FAQ · Cost & value
Can I buy my own batts and just pay you to install?
You can, but it almost always costs you more, not less. I buy product at about 30% under retail, and that margin is what keeps the install affordable. Buy retail and pay labour-only and you’ve paid the markup and the full install.
It’s one of the most common questions I get, and it’s a sensible one to ask. Here’s the maths on why supplying your own batts usually backfires, what the ICANZ 2024 ceiling insulation guidelines say about batt gaps and real R-value, why the joists are the weak link nobody mentions, and why a pumped-in cellulose ceiling gives you the R-value you paid for — not the R-value that was on the bag.
What customers say
Don’t just take our word for it.
This customer chose to let us handle supply and install rather than buying batts herself. Hear what she said when we came back out of the roof. The video runs right here — no ads, no link off to YouTube.
Real customer · South East Queensland · filmed on site the day of the job · press play for more testimonials in the playlist
A few more who were glad they let us handle the whole job.
"I can feel the temperature difference already walking in. It's not even a real hot day yet. Really good."
"There's a lot of misinformation out there — you explained it clearly and found a transformer issue that could've caused real problems."
"You said 8:30, you were there at 8:30. I'm really pleased with the way you kept me informed the whole way through. Definitely would recommend you to anybody."
The margin is what carries the labour.
Here’s the bit that isn’t obvious from the outside. I buy cellulose insulation wholesale — roughly 30% underwhat you’d pay at a hardware store — and that margin is exactly what subsidises putting it in. So when a supply-and-install price looks sharp, it’s because the product is helping carry the labour.
Pull the product out of that deal and the labour has to stand on its own two feet, so the install rate goes up. Meanwhile you’ve paid full retail for the batts, plus delivery on something bulky and awkward to cart home. Add it all together and the “I’ll supply my own” approach usually lands about 30% dearerthan just letting me supply and install. I’d rather you heard that from me now than worked it out after the fact.
The R-value reality — what ICANZ found in 2024
Six percent gaps roughly halve the effective R-value you paid for.
The Insulation Council of Australia and New Zealand’s 2024 ceiling insulation guidelines for existing homes found that gaps of around 6% of the ceiling area roughly halve the effective R-value. That’s not 6% of the insulation missing — that’s 6% of the total ceiling area left uninsulated. In a cut-to-fit batt job, 6% gaps are not unusual. Every bay has to be sized and cut. Every pipe penetration, every corner, every joist run is a chance for a gap to open up. The Sustainability Victoria Energy Smart Housing Manual (Figure 5.18) shows a government nomogram of the same collapse: add even a small percentage of uninsulated ceiling area and the effective R-value falls off a cliff.
What that means in plain numbers for your roof:
| Product | R-value on the bag | 6% gaps (ICANZ 2024) | Effective R in your roof |
|---|---|---|---|
| Fibreglass batts | R3.0 | ÷ 2 | ≈ R1.5 |
| Fibreglass batts | R5.0 | ÷ 2 | ≈ R2.5 |
| Fibreglass batts | R6.0 | ÷ 2 | ≈ R3.0 |
| Our pumped-in cellulose | R3.0 | No gaps | ≈ R3.0 in the real world |
To match our R3 cellulose in real-world conditions, you’d need to buy R6 batts and have them installed perfectly.
Source: ICANZ — Ceiling Insulation Guidelines: Existing Homes (2024) · Sustainability Victoria — Energy Smart Housing Manual (2018), Fig 5.18
Then there are the joists — and almost nobody talks about this.
Even if a batt job were installed perfectly with zero gaps, there’s a second problem that doesn’t show up on the bag. Batts sit betweenthe joists. They don’t go over them.
A timber joist carries a thermal resistance of roughly R1.5. In a typical ceiling there’s a joist running every 450mm for the full length of your roof — so regardless of what R-value you buy in batts, you end up with stripes of R1.5 running across your ceiling every 450mm. In a steel-frame home it’s worse still: steel has effectively no R-value, so those stripes are near-zero.
That’s what builders call a cold bridge — and in summer, a hot bridge. Heat moves straight through the joists and into your home no matter how good the batts are in between them.
