Why cellulose: all 14 reasons
The full case for the only product I'd use in my own home.
Compare · The three products I sell · SE Queensland
Insulation comparison table: cellulose vs polyester vs fibreglass.
I sell all three products, but I only recommend the pumped-in cellulose fibre. Here’s the scorecard (gaps, effective R-value, fire, pests, leaks, settling, guarantee and price) laid out side by side.
I fit fibreglass and polyester batts every week for the people who want them, and the polyester's a decent product. But after 40 years and 6,000 roofs, pumped cellulose is the only one I’d put in my own mother’s house. Every figure below cites a real, checkable source.
This is cellulose
one seamless blanket, no gaps, what an R-rating is supposed to mean
Start here
Three products. One I’d use in my own home.
There are basically three types of insulation for houses in Queensland: pumped-in cellulose fibre, polyester batts and fibreglass batts. I fit all three. In the end about 92% of my customers go with the cellulose, 6% with the polyester batts (the King of batts, locally made and non-itchy) and just 2% with the cheap fibreglass, and most of them came in wanting batts. They left with cellulose once they understood what’s actually inside the bag.
I don’t have a dog in the fight between my own two products, so when I tell you the cellulose wins it’s because after 6,000 roofs I’ve watched what each one does over time. The single most important line on this whole page is this: an R-rating only counts if there are no gaps, and batts always have gaps, so an R5 batt isn’t really an R5 in your roof. Choice Magazine reckons just 5% gaps in batts can cut efficiency by as much as 70%, and you can see the same mechanism in the Australian Government’s yourhome guide.
“I sell all 3 but, after installing insulation since 1988, I only recommend the pumped-in cellulose fibre. It’s the only one I’d use in my own home.”Peter Johnson, Comfort Zone Insulation Team
★ Recommended
Comfort Zone® cellulose
Pump-in, recycled-paper fibre
By far the best product to use, and the only one I’d put in my mother’s home. It pumps in as a seamless blanket with full contact across every inch of the ceiling, so there are no gaps, which is the whole ballgame, because an R-rating only counts if there are no gaps. Borax-treated for fire and pests, hygroscopic for leaks, and backed by a transferable Life-of-House guarantee.
The King of batts
Polyester batts
Locally made, non-itchy
If you’ve decided you want a batt, the polyester ones are the best of them. They’re non-itchy, locally made and safe to handle, and in 30-odd years I’ve never seen a polyester batt settle the way fibreglass does. Under a floor, where pumped cellulose is the wrong product, polyester is exactly what I’d use. But a batt is still a batt: it has to be cut into every bay, so it still has joins.
Not recommended
Fibreglass batts
Earthwool®, Gold Batts®, Pink Batts®
These are the itchy ones, and they’re all fibreglass. They’re the cheapest insulation you can buy, and that’s the only thing they’ve got going for them, a very cheap solution, but you’d be lucky if you’re just not buying trouble for the future. Only about 2% of my customers choose them once they understand the trade-offs: itchy install, gaps from day one, settling, and rodents love them.
Side by side
The full comparison: every axis a homeowner cares about.
Twelve things that actually matter in your roof, with the winner flagged on each, including the one axis where fibreglass wins (price to buy).
| What matters | Comfort Zone® cellulose ★ Recommended | Polyester batts the King of batts | Fibreglass batts Not recommended |
|---|---|---|---|
| Who chooses it | About 92% of my customers, once they understand why. | About 6%, the people who’ve decided on a batt. | About 2%, the cheapest option, on price alone. |
| Install method & gaps | Pumped in as one seamless blanket: full contact across every inch of the ceiling, no gaps. | Cut to fit every bay. My team cuts each piece to fit, but a batt by nature still has joins. | Cut to fit, with gaps from day one, and the tight, hot corners get short-changed. |
| What an R-rating delivers | No gaps, so the rating counts: about 40% higher effective R-value than batts after install. | R-rating as marked, but the real result still depends on no gaps. | An R5 is only an R5 with no gaps. Choice says 5% gaps cut efficiency up to 70%. |
| Fire behaviour | Borax fire-retardant treated: Sustainability Victoria says the treatment stops flame spreading; gives off only CO₂ and steam. | Not fire-treated; I don’t sell it on fire performance. | Melts away in a fire and leaves your timber exposed; binders can give off poison gas. |
| Pests, rats & insects | Borax keeps insects out, so they won’t live in it: no food for rats and no food for snakes. I’ve never seen a nest in pumped cellulose. | No pest treatment: mice can still nest in a batt. | Rodents love them; mice push the loose batts up and nest underneath. |
| Roof leaks & moisture | Hygroscopic: absorbs a leak in one spot, dries out, and shows a discoloured patch so we can pinpoint it. | Sheds water; a leak runs under the batt rather than being held. | Hydrophobic: water flows under the batts and spreads across the whole ceiling. |
| Health & handling on install | Recycled-paper plant fibre: no SDS skin warning. Like any loose-fill we wear dust masks; installers go home in the same clothes. | Non-itchy and locally made, pleasant to handle. | The maker’s own SDS says wear a P2 dust mask and wash work clothes separately. |
| Hard roofs (A-frame, flat, raked, Super-6, steel-frame) | One of very few solutions that works: pumped right into the cavity and over steel battens. | Limited: a batt can’t fill a sealed or raked cavity. | Limited: most batt companies say these roofs “can’t be done.” |
| Packaging waste | Reusable poly bags that go back to the factory and get refilled, effectively no waste plastic from your job. | Plastic-wrapped packs. | Trailer-loads of plastic wrap. I dump whole trailers of it every month. |
| Guarantee | Transferable Comfort Zone® Life-of-House Guarantee. We don’t know of another insulation in Australia that carries it. | Our Best Service Guarantee, no life-of-house guarantee. | Our Best Service Guarantee, no life-of-house guarantee. |
| Price to buy | Dearer, but for a little extra cost, a far better result over the life of the house. | Around 20% cheaper than cellulose. | Cheapest, but you’d be lucky if you’re just not buying trouble for the future. |
| Peter’s verdict | The one I’d put in my own mother’s house. | The best of the batts, the only ones I’ll quote with a straight face. | I don’t recommend these. |
Sources for the figures above: yourhome.gov.au (Insulation) for the gaps and effective-R-value mechanism; Sustainability Victoria: Energy Smart Housing Manual for the fire-retardant statement; and CSIRO: Thermal Insulation for the handling and settling notes. The customer-split and field-experience figures are Peter’s own, from 40 years on the tools.
