Compare · Cellulose vs polyester · We sell both
Cellulose vs polyester, which one goes where.
For a ceiling I’d use pumped-in cellulose: seamless, with a pest, fire and mould edge. For underfloor or a dust-sensitive home, polyester batts. I sell both, so I’ve no reason to push one over the other.
These are my own two products: Comfort Zone® cellulose that we make in Tiaro, and the polyester batts I rate as the King of batts. I don’t have a dog in the fight between them. This page lays out which one actually belongs in which part of your house.
Both products, one house
cellulose on the ceiling, clean polyester in the wall
Why you can trust this comparison
I don’t have a dog in this fight.
Most insulation comparisons you’ll read online are written by someone who only sells one product, so the answer is always “buy the thing I sell.” This one’s different. I sell both of these products. We manufacture the Comfort Zone® cellulose ourselves in Tiaro, and we stock and fit the polyester batts every week. So when I tell you cellulose belongs in your ceiling and polyester belongs under your floor, it’s just me matching the right product to the right cavity, the same way I’d do it in my own house.
That’s the whole credibility play, and it’s the truth: I make more on the cellulose, but I’d never pump it under a floor, because it’s the wrong tool for that job. When someone talks you out of their higher-margin product where it doesn’t belong, you can probably trust them when they say it’s the right one where it does.
“I sell both. I’ve got no reason to push one over the other. I just put the right product in the right part of your house.”Peter Johnson, Comfort Zone Insulation Team
The short version
Cellulose in the ceiling. Polyester under the floor (or for a dust-sensitive home). Two good products, two different jobs.
Cellulose owns the ceiling.
The ceiling is a sealed cavity, and that’s exactly where a pumped loose-fill product wins. Cellulose goes in as one seamless blanket with full contact across every inch: no cutting, no joins, no gaps. That matters because an R-rating only counts if there are no gaps, and a batt has to be cut to fit every bay, so it always leaves some. Pumped cellulose also covers over the top of the joists and gets into the awkward corners a batt could never reach.
On top of the seamless cover, cellulose brings the edges polyester doesn’t: it’s borax-treated, so the insects that bring rats can’t survive in it (no insects, no food for rats), and the same treatment has been shown to slow fire spread. The full-contact cover also closes the cold spots where ceiling mould tends to form, because there are no gaps for roof-cavity heat to hit the cool plaster and condense. And it carries a transferable Life-of-House guarantee. For a ceiling, that’s the product I’d put in my own mum’s house.
Polyester is the King of batts, and it owns the floor.
Under the floor, the picture flips. A crawlspace under a Queenslander is open, breezy and sometimes damp, and loose-fill cellulose is made to sit captive in a sealed ceiling, not hang upside-down in the open air under your floorboards. So under the floor I don’t pump cellulose; I fit polyester. It’s hydrophobic, so the humidity under the house won’t waterlog it, it’s self-supporting between the joists, and it lifts out cleanly if a plumber ever has to get in and goes straight back after.
Polyester is the King of batts for a reason: locally made, non-itchy and safe to handle, with no glass fibre and no safety-data-sheet skin warning. In 30-odd years I’ve never seen a polyester batt settle the way fibreglass does. That non-itch quality is also why it’s my pick for anyone with a dust or fibre sensitivity who can’t have a loose-fill product blown in. A fitted polyester batt is the gentler choice. It’s still a batt, so it has to be cut to fit every bay, but where it belongs, it’s exactly the right product.
Side by side
Cellulose vs polyester: the clean comparison.
Nine things a homeowner actually cares about. On some, cellulose wins; on some, polyester does; on plenty, the answer is “depends on the cavity.” I've flagged each one.
| What matters | Cellulose fibre (pump-in) Ceilings | Polyester batts Underfloor & sensitivities |
|---|---|---|
| Best for | Ceilings: pumped in as one seamless blanket over the whole roof cavity.depends on the job | Underfloor, and ceilings for households that can't have a loose-fill product. |
| Install method & gaps | Pumped in dry: full contact across every inch of the ceiling, no cutting and no joins, so no gaps. better here | Cut to fit every bay and corner. My team cuts each piece to fit, but a batt always has more joins and edges than a pumped blanket. |
| Fire | Borax-treated: shown to slow fire spread, and gives off only CO₂ and steam. better here | Not something I'd sell polyester on either way. It isn't fire-rated as a selling point. |
| Pests & rodents | Borax keeps insects out, so there's no food for rats and no food for snakes. I've never pulled a rat nest out of pumped cellulose. better here | No pest treatment: like any batt, a determined mouse can nest in it. |
| Moisture & humidity | Hygroscopic: handles an incidental roof leak by absorbing it in one spot and drying out. Made for a sealed ceiling, not an open crawlspace.depends on the job | Hydrophobic: shrugs off moisture, which is exactly what you want in a breezy, sometimes-damp underfloor space. |
| Handling & sensitivities | Recycled-paper plant fibre, gentle to handle, but like any loose-fill it's dusty while we pump it in. | Soft, non-itchy fibre, no glass, no SDS skin warning, the gentler pick for a dust-sensitive household. better here |
| Settling over time | Installed to a specified density so it holds its thickness. In 6,000 jobs I've never seen our cellulose settle.depends on the job | In 30-odd years I've never seen a polyester batt settle the way fibreglass does. |
| Removability | Can be vacuumed out and reinstalled if the ceiling is ever replaced.depends on the job | Lifts out cleanly so a plumber or electrician can get into the underfloor and put it back. |
| Guarantee | Carries a transferable Comfort Zone® Life-of-House Guarantee. We don't know of another insulation in Australia that does. better here | Backed by our Best Service Guarantee plus the maker's product warranty. |
That’s the scorecard. Cellulose wins where the cavity is sealed, the ceiling, on gaps, fire, pests and the guarantee. Polyester wins where the space is open or the household is sensitive, underfloor and dust-sensitive homes. Neither one is the “better product” in the abstract; the better product is the one that fits the job. Want all three side by side, including the fibreglass batts I don’t recommend? See the full three-way comparison table.