Pumped-in cellulose goes over the joists. We dense-pack it over the whole ceiling to a minimum of about 100mm above the ceiling — our standard depth for R3, measured from the ceiling, not the top of the joists — so it sits over the joists as well as between them: one continuous blanket with no stripes, no cold bridges, and no weak spots. The Australian Government’s Your Home guide lists thermal bridging as one of the key factors that reduces the total R-value you actually receive from your insulation.
If you want R5, buy R5 from us and you will get R5 — not R5 divided by gaps, not R5 with stripes of R1.5 running across every joist. A real R5 across your whole ceiling, guaranteed for the life of the house.
The hidden cost
The cheap install is where the benefit quietly disappears.
Once you’ve bought the batts, the temptation is to find the cheapest pair of hands to put them in. The trouble is that since Queensland removed the insulation trade qualification in 2003, anyone with a ute can do it with no training and often no insurance, and people have died installing insulation because of this.
The quieter cost is coverage. The ICANZ 2024 guidelines found that gaps of around 6% of the ceiling area can roughly halvethe effective R-value you paid for. A gappy, half-finished batt job looks perfectly fine from the manhole, then quietly takes half the benefit away. That’s the part you don’t see until your power bill doesn’t move and you call me back in to fix the last mob’s work.
“People come to me trying to save a few hundred dollars supplying their own batts, and I have to show them the maths: they’d have paid more and got a gappier roof. I’d rather lose the upsell than let that happen.”
If you’ve already bought them
Sell them, and put the money into a job with no gaps.
If you’re already holding the batts and can’t take them back, my advice is usually to sell them in the paper or online and put the cash toward pumped-in cellulose. Even after what you lose on the resale, you generally come out in front — because you end up with a seamless blanket that fills every gap, covers the joists, and delivers the R-value you actually paid for, instead of cut-to-fit batts that always leave gaps somewhere. And it’s guaranteed for the life of the house.
If a job actually calls for batts — a wall cavity, a spot where access is tight — we lay them properly, sealed and full-coverage, and we use polyester rather than fibreglass for everything we touch. But given a free choice and the same money, pumped-in cellulose is what I’d put in my own roof. The comparison between cellulose and fibreglass batts is not close once you account for gaps, cold bridges, and long-term performance.
“People come to me trying to save a few hundred dollars supplying their own batts, and I have to show them the maths: they’d have paid more and got a gappier roof. I’d rather lose the upsell than let that happen.”
See it for yourself — what happens when the install goes wrong.
These are real jobs from real roofs in South East Queensland. The first clip shows exactly how a cheap install wrecks the value you paid for. The second shows what a batt install actually looks like going in — where the gaps form. The third shows how deep we pump cellulose and why covering the joists is the whole game. All three run right here on the page.
Read the transcript
Okay, so this is inside the typical little hot roof. You can see they tried to put batts in here, but it's quite narrow in the corners, so they didn't quite get them over there. And then the electricians have come in and put in fans and that, and tossed batts around everywhere. That's just the white batt I'm about to put over the manhole. But this is typical of what electricians do: they'll put in those downlights, and look at the huge big space they left — they only need five centimetres around the downlight, and they've pulled those batts out and just chucked them around, and they've actually wrecked the insulation for the customer. These are just more of the downlights here; the electricians put in a downlight and chucked the batts around. That's the polyester batt I've just put in to do the manhole itself, but over there the batts are just tossed all over the place. Whoever was in here to do the job didn't do it well, and then the electricians came and wrecked the rest of it. So that's that gaps thing again. We're just going to tidy up these batts, put the shrouds around the downlights, and then pump the whole job with cellulose fibre insulation so there's no gaps.
Read the transcript
Okay, so this is a job that we've just done in Earthwool fibreglass batts. You can see those all nicely laid in the bays. Earthwool's thing is that they don't dye the batts, so they're just the natural colour that they come out of the process — that way they're better for the environment. Anyway, so that's what it all looks like when it's done.
