It is saying that with the appropriate vapour control barrier inside and out, that new builds do not need an air gap in the "cavity", it can now be filled with insulation.
You just have to control the temperature and moisture levels so that you do not get condensing humidity in the middle of the wall. That is often a problem with timber frame and celotex fill for example.
You just have to control the temperature and moisture levels so that you do not get condensing humidity in the middle of the wall. That is often a problem with timber frame and celotex fill for example.