What Is The Difference Between Internal and External Batts

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I’m very glad you asked!!

Looking at them both there is very little visual difference however the main purpose of an external batt is to provide a thermal rating and the main purpose of an internal batt is to provide an acoustic rating.


When we look at thermal batt R Values there is a good range from basic comfort levels to premium top of the line insulation.

R1.5/R2.0/R2.5 and R2.7 are the most common thermal numbers you will see in the Australian market place for wall batts.


The term “Acoustic Batts” refers to sound reducing insulation products. Whilst standard thermal insulation batts do provide a minimal level of sound reduction, Acoustic Batts are specifically designed to provide higher Acoustic values.
The key difference is the density. In sound reduction, density is everything! Acoustic Batts are made at a much higher density than standard thermal insulation batts.
Acoustic batts start having an effect on sound reduction at 11kgm3. Other densities for sound reduction are 14kg/m3, 18kg/m3, 20kg/m3, 24kg/m2, 27kg/m3, 32kg/m3 and even 48kg/m3.

It Pays To Be Dense

When comparing two batts that have the same thickness, the higher density batt will perform better acoustically. If you have two acoustic batts that are 75mm thick, but one is 18kg/m3 and the other is 24kg/m3, the 24kg/m3 acoustic batt will be acoustically superior.

For each wall of your house, you need to determine what it is you wish to achieve. Is is thermal insulation or acoustic sound reduction or both.

Can I Have It All?

If you have an external wall that faces a noisy road, you might want thermal and accoustic properties. In this case, look for a high R-rated batt such as an R2.5 or R2.7. These will have both thermal and acoustic benefits.

DIO our range covers all thermal and acoustic requirements when it comes to your project. And if you still can’t decide which batt is best for your project, then give us a call on (02) 6188 4235.