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How to install Earthwool insulaton batts?

Hi all

I bought a pack of Earthwool R6.0 ceiling bats as there's a few missing gaps in my roof

Apart from cutting them in half to size. They are double the thickness of what I got in my current roof

So my question is am I supposed to slice them in half to make them thinner? Or just pay the big fat thick batt down?

When the builders do this do they split them in half ? I am pretty sure they use Bradford insulation batts (yellow in colour) and the thickness is about half of the earthwool product I got. Or are Earthwool brand just thicker in nature ?

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Comments

EricL

Hello @pat83

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your Earthwool insulation.

Earthwool R6.0 ceiling batts are designed to be thicker because they provide a higher insulation rating than the more common R2.5 or R3.5 batts you often see in existing homes. The R-value refers to thermal resistance, so the higher the number, the better the insulation. To achieve R6.0, the product simply has to be bulkier.

You should not slice them in half to make them thinner, because doing so halves their R-value and defeats the purpose of buying high-rated batts. They are meant to be installed at full thickness, laid flat between the joists. Builders don’t usually cut these batts thinner either; instead, they use whichever R-rating is specified for the job. In many homes, particularly older ones, the builders used R2.5 or R3.0 ceiling batts which are about half the thickness of your new ones. That’s why your existing insulation looks thinner and yellow (Bradford Glasswool), while Earthwool looks thicker and denser.

The only cutting you need to do is to trim batts to fit snugly between joists or around obstacles like downlights, vents, or wiring. If the new R6.0 batts are taller than your ceiling joists, it’s still fine, they’ll compress slightly without losing too much effectiveness, but ideally, they should be left uncompressed as much as possible for full performance.

If you need further assistance, please let us know.

Eric

pat83

https://www.workshop.bunnings.com.au/discussion/comment/56951#Comment_56951

Thanks

Good info

It's.dissapointing that builders use low rated batts where in Victoria where I live Google says to use r6 for ceiling

So the Bradford ones in my home which was built only 5 years ago is only about the same thickness as a ceiling joist ( 100mm roughly)

If I gradually get more batts especially in colder rooms and lay the R6 on top of the existing thinner batts would insulate my home even better? Or would it have a sort of diminishing result?

For the moment I'm just putting them i. Spots that are missing entirely

EricL

https://www.workshop.bunnings.com.au/discussion/comment/90791#Comment_90791

Hello @pat83

If you gradually add R6.0 Earthwool batts over the top of your existing Bradford ones, you will definitely improve your home’s insulation. Insulation works by resisting heat transfer, and stacking layers adds up. So R2.5 plus R6.0 will essentially perform like R8.5 in total, provided they are installed properly with minimal compression and no gaps. It won’t be a case of diminishing returns in the sense that it stops working, but the jump from no insulation to R2.5 is far more dramatic than the jump from R6.0 to R8.5. Each additional step still helps, it just becomes less noticeable to your comfort as you go higher.

Where you’ll feel it most is in the rooms you’re targeting, warmer in winter, cooler in summer, and more stable overall. Your heating and cooling bills should also drop. The key is to make sure the new batts sit snugly over the old ones and cover the joists as well, since timber itself conducts heat. That way, you get a continuous blanket effect rather than just doubling thickness between joists.

If you need further assistance, please let us know.

Eric

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