You basically want something so that if water / condensation / vapor manages to penetrate the siding (and it always will), it will DRY OUT vs absorbing into whatever the next layer is.
As others have described there are wraps. We just used firring strips made out of PVC. Others do it with ripped strips of pressure treated 2x4s.
You SHOULD still do it over the exterior insulation if it is there, so there is a space for things to dry out.
The reason you see old 100+ year old uninsulated houses standing is that, while they were crappy for retaining heat and combatting airflow, they did at least always dry out after they got wet. This is even more important in a modern home where all your materials are preventing that drying out, so you have to plan for it.
As others have described there are wraps. We just used firring strips made out of PVC. Others do it with ripped strips of pressure treated 2x4s.
You SHOULD still do it over the exterior insulation if it is there, so there is a space for things to dry out.
The reason you see old 100+ year old uninsulated houses standing is that, while they were crappy for retaining heat and combatting airflow, they did at least always dry out after they got wet. This is even more important in a modern home where all your materials are preventing that drying out, so you have to plan for it.