Straight answers
Cellulose vs polyester: the questions I get asked most.
Cellulose or polyester, which one should I actually use?+
It depends on the cavity. For a ceiling, I'd use pumped-in cellulose every time: it goes in as one seamless blanket with no gaps, it's borax-treated so pests won't live in it and it has been shown to slow fire spread, and it carries a transferable Life-of-House guarantee. For underfloor, where a loose-fill product is the wrong tool, polyester batts are exactly what I'd reach for. I sell and fit both, so I've got no reason to push one over the other. I just match the product to the job.
Why don't you pump cellulose under the floor?+
Because a crawlspace under a Queenslander is an open, breezy, sometimes-damp space, and loose-fill cellulose is made to sit captive in a sealed ceiling cavity, not hang upside-down in the open air under your floorboards. Underfloor wants a batt that's cut to fit between the joists and stays put: polyester. It's hydrophobic so the humidity under the house doesn't waterlog it, it's non-itchy to handle, and it lifts out cleanly if a plumber ever needs to get in. So under the floor I use polyester, not cellulose, even though I make the cellulose myself.
Is polyester insulation any good, or is it just a cheaper batt?+
Polyester is the King of batts, a solid product, and I fit it every week. It's locally made, non-itchy and safe to handle, there's no nasty glass-fibre dust to wash off your work clothes, and it shrugs off moisture. In 30-odd years I've never seen a polyester batt settle the way fibreglass does. It's the right choice underfloor, and it's the right choice for anyone with a sensitivity who can't have a loose-fill product. It's still a batt, so it has to be cut to fit every bay, but if it has to be a batt, this is the one.
I'm sensitive to dust. Is polyester or cellulose better for me?+
If you've got a genuine dust or fibre sensitivity, polyester is usually the gentler choice: it's a soft, non-itchy fibre with no glass in it and no safety-data-sheet skin warning. Cellulose is a recycled-paper plant fibre and is gentle to handle too, but like any loose-fill it's dusty while we're pumping it in, so for a sensitive household, fitted polyester batts can be the easier call. Tell me about the sensitivity when I quote and I'll steer you to whichever product suits your home and your health best.
See it for yourself
Watch: cellulose vs the batts.
Seamless cellulose vs polyester batts
A quick demonstration of how pumped-in cellulose fills a space seamlessly where cut polyester batts leave gaps.
Read the transcript
I'm just demonstrating the difference between seamless fibre insulation as opposed to polyester that, but if you put a flame on seamless fibre it does proceed from the flame. It's only insulation on the mask that doesn't, so if this comes into your roof and sitting beside your joist it can actually protect your joist from the heat of the flame. So that's one of the reasons why it's far more fired. If you imagine the difference, that's polyester that. They're a fantastic insulation, great that, but if you have that in your roof it just melts away as opposed to the joist for the flame and also producing as well. Just on a side note, we've actually treated this with the same product as we treat the sea-less with and you can see it's a lot more fired than with that treatment.
How the different insulation types behave
Peter runs through how the common insulation types actually behave in a real Queensland roof.
Read the transcript
Hi there, Peter here from Comfort Zone Insulation. So if you wanted to know how different insulations perform under a flame test side by side, I'll just show you. So here we've got a fiberglass bat. They're very, very common. They're one of the cheaper of the insulation products on the market. Then we've got the polyester bat. The polyester bat's a non-allergenic, non-itchy bat and it's really quite good as far as an insulation goes. It's harder for rats and mice to build nests in it than it is for the earth form. And here we've got the cellulose fiber insulation. Now here's a bit of polyurethane that we pulled out of a house the other day. It's commonly used on chook sheds and things like that. I don't think it complies with the standard for pumping into residential buildings, but every now and again people want to put it in because they think that it should. I'll just light up my little locks and torch here. I'll just show you. We've put the flame onto the fiberglass bat. You can see now, you're just trying to cut through the bat. Even though the bat doesn't touch on fire, there's nothing stopping that from burning your house down. Because the bat just melts away from the flame. The polyester has just been starting to burn. The gas is coming off it out of quite poisonous and if you had a fire, that's out of the flame. Yeah. Polyurethane, that stuff is dangerous. It just catches fire. Very angry. It does a really black smoke. It doesn't have a bat in your house. The one that I prefer is obviously just the spider. There's a bit of flame on the side of the spider. You've never seen one there for a long time and it doesn't receive from the flame so therefore it can help protect your home in the fire and the flame just goes out. If we break that apart there, you'll see that the flame's only actually burned into there. A couple millimeters in the top. That's where it can protect your house from the fire and that's how they're still burning. Let me just put that out for some taste. That's where the sales will put out the risk of other things in the room. Often times we can't say that they're on top of polyester or fire glass or polyurethane to make sure there's no fire. I hope that answers your questions and I hope that you have the same opinion as I am now that the sale is as far as a far better option. The borax in the fields in the end, the
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Not sure which one your house needs?
Tell me what you’re trying to fix (a hot ceiling, a cold floor, a dust sensitivity) and I’ll match the right product to the right cavity and give you a fixed-price quote within 48 hours for most houses. Cellulose, polyester, or both: I sell both, so I’ll just tell you what your house actually needs.
Peter Johnson
Owner / installer · Comfort Zone Insulation Team® · Since 1986
Want the bigger picture? Read why cellulose wins in a ceiling, compare cellulose vs fibreglass, or just get your quote started.
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