Read the transcript
Another thing to note with the construction of this roof is that these beams don't have the plaster attached on the bottom of them — they've actually got a batten that runs through underneath. So it's about a two-inch-high batten, 40 or 50 millimetres, and then you've got 100 millimetres of beam, so you've got nearly 150 millimetres there. When we fill it up with insulation, we only put in 100 millimetres, so the beams will stick out the top of the insulation in this roof. But if the beams were only 100 millimetres, it would be flush with the top of them. That's important to note, because sometimes people hop up and have a look and go, "Oh, you said it would be to the top of the joists" — but their joists have got a batten underneath, so our height is actually a bit higher.
The clips play right here on the page, or open the playlist to watch them all on YouTube and subscribe.
Some of these were filmed a while back. Our methods, safety standards and products have moved on since. For how we work today, see the rest of this page.
Some of these were filmed a while back. Our methods, safety standards and products have moved on since then.
More on supplying your own insulation batts
Can I just buy the batts and pay you for labour only?+
You can, but it almost always works out dearer, not cheaper. I buy product at roughly 30% under what you'd pay at retail, and that margin is the bit that keeps the install affordable. When you buy the batts at full retail and ask me for labour only, you've paid the shop's markup AND the full install on top, plus you've carted something bulky home yourself. The saving you were chasing has gone the other way. Nine times out of ten you're better off putting that money toward a pumped-in cellulose job that fills every gap and is guaranteed for the life of the house.
If ICANZ says 6% gaps roughly halve the R-value, what does that mean for my roof?+
It means the R-value on the bag is not the R-value in your roof — not with batts. If the installer leaves 6% of your ceiling area as gaps (which is common in a cut-to-fit batt job), your R5 batts are performing at about R2.5, and your R3 batts are performing at roughly R1.5. To get a real R3 in your ceiling from batts, you'd need to start with R6 batts and have a flawless, gap-free install. Our pumped-in cellulose has no cut-to-fit gaps — what you order is what ends up in your ceiling.
What's a cold bridge, and why does it matter if I use batts?+
A cold bridge is a path where heat moves freely through your ceiling structure, bypassing the insulation entirely. Batts sit between the joists — they don't cover them. A timber joist has a thermal resistance of roughly R1.5, and there's one every 450 to 600mm running the full length of your ceiling. In a steel-frame home the joists are near R0. So even a perfect, gap-free batt install leaves stripes of low R-value running across your roof. Pumped-in cellulose covers the joists — it's dense-packed over the whole ceiling to a minimum of about 100mm above the ceiling (our standard depth for R3, measured from the ceiling rather than the top of the joists), so it sits across the tops of the joists as well as between them, and the ceiling becomes one continuous blanket with no stripes and no bridges.
I've already bought the batts. What should I do now?+
If they're still in the bags and you can take them back, do that. If you're stuck with them, you've got two options. You can have us lay them properly — when a job actually calls for batts we lay them the right way, sealed and full-coverage. Or, and this is what I'd usually say, sell them in the paper or online and put the cash toward pumped-in cellulose. Even allowing for what you lose reselling, you generally come out in front, because you end up with a seamless blanket that covers the joists and leaves no gaps, instead of cut-to-fit batts that always do.
Isn't it always cheaper to supply the material myself?+
It feels like it should be, but the maths says otherwise. The reason a supply-and-install price looks so sharp is that the product margin is helping carry the labour. Strip the product out and the labour has to stand on its own, so the install rate goes up, and you've already paid retail (plus delivery) for the batts. Add it together and supply-it-yourself is usually about 30% more than letting me supply and install. Better you hear that up front than find out after the fact.
Can't a handyman install batts I supply for a couple of hundred dollars?+
They can, and some do it fine, but you're taking on the risk that used to sit with a licensed trade. Since the insulation trade qualification was dropped in Queensland around 2003, anyone with a ute can install batts with no training and often no insurance, and people have died doing it. The quieter cost is coverage: the ICANZ 2024 ceiling insulation guidelines found that gaps of around 6% of the ceiling area can roughly halve the effective R-value you paid for. A cheap, gappy batt job can quietly take half the benefit away while looking finished from the manhole. That's the part you don't see until your power bill doesn't move.
Comfort Zone Franchise
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