The quick-scan version
Same three products, the short answers.
If you just want the headline on each, here's the at-a-glance grid. The cellulose column is the one I'd choose.
Comfort Zone cellulose pumped-in, recommended ★ Recommended | Polyester batts the best of the batts | Fibreglass batts the cheap ones | |
|---|---|---|---|
| Gaps | Seamless, no gaps | Cut to fit | Gaps from day one |
| Settling over time | I've never seen it settle | Doesn't settle | Settles after ~10 yrs |
| Pests & vermin | Borax-treated, insects won't live in it | Mice can nest | Rodents love them |
| Fire | Shown to slow fire spread | — | Useless in a fire |
| Sound | Fills the cavity, quieter, for the same thickness | Standard | Not even STC-rated |
| Roof leaks | Absorbs, dries, shows the leak | — | Water spreads under the batts |
| Air-tightness | Air can't be forced through it | Air passes through | Hold a batt to a fan, air blows straight through |
| Packaging waste | Reusable bags, zero waste | Plastic packs | Trailer-loads of plastic |
| Guarantee | Transferable Life-of-House | None | None |
| Peter's verdict | The one I'd put in my mum's house | The best of the batts | I don't recommend these |
That’s the scorecard. The cellulose wins on the things you’ll live with for the life of the house, and the one thing fibreglass beats it on is the price to buy. For a little extra cost the cellulose gives you a far better result over the life of the house, and you only insulate once, so you can’t stand in your living room and compare the two later. You have to pick.
The line on the table I get asked about most
Rats love batts. In my roofs, they leave the cellulose alone.
Of every row in that table, “pests” is the one people ask me about most. Cellulose is treated with borax, a natural mineral salt about as toxic to you as table salt, and insects won’t live in it. No insects means no food for rats, and no food for rats means no food for snakes. So a cellulose roof after 40 years is far cleaner than a batt roof. Batts are the opposite: they sit so loosely that mice push them up and nest underneath, and the urine and droppings soak straight into your ceiling sheets.
“I pull rat nests out of batt-insulated roofs every week. I have NEVER pulled a rat nest out of a roof that was pumped with cellulose.”
How to read this table
Which column is right for you?
If you’re insulating a ceiling and you want it done once and done right, the cellulose column is the one I’d point you to every time. It’s the seamless cover with no gaps, the borax for fire and pests, and the transferable guarantee. If you’ve already decided on a batt (say for an under-floor job, where pumped cellulose is the wrong product) then the polyester column is the one I’d quote you with a straight face: locally made, non-itchy, and it doesn’t settle the way fibreglass does.
The fibreglass column wins on exactly one thing, the price to buy. Here’s the rest of it: itchy install, gaps from day one, settling after about ten years, and rodents love them. It’s a very cheap solution, but you’d be lucky if you’re just not buying trouble for the future. I’ll still fit it if it’s what you want. Whatever you choose, send me your address and I’ll give you a fixed-price quote within 48 hours for most houses, with no deposit to pay.
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Go deeper
Two products at a time.
This page lines all three up at once. If you want the full story on a single matchup, here are the head-to-head comparisons.
Cellulose vs fibreglass batts
Why an R5 batt isn't really an R5 in your roof.
Cellulose vs polyester batts
Ceilings versus floors, and where each one wins.
Cellulose vs spray foam
Moisture, removal and the install-health question.
Polyester vs fibreglass batts
If it has to be a batt, make it the polyester.
Spray foam vs polyester (underfloor)
The under-floor comparison, plainly laid out.
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Seen all three? Let’s get you a price.
You’ve seen the three products side by side, the one I’d put in my own mum’s ceiling, and the one row where the cheap fibreglass wins. Whatever you decide, I’ll give you a straight quote for your roof. Fill in the simple online form and you’ll have a detailed fixed-price quote within 48 hours for most houses.
Peter Johnson
Owner / installer · Comfort Zone Insulation Team® · Since 1986
In the trade and want to install it yourself? We make our cellulose in Tiaro and run exclusive territories. Franchise with the family.