when batts are handled or disturbed, and when it does, a modern glass wool fibre is 3 to 5 microns across on the manufacturer’s own safety data sheet Knauf Insulation Glasswool SDS, Rev 3.0, 2020, s.9 ↗. A wood-pulp fibre, which is what the upcycled plant fibre in our product is, is 25 to 45 microns across Ellis & Rudie, Institute of Paper Science and Technology, 1991, Table 1 ↗. Fine fibre floats longer and settles slower; the US National Toxicology Program notes that the airborne fibre diameter falls as the product’s nominal fibre diameter falls and that thinner fibres deposit deeper in the lung NTP, Report on Carcinogens, glass wool fibres profile, pp.2 and 6 ↗.
What is actually in your vacuum
Macquarie University’s DustSafe researchers put it this way: “You and your pets are constantly contributing skin cells and hair to dust. Dust is also made up of decomposing insects, bits of food, plastic and soil”, and about 67% of it comes from outdoors Taylor, Isley, Fry & Gillings, The Conversation, 28 Sep 2021 ↗. A survey of 72 dust samples from US homes found skin cells, soil minerals, plant fragments, hair, cotton fibres and starch in over 90% of samples Millette, AAFS 2019, abstract D7 ↗. It is grey because it is a mix of everything in the house. Cellulose Fibre Insulation is pale and papery and holds together when you pinch it. If what you are vacuuming up is grey, fluffy and full of hair, it is the house, not the roof.
Roof spaces are dusty places. Soil blows in under the tiles, old debris collects, and the same researchers note dust can leak from ceiling cornices and roof spaces into the rooms below Taylor, Isley, Fry & Gillings, The Conversation, 28 Sep 2021 ↗. Through a cornice gap or an open downlight, that grey roof dust can come down. It is still not the insulation, and the pinch test settles it.
Glass wool is different while it is being handled. Its manufacturers’ own safety sheets tell installers to use respiratory protection in dusty or poorly ventilated work Fletcher Insulation FBS-1 Safety Use Information Sheet, Rev 3, Oct 2024, s.8 ↗, and Your Home gives the same advice for glass wool, mineral wool and cellulose fibre Your Home, Insulation ↗. A roof full of old batts that gets disturbed by a tradesman, a possum or a removal is where fibreglass dust in a house comes from. Our guide on fibreglass dust goes through the manufacturers’ handling sheets.
Our own Cellulose Fibre Insulation makes fluff while it is being pumped and the crew wears masks. CSIRO notes cellulose fibre “may contain high levels of dust, so dust masks should be worn during installation” CSIRO, Thermal Insulation, 2021, p.2 ↗.
Old batts and the cancer question, in plain words
People ask me whether twenty-year-old batts are a cancer risk. In 1988 the International Agency for Research on Cancer called glass wool “possibly carcinogenic to humans” (Group 2B) IARC Monographs Vol. 43, p.152 ↗. In 2002, after its 2001 review, it moved insulation glass wool to Group 3, “not classifiable as to their carcinogenicity to humans” IARC Monographs Vol. 81, p.339 ↗. Safe Work Australia’s current exposure standards put fibre that was never tested for biopersistence, or failed the test, in an advisory “presumed” category 1B. Fibre that passed does not carry it Safe Work Australia, Workplace Exposure Standards, amended Nov 2025, note (l) p.11 and the table p.27 ↗. That default is about missing test paperwork for untested fibre. IARC’s 2001 review took in workers who had made and breathed the old fibre. Its rating was “possibly” from 1988 to 2002, never “probably”. Whether the batts in your ceiling were ever tested is a question nobody can answer by looking at them. Our fibreglass pages go through it properly.
How to check your own roof in five minutes
- 1
Open the manhole in daylight and look, don’t climb. Level and crusted is normal. Drifts and bare patches are not.
- 2
Pinch a sample from the edge and put it on a plate next to what the vacuum has. Pale and papery versus grey and hairy.
- 3
Check every downlight from below: if you can see light around the fitting, that gap is the only way anything gets in.
- 4
Measure the depth against a joist. Our R-value tool gives the R-value the code wants for your suburb’s climate zone; we turn that into a depth and leave a marker on every job.
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Send me the photos. I will tell you whether it is a top-up, a downlight job, or nothing at all.
Questions people ask
Questions about dust in the house and Cellulose Fibre Insulation
Does cellulose insulation come through the ceiling?
Not through plasterboard. A plaster ceiling is sealed and settled loose-fill does not blow around. The only path is a gap around an old downlight can, and the fix is the fitting. During a job a few crumbs can drop through a light gap and the crew vacuums them up before leaving.
Why is there grey fluffy dust in my house then?
Because that is what house dust is: skin cells, hair, insect fragments, food, plastic and soil, about 67% of it from outdoors (Macquarie University DustSafe, 2021). Cellulose Fibre Insulation is pale and papery. Put a pinch from the roof next to the vacuum contents and the difference is obvious.
Is cellulose insulation dusty to live with?
Once installed it sits where it is put. CSIRO’s table has loose-fill cellulose fibre at about 35 kilograms a cubic metre, two to four times a glass wool batt, which is why it lies flat and knits together instead of drifting. It makes fluff while it is being pumped, and the crew wears masks and vacuums up before leaving. Glass wool is the one that floats when it is handled or disturbed, which is why its manufacturers tell installers to use respiratory protection in dusty work.
My cellulose is shallow. Can you top it up?
Yes. We pump new Cellulose Fibre Insulation over the old to the depth the code wants for your climate zone and leave a depth marker. The old product stays; it is still doing its job.
What about old fibreglass batts and cancer?
IARC called glass wool ‘possibly carcinogenic’ (Group 2B) in 1988. In 2002, after its October 2001 review of workers who had breathed the old fibre, it moved insulation glass wool to Group 3, not classifiable. Safe Work Australia’s current workplace exposure standards give fibre that was never tested for biopersistence, or failed, an advisory ‘presumed’ 1B category. Fibre that passed does not carry it. Batts made before 1999 predate that test, so the default is about missing paperwork, and nobody can tell which batch is in a twenty-year-old ceiling by looking. Read our fibreglass pages for the full history with the sources.
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Not sure what you are vacuuming up? Send me a photo.
A photo of the roof from the manhole and a photo of the vacuum contents is all I need. I will tell you whether it is the roof, a downlight, or just the house.
Peter Johnson
Owner / installer · Comfort Zone Insulation Team® · Since 1986