From a recent thread on rendering:

On 16 Nov, 09:30, Tim Lamb wrote:

When the farmhouse was *done up*, the exterior was re-rendered over 25mm
of insulation.

I'm facing a bunch of this for refurbs over the next couple of years.
The main house isn't going to be changed, but I've thin-walled
extensions to the rear (pantry etc.) and various sheds that are
certainly candidates for adding wall insulation. The rendering,
particularly one shed, isn't impressive at present anyway.

So what are my pros and cons for adding insulation to either the
inside or outside of the wall?

Thanks