How to select and install insulation product?

[PatD]

I am removing a number of windows in a living room wall in a weatherboard house.  The gap created for each is about 1500 x 800 mm.between wall suds. 

I want to fill the gaps with insulation before plastering.  I would prefer to install bats. 

What type of insulation is recommended?

[MitchellMc]

Welcome to the Bunnings Workshop community @PatD. It's wonderful that you've joined us and many thanks for your question about insulation.

Insulation batts would be suitable for this application. Since you've got a bit of an odd size, you need to cut the batts up to suit it. If you were to place two Bradford R2.7 1160 x 420 x 90mm 2.8m2 Gold High Performance Wall Batts side-by-side that would fill your 800mm gap and then one laid horizontally above would fill the remaining area.

Does your home have a sarking layer? If so, it would be best to restore it over the gap by taping it to the existing sarking with Ametalin 48mm x 50m Insulation / Ducting Tape.

You should find this step-by-step guide useful: How to insulate walls

Please let me know if you have any questions.

Mitchell