The left is a standard wall, 3/4" siding, 1/2" sheathing, batt insulation and 1/2" sheetrock, if you remove the siding and apply 1-1/4" of hemp-lime to the sheathing, 1/2" furring for condensation then replace the siding you get what's on the right side. Notice how much heat has penetrated the standard wall and how little by adding the hemp-lime, this can be blown on like concrete or hand applied. The temperature reads 4.1C for the standard wall and 1.2C for the wall with the upgrade after 400-minutes, a 70% reduction.
That's a fairly radical improvement in thermal resistance, the hemp adds insulation to the lime mortar and by having the furring strips the conduction from the siding is greatly reduced. This will matter where it's windy and cold. I've done a lot of combinations now and this seems to add the most for the least, the hemp-lime fungus resistant, allows moisture to move and is basically fireproof. Insulation board can be used instead of the hemp-lime.
These are only conduction so not a full analysis but reveal much, this free software is basic, yet you can modify properties and all, the desktop download gives better results and the pages have a choice of practical setups to download and use that are very practical:
Property values I used, not confident on all these yet, most from engineeringtoolbox.com:
pine glass wool